1
DESCRIPTION
Title of Invention
METHOD FOR PRODUCING SINGLE-RING AROMATIC HYDROCARBONS
5
Technical Field
[OOOl]
The present invention relates to a method for producing a monocyclic aromatic
hydrocarbon.
10 Priority is claimed on Japanese Patent Application No. 201 1-067690 and
Japanese Patent Application No. 201 1-067691, filed March 25,201 1, the contents of
which are incorporated herein by reference.
Background Art
15 [0002]
Light cycle oil (hereinafter, referred to as "LCO"), which is cracked light oil
produced with a fluid catalytic cracking (hereinafter, referred to as "FCC") units, contains
a large amount of polycyclic aromatic hydrocarbons, and have been utilized as diesel or
fuel oil. However, in recent years, investigations have been conducted to obtain
20 monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms with a high added value
(for example, benzene, toluene, xylene, and ethylbenzene) that can be utilized as high
octane gasoline base materials or petroleum chemistry feedstocks, from the LCO.
For example, in PTL 1 to PTL 3, there have been suggested methods for
producing a monocyclic aromatic hydrocarbon from a polycyclic aromatic hydrocarbon
25 that is contained in LC0 or the like in a large amount, using a zeolite catalyst.
Citation List
Patent Literature
[0003]
5 [PTL 11 Japanese Unexamined Patent Application, First Publication No.
H3-2128
[PTL 21 Japanese Unexamined Patent Application, First Publication No.
H3-52993
[PTL 31 Japanese Unexamined Patent Application, First Publication No.
10 H3-26791
Summary of Invention
Technical Problem
[0004]
15 However, in the methods described in Patent Documents 1 to 3, it cannot be said
that the yield of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms is
sufficiently high.
Thus, it is contemplated that in order to sufficiently increase the yield of
monocyclic aromatic hydrocarbons, the LC0 or the like is subjected to cracking
20 reforming, the product thus obtained is hydrogenated, and these hydrogenation products
are recycled again to a cracking reforming reaction step.
[0005]
Here, the product obtainable by subjecting LC0 or the like to cracking
reforming contains a large amount (for example, 50 mass% to 95 mass%) of polycyclic
25 aromatic hydrocarbons in the heavy fraction. Polycyclic aromatic hydrocarbons may
3
vary depending on the composition of the feedstock oil, but mainly include bicyclic
aromatic hydrocarbons. Therefore, the polycyclic aromatic hydrocarbons serve as a
satisfactory feedstock for monocyclic aromatic hydrocarbons through partial
hydrogenation. Therefore, as described above, the yield of the monocyclic aromatic
5 hydrocarbons can be sufficiently increased by recycling hydrogenation products of
polycyclic aromatic hydrocarbons and supplying the hydrogenation product again to a
cracking reforming reaction step.
[0006]
However, the hydrogenation of bicyclic aromatic (polycyclic aromatic)
10 hydrocarbons is an exothermic reaction, and the amount of heat generation is very large.
Therefore, when the product containing such polycyclic aromatic hydrocarbons in a large
amount is hydrogenated, the reaction temperature at the reactor extremely increases, and
it is difficult to carry out an appropriate reaction in conventional facilities. Furthermore,
for example, it is possible to suppress an increase in the reaction temperature and achieve
15 an appropriate reaction by supplying hydrogen stepwise from the middle of the reactor
(hydrogen quench or the like); however, in that case, the apparatus configuration of the
reactor is complicated, and a sharp increase in the facility cost is brought about.
[0007]
The present invention was achieved in view of such circumstances, and an
20 object of the invention is to provide a method for producing monocyclic aromatic
hydrocarbons, which can produce monocyclic aromatic hydrocarbons having 6 to 8
carbon atoms with a high yield from a feedstock oil containing polycyclic aromatic
hydrocarbons, and can suppress extreme heat generation at the time of the hydrogenation
so that a sharp increase in the facility cost of the hydrogenation reactor can be avoided.
25
Solution to Problem
[OOOS]
The present invention relates to a method for producing monocyclic aromatic
hydrocarbons, by which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
5 are produced from a feedstock oil having a 10 vol% distillation temperature of 140°C or
higher and a 90 vol% distillation temperature of 380°C or lower, the method including:
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
10 aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
carbon atoms;
a hydrogenation step of hydrogenating a liquid fraction separated from the
product produced in the cracking reforming reaction step;
a dilution step of adding a portion of a hydrogenation product of the heavy
15 fraction having 9 or more carbon atoms obtained in the hydrogenation step, or a diluent
to the liquid fraction; and
a recycling step of returning the other portion of the hydrogenation product of
the heavy fraction obtained in the hydrogenation step to the cracking reforming reaction
step.
20 [0009]
More specifically, the method for producing monocyclic aromatic hydrocarbons
related to a first aspect of the invention is a method for producing monocyclic aromatic
hydrocarbons, by which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
are produced from a feedstock oil having a 10 vol% distillation temperature of 140°C or
25 higher and a 90 vol% distillation temperature of 380°C or lower, the method including:
5
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a react, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
5 carbon atoms;
a purificationJrecovery step of purifying and recovering monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms separated from the product produced in the
cracking reforming reaction step;
a hydrogenation step of hydrogenating the heavy fraction having 9 or more
10 carbon atoms separated from the product produced in the cracking reforming reaction
step;
a dilution step of returning a portion of a hydrogenation product of the heavy
fraction having 9 or more carbon atoms obtained in the hydrogenation step, as a diluent
oil to the hydrogenation step; and
15 a recycling step of returning the other portion of the hydrogenation product of
the heavy fraction obtained in the hydrogenation step to the cracking reforming reaction
step.
[OO lo]
Furthermore, in regard to the method for producing monocyclic aromatic
20 hydrocarbons, it is preferable that in the dilution step, the amount of the diluent oil that is
returned to the hydrogenation step be adjusted such that the mass ratio of the heavy
fraction having 9 or more carbon atoms separated from the product produced in the
cracking reforming reaction step and supplied to the hydrogenation step, to the diluent oil
is in the range of 10:90 to 80:20.
2 5 [OO 1 11
6
Furthermore, another method for producing monocyclic aromatic hydrocarbons
of the invention is a method for producing monocyclic aromatic hydrocarbons, by which
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are produced from a
feedstock oil having a 10 vol% distillation temperature of 140°C or higher and a 90 vol%
5 distillation temperature of 380°C or lower, the method including:
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
10 carbon atoms;
a hydrogenation step of hydrogenating a portion separated from the product
produced in the cracking reforming reaction step;
a purificatiodrecovery step of distilling the hydrogenation product obtained in
the hydrogenation step to purifj monocyclic aromatic hydrocarbons having 6 to 8 carbon
15 atoms, recovering the monocyclic aromatic hydrocarbons, and separating a heavy
fraction having 9 or more carbon atoms from the monocyclic aromatic hydrocarbons
having 6 to 8 carbon atoms;
a dilution step of returning a portion of the heavy fraction having 9 or more
carbon atoms separated in the purificatiodrecovery step, as a diluent oil to the
20 hydrogenation step; and
a recycling step of returning the other portion of the heavy fraction separated in
the purification/recovery step to the cracking reforming reaction step.
[OO 121
Furthermore, in regard to the method for producing monocyclic aromatic
25 hydrocarbons, it is preferable that in the dilution step, the amount of the diluent oil that is
7
returned to the hydrogenation step be adjusted such that the mass ratio of the product
separated from the product produced in the cracking reforming reaction step and supplied
to the hydrogenation step, to the diluent oil is in the range of 20:80 to 80:20.
[00 1 31
5 Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable that in the dilution step, the diluent oil be returned to the
hydrogenation step such that the concentration of polycyclic aromatic hydrocarbons in a
mixed oil of the product separated from the product produced in the cracking reforming
reaction step and supplied to the hydrogenation step, and the diluent oil is 5 mass% to 50
10 mass%.
[00 141
Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable that in the hydrogenation step, the hydrogenation pressure
be set to 0.7 MPa to 13 MPa.
15 [00 1 51
A method for producing monocyclic aromatic hydrocarbons related to a second
aspect of the invention is a method for producing monocyclic aromatic hydrocarbons, by
which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are produced from
a feedstock oil having a 10 vol% distillation temperature of 140°C or higher and a 90
20 vol% distillation temperature of 380°C or lower, the method including:
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
25 carbon atoms;
8
a purificationlrecovery step of purifiing and recovering monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms separated from the product produced in the
cracking reforming reaction step;
a dilution step of adding a diluent comprising hydrocarbons to the heavy fraction
5 having 9 or more carbon atoms separated from the product produced in the cracking
reforming reaction step;
a hydrogenation step of hydrogenating the mixture; and
a recycling step of returning the hydrogenation product of the mixture obtained
in the hydrogenation step to the cracking reforming reaction step.
10 [OO 161
Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable that the method include a diluent recovering step of
separating and removing the diluent from the hydrogenation product of the mixture
obtained in the hydrogenation step, recovering the diluent, and reutilizing the diluent as a
15 diluent to be added to the heavy fraction having 9 or more carbon atoms.
[00 171
Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable to use a hydrocarbon oil having a boiling point of lower
than 185°C as the diluent.
20 Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable to use a substance having a concentration of polycyclic
aromatic hydrocarbons of 50 mass% or less as the diluent.
[00 181
Furthermore, in regard to the method for producing monocyclic aromatic
25 hydrocarbons, it is preferable that in the dilution step, the amount of the diluent be
9
adjusted such that the mass ratio of the heavy fraction having 9 or more carbon atoms
separated from the product produced in the cracking reforming reaction step and supplied
to the hydrogenation step, to the diluent is in the range of 10:90 to 80:20.
[00 191
Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable that in the dilution step, a diluent be added such that the
concentration of polycyclic aromatic hydrocarbons in a mixture obtainable by adding a
diluent to the heavy fraction having 9 or more carbon atoms is 5 mass% to 50 mass%.
[0020]
Furthermore, in regard to the method for producing monocyclic aromatic
hydrocarbons, it is preferable that in the hydrogenation step, the hydrogenation pressure
be set to 0.7 MPa to 13 MPa.
Advantageous Effects of Invention
15 1002 11
According to the method for producing monocyclic aromatic hydrocarbons of
the invention, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be
produced from a feedstock oil containing polycyclic aromatic hydrocarbons with a high
yield. Furthermore, since the method includes a dilution step, extreme heat generation
20 attributable to the hydrogenation of polycyclic aromatic hydrocarbons in the
hydrogenation step is suppressed, and thereby a stabilized hydrogenation is enabled.
Thus, a sharp increase in the facility cost of the hydrogenation reactor can be avoided.
Brief Description of Drawings
[0022]
10
FIG. 1 is a diagram for illustrating Exemplary Embodiment 1 of the method for
producing monocyclic aromatic hydrocarbons related to a first aspect of the invention.
FIG. 2 is a diagram for illustrating Exemplary Embodiment 2 of the method for
producing monocyclic aromatic hydrocarbons related to the first aspect of the invention.
FIG. 3 is a diagram for illustrating Exemplary Embodiment 1 of the method for
producing monocyclic aromatic hydrocarbons related to a second aspect of the invention.
FIG. 4 is a diagram for illustrating Exemplary Embodiment 2 of the method for
producing monocyclic aromatic hydrocarbons related to the second aspect of the
invention.
Description of Embodiments
[0023]

[Exemplary Embodiment 11
Hereinafter, Exemplary Embodiment 1 of the method for producing monocyclic
aromatic hydrocarbons related to the first aspect of the invention will be described.
FIG. 1 is a diagram for illustrating Exemplary Embodiment 1 of the method for
producing monocyclic aromatic hydrocarbons related to the first aspect of the invention,
and the method for producing monocyclic aromatic hydrocarbons of the present
20 exemplary embodiment is a method of producing monocyclic aromatic hydrocarbons
having 6 to 8 carbon atoms from the feedstock oil.
[0024]
That is, the method for producing monocyclic aromatic hydrocarbons of the
present exemplary embodiment is, as illustrated in FIG 1 :
(a-1) a cracking reforming reaction step of bringing a feedstock oil into contact
11
with a catalyst for monocyclic aromatic hydrocarbon production to effect a reaction,
thereby obtaining a product containing monocyclic aromatic hydrocarbons having 6 to 8
carbon atoms and a heavy fraction having 9 or more carbon atoms;
(b-1) a separation step of separating the product produced in the cracking
5 reforming reaction step into plural fractions;
(c-1) a purification/recovery step of purifying and recovering monocyclic
aromatic hydrocarbons separated in the separation step;
(d-1) a hydrogenation step of hydrogenating whole or a portion of the heavy
fraction having 9 or more carbon atoms obtainable from the fractions separated in the
10 separation step;
(e-1) a dilution step of returning a portion of the hydrogenation product of the
heavy fraction having 9 or more carbon atoms obtained in the hydrogenation step to the
hydrogenation step;
(f-1) a recycling step of returning the residual portion of the hydrogenation
15 product of the heavy fraction obtained in the hydrogenation step to the cracking
reforming reaction step;
(g-1) a hydrogen recovery step of recovering hydrogen produced as a by-product
in the cracking reforming reaction step from the gas components separated in the
separation step; and
20 (h-1) a hydrogenation supply step of supplying the hydrogen collected in the
hydrogen recovery step to the hydrogenation step.
Among the steps (a-1) to (h-1), the steps (a-1), (c-1), (d-1), (e-1), and (f-1) are
essential steps for Exemplary Embodiment 1 of the first aspect of the invention, and the
steps (b-1), (g-1), and (h-1) are optional steps.
2 5 [0025]
12
Hereinafter, the respective steps will be described in detail.

In the cracking reforming reaction step, a feedstock oil is brought into contact
with a catalyst for monocyclic aromatic hydrocarbon production, and using saturated
5 hydrocarbons contained in the feedstock oil as a hydrogen donating source, polycyclic
aromatic hydrocarbons are partially hydrogenated by a hydrogen transfer reaction from
the saturated hydrocarbons. Thus, ring-opening is carried out, and thereby the
polycyclic aromatic hydrocarbons are converted to monocyclic aromatic hydrocarbons.
Furthermore, the saturated hydrocarbons that are present in the feedstock oil or are
10 obtainable in a separation operation can also be converted to monocyclic aromatic
hydrocarbons through cyclization and dehydrogenation. Also, monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms can also be obtained by cracking monocyclic
aromatic hydrocarbons having 9 or more carbon atoms. Thereby, a product containing
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction
15 having 9 or more carbon atoms is obtained.
[0026]
This product includes, in addition to the monocyclic aromatic hydrocarbons or
the heavy fraction, hydrogen, methane, ethane, ethylene, LPG (propane, propylene,
butane, butene and the like), and the like. Furthermore, the heavy fraction includes a
20 large amount of bicyclic aromatic hydrocarbons such as naphthalene, methylnaphthalene
and dimethylnaphthalene, and also, aromatic hydrocarbons having three or more rings,
such as anthracene, may also be included depending on the feedstock oil. In the present
application, these bicyclic aromatic hydrocarbons and aromatic hydrocarbons having
three or more rings are collectively described as polycyclic aromatic hydrocarbons.
25 [0027]
13
In this cracking reforming reaction step, regarding components such as
naphthenobenzenes, paraffins and naphthenes in the feedstock oil, a majority of the
components are lost by producing monocyclic aromatic hydrocarbons. Furthermore,
polycyclic aromatic hydrocarbons are such that a portion thereof is converted to
5 monocyclic aromatic hydrocarbons by cracking and hydrogen transfer with saturated
hydrocarbons, but at the same time, as alkyl side chains are cleaved, bicyclic aromatic
hydrocarbons having fewer side chains, such as naphthalene, methylnaphthalene and
dimethylnaphthalene, are also mainly produced as by-products. Therefore, in this
cracking reforming reaction step, monocyclic aromatic hydrocarbons are produced with a
10 high yield, and at the same time, bicyclic aromatic hydrocarbons are also produced as
by-products as a heavy fraction having 9 or more carbon atoms.
[0028]
(Feedstock oil)
The feedstock oil used in the invention is an oil having a 10 vol% distillation
15 temperature of 140°C or higher and a 90 vol% distillation temperature of 380°C or lower.
Regarding an oil having a 10 vol% distillation temperature of lower than 140°C, since
the oil is light oil, monocyclic aromatic hydrocarbons are produced, so that the oil does
not suit the purpose of the invention. Furthermore, in the case of using an oil having a
90 vol% distillation temperature of higher than 380°C, the yield of monocyclic aromatic
20 hydrocarbons is decreased, the amount of coke deposition on the catalyst for monocyclic
aromatic hydrocarbon production increases, and a rapid decrease in the catalyst activity
tends to occur.
The 10 vol% distillation temperature of the feedstock oil is preferably 150°C or
higher, and the 90 vol% distillation temperature of the feedstock oil is preferably 360°C
or lower.
[0029]
In addition, the 10 vol% distillation temperature and the 90 vol% distillation
temperature as used herein mean values measured according to JIS K2254 "Petroleum
5 products - Distillation Testing Methods."
Examples of feedstock oils having a 10 vol% distillation temperature of 140°C
or higher and a 90 vol% distillation temperature of 380°C or lower include LCO,
hydrogenation purified oil of LCO, coal liquefaction oil, heavy oil hydrocracking
purified oil, straight run kerosene, straight run gas oil, coker kerosene, coker gas oil, and
10 oil sand hydrocracking purified oil.
[0030]
Polycyclic aromatic hydrocarbons are materials that have low reactivity and are
not easily converted to monocyclic aromatic hydrocarbons in the cracking reforming
reaction step of the invention. However, on the other hand, when hydrogenated in the
15 hydrogenation step, polycyclic aromatic hydrocarbons are converted to
naphthenobenzenes, and can be further converted to monocyclic aromatic hydrocarbons
by being supplied to be recycled again to the cracking reforming reaction step.
Therefore, the feedstock oil is not particularly limited in view of containing a large
amount of polycyclic aromatic hydrocarbons. However, among the polycyclic aromatic
20 hydrocarbons, aromatic hydrocarbons having three or more rings consume a large
amount of hydrogen in the hydrogenation step, and even though those hydrocarbons are
hydrogenation products, since the reactivity in the cracking reforming reaction step is low,
it is not preferable for the feedstock oil to contain a large amount of the polycyclic
aromatic hydrocarbons. Therefore, the content of aromatic hydrocarbons having three
25 or more rings in the feedstock oil is preferably 25 vol% or less, and more preferably 15
15
vol% or less.
In addition, regarding the feedstock oil containing bicyclic aromatic
hydrocarbons that are converted to naphthenobenzene in the hydrogenation step and
intended to reduce aromatic hydrocarbons having three or more rings, for example, it is
5 more preferable that the 90 vol% distillation temperature of the feedstock oil be 330°C or
lower.
Furthermore, the polycyclic aromatic hydrocarbons as used herein mean the total
value of the content of bicyclic aromatic hydrocarbons (bicyclic aromatic fraction) and
the content of aromatic hydrocarbons having three or more rings (tricyclic or
10 higher-cyclic aromatic fraction) that are measured according to PI-5s-49 "Petroleum
products - Hydrocarbon type test methods - High performance liquid chromatography
method", or analyzed by an FID gas chromatographic method or a two-dimensional gas
chromatographic method. Hereinafter, when the contents of polycyclic aromatic
hydrocarbons, bicyclic aromatic hydrocarbons, and aromatic hydrocarbons having three
15 or more rings are expressed in vol%, the contents are values measured according to
PI-5s-49, and when the contents are expressed in mass%, the values are measured based
on an FID gas chromatographic method or a two-dimensional gas chromatographic
method.
[003 11
20 (Reaction type)
Regarding the reaction type at the time of bringing the feedstock oil into contact
with a catalyst for monocyclic aromatic hydrocarbon production and causing the
feedstock oil to react, examples thereof include a fixed bed, a moving bed, and a
fluidized bed. In this invention, since a heavy fraction is used as the feedstock, a
25 fluidized bed in which the coke fraction adhered to the catalyst can be continuously
16
removed and the reaction can be carried out in a stable manner, is preferred, and a
continuous regeneration type fluidized bed in which a catalyst is circulated between a
reactor and a regenerator and thus reaction and regeneration can be continuously repeated,
is particularly preferred. The feedstock oil at the time of bringing the catalyst for
5 monocyclic aromatic hydrocarbon production into contact is preferably in a gaseous state.
Furthermore, the feedstock may be diluted by means of a gas as necessary.
[0032]
(Catalyst for monocyclic aromatic hydrocarbon production)
The catalyst for monocyclic aromatic hydrocarbon production contains a
10 crystalline aluminosilicate.
[0033]
[Crystalline aluminosilicate]
The crystalline aluminosilicate is preferably a medium-pore zeolite and/or a
large-pore zeolite, from the viewpoint that the yield of monocyclic aromatic
15 hydrocarbons can be further increased.
A medium-pore zeolite is a zeolite having a 10-membered ring skeletal structure,
and examples of the medium-pore zeolite include zeolites having crystal structures of
AEL type, EUO type, FER type, HEU type, MEL type, MFI type, NES type, TON type,
and WE1 type. Among these, from the viewpoint of further increasing the yield of
20 monocyclic aromatic hydrocarbons, MFI type is preferred.
A large-pore zeolite is a zeolite having a 12-membered ring skeletal structure,
and examples of the large-pore zeolite include zeolites having crystal structures of AFI
type, AT0 type, BEA type, CON type, FAU type, GME type, LTL type, MOR type,
MTW type, and OFF type. Among these, from the viewpoint of being industrially
25 usable, zeolites of BEA type, FAU type and MOR type are preferred, and from the
17
viewpoint of further increasing the yield of monocyclic aromatic hydrocarbons, a zeolite
of BEA type is preferred.
[0034]
The crystalline aluminosilicate may contain a small-pore zeolite having a
5 10-membered or fewer-membered ring skeletal structure, or an ultralarge-pore zeolite
having a 14-membered or more-membered ring skeletal structure, in addition to the
medium-pore zeolite and the large-pore zeolite.
Here, examples of the small-pore zeolite include zeolites having crystal
structures of ANA type, CHA type, ERI type, GIs type, KFI type, LTA type, NAT type,
10 PAU type, and YUG type.
Examples of the ultralarge-pore zeolite include zeolites having crystal structures
of CLO type and VPI type.
[0035]
When the cracking reforming reaction step is carried out by a fixed bed reaction,
15 the content of the crystalline aluminosilicate in the catalyst for monocyclic aromatic
hydrocarbon production is preferably 60 mass% to 100 mass%, more preferably 70
mass% to 100 mass%, and particularly preferably 90 mass% to 100 mass%, when the
total amount of the catalyst for monocyclic aromatic hydrocarbon production is
designated as 100 mass%. If the content of the crystalline aluminosilicate is 60 mass%
20 or more, the yield of monocyclic aromatic hydrocarbons can be sufficiently increased.
[0036]
When the cracking reforming reaction step is carried out by a fluidized bed
reaction, the content of the crystalline aluminosilicate in the catalyst for monocyclic
aromatic hydrocarbon production is preferably 20 mass% to 60 mass%, more preferably
25 30 mass% to 60 mass%, and particularly preferably 35 mass% to 60 mass%, when the
18
total amount of the catalyst for monocyclic aromatic hydrocarbon production is
designated as 100 mass%. If the content of the crystalline aluminosilicate is 20 mass%
or more, the yield of monocyclic aromatic hydrocarbons can be sufficiently increased.
If the content of the crystalline alurninosilicate is more than 60 mass%, the content of the
5 binder that can be incorporated into the catalyst is reduced, and the catalyst may become
unsuitable for fluidized bed applications.
[0037]
[Gallium and zinc]
The catalyst for monocyclic aromatic hydrocarbon production can contain
10 gallium and/or zinc as necessary. When gallium and/or zinc is incorporated, the
production proportion of the monocyclic aromatic hydrocarbons can be further increased.
Examples of the form of gallium incorporation in the catalyst for monocyclic
aromatic hydrocarbon production include a form in which gallium is incorporated into
the lattice skeleton of the crystalline aluminosilicate (crystalline aluminogallosilicate), a
15 form in which gallium is supported on the crystalline aluminosilicate (gallium-supported
crystalline aluminosilicate), and a form including both.
[003 81
Examples of the form of zinc incorporation in the catalyst for monocyclic
aromatic hydrocarbon production include a form in which zinc is incorporated into the
20 lattice skeleton of the crystalline aluminosilicate (crystalline aluminozincosilicate), a
form in which zinc is supported in the crystalline aluminosilicate (zinc-supported
crystalline aluminosilicate), and a form including both.
A crystalline aluminogallosilicate and a crystalline aluminozincosilicate have a
structure in which Si04, A104 and Ga04/Zn04 structures exist in the skeleton.
25 Furthermore, the crystalline aluminogallosilicate and crystalline aluminozincosilicate are
19
obtained by, for example, gel crystallization based on hydrothermal synthesis, a method
of inserting gallium or zinc into the lattice skeleton of a crystalline aluminosilicate, or a
method of inserting aluminum into the lattice skeleton of a crystalline gallosilicate or a
crystalline zincosilicate.
[0039]
A gallium-supported crystalline aluminosilicate is a material in which gallium is
supported on a crystalline aluminosilicate according to a known method such as an ion
exchange method or an impregnation method. The gallium source used at that time is
not particularly limited, but examples thereof include gallium salts such as gallium nitrate
10 and gallium chloride, and gallium oxide.
A zinc-supported crystalline aluminosilicate is a material in which zinc is
supported on a crystalline aluminosilicate according to a known method such as an ion
exchange method or an impregnation method. The zinc source used at that time is not
particularly limited, but examples thereof include zinc salts such as zinc nitrate and zinc
15 chloride, and zinc oxide.
[0040]
When the catalyst for monocyclic aromatic hydrocarbon production contains
gallium andlor zinc, the content of gallium andlor zinc in the catalyst for monocyclic
aromatic hydrocarbon production is preferably 0.01 mass% to 5.0 mass%, and more
20 preferably 0.05 mass% to 2.0 mass%, when the total amount of the catalyst is designated
as 100 mass%. If the content of gallium and/or zinc is 0.0 1 mass% or more, the
production proportion of the monocyclic aromatic hydrocarbons can be further increased,
and if the content is 5.0 mass% or less, the yield of the monocyclic aromatic
hydrocarbons can be further increased.
[004 11
20
[Phosphorus and boron]
For the catalyst for monocyclic aromatic hydrocarbon production, it is preferable
that the catalyst contain phosphorus andlor boron. When the catalyst for monocyclic
aromatic hydrocarbon production contains phosphorus andlor boron, a decrease over time
5 in the yield of the monocyclic aromatic hydrocarbons can be prevented, and coke
production at the catalyst surface can be suppressed.
[0042]
Examples of the method for incorporating phosphorus into the catalyst for
monocyclic aromatic hydrocarbon production include a method of supporting phosphorus
10 on a crystalline aluminosilicate, a crystalline aluminogallosilicate, or a crystalline
aluminozincosilicate by means of an ion exchange method, an impregnation method or
the like; a method of incorporating a phosphorus compound at the time of zeolite
synthesis, and thereby substituting a portion in the skeleton of a crystalline
aluminosilicate with phosphorus; and a method of using a crystallization accelerator
15 containing phosphorus at the time of zeolite synthesis. The phosphate ion-containing
aqueous solution to be used at that time is not particularly limited, but aqueous solutions
prepared by dissolving phosphoric acid, diammonium hydrogen phosphate, ammonium
dihydrogen phosphate, and other water-soluble phosphoric acid salts in water at arbitrary
concentrations can be preferably used.
20 [0043]
Examples of the method for incorporating boron into the catalyst for monocyclic
aromatic hydrocarbon production include a method of supporting boron on a crystalline
aluminosilicate, a crystalline aluminogallosilicate, or a crystalline aluminozincosilicate
by means of an ion exchange method, an impregnation method or the like; a method of
25 incorporating a boron compound at the time of zeolite synthesis and thereby substituting
2 1
a portion in the skeleton of a crystalline aluminosilicate with boron; and a method of
using a crystallization accelerator containing boron at the time of zeolite synthesis.
[0044]
The content of phosphorus and/or boron in the catalyst for monocyclic aromatic
5 hydrocarbon production is preferably 0.1 mass% to 10 mass%, more preferably 0.5
mass% to 9 mass%, and even more preferably 0.5 mass% to 8 mass%, when the total
amount of the catalyst is designated as 100 mass%. If the content of phosphorus and/or
boron is 0.1 mass% or more, a decrease over time in the yield can be further prevented,
and if the content is 10 mass% or less, the yield of the monocyclic aromatic
10 ' hydrocarbons can be further increased.
[0045]
[Shape]
The catalyst for monocyclic aromatic hydrocarbon production is formed into, for
example, a powder form, a particulate form, or a pellet form, depending on the reaction
15 type. For example, in the case of a fluidized bed, the catalyst is formed in a powder
form, and in the case of a fixed bed, the catalyst is formed into a particulate form or a
pellet form. The average particle size of the catalyst used in a fluidized bed is
preferably 30 pm to 180 pm, and more preferably 50 pm to 100 pm. Furthermore, the
bulk density of the catalyst used in a fluidized bed is preferably 0.4 glcc to 1.8 g/cc, and
20 more preferably 0.5 glcc to 1.0 glee.
[0046]
In addition, the average particle size represents a particle size which corresponds
to 50 mass% in a particle size distribution obtained by classification with sieves, and the
bulk density is a value measured by the method of JIS Standard R9301-2-3.
In the case of obtaining a particulate or pellet-shaped catalyst, according to
22
necessity, an inert oxide is incorporated into the catalyst as a binder, and then the blend
may be molded using various molding machines.
When the catalyst for monocyclic aromatic hydrocarbon production contains an
inorganic oxide such as a binder, a binder containing phosphorus may be used without
5 any problem.
[0047]
(Reaction temperature)
The reaction temperature at the time of bringing feedstock oil into contact with a
catalyst for monocyclic aromatic hydrocarbon production to react, is not particularly
10 limited, but the reaction temperature is preferably set to 400°C to 650°C. If the lower
limit of the reaction temperature is 400°C or higher, the feedstock oil can be made to
react easily, and the lower limit is more preferably 450°C or higher. Furthermore, if the
upper limit of the reaction temperature is 650°C or lower, the yield of the monocyclic
aromatic hydrocarbons can be sufficiently increased, and the upper limit is more
15 preferably 600°C or lower.
[0048]
(Reaction pressure)
The reaction pressure at the time of bringing feedstock oil into contact with a
catalyst for monocyclic aromatic hydrocarbon production to react, is preferably set to 1.5
20 MPaG or less, and more preferably set to 1.0 MPaG or less. If the reaction pressure is
1.5 MPaG or less, production of by-products of light gas can be suppressed, and also,
pressure resistance of the reaction apparatus can be lowered.
[0049]
(Contact time)
23
In regard to the contact time for the feedstock oil and the catalyst for monocyclic
aromatic hydrocarbon production, there are no particular limitations as long as a desired
reaction substantially proceeds; however, for example, the contact time as the time for
gas passage on the catalyst for monocyclic aromatic hydrocarbon production is
5 preferably 1 second to 300 seconds, and it is more preferable to set the lower limit to 5
seconds and the upper limit to 150 seconds. If the contact time is 1 second or longer,
the reaction can be carried out reliably, and if the contact time is 300 seconds or less,
accumulation of carbonaceous materials on the catalyst due to coking or the like can be
suppressed. Also, the amount of generation of light gas due to cracking can be
10 suppressed.
[0050]

In the separation step, the product produced in the cracking reforming reaction
step is separated into plural fractions.
15 In order to separate the product into plural fractions, known distillation
apparatuses and gas-liquid separation apparatuses may be used. An example of the
distillation apparatuses may be an apparatus capable of separation by distillation into
plural fractions by means of a multistage distillation apparatus such as a stripper. An
example of the gas-liquid separation apparatus may be an apparatus including a
20 gas-liquid separation tank; a product inlet pipe through which the product is introduced
into the gas-liquid separation tank; a gas component outflow pipe that is provided in the
upper part of the gas-liquid separation tank; and a liquid component outflow pipe that is
provided in the lower part of the gas-liquid separation tank.
[005 11
2 5 In the separation step, at least a gas component and a liquid fraction are
24
separated, and also, the liquid fraction is further separated into plural fractions.
Examples of such a separation step include a form of separating the product into a gas
component mainly containing components having 4 or fewer carbon atoms (for example,
hydrogen, methane, ethane, and LPG) and a liquid fraction; a form of separating the
5 product into a gas component containing components having 2 or fewer carbon atoms
(for example, hydrogen, methane, and ethane) and a liquid fraction; a form of further
separating the liquid fraction into a fraction containing monocyclic aromatic
hydrocarbons and a heavy fraction; a form of separating the liquid fraction again into
LPG, a fraction containing monocyclic aromatic hydrocarbons, and a heavy fraction; and
10 a form of separating the liquid fraction again into LPG a fraction containing monocyclic
aromatic hydrocarbons, and plural heavy fractions.
[0052]
In this exemplary embodiment, a form of separating the product into a gas
component containing components having 4 or fewer carbon atoms (for example,
15 hydrogen, methane, ethane, and LPG) and a liquid fraction, and also, further separating
the liquid fraction into a fraction containing monocyclic aromatic hydrocarbons having 6
to 8 carbon atoms and a fraction heavier than this (heavy fraction having 9 or more
carbon atoms), is suitably employed. Here, the heavy fraction having 9 or more carbon
atoms that is separated in the separation step may vary depending on the nature of the
20 feedstock oil or the conditions for the cracking reforming reaction step, separation step
and the like; however, the concentration of polycyclic aromatic hydrocarbons is as high
as 50 mass% to 95 mass%.
[0053]

2 5 In the purification/recovery step, the monocyclic aromatic hydrocarbons having
25
6 to 8 carbon atoms obtained in the separation step is purified and collected.
In this purification/recovery step, since a fraction heavier than the monocyclic
aromatic hydrocarbons is separated in the separation step, a step of recovering
benzene/toluene/xylene from the fraction containing monocyclic aromatic hydrocarbons
5 having 6 to 8 carbon atoms is employed. Here, the fraction heavier than monocyclic
aromatic hydrocarbons is a heavy fraction having 9 or more carbon atoms, and contains
polycyclic aromatic hydrocarbons as main components. Particularly, the heavy fraction
contains a large amount of bicyclic aromatic hydrocarbons such as naphthalenes.
[0054]
Further, when a form in which a liquid fraction is not fractionated is employed
as the separation step, in this purification/recovery step, a step of separating and
removing the fraction heavier than monocyclic aromatic hydrocarbons, and recovering
monocyclic aromatic hydrocarbons or benzene/toluene/xylene (monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms) is employed.
15 Furthermore, when the liquid fraction is not fractionated satisfactorily in the
separation step, and when monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
are collected, a fraction other than the monocyclic aromatic hydrocarbons is contained in
a large amount, this fraction may be separated and supplied to, for example, the
hydrogenation step that will be described below. The fraction heavier than the
20 monocyclic aromatic hydrocarbons contains polycyclic aromatic hydrocarbons as main
components, and particularly contains a large amount of bicyclic aromatic hydrocarbons
such as naphthalenes.
[0055]

In the hydrogenation step, all or a portion of the heavy fraction having 9 or more
26
carbon atoms obtained from the fraction separated in the separation step is hydrogenated.
Specifically, the heavy fraction and hydrogen are supplied to a hydrogenation reactor,
and at least a portion of the polycyclic aromatic hydrocarbons contained in the heavy
fraction is hydrogenation treated using a hydrogenation catalyst. Here, the heavy
5 fraction that is separated in the separation step or the purificationJrecovery step and
supplied to the hydrogenation step, that is, the heavy fraction having 9 or more carbon
atoms, contains a large amount of bicyclic aromatic (polycyclic aromatic) hydrocarbons
such as naphthalenes.
Thus, in the hydrogenation step, it is preferable to hydrogenate these polycyclic
10 aromatic hydrocarbons until the hydrocarbons each have one aromatic ring. For
example, naphthalene is preferably hydrogenated until it becomes tetraline
(naphthenobenzene), and also, alkylnaphthalenes such as methylnaphthalene and
dimethylnaphthalene are preferably converted to naphthenobenzene, that is, an aromatic
hydrocarbon having one aromatic ring and having a tetraline skeleton. Similarly,
15 indenes are preferably converted to aromatic hydrocarbons having an indane skeleton,
anthracenes are preferably converted to aromatic hydrocarbons having an
octahydroanthracene skeleton, and phenanthrenes are preferably converted to aromatic
hydrocarbons having an octahydrophenanthrene skeleton.
Further, when a portion of the heavy fraction having 9 or more carbon atoms is
20 not supplied to the hydrogenation step, the heavy fraction may also be used for the
production of naphthalenes by separating naphthalene or the like, or may be used as a
fuel base material.
[0056]
If hydrogenation is carried out until the hydrocarbons have one aromatic ring
25 each, when these hydrogenation products are returned to the cracking reforming reaction
27
step at the recycling step that will be described below, the hydrogenation products,
particularly aromatic hydrocarbons having a tetraline skeleton, are easily converted to
monocyclic aromatic hydrocarbons. As such, in order to increase the yield of
monocyclic aromatic hydrocarbons in the cracking reforming reaction step, the content of
5 polycyclic aromatic hydrocarbons in the hydrogenation products obtainable in this
hydrogenation step is preferably adjusted to 40 mass% or less, more preferably 25
mass% or less, and even more preferably 15 mass% or less.
[0057]
Also, although the composition may vary depending on the operation conditions,
10 under conventional conditions, the hydrogenation products obtainable in this
hydrogenation step contains about several mass% to 30 mass% of bicyclic aromatic
hydrocarbons, about 40 mass% to 90 mass% of monocyclic naphthenobenzene, and
about several mass% to 30 mass% of bicyclic naphthene.
Furthermore, the content of polycyclic aromatic hydrocarbons in the
15 hydrogenation products is preferably smaller than the content of polycyclic aromatic
hydrocarbons in the feedstock oil. In regard to the content of polycyclic aromatic
hydrocarbons in the hydrogenation products, that is, the concentration of polycyclic
aromatic hydrocarbons, the concentration can be lowered by increasing the amount of the
hydrogenation catalyst or by increasing the reaction pressure. However, it is not
20 necessary to carry out the hydrogenation treatment until all of the polycyclic aromatic
hydrocarbons become saturated hydrocarbons. Excessive hydrogenation brings about
an increase in the amount of hydrogen consumption, and also causes an excessive
increase in the amount of heat generation.
[OOS 81
2 5 Regarding the reaction type in the hydrogenation step, a fixed bed is suitably
2 8
employed.
Regarding the hydrogenation catalyst, known hydrogenation catalysts (for
example, nickel catalysts, palladium catalysts, nickel-molybdenum-based catalysts,
cobalt-molybdenum-based catalysts, nickel-cobalt-molybdenum-based catalysts, and
5 nickel-tungsten-based catalysts) can be used.
The hydrogenation temperature may vary depending on the hydrogenation
catalyst used, but the hydrogenation temperature is considered to be usually in the range
of 100°C to 450°C, more preferably 200°C to 400°C, and even more preferably 250°C to
380°C.
10 [0059]
The hydrogenation pressure is preferably set to from 0.7 MPa to 13 MPa.
Particularly, the hydrogenation pressure is more preferably set to from 1 MPa to 10 ma,
and even more preferably set to from 1 MPa to 7 MPa. If the hydrogenation pressure is
set to 13 MPa or less, a hydrogenation reactor having a relatively low durable pressure
15 can be used, and the facility cost can be reduced. Furthermore, since the pressure of
hydrogen collected in the hydrogen recovery step is usually 13 MPa or less, the collected
hydrogen can be used without increasing the pressure. On the other hand, if the
hydrogenation pressure is set to 0.7 MPa or higher, the yield of the hydrogenation can be
maintained sufficiently appropriately.
The amount of hydrogen consumption also varies depending on the amount of
the diluent oil conveyed in the dilution step that will be described below, but the amount
of hydrogen consumption is preferably 2000 scfb (337 Nm3/m3) or less, more preferably
1500 scfb (253 ~ r n ~ l omr l~es)s, and even more preferably 1000 scfb (169 Nm3/m3)o r
less.
On the other hand, the amount of hydrogen consumption is preferably 100 scfb
29
(17 ~ m ~ / omr m~o)re in view of the yield of the hydrogenation.
The liquid hourly space velocity (LHSV) is preferably set to from 0.1 h-' to 20
h-', and more preferably from 0.2 h-' to 10 h-'. If the LHSV is set to 20 h-' or less,
polycyclic aromatic hydrocarbons can be sufficiently hydrogenated at a lower
5 hydrogenation pressure. On the other hand, when the LHSV is set to 0.1-' or more, an
increase in the scale of the hydrogenation reactor can be avoided.
[0060]
Here, since polycyclic aromatic hydrocarbons, for example, bicyclic aromatic
hydrocarbons occupying a majority thereof, have a large amount of heat generation at the
10 time of the hydrogenation as described above, in the case of a feedstock having a high
component ratio of polycyclic aromatic hydrocarbons, in order to carry out the reaction
in a stable manner, it is preferable to employ a technique for suppressing an excessive
increase in the reaction temperature. In this invention, regarding the method for
suppressing the reaction temperature, a general technique can be employed, and
15 techniques such as circulating hydrogen gas quenching that is employed in conventional
kerosene-gas oil desulfurization apparatuses, and liquid quenching using a cooling oil,
can be used. However, the heavy fraction that is separated in the separation step and is
directly supplied to this hydrogenation step, has a very high concentration of polycyclic
aromatic hydrocarbons, for example, as high as 50 mass% to 95 mass%, as described
20 above. Therefore, if it is attempted to suppress heat generation only by circulating
hydrogen gas quenching and/or liquid quenching, quenching facilities in a number close
to a two-digit number are needed, and the configuration around the reaction apparatus for
suppressing heat generation becomes very complicated. Furthermore, since the reaction
apparatus becomes a reaction apparatus associated with an extremely large amount of
25 heat generation, it is evaluated to be an apparatus with a high risk at the time of
emergency.
[006 11
Furthermore, it is difficult to control the hydrogenation itself, and the reaction in
which bicyclic aromatic (polycyclic aromatic) hydrocarbons are converted to
5 naphthenobenzene that is suitable as a feedstock for monocyclic aromatic hydrocarbons,
is not carried out properly.
[0062]
Thus, in the present exemplary embodiment, the concentration of polycyclic
aromatic hydrocarbons in the heavy fraction that is supplied to the hydrogenation step is
10 adjusted by the dilution step that will be described below, and heat generation occurring
as a result of the hydrogenation of polycyclic aromatic hydrocarbons is suppressed.
Thus, for example, a hydrogenation which is sufficiently adequate even with a
conventional general hydrogenation reactor that is used for desulfurization of
kerosene-gas oil, can be carried out. At the same time, by returning a portion of
15 polycyclic aromatic hydrocarbons that have not reacted in the hydrogenation step again
to the hydrogenation step, an effect of increasing the yield of monocyclic aromatic
hydrocarbons is also obtained.
[0063]

20 In the dilution step, a portion of the hydrogenation product of the heavy fraction
having 9 or more carbon atoms obtained in the hydrogenation step is returned as diluent
oil to the hydrogenation step, and the concentration of the polycyclic aromatic
hydrocarbons in the heavy fraction that is supplied to the hydrogenation step is decreased
to an appropriate concentration. That is, the heavy fraction that is separated in the
25 separation step and is directly supplied to the hydrogenation step (heavy fraction that is
3 1
supplied separately from the diluent oil) has a very high concentration of polycyclic
aromatic hydrocarbons, for example, as high as 50 mass% to 95 mass%, as described
above. In this regard, in the hydrogenation step, since the polycyclic aromatic
hydrocarbons in the heavy fraction supplied as described above are hydrogenated until
5 the polycyclic aromatic hydrocarbons have one aromatic ring each, the concentration of
polycyclic aromatic hydrocarbons in the hydrogenation product of the heavy fraction
obtained in this hydrogenation step decreases to a large extent, for example, by about 5
mass% to 40 mass%, although the decrease may vary depending on the conditions for the
hydrogenation.
10 [0064]
Thus, as such, when a hydrogenation product with a decreased concentration of
the polycyclic aromatic hydrocarbons is returned as diluent oil to the hydrogenation step,
the concentration of polycyclic aromatic hydrocarbons in the heavy fraction having 9 or
more carbon atoms that is supplied to the hydrogenation step can be decreased to an
15 appropriate concentration.
Specifically, in this dilution step, it is preferable to return the diluent oil to the
hydrogenation step such that the concentration of polycyclic aromatic hydrocarbons in a
mixed oil composed of the product (heavy fraction having 9 or more carbon atoms) that
is separated from the product produced in the cracking reforming reaction step and is
20 supplied to the hydrogenation separately from the diluent oil and the diluents oil, that is,
a mixed oil that is actually supplied to the hydrogenation step, is from 5 mass% to 50
mass%. Furthermore, it is more preferable to return the diluent oil such that the
concentration of polycyclic aromatic hydrocarbons is from 15 mass% to 35 mass%.
[0065]
2 5 When the concentration of the polycyclic aromatic hydrocarbons in the mixed
32
oil is adjusted to 50 mass% or less, heat generation due to the hydrogenation is
suppressed, so that an extreme increase in the reaction temperature at the hydrogenation
reactor is prevented, and an appropriate hydrogenation (for example, conversion from
bicyclic aromatic hydrocarbons to naphthenobenzenes) can be achieved. Furthermore, a
5 general hydrogenation reactor can be used. Furthermore, by adjusting the concentration
to 5 mass% or more, the conversion from polycyclic aromatic hydrocarbons to
naphthenobenzenes, which is the main purpose of the hydrogenation step, can be
achieved with desired efficiency.
[0066]
10 However, if the concentration of polycyclic aromatic hydrocarbons in the mixed
oil is too low, the conversion efficiency from the polycyclic aromatic hydrocarbons to
naphthenobenzenes is lowered, so that the scale of the hydrogenation reactor is increased,
which is not preferable. Therefore, in order to further increase the conversion efficiency,
it is more preferable to adjust the concentration of polycyclic aromatic hydrocarbons to
15 15 mass% or more as described above. Furthermore, in order to suppress heat
generation due to the hydrogenation more sufficiently, it is more preferable to adjust the
concentration of polycyclic aromatic hydrocarbons to 35 mass% or less.
[0067]
In this dilution step, in order to adjust the concentration of polycyclic aromatic
20 hydrocarbons to a concentration such as described above, the amount of the diluent oil to
be conveyed is appropriately determined. At that time, the amount of the diluent oil is
largely affected by the concentration of the polycyclic aromatic hydrocarbons in the
product (heavy fraction having 9 or more carbon atoms) that is separated from the
product produced in the cracking reforming reaction step and is supplied to the
25 hydrogenation step. That is, if the concentration of polycyclic aromatic hydrocarbons in
3 3
the product is high, it is necessary to make the amount of the diluent oil relatively high,
and if the concentration of polycyclic aromatic hydrocarbons in the product is low, the
amount of the diluent oil can be relatively decreased.
[0068]
Usually, the concentration of polycyclic aromatic hydrocarbons in the heavy
fraction (product) that is directly supplied from the separation step to the hydrogenation
step as described above is 50 mass% to 95 mass%.
Therefore, the concentration of polycyclic aromatic hydrocarbons in the heavy
fraction (product) and the concentration of polycyclic aromatic hydrocarbons in the
10 diluent oil are measured according to, for example, JPI-5S-49 "Petroleum products -
Hydrocarbon type test methods - High performance liquid chromatographic method", or
is identified by an FID gas chromatographic method, a two-dimensional gas
chromatographic method or the like, and the mixing amounts of the heavy fraction
(product) and the diluent oil are determined such that the concentration of polycyclic
15 aromatic hydrocarbons in the mixed oil after being diluted with the diluent oil is 5
mass% to 50 mass%, and preferably 15 mass% to 35 mass%. Usually, the mass ratio
(mixing ratio) of the heavy fraction that is directly supplied from the separation step to
the hydrogenation step (heavy fraction having 9 or more carbon atoms that is separated
from the product produced in the cracking reforming reaction step and is supplied to the
20 hydrogenation step) and the diluent oil may vary depending on the concentration of
polycyclic aromatic hydrocarbons in the heavy fraction (product) or the hydrogenation
pressure at which the diluent oil is supplied; however, the mass ratio is adjusted to be in
the range of 10:90 to 80:20.
[0069]
Here, the concentration of polycyclic aromatic hydrocarbons of the diluent oil
3 4
varies depending on the conditions of the hydrogenation step. However, when the
dilution step is carried out under the conditions in which the content (concentration) of
polycyclic aromatic hydrocarbons in the hydrogenation product obtainable in the
hydrogenation step is 40 mass% or less as described above, the concentration of
5 polycyclic aromatic hydrocarbons in the mixed oil can be adjusted to 5 mass% to 50
mass%, and preferably 15 mass% to 35 mass%, by setting the mass ratio of the heavy
fraction and the diluent oil to the range described above.
[0070]
Furthermore, when the flow rate per unit time of the heavy fraction that is
10 directly supplied from the separation step to the hydrogenation step is constant, the flow
rate per unit time of the diluent oil is also made constant and the diluents oil is returned
to the hydrogenation step under the conditions in which the mass ratio is in the range
described above. Furthermore, when the flow rate per unit time of the heavy fraction
varies, the flow rate of the diluent oil is also varied in accordance with this change.
15 [007 11
When the mass ratio is adjusted to be in such a range, and the hydrogenation
product in the adjusted amount is returned to the hydrogenation step as a diluent oil, heat
generation caused by the hydrogenation in the hydrogenation step is suppressed, an
extreme increase in the reaction temperature at the hydrogenation reactor is prevented,
20 and an appropriate hydrogenation (for example, conversion from bicyclic aromatic
hydrocarbons to naphthenobenzenes) can be achieved. Furthermore, a general
hydrogenation reactor can be used. Also, the conversion from polycyclic aromatic
hydrocarbons to naphthenobenzenes, which is the main purpose of the hydrogenation
step, can be carried out with desired efficiency.
25 [0072]
35

In the hydrogen recovery step, hydrogen is collected from the gas component
obtained in the separation step.
Regarding the method of recovering hydrogen, there are no particular limitations
5 as long as hydrogen and other gases that are contained in the gas component obtained in
the separation step can be separated, and examples thereof include a pressure swing
adsorption method (PSA method), a cryogenic separation method, and a membrane
separation method.
[0073]
10
In the hydrogen supply step, hydrogen obtained in the hydrogen recovery step is
supplied to the hydrogenation reactor of the hydrogenation step. The amount of
hydrogen supply at that time is regulated depending on the amount of the mixed oil that
is supplied to the hydrogenation step. Furthermore, if necessary, the hydrogen pressure
15 is regulated.
When the method includes a hydrogenation supply step as in the present
exemplary embodiment, the mixed oil can be hydrogenated using the hydrogen produced
as a by-product in the cracking reforming reaction step. A portion or whole of the
hydrogen supply from an external source can be reduced by preparing a portion or the
20 entire amount of hydrogen from the by-product hydrogen.
100741

In the recycling step, the other portion of the hydrogenation product of the heavy
fraction obtained in the hydrogenation step, that is, the remnant (residual portion) of the
25 hydrogenation product returned to the hydrogenation step in the dilution step, is mixed .
3 6
with the feedstock oil, or is separately returned to the cracking reforming reaction step.
By returning the hydrogenation product of the heavy fraction to the cracking
reforming reaction step, the heavy fraction which is a by-product can also be used as a
feedstock to obtain monocyclic aromatic hydrocarbons. Therefore, not only the amount
5 of by-products can be reduced, but also the amount of production of monocyclic aromatic
hydrocarbons can be increased. Furthermore, since saturated hydrocarbons are also
produced by hydrogenation, the hydrogen transfer reaction in the cracking reforming
reaction step can be accelerated. From these, the overall yield of monocyclic aromatic
hydrocarbons with respect to the amount of supply of the feedstock oil can be enhanced.
10 Furthermore, when the heavy fraction is directly returned to the cracking
reforming reaction step without being hydrogenated treated, since the reactivity of
polycyclic aromatic hydrocarbons is low, the yield of monocyclic aromatic hydrocarbons
is barely increased.
In this recycling step, the entire amount of the remnant (residual portion) of the
15 hydrogenation product returned to the hydrogenation step in the dilution step may not be
necessarily returned to the cracking reforming reaction step. In that case, the
hydrogenation product of the heavy fraction that is not returned may be used as a he1
base material or the like.
[0075]
20 In regard to the method for producing monocyclic aromatic hydrocarbons of the
present exemplary embodiment, since the method includes a hydrogenation step and a
recycling step, the heavy fraction which is a by-product can also be used as a feedstock to
obtain monocyclic aromatic hydrocarbons. Therefore, not only the amount of
by-products can be reduced, but also the amount of production of monocyclic aromatic
25 hydrocarbons can be increased. Accordingly, monocyclic aromatic hydrocarbons
3 7
having 6 to 8 carbon atoms can be produced with a high yield from a feedstock oil
containing polycyclic aromatic hydrocarbons.
Furthermore, since the method includes a dilution step in which a portion of the
hydrogenation product of the heavy fraction obtained in the hydrogenation step is
5 returned as a diluent oil to the hydrogenation step, and the concentration of polycyclic
aromatic hydrocarbons in the heavy fraction supplied to the hydrogenation step is
decreased, extreme heat generation attributable to the hydrogenation of polycyclic
aromatic hydrocarbons in the hydrogenation step is suppressed, so that a stabilized
hydrogenation is enabled, and a sharp increase in the facility cost of the hydrogenation
10 reactor can be avoided.
Furthermore, in regard to the hydrogenation product of the heavy fraction
obtained in the hydrogenation step, a gas component is first separated and removed, and
then the heavy fraction obtained in the hydrogenation reaction step can be returned to the
cracking reforming reaction step through the recycling step, or can also be supplied to the
15 hydrogenation step as a diluent oil through the dilution step.
[0076]
[Exemplary Embodiment 21
Exemplary Embodiment 2 of the method for producing monocyclic aromatic
hydrocarbons related to the first aspect of the invention will be described.
FIG. 2 is a diagram for illustrating Exemplary Embodiment 2 of the method for
producing monocyclic aromatic hydrocarbons related to the first aspect of the invention,
and the method for producing monocyclic aromatic hydrocarbons of the present
exemplary embodiment is also a method for producing monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms from feedstock oil.
[0077]
3 8
That is, the method for producing monocyclic aromatic hydrocarbons of the
present exemplary embodiment includes, as illustrated in FIG 2:
(i-I) a cracking reforming reaction step of bringing a feedstock oil into contact
with a catalyst for monocyclic aromatic hydrocarbon production to react, and thereby
5 obtaining a product containing monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms and a heavy fraction having 9 or more carbon atoms;
0-1) a separation step of separating the product produced in the cracking
reforming reaction step into a gas component and a liquid component;
(k-1) a hydrogenation step of hydrogenating the liquid component separated in
10 the separation step;
(1-1) a purification/recovery step of distilling the hydrogenation product obtained
in the hydrogenation step, and purifying and recovering monocyclic aromatic
hydrocarbons;
(m-1) a dilution step of returning a portion of the hydrogenation product of the
15 heavy fraction separated in the purification/recovery step to the hydrogenation step;
(n-1) a recycling step of returning the residual portion of the hydrogenation
product of the heavy fraction separated in the purification/recovery step to the cracking
reforming reaction step;
(0-1) a hydrogen recovery step of recovering hydrogen that has been produced
20 as a by-product in the cracking reforming reaction step, from the gas component
separated in the separation step; and
(p-I) a hydrogen supply step of supplying the hydrogen collected in the
hydrogen recovery step to the hydrogenation step.
Among the steps (i-1) to (p-1), the steps (i-1), (k-1), (1-I), (m-1) and (n-1) are
25 essential steps for Exemplary Embodiment 2 of the first aspect of the invention, and steps
3 9
Cj-1), (0-1) and (p-1) are optional steps.
[0078]
The (i-1) cracking reforming reaction step can be carried out in the same manner
as in the (a-I) cracking reforming reaction step according to Exemplary Embodiment 1.
The (0-1) hydrogen recovery step can be carried out in the same manner as in
the (g-1) hydrogen recovery step according to Exemplary Embodiment 1.
The (p-1) hydrogen supply step can be carried out in the same manner as in the
(h-1) hydrogen supply step according to Exemplary Embodiment 1.
[0079]
In the (i-I) separation step according to the present exemplary embodiment, for
example, a form of separating the product into a gas component containing components
having 4 or fewer carbon atoms (for example, hydrogen, methane, ethane, and LPG) and
a liquid fraction, is employed. In regard to the liquid fraction, since separation is
carried out in the (1-1) purification/recovery step, a fraction containing monocyclic
15 aromatic hydrocarbons, a heavy fraction and the like are not separated herein, unlike
Exemplary Embodiment 1. However, removing a very heavy fraction that is not
suitable for the recycling intended in the present application, or the catalyst powder or the
like that is incorporated when a fluidized bed is employed in the cracking reforming
reaction step, is appropriately allowed. Even in that case, monocyclic aromatic
20 hydrocarbons, and the heavy fraction intended for hydrogenation and recycling are not
separated.
In the (k-1) hydrogenation step according to the present exemplary embodiment,
the same hydrogenation catalyst as that used in the (d-1) hydrogenation step according to
Exemplary Embodiment 1 can be used.
Furthermore, in the (k-1) hydrogenation step, unlike the (d-I) hydrogenation
40
step according to Exemplary Embodiment 1, since all the liquid component obtained in
the separation step is passed through the hydrogenation reactor, the monocyclic aromatic
hydrocarbons thus obtained are also hydrogenated. However, hydrogenation of
monocyclic aromatic hydrocarbons contradicts the purpose of the invention. Therefore,
5 in the (k-1) hydrogenation step, the amount of loss of the monocyclic aromatic
hydrocarbons due to hydrogenation is preferably adjusted to 5 mass% or less when the
amount of monocyclic aromatic hydrocarbons before the hydrogenation step is
designated as 100 mass%. The reaction conditions to obtain the amount of loss are
generally in the range of the reaction conditions according to Exemplary Embodiment 1;
10 however, in order to avoid excessive hydrogenation of the monocyclic aromatic
hydrocarbons, it is preferable to carry out the reaction at a higher temperature as
compared with Exemplary Embodiment 1.
[OOSO]
For example, the hydrogenation temperature may vary depending on the
15 hydrogenation catalyst used, but usually, the hydrogenation temperature is considered to
be in the range of usually 250°C to 450°C, more preferably 300°C to 400°C, and even
more preferably 320°C to 380°C.
The hydrogenation pressure is preferably set to from 0.7 MPa to 13 MPa.
Particularly, the hydrogenation pressure is more preferably set to from 1 MPa to 10 MPa,
20 and even more preferably from 1 MPa to 7 MPa. If the hydrogenation pressure is set to
13 MPa or less, a hydrogenation reactor having a relatively low durable pressure can be
used, and the facility cost can be reduced. Furthermore, since the pressure of hydrogen
collected in the hydrogen recovery step is usually 13 MPa or less, the collected hydrogen
can be used without increasing the pressure. On the other hand, if the pressure is set to
25 0.7 MPa or greater, the yield of the hydrogenation can be maintained sufficiently
appropriately.
[008 11
The amount of hydrogen consumption may vary depending on the amount of the
diluent oil that is conveyed in the dilution step, but the amount of hydrogen consumption
5 is preferably 2000 scfb (337 ~ m ~ / omr le~ss), m ore preferably 1500 scfb (253 Nm3/m3)
or less, and even more preferably 1000 scfb (169 Nm3/m3) or less. On the other hand,
the amount of hydrogen consumption is preferably 100 scfb (17 ~ m ~ / omr m~or)e in
view of the yield of the hydrogenation.
The liquid hourly space velocity (LHSV) is preferably set to from 0.1 h-' to 20
10 h-', and more preferably from 0.2 h" to 10 h-'. If the LHSV is set to 20 h-' or less,
polycyclic aromatic hydrocarbons can be sufficiently hydrogenated at a lower
hydrogenation pressure. On the other hand, when the LHSV is set to 0.1 -' or more, an
increase in the scale of the hydrogenation reactor can be avoided.
[0082]
15 Furthermore, in the (k-1) hydrogenation step according to the present exemplary
embodiment, the oil that is directly supplied to the hydrogenation step is the entire liquid
fraction (liquid component) obtained in the separation step (provided that a liquid
fraction from which a very heavy fraction that is not suitable for the recycling intended in
the present application, or the catalyst powder or the like that is incorporated when a
20 fluidized bed is employed in the cracking reforming reaction step has been appropriately
removed, may also be used), and contains a large amount of monocyclic aromatic
hydrocarbons. Therefore, as compared with the (d-1) hydrogenation step according to
Exemplary Embodiment 1, in the present exemplary embodiment, the concentration
(content per unit amount) of polycyclic aromatic hydrocarbons in the oil that is directly
25 supplied to the (k-1) hydrogenation step is lower.
42
[0083]
In the (1-1) purification/recovery step, monocyclic aromatic hydrocarbons or
benzene/toluene/xylene is collected, and a heavy fraction having 9 or more carbon atoms
is also separated. Here, the heavy fraction having 9 or more carbon atoms contains a
5 hydrogenation product of polycyclic aromatic hydrocarbons and polycyclic aromatic
hydrocarbons that have not been hydrogenated as main components.
[0084]
In the (m-1) dilution step, similarly to the (e-1) dilution step according to
Exemplary Embodiment 1, a portion of the heavy fraction having 9 or more carbon atoms
10 separated in the purification/recovery step is returned as a diluent oil to the
hydrogenation step. Thereby, the concentration of polycyclic aromatic hydrocarbons in
the product that is supplied to the hydrogenation step is decreased. However, in the
present exemplary embodiment, the concentration (content per unit amount) of
polycyclic aromatic hydrocarbons in the oil that is directly supplied to the hydrogenation
15 step as described above is lower as compared with Exemplary Embodiment 1. Usually,
the concentration of polycyclic aromatic hydrocarbons in the liquid fraction (product)
that is directly supplied from the separation step to the hydrogenation step is about 40
mass% to 75 mass%.
[0085]
20 Therefore, in order to adjust the concentration of polycyclic aromatic
hydrocarbons in the mixed oil that is actually supplied to the hydrogenation step, to from
5 mass% to 50 mass%, and preferably 15 mass% to 35 mass%, as in Exemplary
Embodiment 1, the amount of the diluent oil conveyed can be decreased as compared
with Exemplary Embodiment 1. Even in this case, the concentration of polycyclic
25 aromatic hydrocarbons in the liquid fraction (product) that is directly supplied from the
43
separation step to the hydrogenation step and the concentration of polycyclic aromatic
hydrocarbons in the diluent oil are measured according to, for example, JPI-23-49
"Petroleum products - Hydrocarbon type test methods - High performance liquid
chromatographic method", or are identified by an FID gas chromatographic method, a
5 two-dimensional gas chromatographic method or the like, and thereby the mixing amount
of the diluent oil for diluting to the preferred concentration of polycyclic aromatic
hydrocarbons described above is determined.
Usually, in this dilution step, the mass ratio of the product that is separated from
the product produced in the cracking reforming reaction step and is supplied to the
10 hydrogenation step and the mixed oil composed of a diluent oil is adjusted in the range of
20:80 to 80:20.
[0086]
Here, the concentration of polycyclic aromatic hydrocarbons in the diluent oil
may vary depending on the conditions of the hydrogenation step; however, for example,
15 when the dilution step is carried out under the conditions such that the content
(concentration) of polycyclic aromatic hydrocarbons in the heavy fraction having 9 or
more carbon atoms obtained after monocyclic aromatic hydrocarbons have been
collected in the purificationlrecovery step is 40 mass% or less, the concentration of
polycyclic aromatic hydrocarbons in the mixed oil can be adjusted to 5 mass% to 50
20 mass%, and preferably 15 mass% to 35 mass%, by adjusting the mass ratio of the heavy
fraction and the diluent oil in the range described above.
[0087]
In the (n-1) recycling step, similarly to the (f-1) recycling step according to
Exemplary Embodiment 1, the other portion of the heavy fraction obtained in the
25 purification/recovery step, that is, the remnant (residual portion) of the hydrogenation
44
product returned to the hydrogenation step in the dilution step, is returned to the cracking
reforming reaction step as a mixture with the feedstock oil, or separately therefrom.
[OOSS]
Since the method for producing monocyclic aromatic hydrocarbons of the
5 present exemplary embodiment also includes a hydrogenation step and a recycling step,
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be produced from a
feedstock oil containing polycyclic aromatic hydrocarbons with a high yield.
Furthermore, since the method includes a dilution step in which a portion of the
hydrogenation product of the heavy fraction obtained in the hydrogenation step is
10 returned as diluent oil to the hydrogenation step, and the concentration of polycyclic
aromatic hydrocarbons in the heavy fraction supplied to the hydrogenation step is
decreased, extreme heat generation attributable to the hydrogenation of polycyclic
aromatic hydrocarbons in the hydrogenation step can be suppressed, and a sharp increase
in the facility cost of the hydrogenation reactor can be avoided.
15 In addition, in the present recycling step, it is not necessarily essential to return
the entire amount of the remnant (residual portion) of the hydrogenation product that has
been returned to the hydrogenation step in the dilution step, to the cracking reforming
reaction step. In that case, the hydrogenation product of the heavy fraction that has not
been returned may be used as a fuel base material or the like.
20 [0089]
[Other exemplary embodiments]
This invention is not intended to be limited to the exemplary embodiments
described above, and can have various modifications to the extent that the gist of the
invention is maintained.
2 5 For example, regarding the hydrogen that is used in the hydrogenation step, not
45
the by-product produced in the cracking reforming reaction step, but hydrogen obtained
by a known hydrogen preparation method may also be utilized. Furthermore, hydrogen
produced as a by-product in another catalytic cracking method may also be utilized.
[0090]
Furthermore, in Exemplary Embodiment 1 or Exemplary Embodiment 2, a
heavy fraction discharge step of taking out a certain amount of a portion of the heavy
fraction having 9 or more carbon atoms obtained from the fraction separated in the
separation step, and discharging the portion out of the system, may be provided.
Specifically, in Exemplary Embodiment 1, when the heavy fraction is directly supplied
10 from the separation step to the hydrogenation step, a portion of the heavy fraction may be
taken out before being mixed with the diluent oil, and discharged out of the system.
Furthermore, it is also acceptable to take out a portion of the heavy fraction after the
hydrogenation step or after the dilution step, and to discharge the portion out of the
system.
15 Similarly, also in Exemplary Embodiment 2, a portion of the heavy fraction may
be extracted after the hydrogenation step and the dilution step, and discharged out of the
system.
[009 11

[Exemplary Embodiment 11
Hereinafter, Exemplary Embodiment 1 of the method for producing monocyclic
aromatic hydrocarbons related to the second aspect of the invention will be described.
FIG. 3 is a diagram for illustrating Exemplary Embodiment 1 of the method for
producing monocyclic aromatic hydrocarbons related to the second aspect of the
25 invention, and the method for producing monocyclic aromatic hydrocarbons of the
46
present exemplary embodiment is a method for producing monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms from the feedstock oil.
[0092]
That#is, the method for producing monocyclic aromatic hydrocarbons of the
5 present exemplary embodiment includes, as illustrated in FIG 3:
(a-2) a cracking reforming reaction step of bringing feedstock oil into contact
with a catalyst for monocyclic aromatic hydrocarbon production to react, and thereby
obtaining a product containing monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms and a heavy fraction having 9 or more carbon atoms;
10 (b-2) a separation step of separating the product produced in the cracking
reforming reaction step into plural fractions;
(c-2) a purification/recovery step of purifying and recovering the monocyclic
aromatic hydrocarbons separated in the separation step;
(d-2) a dilution step of adding a diluent to the heavy fraction having 9 or more
15 carbon atoms separated from the product produced in the cracking reforming reaction
step;
(e-2) a hydrogenation step of hydrogenating the mixture obtained in the dilution
step;
(f-2) a recycling step of returning the hydrogenation product of the mixture
20 obtained in the hydrogenation step to the cracking reforming reaction step;
(g-2) a hydrogen recovery step of recovering the hydrogen produced as a
by-product in the cracking reforming reaction step, from the gas component separated in
the separation step; and
(h-2) a hydrogen supply step of supplying the hydrogen collected in the
25 hydrogen recovery step to the hydrogenation step.
47
Among the steps (a-2) to (h-2), steps (a-2), (c-2), (d-2), (e-2), and (f-2) are
essential steps in Exemplary Embodiment 1 of the second aspect of the invention, and
steps (b-2), (g-2) and (h-2) are optional steps.
100931
Hereinafter, the respective steps will be described in detail.

The (a-2) cracking reforming reaction step can be carried out in the same
manner as in the (a-1) cracking reforming reaction step according to Exemplary
Embodiment 1 of the first aspect.
10 [0094]

The (b-2) separation step can be carried out in the same manner as in the (b-I)
separation step according to Exemplary Embodiment 1 of the first aspect.
[0095]
15
The (c-2) purificatiodrecovery step can be carried out in the same manner as in
the (c-1) purificationlrecovery step according to Exemplary Embodiment 1 of the first
aspect.
[0096]
20
In the dilution step, a diluent formed of hydrocarbons that has been prepared
separately in advance is added to the heavy fraction having 9 or more carbon atoms
separated from the product produced in the cracking reforming reaction step, and thereby,
the concentration of polycyclic aromatic hydrocarbons in a mixture composed of the
25 heavy fraction having 9 or more carbon atoms and the diluent is made lower than the
48
concentration of polycyclic aromatic hydrocarbons in the heavy fraction. That is, the
concentration of polycyclic aromatic hydrocarbons in the heavy fraction supplied to the
hydrogenation step that will be described below is decreased to an appropriate
concentration.
[0097]
The heavy fraction that is separated in the separation step and is directly
supplied to the hydrogenation step that will be described below (heavy fraction
obtainable by excluding the diluent from the mixture) has a very high concentration of
the polycyclic aromatic hydrocarbons, for example, as high as 50 mass% to 95 mass%, as
10 described above.
Here, since the polycyclic aromatic hydrocarbons, for example, bicyclic
aromatic hydrocarbons occupying a majority thereof, have a large amount of heat
generation at the time of the hydrogenation as described above, in the case of a feedstock
having a high content ratio of polycyclic aromatic hydrocarbons, in order to carry out the
15 reaction in a stable manner, it is preferable to employ a technique for suppressing an
excessive increase in the reaction temperature. In this invention, regarding the method
for suppressing the reaction temperature, a general technique can be employed, and
techniques such as hydrogen quenching can be used. However, the heavy fraction that
is separated in the separation step and is directly supplied to this hydrogenation step, has
20 a very high concentration of polycyclic aromatic hydrocarbons, for example, as high as
50 mass% to 95 mass%, as described above. Therefore, if it is attempted to suppress
heat generation only by hydrogen quenching, the configuration of the apparatus for
suppressing heat generation becomes very complicated, as compared with a conventional
kerosene-gas oil desulhrization apparatus or the like.
[0098]
49
Thus, in the present exemplary embodiment, the concentration of polycyclic
aromatic hydrocarbons in the oil (mixture) that is supplied to the hydrogenation step is
adjusted in advance by means of the dilution step, and the heat generation occurring as a
result of the hydrogenation of polycyclic aromatic hydrocarbons is suppressed. Thus, it
5 is possible to cause an appropriate hydrogenation to be carried out sufficiently even with
a conventional general hydrogenation reactor.
[0099]
Regarding the diluent, hydrocarbons that are not easily hydrogenated as
compared with polycyclic aromatic hydrocarbons in the hydrogenation step that will be
10 described below, specifically, monocyclic aromatic hydrocarbons such as
trimethylbenzene and tetramethylbenzene (including various isomers); cyclohexanes;
naphthenes such as decalins; and hydrocarbons including paraffin and the like, are
suitably used. At that time, it is necessary to select a feedstock which is compatible
with the diluent and the heavy fraction, and if the concentration of the polycyclic
15 aromatic hydrocarbons is very high, it is preferable to select a monocyclic aromatic
hydrocarbon or the like. On the other hand, when the hydrogenation conditions are set
to a high pressure of, for example, 7 MPa or higher, the monocyclic aromatic
hydrocarbon, which is a diluent, may be hydrogenated per se. As such, it is necessary
to select an appropriate solvent in accordance with the actual hydrogenation conditions.
20 Furthermore, in the case where the diluent is collected and recycled as the diluent, there
is no problem because monocyclic aromatic hydrocarbons also become saturated
hydrocarbons and can be utilized as a diluent, and it is also acceptable to use the diluent
directly in the cracking reforming reaction step. However, since there is a possibility
that a sufficient heat generation preventing effect may not be obtained in the
25 hydrogenation step, care should be taken. Furthermore, regarding the diluent, if the
5 0
concentration (content) of polycyclic aromatic hydrocarbons is lower than that in the
heavy fraction, the diluent may contain the polycyclic aromatic hydrocarbons; however,
at that time, the effect of suppressing heat generation is smaller as compared with a
diluent which does not contain polycyclic aromatic hydrocarbons. Specifically, base
5 materials for oil refinery which contain the monocyclic aromatic hydrocarbons,
naphthenes, paraffins and the like, as well as polycyclic aromatic hydrocarbons, for
example, various cracking base materials and straight-run base materials, such as the
light cycle oil (LCO) that is also used as the feedstock oil, can also be used.
[O 1001
Furthermore, the concentration of polycyclic aromatic hydrocarbons in such a
diluent may be any concentration capable of lowering the concentration of polycyclic
aromatic hydrocarbons in the mixture to be formed to an appropriate concentration, and
the concentration is considered to be preferably 50 mass% or less, more preferably 30
mass% or less, and even more preferably 20 mass% or less.
15 Such a diluent is stored in, for example, a storage tank prepared separately, and
is supplied therefrom to the line which transports the heavy fraction and mixed with the
heavy fraction. Thereby, the diluent lowers the concentration of polycyclic aromatic
hydrocarbons in the mixture thus obtainable, to an appropriate concentration.
[OlOl]
For example, in this dilution step, it is preferable to form a mixture by adding a
diluent to the heavy fraction such that the concentration of polycyclic aromatic
hydrocarbons in the mixture composed of the heavy fraction having 9 or more carbon
atoms that has been separated from the product produced in the cracking reforming
reaction step, and the diluent, that is, a mixture that is actually supplied to the
25 hydrogenation step, is from 5 mass% to 50 mass%. Furthermore, it is more preferable
5 1
to add the diluent such that the concentration of polycyclic aromatic hydrocarbons is
from 15 mass% to 35 mass%.
[O 1 021
By adjusting the concentration of polycyclic aromatic hydrocarbons in the
5 mixture to 50 mass% or less, heat generation by the hydrogenation in the hydrogenation
step that will be described below is suppressed, an extreme increase in the reaction
temperature in the hydrogenation reactor is prevented, and an appropriate hydrogenation
(for example, conversion from bicyclic aromatic hydrocarbons to naphthenobenzenes)
can be achieved. Furthermore, a general hydrogenation reactor can be used.
10 Furthermore, by adjusting the concentration to 5 mass% or more, the conversion from
polycyclic aromatic hydrocarbons to naphthenobenzenes, which is the main purpose of
the hydrogenation step, can be carried out with desired efficiency.
[0 1031
However, if the concentration of polycyclic aromatic hydrocarbons in the
15 mixture is too low, the conversion efficiency from polycyclic aromatic hydrocarbons to
naphthenobenzenes is not a sufficiently profitable efficiency in terms of cost, and for
example, there is a need to increase the size of the hydrogenation reactor. Therefore, in
order to further increase the conversion efficiency, it is more preferable to adjust the
concentration to 15 mass% or more as described above. Furthermore, in order to
20 suppress heat generation by the hydrogenation more sufficiently, it is more preferable to
adjust the concentration to 35 mass% or less.
[0 1041
Furthermore, in this dilution step, the amount of the diluent to be supplied is
appropriately determined in order to adjust the concentration of polycyclic aromatic
25 hydrocarbons in the mixture to a concentration such as described above. In that case,
52
the amount of the diluent is largely affected by the concentration of polycyclic aromatic
hydrocarbons in the heavy fraction having 9 or more carbon atoms that has been
separated from the product produced in the cracking reforming reaction step. That is, if
the concentration of polycyclic aromatic hydrocarbons in the heavy fraction is high, the
5 amount of the diluent needs to be increased to a relatively large amount, and if the
concentration of polycyclic aromatic hydrocarbons in the heavy fraction is low, the
amount of the diluent can be relatively decreased. Furthermore, the amount of the
diluent is also largely affected by the concentration of polycyclic aromatic hydrocarbons
in the diluent. That is, if the concentration of polycyclic aromatic hydrocarbons in the
10 diluent is high, the amount of the diluent needs to be increased to a relatively large
amount, and if the concentration of polycyclic aromatic hydrocarbons in the diluent is
low, the amount of the diluent can be relatively decreased.
[0 1051
Usually, the concentration of polycyclic aromatic hydrocarbons in the heavy
15 fraction separated from the product in the separation step as described above is 50 mass%
to 95 mass%.
Therefore, in regard to the dilution of the heavy fraction, the concentration of
polycyclic aromatic hydrocarbons in the heavy fraction (product) and the concentration
of polycyclic aromatic hydrocarbons in the diluent are measured according to, for
20 example, JPI-5s-49 "Petroleum products - Hydrocarbon type test methods - High
performance liquid chromatographic method", or are identified by an FID gas
chromatographic method, a two-dimensional gas chromatographic method or the like,
and the mixing ratio of the heavy fraction and the diluent is determined such that the
concentration of polycyclic aromatic hydrocarbons in the mixture obtained after being
25 diluted with the diluent is 5 mass% to 50 mass%, and preferably 15 mass% to 35 mass%,
53
as described above. Usually, if the concentration of polycyclic aromatic hydrocarbons
in the diluent is, for example, 20 mass% or less, the mass ratio (mixing ratio) of the
heavy fraction separated in the separation step (heavy fraction having 9 or more carbon
atoms that is separated in the product produced in the cracking reforming reaction step
5 and is supplied to the hydrogenation step) and the diluent is adjusted to be in the range of
10:90 to 80:20.
[O 1061
Furthermore, when the flow rate per unit time of the heavy fraction that is
supplied from the separation step to the hydrogenation step is constant, the flow rate per
10 unit time of the diluent is also made constant under the conditions in which the mass ratio
is in the range described above, and the diluent is then added to the heavy fraction.
Furthermore, when the flow rate per unit time of the heavy fraction varies, the flow rate
of the diluent is also varied in accordance with this variation.
[0 1 071
15
In the hydrogenation step, the mixture formed by adding the diluent to the heavy
fraction having 9 or more carbon atoms in the dilution step is hydrogenated.
Specifically, the mixture and hydrogen are supplied to a hydrogenation reactor, and at
least a portion of polycyclic aromatic hydrocarbons contained in the mixture is
20 hydrogenated using a hydrogenation catalyst. Here, the heavy fraction that is separated
in the separation step or the purification/recovery step and is supplied to the
hydrogenation step, that is, the heavy fraction having 9 or more carbon atoms, contains a
large amount of bicyclic aromatic hydrocarbons (polycyclic aromatic hydrocarbons) such
as naphthalene. Furthermore, although the amount is smaller than the heavy fraction,
25 the diluent also contains bicyclic aromatic (polycyclic aromatic) hydrocarbons depending
on the type.
[0108]
Thus, in the hydrogenation step, it is preferable to hydrogenate these polycyclic
aromatic hydrocarbons until the hydrocarbons have one aromatic ring each. For
5 example, it is preferable to hydrogenate naphthalene until it becomes tetraline
(naphthenobenzene), and also for alkylnaphthalenes such as methylnaphthalene and
dimethylnaphthalene, it is preferable to convert them to naphthenobenzene, that is,
aromatic hydrocarbons each having one aromatic ring with a tetraline skeleton.
Similarly, indenes are preferably converted to aromatic hydrocarbons having an indane
10 skeleton, anthracenes are preferably converted to aromatic hydrocarbons having an
octahydroanthracene skeleton, and phenanthrenes are preferably converted to aromatic
hydrocarbons having an octahydrophenanthrene skeleton.
[0 1 091
If hydrogenation is carried out until the components have one aromatic ring each,
15 when this hydrogenation product is returned to the cracking reforming reaction step in
the recycling step that will be described below, the hydrogenation product, particularly
aromatic hydrocarbons having a tetraline skeleton, are easily converted to monocyclic
aromatic hydrocarbons. As such, in order to increase the yield of monocyclic aromatic
hydrocarbons in the cracking reforming reaction step, the content of polycyclic aromatic
20 hydrocarbons in the hydrogenation product obtainable in this hydrogenation step is
preferably set to 40 mass% or less, more preferably to 25 mass% or less, and even more
preferably to 15 mass% or less.
[OllO]
Furthermore, the content of polycyclic aromatic hydrocarbons in the
25 hydrogenation product thus obtainable is preferably smaller than the content of
55
polycyclic aromatic hydrocarbons in the feedstock oil. In regard to the content of
polycyclic aromatic hydrocarbons in the hydrogenation product, that is, the concentration
of polycyclic aromatic hydrocarbons, the concentration can be lowered by increasing the
amount of the hydrogenation catalyst or increasing the reaction pressure. However, it is
5 not necessary to carry out the hydrogenation treatment until all of the polycyclic aromatic
hydrocarbons become saturated hydrocarbons. Excessive hydrogenation brings about
an increase in the amount of hydrogen consumption, and also brings about an excessive
increase in the amount of heat generation.
[Olll]
Regarding the reaction type in the hydrogenation step, a fixed bed is suitably
employed.
Regarding the hydrogenation catalyst, known hydrogenation catalysts (for
example, nickel catalysts, palladium catalysts, nickel-molybdenum-based catalysts,
cobalt-molybdenum-based catalysts, nickel-cobalt-molybdenum-based catalysts, and
15 nickel-tungsten-based catalysts) can be used.
The hydrogenation temperature may vary depending on the hydrogenation
catalyst used, but the hydrogenation temperature is considered to be in the range of
usually 100°C to 450°C, more preferably 200°C to 400°C, and even more preferably
250°C to 380°C.
[0112]
The hydrogenation pressure is preferably set to from 0.7 MPa to 13 MPa.
Particularly, the hydrogenation pressure is more preferably set to 1 MPa to 10 MPa, and
even more preferably from 1 MPa to 7 MPa. If the hydrogenation pressure is set to 13
MPa or less, a hydrogenation reactor having a relatively low durable pressure can be used,
25 and the facility cost can be reduced. Furthermore, since the pressure of hydrogen
5 6
collected in the hydrogen recovering step is usually 13 MPa or less, the hydrogen thus
collected can be used without increasing the pressure. On the other hand, if the pressure
is set to 0.7 MPa or higher, the yield of the hydrogenation can be maintained sufficiently
appropriately.
[0113]
The amount of hydrogen consumption may vary depending on the amount of the
diluent oil that is conveyed in the dilution step that will be described below, but the
amount of hydrogen consumption is preferably 2000 scfb (337 Nm3/m3) or less, more
preferably 1500 scfb (253 Nm3/m3) or less, and even more preferably 1000 scfb (169
10 ~ m ~ / omr le~ss).
On the other hand, the amount of hydrogen consumption is preferably 100 scfb
(17 ~ m ~ / omr m~or)e from the viewpoint of the yield of the hydrogenation.
The liquid hourly space velocity (LHSV) is preferably set to from 0.1 h-' to 20
h-', and more preferably from 0.2 h-' to 10 h-'. If the LHSV is adjusted to 20 h-' or less,
15 polycyclic aromatic hydrocarbons can be sufficiently hydrogenated at a lower
hydrogenation pressure. On the other hand, if the liquid hourly space velocity is
adjusted to 0.1 -' or more, an increase in the size of the hydrogenation reactor can be
avoided.
[0114]
Here, since polycyclic aromatic hydrocarbons, for example, bicyclic aromatic
hydrocarbons occupying a majority thereof, have a large amount of heat generation at the
time of the hydrogenation as described above, in the case of a feedstock having a high
content ratio of polycyclic aromatic hydrocarbons, in order to carry out the reaction in a
stable manner, it is preferable to employ a technique for suppressing an excessive
25 increase in the reaction temperature. In this invention, regarding the method for
57
suppressing the reaction temperature, a general technique can be employed, and
techniques such as circulating hydrogen gas quenching that is employed in conventional
kerosene-gas oil desulfurization apparatuses can be used. However, the heavy fraction
separated in the separation step has a very high concentration of polycyclic aromatic
5 hydrocarbons, for example, as high as 50 massyo to 95 mass% as described above.
Therefore, if it is attempted to suppress heat generation only by hydrogen quenching,
quenching facilities in a number close to a two-digit number are needed, and the
configuration around the reaction apparatus for suppressing heat generation becomes
very complicated. Furthermore, since the reaction apparatus becomes a reaction
10 apparatus associated with an extremely large amount of heat generation, it is evaluated to
be an apparatus with a high risk at the time of emergency operation. However, in the
present exemplary embodiment, since a mixture is formed by adding a diluent to the
heavy fraction as described above, and the concentration of polycyclic aromatic
hydrocarbons in the mixture is set to 5 mass% to 50 mass%, and preferably 15 mass% to
15 35 mass%, heat generation occurring as a result of the hydrogenation of polycyclic
aromatic hydrocarbons is suppressed, and a sufficiently appropriate hydrogenation can be
carried out even with a conventional general hydrogenation reactor.
[0115]

The (g-2) hydrogen recovery step can be carried out in the same manner as in
the (g-1) hydrogen recovery step according to Exemplary Embodiment 1 of the first
aspect.
[0116]

The (h-2) hydrogen supply step can be carried out in the same manner as in the
5 8
(h-1) hydrogen recovery step according to Exemplary Embodiment 1 of the first aspect.
[0117]

In the recycling step, the hydrogenation product of the mixture obtained in the
5 hydrogenation step is mixed with the feedstock oil and is returned to the cracking
reforming reaction step.
By returning the hydrogenation product of the mixture to the cracking reforming
reaction step, the heavy fraction as a by-product is also used as a feedstock, and thereby
monocyclic aromatic hydrocarbons can be obtained. Therefore, not only the amount of
10 by-products can be reduced, but also the amount of production of monocyclic aromatic
hydrocarbons can be increased. Furthermore, since saturated hydrocarbons are also
produced by hydrogenation, a hydrogen transfer reaction in the cracking reforming
reaction step can be accelerated. From these, the overall yield of monocyclic aromatic
hydrocarbons relative to the amount of supply of the feedstock can be enhanced.
15 Furthermore, in the recycling step, the hydrogenation product may not be
necessarily entirely recycled to the feedstock oil of the cracking reforming reaction step.
In that case, the hydrogenation product that has not been recycled can also be used as a
fuel base material.
[0118]
20 Furthermore, the monocyclic aromatic hydrocarbons, naphthenes and paraffins
in the diluent also contribute to the production of monocyclic aromatic hydrocarbons in
the cracking reforming reaction step. Therefore, this diluent also contributes to an
increase in the yield of monocyclic aromatic hydrocarbons.
When the heavy fraction is directly returned to the cracking reforming reaction
25 step without being hydrogenation treated, since the polycyclic aromatic hydrocarbons
5 9
have low reactivity, the yield of monocyclic aromatic hydrocarbons barely increases.
[0119]
Since the method for producing aromatic hydrocarbons of the present exemplary
embodiment includes a hydrogenation step and a recycling step, monocyclic aromatic
5 hydrocarbons can be obtained by using a heavy fraction which is a by-product as a
feedstock. Therefore, not only the amount of by-products can be reduced, but also the
amount of production of monocyclic aromatic hydrocarbons can be increased.
Therefore, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be
produced with a high yield from a feedstock oil containing polycyclic aromatic
10 hydrocarbons.
Furthermore, since the method includes a dilution step in which the
concentration of polycyclic aromatic hydrocarbons in the mixture obtainable is lowered
than the concentration of polycyclic aromatic hydrocarbons in the heavy fraction by
adding a diluent to a heavy fraction having 9 or more carbon atoms separated from the
15 product produced in the cracking reforming reaction step, extreme heat generation
attributable to the hydrogenation of polycyclic aromatic hydrocarbons in the
hydrogenation step is suppressed, a stabilized hydrogenation is enabled, and a sharp
increase in the facility cost of the hydrogenation reactor can be avoided.
[O 1201
[Exemplary Embodiment 21
Exemplary Embodiment 2 of the method for producing monocyclic aromatic
hydrocarbons related to the second aspect of the invention will be described.
FIG. 4 is a diagram for explaining Exemplary Embodiment 2 of the method for
producing monocyclic aromatic hydrocarbons related to the second aspect of the
25 invention, and the method or producing monocyclic aromatic hydrocarbons of the present
60
exemplary embodiment is a method for producing monocyclic aromatic hydrocarbons
having 6 to 8 carbon atoms from feedstock oil.
[0121]
That is, the method for producing monocyclic aromatic hydrocarbons of the
5 present exemplary embodiment includes, as illustrated in FIG 4:
(i-2) a cracking reforming reaction step of bringing feedstock oil into contact
with a catalyst for monocyclic aromatic hydrocarbon production to react, and thereby
obtaining a product containing monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms, and a heavy fraction having 9 or more carbon atoms;
10 (j-2) a separation step of separating the product produced in the cracking
reforming reaction step into plural fractions;
(k-2) a purification/recovery step of purifying and recovering monocyclic
aromatic hydrocarbons separated in the separation step;
(1-2) a dilution step of adding a diluent to a heavy fraction having 9 or more
15 carbon atoms separated from the product produced in the cracking reforming reaction
step;
(m-2) a hydrogenation step of hydrogenating the mixture obtained in the dilution
step;
(n-2) a diluent recovering step of separating and removing the diluent from the
20 hydrogenation product of the mixture obtained in the hydrogenation step, and recovering
the diluent to recycle the diluent as a diluent for the dilution step;
(0-2) a recycling step of returning the hydrogenation product of the mixture
obtained in the hydrogenation step to the cracking reforming reaction step;
(p-2) a hydrogen recovery step of recovering hydrogen that is produced as a
25 by-product in the cracking reforming reaction step from the gas component separated in
6 1
the separation step; and
(q-2) a hydrogen supply step of supplying the hydrogen collected in the
hydrogen recovery step to the hydrogenation step.
Among the steps (i-2) to (q-2), steps (i-2), (k-2), (1-2), (m-2), (n-2), and (0-2) are
5 essential steps in Exemplary Embodiment 2 of the second aspect of the invention, and
steps Q-2), (p-2) and (q-2) are optional steps.
[O 1221
The (i-2) cracking reforming reaction step can be carried out in the same manner
as in the (a-2) cracking reforming reaction step according to Exemplary Embodiment 1.
10 The 0-2) separation step can be carried out in the same manner as in the (b-2)
separation step according to Exemplary Embodiment 1.
The (k-2) purification/recovery step can be carried out in the same manner as in
the (c-2) purification/recovery step according to Exemplary Embodiment 1.
The (m-2) hydrogenation step can be carried out in the same manner as in the
15 (e-2) hydrogenation step according to Exemplary Embodiment 1.
The (p-2) hydrogen recovery step can be carried out in the same manner as in
the (g-2) hydrogen recovery step according to Exemplary Embodiment 1.
The (q-2) hydrogen supply step can be carried out in the same manner as in the
(h-2) hydrogen supply step according to Exemplary Embodiment 1.
20 [0 1231
The (1-2) dilution step according to the present exemplary embodiment is carried
out in the same manner as in the (d-2) dilution step according to Exemplary Embodiment
1, and a diluent formed of hydrocarbons is added to the heavy fraction having 9 or more
- carbon atoms separated in the separation step so as to lower the concentration of
25 polycyclic aromatic hydrocarbons in the mixture composed of the heavy fraction having
62
9 or more carbon atoms and the diluent to be lower than the concentration of polycyclic
aromatic hydrocarbons in the heavy fraction.
Regarding the diluent used in the present exemplary embodiment, instead of
using hydrocarbons stored in a storage tank that is separately prepared as in Exemplary
5 Embodiment 1, a diluent collected in the diluent recovering step that will be described
below is used by recycling. However, in the case where the diluent is not hlly collected
at the time of start-up or in the diluent recovering step, and there is a lack of diluent,
hydrocarbons are supplied from a storage tank or the like that is separately prepared.
[0 1241
10 Therefore, regarding the diluent, unlike Exemplary Embodiment 1, a diluent that
can be easily separated and collected from the hydrogenation product in the diluent
recovering step, specifically, a diluent that is easily separated from hydrogenation
products of polycyclic aromatic hydrocarbons (particularly naphthenobenzenes) by a
distillation operation, is used. Furthermore, as this diluent, hydrocarbons that are not
15 easily hydrogenated are used as in the case of Exemplary Embodiment 1. Accordingly,
polycyclic aromatic hydrocarbons and the like which have a higher boiling point than
naphthenobenzenes and are prone to undergo a hydrogenation, are not mainly included
thereto. Since the diluent of the present exemplary embodiment is circulated any
number of times through the hydrogenation step, the diluent recovering step, and the
20 dilution step as illustrated in FIG. 4, there may be occurrences in which some of the
diluent may not be collected in the recovery step or the like so that the amount of the
diluent is reduced, or in which the heavy fraction is partially cracked or the like so as to
be collected as the diluent in the diluent recovering step, so that the amount of the diluent
increases. Therefore, if necessary, there is a need to control the amount of circulation of
25 the diluent. However, in any case, a material which is not easily subjected to
63
hydrogenation and cracking more than necessary in the hydrogenation step is preferred.
[0 1251
Therefore, regarding such hydrocarbons, for example, hydrocarbons that can be
produced in the hydrogenation step and have a boiling point lower than that of t-decalin
5 (t-decahydronaphthalene) having a boiling point of 185°C are suitably used. That is,
naphthenes, paraffins, or monocyclic aromatic compounds, which can be easily separated
from polycyclic aromatic hydrocarbons or naphthenobenzenes by a distillation operation
and are not easily hydrogenated, are suitably used as diluents.
In addition, the dilution step of the present exemplary embodiment is the same
10 as the dilution step of Exemplary Embodiment 1, except that such a diluent is used.
That is, in regard to the concentration of polycyclic aromatic hydrocarbons of the mixture
formed by diluting with a diluent, the dilution step is the same as the dilution step of
Exemplary Embodiment 1. Furthermore, regarding the rate of dilution, that is, the mass
ratio (mixing ratio) of the heavy fraction and the diluent, may vary depending on the
15 diluent; since a diluent which does not basically include polycyclic aromatic
hydrocarbons in the present exemplary embodiment is used, the amount of addition of
the diluent can be reduced compared to the mass ratio according to Exemplary
Embodiment 1.
[0 1261
XDiluent recovering step>
In the diluent recovering step, the diluent is separated and removed from the
hydrogenation product of the mixture obtained in the hydrogenation step, and the diluent
is collected. Then, the diluent thus collected is recycled as a diluent to be added to the
heavy fraction having 9 or more carbon atoms in the dilution step,
Regarding the method of separating and removing the diluent from the
64
hydrogenation product of the mixture, a distillation operation is suitably employed as
described above. That is, in this diluent recovering step, for example, components
having a boiling point lower than 185°C and components having a boiling point higher
than this are separated by means of a distillation column. Thereby, for example,
5 components having a boiling point lower than 185°C can be separated from components
having a boiling point higher than 185°C. Therefore, the separated components having
a boiling point lower than 185"C, that is, diluent components are cooled to condensate,
and thereby a diluent can be regenerated.
Therefore, this is sent to the dilution step and added to the heavy fraction to
10 form a mixture, and thereafter, this mixture is circulated through the hydrogenation step,
the diluent recovering step, and the dilution step in sequence.
[0 1271
In the (0-2) recycling step, unlike Exemplary Embodiment 1, instead of
returning the entire amount of the hydrogenation product of the mixture obtained in the
15 hydrogenation step directly to the cracking reforming reaction step, the fraction from
which the diluent has been separated in the diluent recovering step is mixed with the
feedstock oil, or is returned to the cracking reforming reaction step separately.
[0 1281
Even in the method for producing monocyclic aromatic hydrocarbons of the
20 present exemplary embodiment, since the hydrogenation step and the recycling step are
included, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can be
produced with a high yield from a feedstock oil containing polycyclic aromatic
hydrocarbons.
Furthermore, since the method includes a dilution step, extreme heat generation
65
of polycyclic aromatic hydrocarbons in the hydrogenation step is suppressed, and a sharp
increase in the facility cost of the hydrogenation reactor can be avoided.
Moreover, since the method includes a diluent recovering step of separating and
removing the diluent from the hydrogenation product of the mixture, and recovering and
5 recycling the diluent, as the diluent is circulated, a step of continuously supplying a fresh
diluent is unnecessary. Thus, the operation conditions can be simplified.
[0 1291
[Other exemplary embodiments]
The present invention is not intended to be limited to the exemplary
10 embodiments, and various modifications can be made to the extent that the gist of the
invention is maintained.
For example, regarding the hydrogen to be used in the hydrogenation step, not
the hydrogen produced as a by-product in the cracking reforming reaction step, but
hydrogen that is obtained by a known hydrogen production method may be utilized.
15 Furthermore, hydrogen produced as a by-product by another catalytic cracking method
may also be utilized. Furthermore, it is also acceptable to send monocyclic aromatic
hydrocarbons altogether to the hydrogenation step to be separated thereafter, In that
case, the recovery step for the monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms and the diluent recovering step may also be combined.
20 [0130]
Also, in the exemplary embodiments described above, a heavy fraction
discharge step in which a portion of the heavy fraction having 9 or more carbon atoms
obtained from the fraction separated in the separation step is extracted in a certain
amount and is discharged out of the system, may also be provided. Specifically, when
25 the heavy fraction is directly supplied from the separation step to the hydrogenation step,
66
a portion of the heavy fraction may be extracted and discharged out of the system before
the heavy fraction is mixed with a diluent in the dilution step.
[0131]
Furthermore, in the exemplary embodiments described above, the
5 purification/recovery step is carried out after the separation step, but the invention is not
limited to this. For example, the separation step may be carried out after the
hydrogenation step.
Examples
10 [0 1 321
Hereinafter, the present invention will be described more specifically based on
Examples and Comparative Examples, but the invention is not intended to be limited to
these Examples.
[0133]
15 [Preparation Example for catalyst for monocyclic aromatic hydrocarbon
production]
Preparation of catalyst containing gallium and phosphorus-supported crystalline
aluminosilicate:
A solution (A) formed from 1706.1 g of sodium silicate (J Sodium Silicate No. 3,
20 SiOz: 28 mass% to 30 mass%, Na: 9 mass% to 10 mass%, balance: water, manufactured
by Nippon Chemical Industrial Co., Ltd.) and 2227.5 g of water, and a solution (B)
formed from 64.2 g of A12(S04)3. 14-1 8H20 (special grade reagent, manufactured by
Wako Pure Chemical Industries, Ltd.), 369.2 g of tetrapropylammonium bromide, 152.1
g of (97 mass%), 326.6 g of NaC1, and 2975.7 g of water, were respectively
25 prepared.
67
Next, while the solution (A) was stirred at room temperature, the solution (B)
was slowly added to the solution (A).
The mixture thus obtained was vigorously stirred for 15 minutes, and the gel
was crushed to an emulsion-like homogenous and fine state.
[0 1341
Next, this mixture was introduced into an autoclave made of stainless steel, and
under the conditions of a temperature of 165"C, a time of 72 hours, and a stirring rate of
100 rpm, a crystallization operation was carried out under the self-pressure. After
completion of the crystallization operation, the product was filtered, and a solid product
10 was collected. The solid product was subjected to washing using about 5 liters of
deionized water and filtration repeatedly for 5 times. The solid obtained by separation
by filtration was dried at 120°C, and under an air stream, the solid was calcined at 550°C
for 3 hours.
The calcination product thus obtained was subjected to an X-ray diffraction
15 analysis (model name: RIGAKU RINT-2500V), and as a result, it was confirmed that the
calcination product had an MFI structure. Furthermore, the SiO2/Al2O3r atio (molar
ratio) obtained by a fluorescent X-ray analysis (model name: RIGAKU ZSXlOle) was
64.8. Furthermore, the aluminum element contained in the lattice structure as calculated
from these results was 1.32 mass%.
20 [0135]
Next, a 30 mass% aqueous solution of ammonium nitrate was added to the
calcination product thus obtained at a proportion of 5 mL per gram of the calcination
product, and the mixture was heated and stirred for 2 hours at 100°C, and then subjected
to filtration and washing with water. These operations were repeated 4 times, and then
25 the product was dried for 3 hours at 120°C. Thus, an ammonium type crystalline
6 8
aluminosilicate was obtained.
Thereafter, calcination was carried out for 3 hours at 780°C, and a proton type
crystalline aluminosilicate was obtained.
Subsequently, 120 g of the proton type crystalline aluminosilicate thus obtained
5 was impregnated with 120 g of an aqueous solution of gallium nitrate so that 0.4 mass%
(value based on 100 mass% of the total mass of the crystalline alurninosilicate) of
gallium would be supported, and the resultant was dried at 120°C. Thereafter, under an
air stream, the resultant was calcinated for 3 hours at 780°C, and a gallium-supported
crystalline aluminosilicate was obtained.
10 Next, 30 g of the gallium-supported crystalline aluminosilicate thus obtained
was impregnated with 30 g of an aqueous solution of diammonium hydrogen phosphate
such that 0.7 mass% of phosphorus (value based on 100 mass% of the total mass of the
crystalline aluminosilicate) would be supported, and the resultant was dried at 120°C.
Thereafter, under an air stream, the resultant was calcinated for 3 hours at 780°C, and a
15 catalyst A containing crystalline aluminosilicate, gallium and phosphorus was obtained.
[0136]
In the following Examples 1A to 5A, the heavy fraction separated from the
product obtained in the cracking reforming reaction step based on Exemplary
Embodiment 1 according to the first aspect of the invention as illustrated in FIG 1, was
20 hydrogenated in the hydrogenation step, and a portion of the heavy fraction
hydrogenation product was returned to the hydrogenation step as a diluent oil. In the
dilution step, regarding the heavy fraction hydrogenation product for diluting the heavy
fraction in the dilution step, oils that have been hydrogenated under the same
hydrogenation conditions as those used in the hydrogenation step in the respective
Examples were used.
[0137]

(Example 1A)
5 LC0 (10 vol% distillation temperature: 215"C, 90 vol% distillation temperature:
3 18°C) indicated in Table 1, which was feedstock oil, was brought into contact with the
catalyst A (MFI type zeolite having 0.4 mass% of gallium and 0.7 mass% of phosphorus
supported thereon) in a fluidized bed reactor under the conditions of reaction
temperature: 538"C, reaction pressure: 0.3 MPaG and a contact time for contact between
10 the LC0 and the zeolite component contained in the catalyst of 12 seconds, and was
allowed to react. Thus, a cracking reforming reaction step was carried out.
Subsequently, the content of polycyclic aromatic hydrocarbons in the heavy fraction
obtained after recovering monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was measured using a two-dimensional gas chromatography apparatus (manufactured by
15 ZOEX Corp., KT2006 GCxGC system), and the content was 87 mass%.
Next, the heavy fraction was hydrogenated using a commercially available
nickel-molybdenum catalyst under the conditions of a reaction temperature of 350°C, a
reaction pressure of 3 m a , and a LHSV of 0.5 h". A portion of the heavy fraction
hydrogenation product thus obtained was returned as diluent oil to the hydrogenation step,
20 such that the mass ratio of the heavy fraction and the diluent oil was 40/60. At this time,
the content of polycyclic aromatic hydrocarbons in the mixed oil of the heavy fraction
and the diluent oil was 50 mass%. The general conditions for the dilution step and the
hydrogenation step are described in Table 2. For the hydrogen used in the
hydrogenation step, the hydrogen separated in the hydrogen recovery step was used.
70
Furthermore, the heavy fraction hydrogenation product obtained by treating the
mixed oil of the heavy fraction and the diluent oil in the hydrogenation step was recycled
to the cracking reforming reaction step, and thus production of monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms was carried out under the cracking reforming
5 reaction step conditions. The amount of the monocyclic aromatic hydrocarbons having
6 to 8 carbon atoms thus obtained was 46 mass%.
[0138]
[Table 11
[0139]
(Example 2A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example 1 A, except that in the dilution step, the
diluent oil was returned to the hydrogenation step such that the mass ratio of the heavy
fraction and the diluent oil would be 33/67 (the content of polycyclic aromatic
10 hydrocarbons in the mixed oil of the heavy fraction and the diluent oil was 44 mass%).
The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms thus
obtained was 45 mass%.
[0 1401
(Example 3A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
Analysis method
JIS K 2249
JIS K 2283
JIS K 2254
JPI-5s-49
Feedstock properties
Density at 1 S°C
Dynamic viscosity at 30°C
g/cm3
mm21s
OC
"C
oc
OC
"C
vol%
vol%
vol%
vol%
vol%
vol%
Distillation properties
Composition analysis
0.9258
2.817
173
-
215
266
318
346
22.9
2.1
75
27.6
39.5
7.9
Initial distillation point
10 vol% distillation temperature
50 vol% distillation temperature
90 vol% distillation temperature
End point
Saturated fraction
Olefin fraction
Whole aromatic fraction
Monocyclic aromatic fraction
Bicyclic aromatic fraction
Tricyclic or higher-cyclic aromatic fraction
72
was carried out in the same manner as in Example IA, except that in the dilution step, the
diluent oil was returned to the hydrogenation step such that the mass ratio of the heavy
fraction and the diluent oil would be 17/83 (the content of polycyclic aromatic
hydrocarbons in the mixed oil of the heavy fraction and the diluent oil was 34 mass%).
5 The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms thus
obtained was 44 mass%.
[0141]
(Example 4A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
10 was carried out in the same manner as in Example 1 A, except that the reaction pressure
in the hydrogenation step was set to 5 MPa, and in the dilution step, the diluent oil was
returned to the hydrogenation step such that the mass ratio of the heavy fraction and the
diluent oil would be 17/83 (the content of polycyclic aromatic hydrocarbons in the mixed
oil of the heavy fraction and the diluent oil was 22 mass%). The amount of monocyclic
15 aromatic hydrocarbons having 6 to 8 carbon atoms thus obtained was 41 mass%.
[0 1 421
(Example 5A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example IA, except that the reaction pressure
20 in the hydrogenation step was set to 5 MPa, and in the dilution step, the diluent oil was
returned to the hydrogenation step such that the mass ratio of the heavy fraction and the
diluent oil would be 5/95 (the content of polycyclic aromatic hydrocarbons in the mixed
oil of the heavy fraction and the diluent oil was 13 mass%). The amount of monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms thus obtained was 42 mass%.
2 5 [0 1431
73
(Comparative Example 1A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example lA, except that dilution of the heavy
fraction was not carried out. The amount of monocyclic aromatic hydrocarbons having
5 6 to 8 carbon atoms thus obtained was 46 mass%.
[0 1441
The following results are shown in Table 2.
"Heavy fractionheavy fraction hydrogenation product": Mass ratio of the heavy
fraction and the diluent oil
10 "Polycyclic aromatics after dilution": Concentration (mass%) of polycyclic
aromatic hydrocarbons in the mixed oil (mixed oil of the heavy fraction and the diluent
oil) after being diluted in the dilution step
"Reaction pressure": Reaction pressure (MPa) in the hydrogenation step
"Polycyclic aromatics after hydrogenation": Concentration (mass%) of
15 polycyclic aromatic hydrocarbons in the hydrogenation product after the hydrogenation
step
"Heavy fraction processing rate per unit time": Processing rate of the heavy
fraction per unit time (undiluted Comparative Example 1 was taken as 100)
"Amount of heat generation": Calculated value of the amount of heat generation
20 per kg of the oil supplied to the hydrogenation step (undiluted Comparative Example 1
was taken as 100)
"Monocyclic aromatics having 6 to 8 carbon atoms": Amount (mass%) of
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms obtained in the cracking
reforming reaction step
25 [0145]
74
[Table 21
[0 1461
From the results shown in Table 2, as compared with Comparative Example 1A
5 in which the heavy fraction was directly hydrogenated without diluting (undiluted), it
was confirmed that in Examples 1A to 5A that were diluted, the calculated value of the
amount of heat generation per kg of the oil supplied to the hydrogenation step decreased.
This implies that when diluent oil was added to the heavy fraction, the concentration of
polycyclic aromatic hydrocarbons was decreased, and heat generation was relatively
10 suppressed. Thereby, operation of the hydrogenation can be carried out in a stable
manner even in adiabatic large-sized reactors and the like.
[0 1471
(Example 6A)
Dilution
step
Hydrogenation
Reaction
step
Cracking
reforming
Reaction step
Example
1A
40160
50
3
21
50
49
46
Heavy fraction1
Heavy fraction
hydrogenation product
(mass ratio)
Polycyclic aromatics
after dilution, mass%
Reaction pressure,
MPa
Polycyclic aromatics
after hydrogenation,
mass%
Heavy fraction
processing rate per unit
time
(value calculated
relative to Comparative
Example 1A as 100)
Amount of heat
generation
(value calculated
relative to Comparative
Example 1A as 100)
Monocyclic aromatics
having 6 to 8 carbon
atoms, mass%
Example
2A
33/67
44
3
20
33
40
45
Example
3A
17/83
34
3
19
17
20
44
Example
4A
17/83
22
5
11
17
35
41
Example
5A
5/95
13
5
9
5
7
42
Comparative
Example 1A
Undiluted
87
3
22
100
100
46
75
First, based on Exemplary Embodiment 2 related to the first aspect of the
invention as illustrated in FIG. 2, LC0 (10 vol% distillation temperature: 215"C, 90 vol%
distillation temperature: 3 18°C) indicated in Table 1, which was feedstock oil, was
brought into contact with the catalyst A (MFI type zeolite having 0.4 mass% of gallium
5 and 0.7 mass% of phosphorus supported thereon) in a fluidized bed reactor under the
conditions of reaction temperature: 53g°C, reaction pressure: 0.3 MPaG, and a contact
time for contact between the LC0 and the zeolite component contained in the catalyst of
12 seconds, and was allowed to react. Thus, a cracking reforming reaction step was
carried out. A gas component was separated from the product obtained in the cracking
10 reforming reaction step, and the liquid component was collected and analyzed using a
two-dimensional gas chromatography apparatus (manufactured by ZOEX Corp., KT2006
GCxGC system), and it was confirmed that 48 mass% of monocyclic aromatic
hydrocarbons were included.
Thereafter, the collected liquid component was hydrogenated using a
15 commercially available nickel-molybdenum catalyst under the conditions of a reaction
temperature of 350°C, a reaction pressure of 3 MPaG, and a LHSV of 0.5 h-'.
Next, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms were
collected from the hydrogenation product of the liquid component by distillation, and a
portion of the heavy fraction hydrogenation product having 9 or more carbon atoms was
20 returned as diluent oil to the hydrogenation step such that the mass ratio of the liquid
component after the separation step and the diluent oil would be 50150 (the content of
polycyclic aromatic hydrocarbons in the mixed oil of the liquid component after the
separation step and the diluent oil was 32 mass%).
Subsequently, the mixed oil containing the liquid component after the separation
76
step and the diluent oil was hydrogenated under the hydrogenation conditions.
Regarding the hydrogen used in the hydrogenation step, the hydrogen separated in the
hydrogen recovery step was used.
Thereafter, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms were
5 collected by distillation from the hydrogenation product of the mixed oil of the liquid
component after the separation step and the diluent oil, and the heavy fraction
hydrogenation product having 9 or more carbon atoms was recycled to the cracking
reforming reaction step. Thus, production of monocyclic aromatic hydrocarbons having
6 to 8 carbon atoms was carried out under the cracking reforming reaction step
10 conditions. The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms thus obtained was 46 mass%.
[0 1481
(Example 7A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
15 was carried out in the same manner as in Example 6A, except that in the dilution step, the
diluent oil was returned to the hydrogenation step such that the mass ratio of the liquid
component after the separation step and the diluent oil would be 33/67 (the content of
polycyclic aromatic hydrocarbons in the mixed oil of the liquid component after the
separation step and the diluent oil was 29 mass%). The amount of monocyclic aromatic
20 hydrocarbons having 6 to 8 carbon atoms thus obtained was 45 mass%.
[0 1491
(Comparative Example 2A)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example 6A, except that dilution of the heavy
25 fraction was not carried out. The amount of monocyclic aromatic hydrocarbons having
77
6 to 8 carbon atoms was 44 mass%.
[0 1 501
The following results are shown in Table 3.
"Liquid component after separation stepheavy fraction hydrogenation product":
5 Mass ratio of the liquid component after the separation step and diluent oil
"Polycyclic aromatics after dilution": Concentration (mass%) of polycyclic
aromatic hydrocarbons in the mixed oil (mixed oil of the liquid component after the
separation step and the diluent oil) after being diluted in the dilution step
"Reaction pressure": Reaction pressure (MPa) in the hydrogenation step
"Polycyclic aromatics after hydrogenation": Concentration (mass%) of
polycyclic aromatic hydrocarbons in the hydrogenation product after the hydrogenation
step
"Heavy fraction processing rate per unit time": Processing rate of the heavy
fraction per unit time (undiluted Comparative Example 2 was taken as 100)
15 "Amount of heat generation": Calculated value of the amount of heat generation
per kg of the oil supplied to the hydrogenation step (undiluted Comparative Example 2
was taken as 100)
"Monocyclic aromatics having 6 to 8 carbon atoms": Amount (mass%) of
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms obtained in the cracking
20 reforming reaction step
[0151]
[Table 31
[0 1 521
5 From the results shown in Table 3, as compared with Comparative Example 2A
in which the liquid component after the separation step was directly hydrogenated
without diluting (undiluted), it was confirmed that in Examples 6A and 7A that were
diluted, the calculated value of the amount of heat generation per kg of the oil supplied to
the hydrogenation step decreased. This implies that when diluent oil was added to the
10 heavy fraction, the concentration of polycyclic aromatic hydrocarbons was decreased,
and heat generation was relatively suppressed. Thereby, operation of the hydrogenation
can be carried out in a stable manner even in adiabatic large-sized reactors and the like.
[0153]

15 A diluent was added to the heavy fraction separated from the product obtained in
the cracking reforming reaction step to dilute the heavy fraction, in the following
Dilution
step
~ ~ d ~ ~ ~ ~ ~ ~ reaction
step
Cracking
reforming
Reaction step
Example
6A
50150
32
3
17
50
63
46
Liquid component after separation step/
Heavy fraction hydrogenation product
(mass ratio)
Polycyclic aromatics after dilution,
mass%
Reaction pressure, MPa
Polycyclic aromatics after
hydrogenation, mass%
Heavy fraction processing rate per unit
time
(value calculated relative to
Comparative Example 2A as 100)
Amount of heat generation
(value calculated relative to
Comparative Example 2A as 100)
Monocyclic aromatics having 6 to 8
carbon atoms, mass%
Example
7A
33/67
29
3
19
3 3
42
45
Comparative
Example 2A
Undiluted
42
3
11
100
100
44
79
Examples 1B to 3B based on Exemplary Embodiment 1 related to the second aspect of
the invention shown in FIG 4, and in Examples 4B to 7B based on Exemplary
Embodiment 2 related to the second aspect of the invention shown in FIG 5.
[OI 541
5 (Example 1B)
LC0 (1 0 vol% distillation temperature: 2 15"C, 90 vol% distillation temperature:
3 18°C) indicated in Table 1, which was feedstock oil, was brought into contact with the
catalyst A (MFI type zeolite having 0.4 mass% of gallium and 0.7 mass% of phosphorus
supported thereon) in a fluidized bed reactor under the conditions of reaction
10 temperature: 53S°C, reaction pressure: 0.3 MPaQ and a contact time for contact between
the LC0 and the zeolite component contained in the catalyst of 12 seconds, and was
allowed to react. Thus, a cracking reforming reaction step was carried out.
Subsequently, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms thus
obtained were collected by distillation. The content of polycyclic aromatic
15 hydrocarbons in the heavy fraction having 9 or more carbon atoms obtained after
removing the monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was
measured using a two-dimensional gas chromatography apparatus (manufactured by
ZOEX Corp., KT2006 GCxGC system), and the content was 87 mass%.
Next, 1,3,5-trimethylbenzene (TMB) was added as a diluent to the heavy
20 fraction such that the mass ratio would be 17/83 (heavy fractionfdiluent). Thereafter,
the mixed oil of the heavy fraction and the diluent (the content of polycyclic aromatic
hydrocarbons was 15 mass%) was hydrogenated using a commercially available
nickel-molybdenum catalyst under the conditions of a reaction temperature of 350°C, a
reaction pressure of 5 MPa, and a LHSV of 0.5 h-'. Regarding the hydrogen used in the
80
hydrogenation step, the hydrogen separated in the hydrogen recovery step was used.
Furthermore, the hydrogenation product obtained by treating the mixed oil of the
heavy fraction and the diluent in the hydrogenation step, was recycled to the cracking
reforming reaction step, and production of monocyclic aromatic hydrocarbons having 6
5 to 8 carbon atoms was carried out under the cracking reforming reaction step conditions.
The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was 62
mass%.
[0155]
(Example 2B)
10 Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example lB, except that in the dilution step, gas
oil having the properties indicated in Table 4 was used as the diluent. The content of
polycyclic aromatic hydrocarbons in the mixed oil of the heavy fraction and the diluent
was 18 mass%. The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon
15 atoms thus obtained was 45 mass%.
[0156]
[Table 41
[0157]
(Example 3B)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example IB, except that in the dilution step, a
mixture of 50 mass% of 1,3,5-trimethylbenzene (TMB) and 50 mass% of normal decane
was used as the diluent. The content of polycyclic aromatic hydrocarbons in the mixed
10 oil of the heavy fraction and the diluent was 15 mass%. The amount of monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms thus obtained was 53 mass%.
[0158]
(Example 4B)
LC0 (10 vol% distillation temperature: 2 15"C, 90 vol% distillation temperature:
15 3 18°C) indicated in Table 1, which was feedstock oil, was brought into contact with the
Analysis method
JIS K 2249
JIS K 2283
JIS K 2541
JIS K 2254
JPI-5S-49
Properties of gas oil for dilution
Density at 15°C
Dynamic viscosity at 30°C
Sulfur fraction
&m3
mm2/s
mass ppm
"C
"C
"C
"C
"C
vol%
vol%
vol%
vol%
vol%
vol%
Distillation properties
Composition analysis
0.8549
2.716
27
179
203
257
294
308
63.4
0.6
36
33.4
2.4
0.2
Initial boiling point
10 vol% distillation temperature
50 vol% distillation temperature
90 vol% distillation temperature
End point
Saturated fraction
Olefin fraction
Whole aromatic fraction
Monocyclic aromatic fraction
Bicyclic aromatic fraction
Tricyclic or higher-cyclic aromatic fraction
82
catalyst A (MFI type zeolite having 0.4 mass% of gallium and 0.7 mass% of phosphorus
supported thereon) in a fluidized bed reactor under the conditions of reaction
temperature: 53S°C, reaction pressure: 0.3 MPaq and a contact time for contact between
the LC0 and the zeolite component contained in the catalyst of 12 seconds, and was
5 allowed to react. Thus, a cracking reforming reaction step was carried out.
Subsequently, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms thus
obtained were collected by distillation. The content of polycyclic aromatic
hydrocarbons in the heavy fraction having 9 or more carbon atoms obtained after
removing the monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was
10 measured using a two-dimensional gas chromatography apparatus (manufactured by
ZOEX Corp., KT2006 GCxGC system), and the content was 87 mass%.
Next, 1,3,5-trimethylbenzene (TMB) was added as a diluent to the heavy
fraction such that the mass ratio would be 5/95 (heavy fraction/diluent) (dilution step).
Thereafter, the mixed oil of the heavy fraction and the diluent (the content of polycyclic
15 aromatic hydrocarbons was 8 mass%) was hydrogenated using a commercially available
nickel-molybdenum catalyst under the conditions of a reaction temperature of 350°C, a
reaction pressure of 5 MPa, and a LHSV of 0.5 h". Regarding the hydrogen used in the
hydrogenation step, the hydrogen separated in the hydrogen recovery step was used.
Furthermore, the hydrogenation product obtained by treating the mixed oil of the
20 heavy fraction and the diluent in the hydrogenation step, was fractionated into a fraction
having a boiling point higher than 185°C and a fraction having a boiling point of 185°C
or lower, and the fraction having a boiling point lower than 185°C was returned to a point
before the hydrogenation step to be reused as a diluent. The fraction having a boiling
point of 185°C or higher was recycled to the cracking reforming reaction step, and
83
production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms was carried
out under the cracking reforming reaction step conditions. The amount of monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms was 44 mass%.
[0159]
(Example 5B)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example 4B, except that in the dilution step, a
mixture of 50 mass% of 1,3,5-trimethylbenzene (TMB) and 50 mass% of normal decane
was used as the diluent and the mixing ratio of the heavy fraction and the diluent was set
10 to 50150 as a mass ratio; and in the hydrogenation step, the reaction pressure was set to 3
MPa. The content of polycyclic aromatic hydrocarbons in the mixed oil of the heavy
fraction and the diluent was 44 mass%. The amount of monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms thus obtained was 46 mass%.
[0 1 601
(Example 6B)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example 4B, except that in the dilution step, the
mixing ratio of the heavy fraction and the diluent was set to 33/67 as a mass ratio. The
content of polycyclic aromatic hydrocarbons in the mixed oil of the heavy fraction and
20 the diluent was 32 mass%. The amount of monocyclic aromatic hydrocarbons having 6
to 8 carbon atoms thus obtained was 45 mass%.
[0161]
(Example 7B)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
25 was carried out in the same manner as in Example 4B, except that in the dilution step, the
84
mixing ratio of the heavy fraction and the diluent was set to 17/83 as a mass ratio, and the
reaction pressure in the hydrogenation step was set to 7 MPa. The content of polycyclic
aromatic hydrocarbons in the mixed oil of the heavy fraction and the diluent was 15
mass%. The amount of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
5 thus obtained was 43 mass%.
[0 1621
(Comparative Example 1 B)
Production of monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms
was carried out in the same manner as in Example lB, except that dilution of the heavy
10 fraction was not carried out. The amount of monocyclic aromatic hydrocarbons having
6 to 8 carbon atoms thus obtained was 44 mass%.
[0 1 631
The following results are shown in Table 5.
"Diluent": Kind of diluent (in the case of a mixture, the respective mass ratios
15 for the components are shown in the lower line)
"Heavy fractionldiluent": Mass ratio of the heavy fraction and the diluent
"Polycyclic aromatics after dilution": Concentration (mass%) of polycyclic
aromatic hydrocarbons in the mixture after being diluted in the dilution step
"Reaction pressure": Reaction pressure (MPa) in the hydrogenation step
"Polycyclic aromatics after hydrogenation": Concentration (mass%) of
polycyclic aromatic hydrocarbons in the hydrogenation product after the hydrogenation
step
"Hydrogenation conversion ratio of diluent": Ratio (%) of the diluent that has
been hydrogenated
"Heavy fraction processing rate per unit time": Processing rate of the heavy
85
fraction per unit time (undiluted Comparative Example 1 was taken as 100)
"Amount of heat generation": Calculated value of the amount of heat generation
per kg of the oil supplied to the hydrogenation step (undiluted Comparative Example 1
was taken as 100)
"Separation of diluent by distillation": Presence or absence of diluent recovering
step
"Monocyclic aromatics having 6 to 8 carbon atoms": Amount (mass%) of
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms obtained in the cracking
reforming reaction step
10
[Table 51
From the results shown in Table 5, as compared with Comparative Example 1B
in which the heavy fraction was directly hydrogenated without being diluted (undiluted),
Comparative
ExampleIB
Undiluted
87
5
13
100
100
44
it was confirmed that in Examples 1B to 7B that had been diluted, the calculated value of
Dilution step
-lydrogenation
step
Cracking
reforming
reaction step
the amount of heat generation per kg of the oil supplied to the hydrogenation step
decreased. This implies that when a diluent was added to the heavy fraction, the
10 concentration of polycyclic aromatic hydrocarbons was decreased, and heat generation
Example
IB
TMB
17/83
15
5
4
1
17
18
None
62
Diluent (in case of mixture: lower line
indicates mass%)
Heavy fiaction/diluent (mass ratio)
Polycyclic aromatics after dilution
(mass%)
Reaction pressure (MPa)
Polycyclic aromatics after
hydrogenation (mass%)
Hydrogenation conversion ratio of
diluent (%)
Heavy fraction processing rate per unit
time (value calculated relative to
Comparative Example 1 B as 100)
Amount of heat generation (value
calculated relative to Comparative
Example 1B as 100)
Separation of diluent by distillation
.
Monocyclic aromatics having 6 to 8
carbon atoms (mass%)
Example
2B
Gas oil
17/83
18
5
5
17
17
None
45
Example
3B
TMB
Idecane
(50150)
17/83
15
5
3
0
17
18
None
53
Example
4B
TMB
5/95
8
5
4
2
5
6
Done
44
Example
5B
TMB
Idecane
(50150)
50150
44
3
11
0
50
50
Done
46
Example
6B
TMB
33/67
32
5
6
1
33
36
Done
45
Example
7B
TMB
17/83
15
7
3
4
17
19
Done
43
8 7
was relatively suppressed. Thereby, operation of the hydrogenation can be carried out
in a stable manner even in adiabatic large-sized reactors and the like. Furthermore, the
hydrogenation conversion ratio of the diluent was also very low, and it was found that
even in the case of recovering the diluent, the diluent could effectively be used by
5 recycling.
Industrial Applicability
[0 1661
According to the method for producing monocyclic aromatic hydrocarbons of
10 the present invention, monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms can
be produced with a high yield from a feedstock oil containing polycycljc aromatic
hydrocarbons. Furthermore, since the method includes a dilution step, the extreme heat
generation attributable to the hydrogenation of polycyclic aromatic hydrocarbons in the
hydrogenation step is suppressed, and a stabilized hydrogenation is enabled. Thus, a
15 sharp increase in the facility cost for the hydrogenation reactor can be avoided.
Therefore, the present invention is highly useful fkom an industria1 viewpoint.

CLAIMS
1. A method for producing monocyclic aromatic hydrocarbons, by which
monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are produced from a
feedstock oil having a 10 vol% distillation temperature of 140°C or higher and a 90 vol%
distillation temperature of 380°C or lower, the method comprising:
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production comprising a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
carbon atoms;
a hydrogenation step of hydrogenating a liquid fraction separated from the
product produced in the cracking reforming reaction step;
a dilution step of adding a portion of a hydrogenation product of the heavy
fraction having 9 or more carbon atoms obtained in the hydrogenation step, or a diluent
to the liquid fraction; and
a recycling step of returning the other portion of the hydrogenation product of
the heavy fraction obtained in the hydrogenation step to the cracking reforming reaction
step.
2. The method for producing monocyclic aromatic hydrocarbons according to
claim 1, by which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are
produced from a feedstock oil having a 10 vol% distillation temperature of 140°C or
higher and a 90 vol% distillation temperature of 380°C or lower, the method comprising:
89
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
5 carbon atoms;
a purificationJrecovery step of puriQing and recovering monocyclic aromatic
hydrocarbons having 6 to 8 carbon atoms separated from the product produced in the
cracking reforming reaction step;
a hydrogenation step of hydrogenating the heavy fraction having 9 or more
10 carbon atoms separated from the product produced in the cracking reforming reaction
step;
a dilution step of returning a portion of a hydrogenation product of the heavy
fraction having 9 or more carbon atoms obtained in the hydrogenation step, as a diluent
oil to the hydrogenation step; and
15 a recycling step of returning the other portion of the hydrogenation product of
the heavy fraction obtained in the hydrogenation step to the cracking reforming reaction
step.
3. The method for producing monocyclic aromatic hydrocarbons having 6 to 8
20 carbon atoms according to claim 2, wherein in the dilution step, the amount of the diluent
oil returned to the hydrogenation step is adjusted such that the mass ratio of the heavy
fraction having 9 or more carbon atoms that is separated from the product produced in
the cracking reforming reaction step and is supplied to the hydrogenation step, to the
diluent oil is in the range of 10:90 to 80:20.
90
4. The method for producing monocyclic aromatic hydrocarbons according to
claim 1, by which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are
produced from a feedstock oil having a 10 vol% distillation temperature of 140°C or
higher and a 90 vol% distillation temperature of 380°C or lower, the method comprising:
a cracking reforming reaction step of bringing the feedstock oil into contact with
a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
carbon atoms;
10 a hydrogenation step of hydrogenating a portion separated from the product
produced in the cracking reforming reaction step;
a purificatiodrecovery step of distilling the hydrogenation product obtained in
the hydrogenation step to purifL monocyclic aromatic hydrocarbons having 6 to 8 carbon
atoms, recovering the monocyclic aromatic hydrocarbons, and separating a heavy
15 fraction having 9 or more carbon atoms from the monocyclic aromatic hydrocarbons
having 6 to 8 carbon atoms;
a dilution step of returning a portion of the heavy fraction having 9 or more
carbon atoms separated in the purificatiodrecovery step, as a diluent oil to the
hydrogenation step; and
a recycling step of returning the other portion of the heavy fraction separated in
the purification/recovery step to the cracking reforming reaction step.
5. The method for producing monocyclic aromatic hydrocarbons having 6 to 8
carbon atoms according to claim 4, wherein in the dilution step, the amount of the diluent
25 oil returned to the hydrogenation step is adjusted such that the mass ratio of the product
9 1
that is separated from the product produced in the cracking reforming reaction step and is
supplied to the hydrogenation step, to the diluent oil is in the range of 20:80 to 80:20.
6. The method for producing monocyclic aromatic hydrocarbons having 6 to 8
5 carbon atoms according to any one of claims 2 to 5, wherein in the dilution step, the
diluent oil is returned to the hydrogenation step such that the concentration of polycyclic
aromatic hydrocarbons in a mixed oil of the product that is separated from the product
produced in the cracking reforming reaction step and is supplied to the hydrogenation
step, and the diluent oil is 5 mass% to 50 mass%.
10
7. The method for producing monocyclic aromatic hydrocarbons having 6 to 8
carbon atoms according to any one of claims 2 to 6, wherein in the hydrogenation step,
the hydrogenation pressure is set to 0.7 MPa to 13 m a .
15 8. The method for producing monocyclic aromatic hydrocarbons according to
claim 1, by which monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms are
produced from a feedstock oil having a 10 vol% distillation temperature of 140°C or
higher and a 90 vol% distillation temperature of 380°C or lower, the method comprising:
a cracking reforming reaction step of bringing the feedstock oil into contact with
20 a catalyst for monocyclic aromatic hydrocarbon production containing a crystalline
aluminosilicate to effect a reaction, thereby obtaining a product containing monocyclic
aromatic hydrocarbons having 6 to 8 carbon atoms and a heavy fraction having 9 or more
carbon atoms;
a purification/recovery step of purifying and recovering monocyclic aromatic
25 hydrocarbons having 6 to 8 carbon atoms separated from the product produced in the
92
cracking reforming reaction step;
a dilution step of adding a diluent comprising hydrocarbons to the heavy fraction
having 9 or more carbon atoms separated from the product produced in the cracking
reforming reaction step;
a hydrogenation step of hydrogenating the mixture; and
a recycling step of returning the hydrogenation product of the mixture obtained
in the hydrogenation step to the cracking reforming reaction step.
9. The method for producing monocyclic aromatic hydrocarbons having 6 to 8
10 carbon atoms according to claim 8, further comprising a diluent recovering step of
separating and removing the diluent from the hydrogenation product of the mixture
obtained in the hydrogenation step, recovering the diluent, and reutilizing the diluent as a
diluent to be added to the heavy fraction having 9 or more carbon atoms.
15 10. The method for producing monocyclic aromatic hydrocarbons having 6 to
8 carbon atoms according to claim 9, wherein a hydrocarbon oil having a boiling point
lower than 185°C is used as the diluent.
11. The method for producing monocyclic aromatic hydrocarbons having 6 to
20 8 carbon atoms according to any one of claims 8 to 10, wherein a diluent having a
concentration of polycyclic aromatic hydrocarbons of 50 mass% or less is used as the
diluent.
12. The method for producing monocyclic aromatic hydrocarbons having 6 to
25 8 carbon atoms according to any one of claims 8 to 11, wherein in the dilution step, the
9 3
amount of the diluent is adjusted such that the mass ratio of the heavy fraction having 9
or more carbon atoms that is separated from the product produced in the cracking
reforming reaction step and is supplied to the hydrogenation step, to the diluent is in the
range of 10:90 to 80:20.
5
13. The method for producing monocyclic aromatic hydrocarbons having 6 to
8 carbon atoms according to any one of claims 8 to 12, wherein in the dilution step, the
diluent is added such that the concentration of polycyclic aromatic hydrocarbons in the
mixture obtainable by adding the diluent to the heavy fraction having 9 or more carbon
10 atoms, is 5 mass% to 50 mass%.
14. The method for producing monocyclic aromatic hydrocarbons having 6 to
8 carbon atoms according to any one of claims 8 to 14, wherein in the hydrogenation step,
the hydrogenation pressure is set to 0.7 MPa to 13 MPa.