TECHNICAL FIELD
[OOOl]
Thepresentinventionrelatesto anefficient process for
producing a cyclohexanone compound by the hydrogenation
reaction of a phenol compound in a gas phase.
BACKGROUND ART
[0002]
As known in the art, the hydrogenation reaction of phenol
in the presence of a palladium catalyst gives a mixture
including cyclohexanone and cyclohexanol (Patent Literatures
1 and 2). Cyclohexanone is used as a raw material in the
production of caprolactam, and cyclohexanol mixed in the
cyclohexanone is an undesired impurity. For example,
cyclohexanol may be converted into cyclohexanone by
dehydrogenation with a copper oxide/zinc oxide catalyst
(Patent Literature 3). However, additional costs are incurred
in order to separate a cyclohexanone/cyclohexanol mixture
obtained by the hydrogenation reaction of phenol into
cyclohexanone (boiling point 156.4"C) and cyclohexanol
(boiling point 161.l0C) and also to dehydrogenate cyclohexanol.
In consideration of these cos.ts, the occurrenceof cyclohexanol
as a byproduct in the hydrogenation reaction of phenol is
desirably suppressed to the minimum.
[0003]
Because cyclohexanol is formed by the hydrogenation
reaction of cyclohexanone, the amount of byproduct
5 cyclohexanol may be reduced by decreasing the rate of the
conversion of phenol. However, cyclohexanone and phenol, and
cyclohexanol and phenol form maximum-boiling azeotropes and
therefore decreasing the conversion rate gives rise to another
economic problem that a significantly high cost is incurred
10 to separate cyclohexanone andcyclohexanolastheproducts from
the unreacted phenol. Thus, phenol is desirably converted at
, i
I as high a conversion rate as possible.
:I
Further, the hydrogenation reaction of phenol produces
15 high-boiling byproducts based on cyclohexylcyclohexanone, in
addition to cyclohexanol. These byproducts are generally
difficult to convert to cyclohexanone by an affordable method
in contrast to the dehydrogenation of cyclohexanol into
cyclohexanone. Thus, an increase in the amount of
20 cyclohexylcyclohexanone byproduct leads to a decrease in the
yield of cyclohexanone, resultingin poor economic efficiency.
[OOOS]
I
From an industrial viewpoint, the satisfaction of both
high phenol conversion rate andhigh cyclohexanone selectivity
is animportant key tothe economically advantageous production
of cyclohexanone. The production of cyclohexanone by the
hydrogenation reaction of phenol in a gas phase is generally
performed by passing a mixture gas of phenol and hydrogen
5 through a palladium catalyst supported on an alumina carrier.
The process, however, is not applicable to an industrial scale
because the catalyst is frequently deactivatedin a short time.
100061
To address the above problem, for example, it is reported
10 that a palladium catalyst which is supported on a carrier
prepared by mixing alumina with an alkaline earth metal
hydroxide is less prone to deactivation and shows enhanced
cyclohexanone selectivity as comparedtowheny-aluminais used
as the carrier (Patent Literature 4). However, the carrier
15 made by this method has a defect in that mechanical strength
is generally low. Further, the hydrogenation reaction of
phenol involves a large excess of hydrogen and the catalytic
activity is below the level required for use on an industrial
scale.
20 [0007]
To avoid this problem, the use of alumina spinel as a
carrier is reported (Patent Literature 5). This approach
realizes high mechanical strength and sustained catalytic
activity. However, this method entails more complicated
carrier production steps and involves more expensive raw
materials than when usual alumina is used. These facts
inevitably raise the carrier production cost.
[0008]
Fromthe viewpoints described above, the development of
a low-cost and simple process which can produce cyclohexanone
with a high yield is desired.
CITATION LIST
PATENT LITERATURE
[0009]
Patent Literature 1: US3305586
Patent Literature 2: US3076810
Patent Literature 3: US4918239
Patent Literature 4: GB1063357
Patent Literature 5: US5395976
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[OOlO]
In light of the problems in the art discussed above, an
object of the invention is to provide an economical and highly
efficient process for producing a cyclohexanone compound such
as cyclohexanone.
SOLUTION TO PROBLEM
[OOll]
In order to achieve the above object, the present
inventors carried out extensive studies on the production of
a cyclohexanone compoundsuchas cyclohexanonebythe gas-phase
hydrogenationreactionofaphenolcompoundsuchasphenolusing
5 a palladium catalyst supported on a carrier. As a result, the
present inventors have found that the presence of a specific
nitrogen compound in the hydrogenation reaction enhances the
catalytic activity, suppresses the formation of byproducts to
improve the selectivity for the cyclohexanone compound such
10 as cyclohexanone, and retards the decrease in catalytic
activity. The present invention has been completed based on
the finding.
[0012]
Specifically, the invention includes the following
15 aspects.
[0013]
[I] A process for producing a cyclohexanone compound by
performing hydrogenation reaction of a phenol compound in a
gas phase in the presence of a palladium catalyst supported
20 on a carrier to produce the corresponding cyclohexanone
compound, wherein the hydrogenation reaction is carried out
in the presence of at least one nitrogen compound selected from
ammonia, amine compounds and heteroaromatic compounds.
[0014]
[2] A process for producing cyclohexanone by performing
hydrogenation reaction of phenol in a gas phase in the presence
of a palladium catalyst supported on a carrier to produce the
cyclohexanone, wherein the hydrogenation reaction is carried
out in the presence of at least one nitrogen compound selected
from ammonia, amine compounds and heteroaromatic compounds.
[0015]
[3] The process for producing cyclohexanone describedin
[2], wherein the nitrogen compound is free from a structure
formed by the bonding of a hydrogen atom to a nitrogen atom.
[0016]
[4] The process for producing cyclohexanone describedin
[3], wherein the nitrogen compound is an amine compound having
a tertiary amine structure.
[0017]
[5] The process for producing cyclohexanone describedin
[4], wherein the nitrogen compound is composed solely of
hydrogen, carbon and nitrogen atoms.
[0018]
[6] The process for producing cyclohexanone describedin
any of [2] to [5], wherein the nitrogen compound is thenitrogen
compound attached to the surface of the catalyst as a result
of a contact with the palladium catalyst before the
hydrogenation reaction.
[0019]
[7] The process for producing cyclohexanone described in
any of [2] to [5], wherein the nitrogen compound is the nitrogen
compound added together with the raw material phenol.
5 [0020]
[8] The process for producing cyclohexanone described in
[ 7 ] , wherein the amount of the supply of the nitrogen compound
is 0.005to 0.05 wt% relative tothe amount ofthe feed of phenol
taken as 100 wt%.
10 [0021]
[9] The process for producing cyclohexanone described in
[7], wherein the amount of the supply of the nitrogen compound
is 0.01to 0.05 wt% relative to the amount ofthe feed of phenol
taken as 100 wt%.
15 [0022]
[lo] The process for producing cyclohexanone described
in any of [2] to [9], wherein the carrier is porous alumina.
[0023J
[Ill The process for producing cyclohexanone described
20 in any of [2] to [lo], wherein the palladium catalyst supported
on the carrier further includes at least one metal element
selected from lithium, sodium, potassium, magnesium, calcium
and barium.
[0024]
[12] The process for producing cyclohexanone described
in any of [2] to [Ill, wherein the reaction is performed in
the presence of water.
[0025]
5 [13] A process for producing caprolactam, wherein the
process uses cyclohexanone produced by the production process
described in any of [21 to [121.
[0026]
[14] Acatalystobtainedbybringingatleastonenitrogen
10 compound selected from ammonia, amine compounds and
heteroaromatic compounds into contact with a palladium
catalyst supported on a carrier so as to attach the nitrogen
compound to the surface of the catalyst.
ADVANTAGEOUS EFFECTS OF INVENTION
15 [0027]
The process for producing a cyclohexanone conipound
according to the present invention is excellent in particular
in terms of production cost, and the target cyclohexanone
compound may be produced while achieving process advantages
20 and economic advantages.
[0028]
Further, the process for producing cyclohexanone
according to the present invention has the following effects
and is excellent in particular in terms of production cost.
Thus, t a r g e t cyclohexanone may be produced with process
advantages and economic advantages.
[0029]
(1) The amount of cyclohexanol formed as a byproduct is
I 5 reduced. Because the load required t o s e p a r a t e cyclohexanone
andcyclohexanolis reduced, t h e p u r i f i c a t i o n c o s t m a y b e saved.
Further, t h e dehydrogenation of cyclohexanol t o recover
cyclohexanoneis f e a s i b l e with a smaller dehydrogenationunit.
10 ( 2 ) The amountofhigh-boilingbyproducts is reduced, and
i thereby the b a s i c u n i t of cyclohexanone may be enhanced.
[0031]
I
(3) The c a t a l y t i c a c t i v i t y i s enhancedtomakeitpossible
t o reduce the amounts of hydrogen and t h e c a t a l y s t t h a t a r e
15 used. Thus, the hydrogenation r e a c t o r may be reduced i n s i z e ,
and t h e c a t a l y s t cost may be saved.
( 4 ) The decrease i n c a t a l y t i c a c t i v i t y with time may be
r e t a r d e d . Consequently, t h e c a t a l y s t r e g e n e r a t i o n c y c l e s may
.I 20 be extended and the l o s s of production d u r i n g t h e regeneration !
I periods may be reduced.
i
BRIEF DESCRIPTION OF DRAWINGS
[GO331
[Fig. 11 F i g . 1 i s a s c h e m a t i c v i e w i l l u s t r a t i n g a r e a c t i o n
apparatus used in Examples of the invention.
[Fig. 21 Fig. 2 is a diagram plotting changes with time
in the phenol conversion rate after the lapse of 1.5 hours,
3.5 hours and 5.5 hours during the hydrogenation reaction in
5 Inventive Examples and Comparative Examples.
DESCRIPTION OF EMBODIMENTS
[0034]
In a process for producing a cyclohexanone compound
according to the invention, the hydrogenation reaction of a
10 phenol compound is performed in a gas phase in the presence
of a palladium catalyst supported on a carrier to produce the
corresponding cyclohexanone compound. The process is
characterized in that the hydrogenation reaction is carried
out in the presence of at least one nitrogen compound selected
15 from ammonia, amine compounds and heteroaromatic compounds.
Details of the process will be described below.
[0035]
Examples of the phenol compounds used in the invention
include phenol, cresol, butylphenol, other monoalkylphenols,
20 and dialkylphenols. Phenol compounds having 6 to 12 carbon
atoms in the molecule are preferable.
[0036]
In the cyclohexanone compound production process of the
invention, the phenol compound is hydrogenated to give the
corresponding cyclohexanone compound. The term
"corresponding cyclohexanone compound" means that the benzene
ring of the phenol compound used as the raw material is
hydrogenated into the cyclohexane ring and the C-OH structure
5 in the phenol compoundis convertedtothecarbonyl (C=O). When
phenol is used as the phenol compound, the corresponding
cyclohexanone compound is cyclohexanone. When the phenol
compound is cresol, the corresponding cyclohexanone compound
is methylcyclohexanone.
10 [ 0 0 3 7 ]
In the cyclohexanone compound production process of the
invention, it is preferable that the phenol compound is phenol
and the cyclohexanone compound is cyclohexanone.
roo381
15 That is, the cyclohexanone compound production process
of the invention is preferably a process for producing
cyclohexanone. In the process for producing cyclohexanone
according to the invention, the hydrogenation reaction of
phenolisperformedinagasphaseinthepresenceofapalladium
20 catalyst supported ona carrier to produce cyclohexanone. The
process is characterized in that the hydrogenation reaction
is carried out in the presence of at least one nitrogen compound
selected from ammonia, amine compounds and heteroaromatic
compounds.
[0039]
Hereinbelow, details will be described with respect to
the process for producing cyclohexanone.
[0040]
5 (Catalysts)
Inthe invention, thehydrogenationreaction is catalyzed
by a palladium catalyst supported on a carrier. (In the
following description, the catalyst is sometimes written
simply as the "supported palladium catalyst".)
10 [0041]
The carrier is not particularly limited as long as the
carrier is inert in the hydrogenation reaction. Examples
' I
include metal oxides such as silica, alumina, silica-alumina,
magnesia, titania and zirconia. Of these, alumina is
15 preferable, and porous alumina is particularly preferable.
The average pore diameter of the porous alumina is preferably
10 to 500 nm. The average pore volume per unit weight of the
porous alumina is preferably about 0.2 to 3 ml/g. The specific
surface area per unit weight ofthe porous aluminais preferably
I
20 about 10 to 200 m2/g.
Metallicpalladiummaybe supported on the carrier by any
known method without limitation. For example, metallic
palladium may be supported by impregnating the carrier with
an aqueous solution of a palladium compound such as sodium
tetrachloropalladate (11) andbringingtheimpregnatedcarrier
into contact with a reductant such as hydrazine. The
proportion of the palladium supported on the carrier in 100
parts by weight of the catalyst is usually in the range of 0 . 1
to 10.0 parts by weight, and preferably 0 . 1 to 3.0 parts by
weight.
[ 0 0 4 3 ]
The shape of the supported palladium catalyst is not
particularly limited and may be any of various shapes such as
spheres, pellets, extrudates andirregularlyshapedfragments.
Spheres are particularly preferable. In the case of the
spherical catalyst, the average particle diameter is usually
in the range of 1 to 1 0 mm, and preferably 2 to 5 mm.
[ 0 0 4 4 ]
In the supported palladium catalyst, a compound(s) of an
alkali metal and/or an alkaline earth metal may be further
supported. That is, the supported palladium catalyst may
further include a compound(s) of an alkali metal and/or an
alkaline earth metal, more specifically, may further include
at least one metal element selected from lithium, sodium,
potassium, magnesium, calcium and barium.
LO0451
The compound(s) of an alkali metal and/or an alkaline
earthmetalmaybe supportedonthe supportedpalladiumcatalyst
by a known method. For example, the metals may be supported
on the catalyst by impregnating the supported palladium
catalyst still free fromany alkalimetal and/or alkaline earth
5 metal compounds with an aqueous solution of any of compounds
I such as hydroxides, nitrate salts, acetate salts and carbonate
salts of metals such as lithium, sodium, potassium, magnesium,
calcium and barium, followed by drying or calcination. The
proportion of the alkali metal and/or the alkaline earth metal
10 supported on the catalyst in 100 parts by weight of the whole
catalyst is usually in the range of 0.1 to 10.0 parts by weight,
and preferably 0.2 to 5.0 parts by weight. The compounds of
alkali metals and alkaline earth metals may be used singly,
or two or more may be used in combination.
(Nitrogen compounds)
In the invention, the gas-phase hydrogenation reaction
of phenol is performed in the presence of the supported
palladium catalyst and also in the presence of at least one
20 nitrogen compound selected from ammonia, amine compounds and
heteroaromatic compounds. While the compounds of alkali
metals and/or alkaline earth metals that are conventionally
used in the production of cyclohexanone are necessarily
in the present application does not require a carrier and the
use thereof is a simple method capable of controlling the
acidity on the surface of the catalyst.
[0047]
5 In the invention, the "at least one nitrogen compound
selected from ammonia, amine compounds and heteroaromatic
compounds" is also written simply as the "nitrogen compound".
[0048]
The nitrogen compounds may be used singly, or two or more
10 may be used in combination.
[0049]
The nitrogencompound is a compoundhaving anitrogenatom
in the molecule and is at least one compound selected from
ammonia, amine compounds and heteroaromatic compounds.
15 [0050]
The amine compound is a substance which has a structure
resulting from the substitution of a hydrogen atom in ammonia
with a hydrocarbon group. The heteroaromatic compound is an
aromatic heterocyclic compound.
20 [0051]
The nitrogen compound is preferably free froma structure
formed by the bonding of a hydrogen atom to a nitrogen atom.
When the nitrogen compound free from a structure formed by the
bonding of a hydrogen atom to a nitrogen atom, the amount of
high-boiling compounds formed as byproducts tends t o be
advantageously reduced.
[0052]
Examples o f t h e n i t r o g e n compounds f r e e from a s t r u c t u r e
5 formed by the bonding of a hydrogen atom t o a nitrogen atom
include t e r t i a r y amines (A) which have one or more amine
s t r u c t u r e s i n t h e molecule and a l l t h e amine s t r u c t u r e s have
a t e r t i a r y amine s t r u c t u r e , and p y r i d i n e . Examples of t h e
nitrogen compounds t h a t have a s t r u c t u r e formed by the bonding
10 of a hydrogen atomto a n i t r o g e n atominclude ammonia andamines
having aprimaryamine s t r u c t u r e or a secondaryamine s t r u c t u r e
i n t h e molecule.
[0053]
It is d e s i r a b l e t h a t t h e n i t r o g e n compound be as i n e r t
15 as p o s s i b l e t o phenol, hydrogen, and cyclohexanone and
cyclohexanol as t h e products under r e a c t i o n c o n d i t i o n s . From
t h i s viewpoint, t h e nitrogen compound f r e e from a s t r u c t u r e
formed by the bonding of a hydrogen atom t o a nitrogen atom
is p r e f e r a b l e . The reasons as t o why t h e use of the nitrogen
20 compound f r e e from a s t r u c t u r e formed by t h e bonding of a
hydrogenatomto a nitrogen a t o m i s p r e f e r a b l e w i l l b e described
i n d e t a i l below. The present i n v e n t o r s assume t h a t the
n i t r o g e n compound f r e e from a s t r u c t u r e formed by rhe bonding
of a hydrogen atom t o a n i t r o g e n atom a r e the t r u e compounds
that contribute to the enhancements in reaction results such
as phenol conversion rate and cyclohexanone selectivity. The
nitrogen compound having a hydrogen-nitrogen bond in its
molecule probably undergoes dehydration condensation with ~ 5 cyclohexanone as a raw material under reaction conditions
adoptedinthepresentinvention, forminganimine or anenamine
as an intermediate product. These intermediates are
hydrogenated under the reaction conditions and are finally
converted to nitrogen compounds free from a structure formed
10 by the bonding of a hydrogen atom to a nitrogen atom. The
present inventors assume that the advantageous effects in the
hydrogenationreactionoftheinventionareachievedas a result
of the above mechanism. Because, however, part of
cyclohexanone that is the desired product is consumed by the
15 dehydration condensation with the nitrogen compound having a
hydrogen-nitrogen bond, the cyclohexanone selectivity is
lowered. Thus, the nitrogen compound having a
hydrogen-nitrogen bond and the nitrogen compound free from a
structure formedbythe bonding of a hydrogen atomto a nitrogen
20 atom may be used as the same when only an enhancement in phenol
conversion rate is desired. When, however, not onlythe phenol
conversion rate but also the cyclohexanone selectivity are to
be enhanced, it is preferable to use the nitrogen compound free
from a structure formed by the bonding of a hydrogen atom to
a nitrogen atom.
[0054]
The nitrogen compound is preferably an amine compound
having a tertiary amine structure. The tertiary amine
5 structure is advantageous in that it tends to exhibit a strong
interaction with an acid site of the carrier in the supported
palladium catalyst.
[0055]
The nitrogen compound is preferably composed solely of
10 hydrogen, carbon and nitrogen atoms. If atoms other than
hydrogen, carbon and nitrogen atoms are present, the compound
may be decomposed during the reaction to form impurities. For
this reason, thenitrogencompounds composed solelyofhydrogen,
carbon and nitrogen atoms are preferable.
15 [0056]
Specific examples of the nitrogen compounds include
ammonia, trimethylamine, triethylamine, triisopropylamine,
tributylamine, trioctylamine, N,N-dimethylaniline,
N,N-dimethylbenzylamine,
20 N,N,Nr,N'-tetramethylethylenediamine,
N, N, N' , N",Nn-pentamethyldiethylenetriamine,
N-methylpiperidine, N-methylmorpholine,
N,N1-dimethylpiperazine, quinuclidine,
1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine,
N,N-dimethylaminopyridine, 1,5-diazabicyclo[4.3.0]-5-nonene,
1,8-diazabicyclo[5.4.0]-7-undecene, pyridine, quinoline,
pyrazine, triazine, N,N,Nr,N'-tetramethylguanidine,
diethylaminopropylamine, imidazole, methylamine, ethylamine,
5 n-propylamine, isopropylamine, n-butylamine, n-pentylamine,
isoamylamine, cyclohexylamine, aniline, toluidine,
ethylenediamine, diethylenetriamine, triethylenetetramine,
tetraethylenepentamine, propylenediamine,
N-methylpropylamine, N-methyl-n-butylamine,
10 N-methyldodecylamine, N-methyl-n-octadecylamine,
N-ethyl-n-butylamine, N-ethyldodecylamine,
N-ethyl-n-octadecylamine, piperidine, piperazine and
morpholine.
LO0571
15 Of these nitrogen compounds, those nitrogen compounds
free from a structure formed by the bonding of a hydrogen atom
to a nitrogen atom are preferable, with examples including
trimethylamine, triethylamine, triisopropylamine,
tributylamine, trioctylamine, N,N-dimethylaniline,
20 N,N-dimethylbenzylamine,
N,N,N1,N'-tetramethylethylenediamne,
N,N,N',Nr',N"-pentamethyldiethylenetriamine,
N-methylpiperidine, N-methylmorpholine,
N,Nf-dimethylpiperazine, quinuclidine,
1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine,
N,N-dimethylaminopyridine, 1,5-diazabicyclo[4.3.0]-5-nonene,
1,8-diazabicyclo[5.4.0]-7-undecene, pyridine, quinoline,
pyrazine and triazine.
[0058]
Of these nitrogen compounds free from a structure formed
by the bonding of a hydrogen atom to a nitrogen atom, amine
compounds having a tertiary amine structure are preferable,
with examples including trimethylamine, triethylamine,
triisopropylamine, tributylamine, trioctylamine,
N,N-dimethylaniline, N,N-dimethylbenzylamine,
N,N,Nt,N'-tetramethylethylenediamine,
N,N,Nf ,N",Nr'-pentamethyldiethylenetriamine,
N-methylpiperidine, N-methylmorpholine,
N,N1-dimethylpiperazine, quinuclidine,
1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine,
N,N-dimethylaminopyridine, 1,5-diazabicyclo[4.3.0]-5-nonene
and 1,8-diazabicyclo[5.4.0]-7-undecene.
[0059]
Of these amine compounds with a tertiary amine structure
and free from a structure formed by the bonding of a hydrogen
atom to a nitrogen atom, those compounds composed solely of
hydrogen, carbon and nitrogen atoms are preferable, with
examples including trimethylamine, triethylamine,
triisopropyiamine, tributylamine, trioctylamine,
N,N-dimethylaniline, N,N-dimethylbenzylamine,
N,N,N',N1-tetramethylethylenediamine,
N,N,N',N",Nr'-pentamethyldiethylenetriamine,
5 N-methylpiperidine, N,N'-dimethylpiperazine, quinuclidine,
1,4-diazabicyclo[2.2.2]octane, hexamethylenetetramine,
N,N-dimethylaminopyridine, 1,5-diazabicyclo[4.3.0]-5-nonene
and 1,8-diazabicyclo[5.4.0]-7-undecene.
[0060]
10 From the point of view that the removal from target
cyclohexanone is easy, the nitrogen compound used in the
invention is preferably an amine having a widely different
boiling point from cyclohexanone. An amine compound having 1
to 3 nitrogen atoms in the molecule is preferable, and an amine
15 compound having one nitrogen atom in the molecule is more
preferable.
[0061]
Themolecular weight ofthe nitrogen compoundusedinthe
invention is preferably 50 to 500, and more preferably 50 to
20 400 because an amine having a widely different boiling point
from cyclohexanone may be easily removed from target
cyclohexanone.
[0062]
From the point of view that the removal from target
cyclohexanone is easy, trimethylamine, triethylamine,
triisopropylamine, tributylamine and trioctylamine are
particularly preferably used as the nitrogen compounds in the
invention.
5 [0063]
A desired nitrogen compound is an amine having a widely
different boiling point from cyclohexanone because it may be
easily removed from target cyclohexanone by a general
distillation operation. In the case where separation by
10 distillation is difficult, other removal methods such as
adsorption may be adopted.
[0064]
In the production process of the invention, the
hydrogenation reaction is performed in the presence of the
15 nitrogen compound described above. The nitrogen compound may
be the nitrogen compound added together with the raw material
phenol or may be the nitrogen compound attached to the surface
of the catalyst as a result of a contact with the palladium
catalyst before the hydrogenation reaction. Preferably, the
20 nitrogen compound is the nitrogen compound attached to the
surface of the catalyst as a result of a contact with the
palladium catalyst before the hydrogenation reaction.
LO0651
The nitrogen compound may be involved in the reaction
system together with t h e supported palladium c a t a l y s t by any
method without l i m i t a t i o n . The following t h r e e methods a r e
main examples whichmaybe s e l e c t e d a p p r o p r i a t e l y i n accordance
with c h a r a c t e r i s t i c s such as t h e b o i l i n g point and t h e
5 s o l u b i l i t y i n s o l v e n t s of t h e n i t r o g e n compound used. These
methods may be used s i n g l y , or two or more may be used i n
combination.
(1) The supported palladium c a t a l y s t t h a t has been
c o n t a c t e d w i t h the l i q u i d n i t r o g e n compound is used as the
10 c a t a l y s t i n t h e hydrogenation r e a c t i o n of phenol: When t h e
nitrogen compound is i n a l i q u i d form, t h e nitrogen compound
may be used i n t h e contact as such without a solvent; and when
t h e nitrogen compound is viscous l i q u i d or s o l i d , t h e compound
maybe a p p r o p r i a t e l y u s e d i n t h e formof a s o l u t i o n i n a s o l v e n t .
15 100661
The l i q u i d amine is p r e f e r a b l y brought i n t o contact with
t h e catalystbyimpregnatingthe c a t a l y s t with the l i q u i d amine
byabatchwise operation, orbycontinuouslypassingtheliquid
aminethroughthe c a t a l y s t p a c k e d i n a f i x e d b e d r e a c t o r . After
20 the c o n t a c t , t h e c a t a l y s t is separated from the l i q u i d amine
,
I and may be d r i e d using an a p p r o p r i a t e method such as nitrogen
gas flow, vacuum or heating.
100671
Although the nitrogen compound may be used i n any amount
without limitation, the amount is preferably 0.5 to 10 times
by weight the amount of the catalyst. If the amount is below
this range, the nltrogen compound may not have a sufficient
contact with the catalyst and may fail to improve the catalyst
5 performance sufficiently. The contact time is usually in the
I range of 1 minute to 10 hours, and preferably in the range of
10 minutes to 5 hours. The treatment temperature is usually
in the range of 0 to 20OoC, and preferably in the range of 20
10 (2) The supported palladium catalyst that has been
contacted with the gaseous nitrogen compound is used as the
catalyst in the hydrogenation reaction of phenol. The gaseous
i: amine is preferably brought into contact with the supported
palladium catalyst by vaporizing the nitrogen compound by
15 heating the compound to or above its boiling point under
operation conditions, andpasslngthe gas through the catalyst
packed in a fixed bed reactor. In this method, the gaseous
amine may be supplied together with an Inert gas such as, for
example, nitrogen, methane or ethane.
20 [0068]
Although the nitrogen compound may be used in any amount
without limitation, the amount is preferably 0.1 to 10 times
by weight the amount of the catalyst. The contact time is
usually in the range of 1 minute to 10 hours, and preferably
i n t h e range of 10 minutes t o 5 hours. The treatment
temperature is notparticularlylimitedas long as t h e n i t r o g e n
compound used is i n t h e gaseous s t a t e , but is u s u a l l y i n t h e
range of 0 t o 300°C, and p r e f e r a b l y i n t h e range of 50 t o 200°C.
5 [0069]
In the methods (1) and ( 2 ) , the n i t r o g e n compound is
brought i n t o contact with the supported palladium c a t a l y s t .
The r e s u l t a n t c a t a l y s t has t h e n i t r o g e n compound attached t o
t h e surface of t h e supported palladium c a t a l y s t .
10 (3) The nitrogen compound is continuously s u p p l i e d t o t h e
r e a c t o r while concurrently performing the hydrogenation
i
i r e a c t i o n of phenol. In t h i s case, t h e nitrogen compound is
'!
d e s i r a b l y gas under the hydrogenation r e a c t i o n c o n d i t i o n s .
The nitrogen compound may be supplied t o the r e a c t o r
15 i n d i v i d u a l l y o r as a s o l u t i o n i n t h e r a w m a t e r i a l phenol. When
t h e nitrogen compound is suppliedindividuallytothe r e a c t o r ,
t h e supply may take place i n t h e absence of solvents or the
compoundmaybe s u p p l i e d a s a s o l u t i o n i n a n a p p r o p r i a t e s o l v e n t .
' 1
' !
Although t h e nitrogen compound may be supplied i n any amount
20 without l i m i t a t i o n , the amount is p r e f e r a b l y i n the range of
0.005 t o 10 w t % , more p r e f e r a b l y i n t h e range of 0.005 t o 0.05
w t % , and s t i l l more p r e f e r a b l y i n the range of 0.01 t o 0.05
w t % r e l a t i v e t o t h e amount of t h e feed of phenol taken as 100
w t % . I f the amount is below t h i s range, t h e compound may f a i l
to improve the catalyst performance sufficiently. If the
amount exceeds the above range, the cost incurred to separate
the nitrogen compound from cyclohexanone produced may be
increased.
5 [0070]
(Hydrogenation reaction)
Inthe cyclohexanoneproductionprocess ofthe invention,
the hydrogenation reaction is performed in a gas phase usually
by supplyingagasmixture of phenol andhydrogen tothe reactor
10 in the presence of the supported palladium catalyst and the
nitrogen compound.
[0071]
In the invention, the hydrogenation reactlon of phenol
is usually performed at a temperature in the range of 100°c
15 to 30O0C, and preferably in the range of 150 to 250°C. At an
excessively low reaction temperature, the reaction rate may
be decreased. If, on the other hand, the reaction temperature
is excessively high, undesired side reactions may take place
to cause problems such as a decrease in cyclohexanone
20 selectivity and a decrease in catalytic activity due to the
buildup of high-boiling byproducts on the catalyst.
LO0721
Themolar ratio of hydrogenuse dinthe reaction tophenol
is usually in the range of 2 to 10, more preferably in the range
of 2.5 t o 8, and s t i l l more p r e f e r a b l y 3.0 t o 5.0 r e l a t i v e t o
1 mol of phenol.
[0073]
The amount of the supported palladium c a t a l y s t used i n
5 t h e invention is not p a r t i c u l a r l y l i m i t e d . For example, the
q u o t i e n t of t h e amount (weight) of supply per hour of the raw
m a t e r i a l (phenol) divided by t h e weight of t h e c a t a l y s t ( t h e
weight of t h e supported palladium c a t a l y s t ) , namely WHSV, i s
p r e f e r a b l y i n t h e range of 0 . 0 1 t o 10 h-l, and more p r e f e r a b l y
i n the range of 0.05 t o 5.0 h-l.
[0074]
Hydrogenmay contain gases which a r e i n e r t i n t h e r e a c t i o n ,
f o r example, methane, ethane and n i t r o g e n . On the other hand,
the contents of gases suchas carbondioxide andcarbonmonoxide
arepreferablyaslowaspossiblebecausethesegasesmayimpair
t h e c a t a l y t i c a c t i v i t y .
LO0751
The r e a c t i o n pressure is u s u a l l y i n t h e range of 0.08 t o
0.8 MPaA. In view of the f a c t t h a t t h e mixture of raw m a t e r i a l
phenol and hydrogen is t o be supplied t o t h e r e a c t o r as a gas
and a l s o i n c o n s i d e r a t i o n of o t h e r f a c t o r s such a s t h e pressure
r e s i s t a n c e of the r e a c t i o n a p p a r a t u s , it is p r e f e r a b l e t h a t
the pressure be s e t t o normal p r e s s u r e t o 0.3 MPaA.
LO0761
The reaction is carried out in a gas phase, and therefore
does notnecessarilyinvolve a solvent. However, a solvent may
be used as required for purposes of, for example, facilitating
the handling of phenol by mixing phenol with a solvent during
5 the raw material supply step to decrease the solidification
temperature of phenol, or decreasing the gasification
temperature of the mixture of phenol and hydrogen. In
particular, those solvents which exhibit high solubility for
phenol and do not inhibit the reaction and the purification
in a later stage are preferable, with examples including
hydrocarbon compounds such as cyclohexane, benzene and toluene
The solvents may be used singly, or two or more may be used
in combination.
[ 0 0 7 7 ]
In the production process of the invention, the reaction
may be performed in the presence of water. When the reaction
involves water, the water may be water attached to the surface
of the catalyst as a result of a contact of the palladium
catalyst with water before the hydrogenation reaction.
Alternatively, water may be supplied in addition to phenol and
hydrogen.
[ 0 0 7 8 ]
The contact of the catalyst with water, and the contact
of the catalyst with the nitrogen compound may take place at
the same time. In this case, for example, the simultaneous
contacts of the catalyst with water and of the catalyst with
the nitrogen compound may be attained by subjecting an aqueous
solution of the nitrogen compound or an aqueous dispersion of
the nitrogen compound to the aforementioned method (1) or (2)
for involving the nitrogen compound in the reaction system.
In this case, the nitrogen compound and water are usually used
in such amounts that the proportion of the nitrogen compound
is in the range of 0.1 to 50 wt% relative to the total of the
nitrogen compound and water talcen as 100 wt%.
[0079]
Whenwater is suppliedin addition topheno landhydrogen,
the amount ofthe supply of water is 10% or less, andpreferably
0.5 to 2.0 wt% or below relative to the amount of the feed of
phenol taken as 100 wt%.
[0080]
The state of water is not particularly limited, and water
may be supplied as a liquid or a gas. Preferably, water is
supplied in the form of a gas, namely, as water vapor.
[0081]
Supplying water is advantageous in that the phenol
conversion rate tends to be enhanced.
[0082]
Cyclohexanone that is the target product in the
production process of the invention may be separated from the
reaction liquid by known methods such as distillation,
extraction and adsorption. The unreacted raw material and the
solvent may be recovered and recycled to the reaction system.
5 [0083]
(Reaction apparatuses)
Because the hydrogenation reaction of phenol is highly
exothermic, the reaction heat needs to be continuously removed
with the progress of the reaction. Because of this fact and
10 inview ofthe characteristicthat the reaction inthe invention
is performed on the fixed bed catalyst in a gas phase, it is
I
preferable to use a multitubular reactor that is ~ a combination I of a heat exchanger and a reactor, or a radial flow reactor.
[0084]
15 Cyclohexanone obtained by the production process of the
invention may be used in various applications in which
cyclohexanone has been conventionally used. Because the
production process of the invention is economical and highly
efficient, the cyclohexanone obtained is preferably used for
20 the production of, for example, caprolactam. That is, the
process for producing caprolactam according to the present
invention is characterized in that the process uses
cyclohexanoneproducedbythe cyclohexanoneproductionprocess
described hereinabove.
EXAMPLES
[0085]
The present invention will be described in detail based
on examples and comparative examples hereinbelow. However,
5 the scope of the invention is not limited to such examples.
[0086]
(Continuous cyclohexanone synthesis reaction)
With a reaction apparatus illustrated in Fig. 1, the
hydrogenationreactionof phenol was performedinthe following
10 manner. The reaction apparatus shown in Fig. 1 had a facility
including supply pipes 1 and 2, a fixed bed reactor 3 filled
with a catalyst, and a gas-liquid separation tank 4. The
reactor 3 was continuously supplied with hydrogen or nitrogen
5 from the supply pipe 1, and with phenol or an amine 6 from
15 the supply pipe 2. The phenol and the amine were suppliedwith
use of a pump.
[0087]
The fixed bed reactor was a SUS 316 reaction tube 18 mm
in outer diameter, 15 mm in inner diameter and 600 mm in length
20 (athermometer well 3.18 mmin outer diameter) which was fitted
with a jacket (a SUS 304 oil jacket 18.4 mm in inner diameter
and 600 mm in length) containing a silicone oil as a heating
mediumll. The reaction product was condensed by being cooled
with a cooling medium 12 in a heat exchanger disposed at the
outlet of the reactor. A vent gas 10 such as excess hydrogen
was separated, and the reaction product 13 was sampled. The
components present in the reaction liquid (the reaction
product) were quantitatively determined by gas chromatography
5 analysis with respect to the reaction liquid, and the phenol
conversion rate and the selectivities for the components were
calculated.
[0088]
(Gas chromatography (GC) analysis)
Chromatograph: GC-2010 (manufactured by Shimadzu
Corporation)
Capillary column: TC-WAX (manufactured by GL Science,
inner diameter 0.32 mm x length 60 m)
Carrier gas: nitrogen (1.4 mL/min)
Measurement temperature conditions: The temperature was
increased from 100°C at 5"C/min. After reachlng 240°C, the
temperaturewas k e p t c o n s t a n t f o r 1 2 m i n u t e s andthemeasurement
was completed.
[0089]
Inlet temperature: 240°C
FID detector temperature: 240°C
Amount of injection: 1.0 pL
(Quantitative determination of components present in reactlon
llquid)
By an absolute calibrationmethod, GC calibration curves
were preparedbeforehandwith respect to phenol, cyclohexanone,
cyclohexanol, cyclohexylcyclohexanone, cyclohexane and
benzene. With reference to the information obtained, the
5 results of the GC measurement were analyzed by a common
procedure to quantitatively determine the contents of the
components present in the reaction liquid.
[0090]
[Example 11
10 The reaction tube was loaded with 4.0 g of 0.5 wt%
palladiumalumina pellets (HD-101manufacturedbyN.E. CHEMCAT
CORPORATION), thereby forming a catalyst-packed layer 8.
Glass beads having a diameter of 2 to 4 mm were placed on the
upper side and the lower side of the catalyst-packed layer in
15 amounts of 60 g and 15 g, respectively (catalyst-packed layers
7 and 9). SUSmeshes w e r e i n t e r p o s e d a t t h e b o u n d a r i e s t o avoid
mixing of the beads with the catalyst.
[0091]
The catalyst was pretreated with an amine by passing
20 triethylamine at 0.5 mL/min and nitrogen at 150 mL/min in the
downward direction from the top to the bottom of the reaction
tube while the temperature of the oil in the jacket was set
at 180°C. The triethylamine was supplied to th'e
catalyst-packed layer as a gas by being vaporized in the
preheating layer that was composed of the glass beads disposed
on the upper side of the catalyst-packed layer. The supply of
triethylamine was terminated after 5 minutes, and nitrogen was
supplied for another 1 hour. The pretreatment operation was
5 thus completed.
[0092]
The hydrogenation reaction of phenol was performed by
passing hydrogen at 4.3 NL/hr and phenol at 6.0 g/hr (the
hydrogen/phenol molar ratio was 4, and the WHSV was 1.5 h-l)
10 in the downward direction from the top to the bottom of the
I
I reaction tube. The phenol was suppliedtothe catalyst-packed
1
'1 layer in the form of a gas by being vaporized in the preheating
j/
layer. The temperature of the oil in the jacket was adjusted
so that the hotspot temperature in the catalyst layer would
15 be 180°C. In this process, the pressure at the inlet and the
outlet ofthe reaction tube was 0.00 MPaG. The reaction liquid
was analyzedby gas chromatographyto quantitatively determine
the components present in the reaction liquid, and the phenol
1 conversion rate and the selectivities for the components were ~
I 20 calculated. The changes with time in the phenol conversion
rate are described in Table 1 and Fig. 2. Further, Table 2
describes the phenol conversion rate and the selectivities for
the components after 1.5 hours of the supply of phenol.
[Example 21
The hydrogenation reaction of phenol was performedinthe
same manner as in Example 1, except that the amine was changed
to diethylamine. The changes with time in the phenol
5 conversion rate are described in Table 1 and Fig. 2. Further,
Table 2 describes the phenol conversion rate and the
selectivities forthe components after 1.5 hours ofthe supply
of phenol.
[0094]
10 [Example 31
The hydrogenation reaction of phenol was performedinthe
same manner as in Example 1, except that the amine was changed
to n-butylamine. The changes with time in the phenol
conversion rate are described in Table 1 and Fig. 2. Further,
Table 2 describes the phenol conversion rate and the
selectivities forthe components after 1.5 hours ofthe supply
of phenol.
[0095]
[Example 41
The hydrogenation reactionof phenol was performedinthe
same manner as in Example 1, except that the amine was changed
to pyridine. The changes with time in the phenol conversion
rate are described in Table 1 and Fig. 2. Further, Table 2
describes the phenol conversion rate and the selectivities for
the components after 1.5 hours of the supply of phenol.
[0096]
[Comparative Example 11
Thehydrogenation reaction of phenol was performedinthe
I 5 same manner as in Example 1, except that the pretreatment with
I
I
I the amine was omitted. The changes with time in the phenol
conversion rate are described in Table 1 and Fig. 2
[0097]
[Comparative Example 21
1
I 10 The hydrogenation reaction of phenol was performedinthe
I
same manner as in Comparative Example 1, except that the
hydrogen supply rate was changed to 2.9 NL/hr and the phenol
supplyratewaschangedto4.0g/hr ( h y d r o g e n / p h e n o l m o l a r r a t i o
= 4, WHSV = 1.0 h-I). The changes with time in the phenol
15 conversion rate are described in Table 1 and Fig. 2. Further,
Table 2 describes the phenol conversion rate and the
selectivities forthe components after 1.5 hours ofthe supply
of phenol.
[0098]
SF-2782
[ T a b l e 11
(Table 1) Changes in phenol conversion rate
Ex. 1 Ex. 2 Ex. 3 Ex. 4 I Comp. EX. 1 / comp. EX. 2 I Triethylamine / Diethylamine / N-butylamine I Pyridine I Amine None None
I
[ T a b l e 21
Selectivities 1)
observed in the high-boiling region on the GC chart was calculated assuming that the molar response factor relative to
cyclohexylcyclohexanone was 1.
Phenol 93.8
conversion
rate [mol%]
After 1.5 hr 97.1 82.0 92.3
76.6
98.0
61.8
96.4
After 5.5 hr 95.9 95.3 96.3 88.6
[0100]
[Example 51
The hydrogenation reactionof phenol was performedinthe
same manner as in Example 1, except that 4.0 g of the 0.5 wt%
5 palladium alumina pellets were replaced by 5.0 g of 0.5 wt%
potassium-0.5 wt% palladium alumina pellets. Table 3
describesthe phenol conversion rate and the selectivities for
the components after 11 hours of the supply of phenol.
[ 0101]
10 [Example 61
Thehydrogenation reaction of phenol was performedinthe
same manner as in Example 1, except that the 0.5 wt% palladium
alumina pellets were replaced by 0.5 wt% potassium-0.5 wt%
palladium alumina pellets and the triethylamine was replaced
15 bya 30 wt% aqueoustrimethylamine solution. Table 3 describes
the phenol conversion rate and the selectivities for the
components after 3.5 hours of the supply of phenol.
[Table 31
(Table 3 ) Phenol conversion rate and selectivities
I Ex. 5 Ex. 6
Phenol conversion rate [mol%l
1) The selectivities for cyclohexanone, cyclohexanol,
9 8 . 0
9 7 . 6
1 . 9 8
0.36
0.02
0.00
Selectivities
1 )
solution
9 9 . 4
9 6 . 0
2.77
1 . 2 6
0 . 0 2
0 . 0 0
Cyclohexanone
Cyclohexanol
Cyclohexylcyclohexanone
Cyclohexane and benzene
Other components
30 wt8 aqueous
Amine Triethylamine trimethylamine
cyclohexylcyclohexanone, cyclohexane and benzene indicate mol% values
determined from the concentrations calculated based on the GC calibration
curves. The selectivity for "other components" observed in the high-boiling
region on the GC chart was calculated assuming that the molar response factor
5 relative to cyclohexylcyclohexanone was 1.
Reference Signs List
I 1 . . . SUPPLY PIPE
!
2 . . . SUPPLY PIPE
10 3 . . . REACTOR
4 . . . GAS-LIQUID SEPARATOR
5 . . ' HYDROGEN OR NITROGEN
6 . . . PHENOL OR AMINE
7 . . . GLASS BEAD LAYER
15 8 . . . CATALYST-PACKED LAYER
9 . . . GLASS :I BEAD LAYER
:I 10 . . . VENT GAS
I!
!
' . 11 . . . HEATING MEDIUM
12 . . . COOLING MEDIUM
2 0 13 . . . REACTION PRODUCT (REACTION LIQUID)
4

CLAIMS
[Claim 11
A process for producing a cyclohexanone compound by
performing hydrogenation reaction of a phenol compound in a
5 gas phase in the presence of a palladium catalyst supported
on a carrier to produce the corresponding cyclohexanone
compound, wherein the hydrogenation reaction is carried out
in the presence of at least one nitrogen compound selected from
ammonia, amine compounds and heteroaromatic compounds.
10 [Claim 21
I A process for producing cyclohexanone by performing
hydrogenation reaction of phenol in a gas phase in the presence
of a palladium catalyst supported on a carrier to produce the
cyclohexanone, wherein the hydrogenation reaction is carried
15 out in the presence of at least one nitrogen compound selected
from ammonia, amine compounds and heteroaromatic compounds.
[Claim 31
The process for producing cyclohexanone according to
claim 2, wherein the nitrogen compound is free from a structure
20 formed by the bonding of a hydrogen atom to a nitrogen atom.
[Claim 41
The process for producing cyclohexanone according to
claim 3, wherein the nitrogen compound is an amine compound
having a tertiary amine structure.
[Claim 51
The process for producing cyclohexanone according to
claim 4, wherein the nitrogen compound is composed solely of
hydrogen, carbon and nitrogen atoms.
[Claim 61
The process for producing cyclohexanone according to any
one of claims 2 to 5, wherein the nitrogen compound is the
nitrogen compound attached to the surface of the catalyst as
a result of a contact with the palladium catalyst before the
hydrogenation reaction.
[Claim 71
The process for producing cyclohexanone according to any
one of claims 2 to 5, wherein the nitrogen compound is the
nitrogen compound addedtogether with the raw material phenol.
[Claim 81
The process for producing cyclohexanone according to
claim 7, wherein the amount of the supply of the nitrogen
compound is 0.005 to 0.05 wt% relative to the amount of the
feed of phenol taken as 100 wt%.
[Claim 91
The process for producing cyclohexanone according to
claim 7, wherein the amount of the supply of the nitrogen
compound is 0.01 to 0.05 wt% relative to the amount of the feed
of phenol taken as 100 wt%.
[Claim 10]
The process for producing cyclohexanone according to any
one of claims 2 to 9, wherein the carrier is porous alumina.
[Claim 11]
5 The process for producing cyclohexanone according to any
one of claims 2 to 10, whereinthe palladium catalyst supported
on the carrier further includes at least one metal element
selected from lithium, sodium, potassium, magnesium, calcium
and barium.
10. [Claim 12]
The process for producing cyclohexanone according to any
one of claims 2 to 11, wherein the reaction is performed in
the presence of water.
[Claim 13]
15 A process for producing caprolactam, wherein the process
uses cyclohexanone produced by the production process
described in any one of claims 2 to 12.
[Claim 14]
A catalyst obtained by bringing at least one nitrogen
2 0 compound selected from ammonia, amine compounds and
heteroaromatic compounds into contact with a palladium
catalyst supported on a carrier so as to attach the nitrogen
compound to the surface of the catalyst.[Claim 10]
The process for producing cyclohexanone according to any
one of claims 2 to 9, wherein the carrier is porous alumina.
[Claim 11]
5 The process for producing cyclohexanone according to any
one of claims 2 to 10, whereinthe palladium catalyst supported
on the carrier further includes at least one metal element
selected from lithium, sodium, potassium, magnesium, calcium
and barium.
10. [Claim 12]
The process for producing cyclohexanone according to any
one of claims 2 to 11, wherein the reaction is performed in
the presence of water.
[Claim 13]
15 A process for producing caprolactam, wherein the process
uses cyclohexanone produced by the production process
described in any one of claims 2 to 12.
[Claim 14]
A catalyst obtained by bringing at least one nitrogen
2 0 compound selected from ammonia, amine compounds and
heteroaromatic compounds into contact with a palladium
catalyst supported on a carrier so as to attach the nitrogen
compound to the surface of the catalyst.