EXHAUST GAS TREATING CATALYST AND METHOD OF MANUFACTURING THE
SAME
This application is based on Japanese patent application
No. 2015-193128, filed on September 30, 2015, the content of
which is incorporated hereinto by reference.
BACKGROUND
TECHNICAL FIELD
[0001]
This invention relates to an exhaust gas treating catalyst
and a method of manufacturing the same.
RELATED ART
[0002]
Temperature of exhaust gas may be lowered down to 80°C
when heat is recovered therefrom. There has therefore been a
need for a catalyst capable of demonstrating a high denitration
performance even when used for treating the exhaust gas at such
low temperatures (approximately 70 to 250°C).
[0003]
A known method of removing NOx in combustion gas relates
to catalytic cracking under the presence of ammonia as a
reducing agent. However, sulfur dioxide often contained in the
combustion gas may degrade the catalytic performance if the
decomposition temperature is 300°C or below, since sulfur
dioxide reacts with ammonia to form ammonium sulfate which can
deposit over the surface of catalyst.
3
[0004]
Also a poisoning substance influential to the combustion
gas treatment catalyst, if contained in the exhaust gas, is
likely to inactivate the combustion gas treatment catalyst.
Major poisoning substances include alkali metal and alkali earth
metal. For example, calcium has been known to be a major
component of dust contained in exhaust gas from cement
manufacturing plants (see JP-A-2013-49580).
SUMMARY
[0005]
It is therefore an object of this invention to provide an
exhaust gas treating catalyst capable of demonstrating a high
denitration performance even when used for purification of
exhaust gas at low temperatures (approximately 70 to 250°C), and
less likely to be inactivated even when used for exhaust gases
rich in poisoning components containing alkali metal or alkali
earth metal, and ammonium sulfate; and a method of manufacturing
the same.
[0006]
There has also been a need for a catalyst capable of
demonstrating a high denitration performance and heat
resistance, even when used for treatment of exhaust gases at 300
to 600°C, such as those exhausted from LNG-fueled turbine.
[0007]
4
After extensive investigations aimed at solving the
aforementioned problems, the present inventors worked out this
invention.
This invention includes (1) to (7) below.
(1) An exhaust gas treating catalyst satisfying conditions
(i) to (iii) below:
(i) having a specific surface area A (SAHg) of 25 to 50
m2/g when measured by mercury intrusion porosimetry over a
pore diameter range from 5 nm to 5400 nm;
(ii) showing a maximum peak within the range from 20 to 50
nm in the pore diameter distribution; and
(iii) when letting X denote the pore diameter (nm) at the
maximum peak, SAX denote specific surface area of pores
whose diameters range from X × 10-0.25 to X × 10+0.25 nm, and
SAtotal denote the total specific face area of the catalyst,
then showing ratio SAX/SAtotal in the range from 0.65 to
0.90,
and,
the exhaust gas treating catalyst comprising a support, a
structure directing agent and an active metal component, and,
the support being composed of inorganic single oxide
and/or inorganic composite oxide, which is at least one species
selected from the group comprising of titanium oxide and
titanium composite oxide.
(2) The exhaust gas treating catalyst according to (1),
wherein the support includes the inorganic single oxide composed
of TiO2, and/or the inorganic composite oxide composed of Ti,
5
and at least one species selected from the group comprising of
W, Mo, Si and V.
(3) The exhaust gas treating catalyst according to (1) or
(2), wherein the active metal component is at least one species
selected from the group comprising of vanadium, molybdenum,
manganese, lanthanum, yttrium and cerium.
(4) The exhaust gas treating catalyst according to any one
of (1) to (3), wherein the structure directing agent is a
compound containing silicon and/or calcium.
(5) A method of manufacturing the exhaust gas treating
catalyst described in any one of (1) to (4), the method
includes:
(a) dehydrating and then calcining a Ti-containing slurry,
or a slurry containing Ti, and at least one species selected
from the group comprising of W, Mo, Si and V, to obtain a raw
inorganic single oxide composed of TiO2, or, a raw inorganic
composite oxide composed of Ti, and at least one species
selected from the group comprising of W, Mo, Si and V; and
(b) mixing the raw inorganic single oxide and/or raw
inorganic composite oxide obtained in (a) with a compound
containing silicon and/or calcium and an active metal component,
and then extruding, drying and calcining the mixture.
(6) The method of manufacturing the exhaust gas treating
catalyst according to (5),
wherein, in step (b) and subsequent to extruding of the
mixture, the mixture is dried while reducing the humidity of
6
environment from 90% or above, down to 30%, at a dehumidifying
speed of 0.20 to 0.97%/hr.
(7) A method of treating exhaust gas using the exhaust gas
treating catalyst described in any one of (1) to (4).
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, advantages and features of
this invention will be more apparent from the following
description of certain preferred embodiments taken in
conjunction with the accompanying drawings, in which:
[0008]
FIG. 1 is a schematic perspective view illustrating a
preferred example of a honeycomb structure;
FIG. 2 is a pore diameter distribution chart of a catalyst
in Example 1;
FIG. 3 is a pore diameter distribution chart of a catalyst
in Example 2;
FIG. 4 is a pore diameter distribution chart of a catalyst
in Example 3;
FIG. 5 is a pore diameter distribution chart of a catalyst
in Example 4; and
FIG. 6 is a pore diameter distribution chart of a catalyst
in Comparative Example 1.
DETAILED DESCRIPTION
The invention will be now described herein with reference
to illustrative embodiments. Those skilled in the art will
7
recognize that many alternative embodiments can be accomplished
using the teachings of this invention and that the invention is
not limited to the embodiments illustrated for explanatory
purposes.
[0009]

The exhaust gas treating catalyst of this invention will
be explained. Note that the exhaust gas treating catalyst of
this invention will hereinafter be referred to as “the catalyst
of this invention” or simply “catalyst”.
[0010]

The support in the catalyst of this invention will be
explained.
In the catalyst of this invention, the support is composed
of TiO2, inorganic composite oxide, or a mixture thereof.
[0011]
The inorganic composite oxide means a composite oxide
composed of Ti, and at least one species selected from the group
comprising of W, Mo, Si and V.
The oxide-equivalent concentration of W, Mo, Si and V in
the composite oxide is preferably 0.05 to 40% by mass in total,
and more preferably 0.1 to 20% by mass.
[0012]
The catalyst preferably contains 50 to 95% by mass, and
more preferably 70 to 95% by mass, of support composed of the
above-described mixture of inorganic single oxide and inorganic
8
composite oxide, or composed of each single component of these
materials.
[0013]
< Structure Directing Agent >
The catalyst contains the structure directing agent. By
using the structure directing agent, the prepared catalyst will
have a pore diameter distribution that is easily controllable
and sharp. It also becomes possible to easily control geometry
and directionality of the pore.
The structure directing agent is preferably an inorganic
structure directing agent, which is exemplified by carbon fiber,
ceramic fiber, glass fiber, synthetic fiber, and chops or
whiskers of these fibers. It is particularly preferable for the
structure directing agent to contain 3 to 20% by mass, and more
preferably 5 to 10% by mass, of a silicon- and/or calciumcontaining
compound, besides the above-described mixture of the
inorganic single oxide and inorganic composite oxide. Both of
crystalline and amorphous compounds may be used.
[0014]
The silicon- and/or calcium-containing compound possibly
contained in the structure directing agent are exemplified by
compounds having structures of MCM-41, MCM-48, SBA-15 and SBA-
16, porous silica (micelle-templated silica) (Langmuir, 16(2),
356 (2000)), amorphous materials such as glass fiber, and claybased
crystalline minerals such as montmorillonitic minerals.
[0015]
9
The structure directing agent may have any geometry
selected from fiber-like, pillar-like, spindle-like and platelike
forms.
[0016]

The active metal component in the catalyst of this
invention will be explained.
In the catalyst of this invention, the active metal
component is supported on the aforementioned support.
In the catalyst of this invention, the active metal
component is preferably at least one species selected from the
group comprising of tungsten, vanadium, molybdenum, manganese,
lanthanum, yttrium and cerium.
[0017]
The catalyst of this invention may contain 20% by mass or
less, preferably 15% by mass or less, more preferably 10% by
mass or less, and even more preferably 7% by mass or less of
component other than the aforementioned support and active metal
component. It is preferable for the catalyst of this invention
to be composed substantially of the aforementioned support, the
structure directing agent and the active metal component. Now
the phrase “composed substantially of” means that the catalyst
could contain impurities inevitably derived from the raw
materials or incorporated in the process of manufacturing, but
nothing else.
10
Such component other than the support, structure directing
agent and active metal component is exemplified by Cr, Fe, Co,
Ni, Cu, Ag, Au, Pd, Nd, In, Sn and Ir.
[0018]

The catalyst of this invention will be explained referring
to a honeycomb structure. Note that, besides the honeycomb
structure, also a column-like or pipe-like form is selectable as
the geometry of the catalyst of this invention.
[0019]
The catalyst of this invention preferably has a specific
surface area A (SAHg) of 25 to 50 m2/g, and more preferably 30 to
50 m2/g, when measured by mercury intrusion porosimetry over a
pore diameter range from 5 nm to 5400 nm.
[0020]
The mercury intrusion porosimetry is a sort of mercury
intrusion method implemented by using a porosimeter, and
typically by using any of known measuring instruments.
[0021]
The catalyst of this invention shows a maximum peak within
the range from 20 to 50 nm in a pore diameter distribution
chart. Letting X denote the pore diameter (nm) at the maximum
peak, SAX denote specific surface area of pores whose diameters
range from X × 0.562 (= 10-0.25) to X × 1.78 (= 10+0.25) nm, and
SAtotal denote the total specific surface area of the catalyst,
then ratio SAX/SAtotal falls in the range from 0.65 to 0.90. SAX
more preferably has a value of 25 to 30 m2/g.
11
Although the reason remains partially unclear, with
SAX/SAtotal value controlled within the range from 0.65 to 0.90,
diffusion of a reaction gas containing ammonia as a reducing
agent, and absorption of ammonia to an active site may
appropriately be balanced at low temperatures typically at 70 to
250°C, and this is supposed to be a basis of denitration
performance at low temperatures.
With SAX/SAtotal value controlled within the above-described
range, the catalyst can demonstrate a high denitration
performance even when used for purification of exhaust gas at
low temperatures typically at 70°C, and is less likely to be
inactivated even if it is used for an exhaust gas rich in
poisoning component containing alkali metal or alkali earth
metal (calcium, in particular), and ammonium sulfate.
[0022]
The catalyst of this invention can demonstrate a high
denitration performance, and also has a high heat resistance, at
the temperature range from 70 to 600°C or around.
[0023]

The catalyst of this invention preferably forms a
honeycomb-like structure in which the active metal component is
supported on the aforementioned support.
The honeycomb structure means a structure having a large
number of fine through-pores (cells) aligned in parallel. The
catalyst having such structure is typically used while being
tightly packed in a reaction tube. The cell geometry (cross12
sectional shape) includes hexagon, quadrilateral, triangle and
circle. The cell size (diameter) is usually referred to as
aperture, a wall between the adjacent cells is referred to as a
partition, and the center-to-center distance of the laterally or
vertically opposing walls of a single cell is referred to as
pitch.
[0024]
FIG. 1 shows a schematic perspective view of an exemplary
honeycomb structure of the catalyst of this invention.
In FIG. 1, the catalyst of this invention (1) has cells
(3) arranged in eight rows and eight columns, where each cell
has a quadrilateral cross-section. The size (diameter) of the
cell (3) is referred to as aperture (5) (width of opening), the
wall between the adjacent cells (3) is referred to as partition
(7), and the thickness of the partition (7) is referred to as
wall thickness (9). The faces in which the opening of the cell
(3) exposes are referred to as end faces (11), and the other
faces are referred to as side faces (13). The longitudinal size
of the honeycomb structure is denoted as length X.
[0025]

Next, a method of manufacturing the catalyst of this
invention will be explained.
The support used in the catalyst of this invention may be
manufactured according to the method disclosed, for example, in
JP-A-2004-41893 or JP-A-2005-021780.
13
The catalyst of this invention may be manufactured by a
method of obtaining a mixture after mixing the support or its
raw material with the active metal component or its raw
material, and then extruding the mixture into the honeycomb
structure typically by extrusion; or by a method of making a
honeycomb base impregnated and supported thereon, a support
component and an active component; or by a method of making a
support component, having the honeycomb structure, impregnated
and supported thereon an active component.
[0026]
The catalyst of this invention is preferably manufactured
by a method that includes the steps (a) and (b) below:
(a) dehydrating and then calcining a Ti-containing slurry,
or a slurry containing Ti, and at least one species selected
from the group comprising of W, Mo, Si and V, to obtain a raw
inorganic single oxide composed of TiO2, or, a raw inorganic
composite oxide composed of Ti, and at least one species
selected from the group comprising of W, Mo, Si and V; and
(b) mixing the raw inorganic single oxide or raw inorganic
composite oxide obtained in (a) with a compound containing
silicon and/or calcium and an active metal component, and then
extruding the mixture into a honeycomb structure, followed by
drying and calcining.
The individual steps of such preferred method of
manufacturing will be explained below.
[0027]

14
In Step (a), first, a Ti-containing slurry, or a slurry
containing Ti, and at least one species selected from the group
comprising of W, Mo, Si, and V, is obtained.
The slurry may be obtained by dissolving, for example, a
Ti-containing compound and additionally a compound containing W,
Mo, Si or V into water or other solvent, and then by controlling
pH with an acid or alkali, to thereby allow an oxide of Ti, and
additionally an oxide of W, Mo, Si or V to deposit. After the
deposition, the oxides are preferably ripened at 20 to 98°C for
0.5 to 24 hours.
[0028]
The Ti-containing compound is preferably titanium sulfate
obtained in the form of solution, or metatitanic acid, both
obtainable in the process of manufacturing titanium dioxide
based on the sulfuric acid method.
[0029]
The W-containing compound is exemplified by tungstencontaining
nitrogen compounds such as ammonium paratungstate,
ammonium metatungstate, ammonium phosphotungstate and ammonium
tetrathiotungstate; tungsten-containing sulfur compounds such as
tungsten disulfide and tungsten trisulfide; tungsten
hexachloride, tungsten dichloride, tungsten trichloride,
tungsten tetrachloride, tungsten pentachloride, tungsten
dichloride dioxide, and tungsten tetrachloride oxide.
[0030]
The Mo-containing compound is exemplified by molybdenumcontaining
nitrogen compounds such as ammonium paramolybdate,
15
ammonium metamolybdate, ammonium phosphomolybdate and ammonium
tetrathiomolybdate; molybdenum-containing sulfur compounds such
as molybdenum disulfide and molybdenum trisulfide; molybdenum
hexachloride, molybdenum dichloride, molybdenum trichloride,
molybdenum tetrachloride, molybdenum pentachloride, molybdenum
dichloride dioxide, and molybdenum tetrachloride oxide.
[0031]
The Si-containing compound is exemplified by silica gel,
silicate solution, fumed silica, and silicon alkoxide.
[0032]
The V-containing compound is exemplified by vanadyl
sulfate, vanadyl oxalate, and ammonium metavanadate.
[0033]
When the W-, Mo-, Si- or V-containing compound is used in
addition to the Ti-containing compound, the ratio of consumption
of the Ti-containing compound and the W-, Mo-, Si- or Vcontaining
compound is not specifically limited. The ratio per
100% by mass of TiO2 (all Ti is assumed to stoichiometrically
form TiO2) is preferably controlled to 3 to 20% by mass.
[0034]
The thus obtained slurry is then dehydrated and calcined.
Method of dehydration is not specifically limited, and may
be implemented typically by any of known methods, and more
specifically by centrifugation or the like.
Method of calcining is not specifically limited, and may
be implemented by any of known methods, and more specifically by
using a calcining furnace of the like. The calcining
16
temperature is typically 110°C or above (preferably 300°C or
above), and 700°C or below.
A cake obtained after dehydration may be dried before
calcining. The drying may be implement by any or known methods,
and more specifically by using an electric drying apparatus.
The drying temperature is typically 30 to 200°C.
[0035]
By employing such step (a), the Ti-containing slurry, or,
the raw inorganic composite oxide containing Ti, and at least
one species selected from the group comprising of W, Mo, Si and
V, may be obtained.
[0036]

In Step (b), the raw inorganic single oxide or the raw
inorganic composite oxide obtained in Step (a), a silicon and/or
calcium-containing compound, and an active metal component are
mixed, preferably together with water added thereto.
Although the ratio of mixing is not specifically limited,
the ratio of the raw inorganic single oxide or raw inorganic
composite oxide, relative to the total of the raw inorganic
single oxide or raw inorganic composite oxide, the silicon
and/or calcium-containing compound, the active metal component,
and water ((raw inorganic single oxide or raw inorganic
composite oxide)/( raw inorganic single oxide or raw inorganic
composite oxide + silicon and/or calcium-containing compound +
active metal component + water) × 100) is preferably 10 to 70%
by mass.
17
The ratio of silicon and/or calcium-containing compound
((silicon and/or calcium-containing compound)/( raw inorganic
single oxide or raw inorganic composite oxide + silicon and/or
calcium-containing compound + active metal component + water) ×
100) is preferably 15% by mass or smaller.
The ratio of the active metal component (active metal
component/( raw inorganic single oxide or raw inorganic
composite oxide + silicon and/or calcium-containing compound +
active metal component + water) × 100) is preferably 5% by mass
or smaller.
[0037]
When the raw inorganic single oxide or raw inorganic
composite oxide, the silicon and/or calcium-containing compound,
and the active metal component are mixed, together with water
added thereto, a extruding auxiliary may further be added and
mixed.
[0038]
The extruding auxiliary may be any of known substances,
and is specifically exemplified by organic substances such as
polyethylene oxide, crystalline cellulose, glycerin and
polyvinyl alcohol.
[0039]
The thus obtained mixture is then extruded typically by
using a known extruding machine typically into a honeycomb form,
and then calcined. The extrusion is preferably followed by
drying.
[0040]
18
Method of drying is preferably implemented after the
extruding, while reducing the humidity of environment from 90%
or above, down to 30%, at a dehumidifying speed of 0.20 to
0.97%/hr. The drying may specifically be implemented by using a
temperature/humidity controlled oven or the like. The drying
speed is typically set to 30 to 200°C.
[0041]
If the dehumidifying speed is faster than 0.97%/hr, the
extrusion may crack, and the strength thereof may be nondurable
against practical use.
[0042]
If the dehumidifying speed is slower than 0.20%/hr, the
productivity may be degraded, suggesting that such speed may be
not practical.
[0043]
Method of calcining is not specifically limited, and may
be implemented typically by using any of known methods, and more
specifically by using a calcining furnace or the like. The
calcining temperature is typically set to 400 to 700°C.
[0044]
By employing such method of manufacturing according to
this invention, the catalyst of this invention may be obtained.

[0045]
The catalyst of this invention may suitably be used as a
catalyst for treating exhaust gases from thermal power plant,
19
cement plant, incineration plant, glass melting furnace, and
coke oven for iron and steel making.
[0046]
The catalyst of this invention is also applicable to
apparatuses for decomposing and removing organochlorine
compounds (dioxin, etc.) if contained in the exhaust gases.
[0047]
The catalyst of this invention is also applicable to
apparatuses for halogenating mercury if contained in the exhaust
gases.
EXAMPLES
[0048]
This invention will now be explained referring to
Examples. This invention is not limited to these Examples.
[0049]
[Raw Preparation 1 (Raw Ti Oxide: Raw TiO2-1)]
A metatitanic acid slurry (from Ishihara Sangyo Kaisha,
Ltd.) was placed in a mixer equipped with a condenser, a 35%-bymass
H2O2 water was added thereto so that 9 parts by mass of H2O2
would be contained per 90 parts by mass of TiO2, a 25%-by-mass
ammonia water was gradually added to the mixture so as to attain
pH9.0, and the mixture was then thoroughly stirred at 40°C for 3
hours for isothermal aging. A 25%-by-mass aqueous sulfuric acid
solution was gradually added to the mixture so as to attain
pH2.0, the mixture was thoroughly stirred at 40°C for one hour,
a 25%-by-mass ammonia water was gradually added thereto so as to
20
attain pH7.5, and the mixture was thoroughly stirred at 40°C for
3 hours for isothermal aging. The obtained slurry was
dehydrated and washed, and the obtained dehydrated cake was
dried at 110°C and then calcined at 150°C, to obtain raw Ti
oxide-1.
[0050]
[Raw Preparation 2 (Raw Ti Oxide: Raw TiO2-2)]
A metatitanic acid slurry (from Ishihara Sangyo Kaisha,
Ltd.) was placed in a mixer equipped with a condenser, a 25%-bymass
ammonia water was added thereto so as to attain pH7.5 or
above, and the mixture was thoroughly stirred at 60°C for 3
hours for isothermal aging. The obtained slurry was dehydrated
and washed, and the obtained dehydrated cake was dried at 110°C
and then calcined at 600°C, to obtain raw Ti oxide-2.
[0051]
[Raw Preparation 3 (Raw Ti-W-V: Raw TiO2-5% by mass WO3-4.35% V2O5
Composite Oxide)]
A metatitanic acid slurry (from Ishihara Sangyo Kaisha,
Ltd.) was placed in a mixer equipped with a condenser, a 35%-bymass
H2O2 water was added thereto so that 8.9 parts by mass of
H2O2 would be contained per 88.5 parts by mass of TiO2, ammonium
paratungstate (from Japan New Metals Co., Ltd.) was added
thereto so that 5 parts by mass of WO3 would be contained per
88.85 parts by mass of TiO2, vanadyl sulfate (from Shinko
Chemical Co., Ltd.) was further added thereto so that 6.15 parts
by mass of V2O5 would be contained per 88.85 parts by mass of
TiO2, a 25%-by-mass ammonia water was added thereto so as to
21
attain pH7.5 or above, and the mixture was thoroughly stirred at
60°C for 3 hours for isothermal aging. The obtained slurry was
dehydrated and washed, and the obtained dehydrated cake was
dried at 110°C and then calcined at 400°C, to obtain raw Ti-W-V
composite oxide A. Next, a metatitanic acid slurry (from
Ishihara Sangyo Kaisha, Ltd.) was placed in a mixer equipped
with a stirrer, raw Ti-W-V composite oxide A was added thereto
so that 70 parts by mass of raw Ti-W-V composite oxide A would
be contained per 30 parts by mass of TiO2 derived from the
metatitanic acid slurry, a 25%-by-mass ammonia water was further
added thereto so as to attain pH7.2, and the mixture was
thoroughly stirred at 40°C for 3 hours for isothermal aging.
The obtained slurry was dehydrated and washed, and the obtained
dehydrated cake was dried at 110°C and then calcined at 600°C,
to obtain raw Ti-W-V composite oxide.
[0052]
[ Raw Preparation 4 (Raw Ti-Mo-Si: Raw TiO2-5% by mass MoO3-10%
by mass SiO2 Composite Oxide)]
A metatitanic acid slurry (from Ishihara Sangyo Kaisha,
Ltd.) was placed in a mixer equipped with a condenser, a 35%-bymass
H2O2 water was added so that 10 parts by mass of H2O2 would
be contained per 90 parts by mass of TiO2, ammonium
paramolybdate was further added so that 5 parts by mass of MoO3
would be contained per 85 parts by mass of TiO2, silica gel (S-
20L, from JGC Catalysts and Chemicals Co., Ltd.) was further
added so that 10 parts by mass of SiO2 would be contained per 85
parts by mass of TiO2, and additionally a 25%-by-mass ammonia
22
water was gradually added thereto so as to attain pH7.2, and the
mixture was thoroughly stirred at 40°C for 24 hours for
isothermal aging. The obtained slurry was dehydrated and
washed, and the obtained dehydrated cake was dried at 110°C and
then calcined at 500°C, to obtain raw Ti-Mo-Si composite oxide.
[0053]
[Raw Preparation 5 (Raw Ti-Si: Raw TiO2-20% by mass SiO2
Composite Oxide]
A titanyl sulfate solution in sulfuric acid (prepared by
dissolving TM crystal from Tayca Corporation into water) was
placed in a mixer equipped with a condenser, a 35%-by-mass H2O2
water was added thereto so that 8 parts by mass of H2O2 would be
contained per 80 parts by mass of TiO2, silica gel (S-20L, from
JGC Catalysts and Chemicals Co., Ltd.) was further added so that
20 parts by mass of SiO2 would be contained per 80 parts by mass
of TiO2, and additionally a 32.5%-by-mass urea water was added
so that 27 parts by mass of urea could be contained per 80 parts
by mass of TiO2, the mixture was then heated to 95°C, and
thoroughly stirred for 12 hours for aging. The obtained slurry
was dehydrated and washed, and the obtained dehydrated cake was
dried at 110°C and then calcined at 500°C, to obtain raw Ti-Si
composite oxide.
[0054]

[0055]
[Example 1]
23
To 22.7 kg of raw Ti oxide-1 obtained as described above,
added were 1.285 kg of ammonium metavanadate (from Shinko
Chemical Co., Ltd.), 920 g of ammonium paramolybdate (from Taiyo
Koko Co., Ltd.), 1.25 kg of glass fiber, 2.10 kg of 25% by mass
ammonia water and additional water, 125 g of polyethylene glycol
(PEG-20000, from DKS Co., Ltd.), and 125 g of crystalline
cellulose (Ceolus TG-101). The mixture was kneaded in a mixer
so as to adjust the water content to 30% by mass, and then
extruded into a honeycomb extrusion. The obtained extrusion was
dried in an environment whose humidity was gradually reduced
from 90% down to 30% over 3 days (equivalent to a dehumidifying
speed of 0.83%/hr), and whose temperature was gradually elevated
from 40°C up to 60°C over 3 days. The extrusion was then
calcined at 500°C for 3 hours to obtain a catalyst. The
obtained honeycomb-like catalyst was found to have a thickness
of partition of 0.50 mm, an aperture of 3.20 mm, and an outer
diameter of 75 mm.
[0056]
[Comparative Example 1]
To 24.7kg of raw Ti oxide-2 obtained as described above,
added were 1.285 kg of ammonium metavanadate (from Shinko
Chemical Co., Ltd., 2.30 kg of a 25%-by-mass ammonia water and
additional water, 125 g of polyethylene glycol (PEG-20000, from
DKS Co., Ltd.), and 125 g of crystalline cellulose (Ceolus TG-
101). The mixture was kneaded in a mixer so as to adjust the
water content to 30% by mass, and then extruded into a honeycomb
extrusion. The extrusion was dried under the drying conditions
24
same as described in Example 1, and then calcined at 500°C for 3
hours, to obtain a honeycomb-like catalyst having a thickness of
partition of 0.50 mm, an aperture of 3.20 mm, and an outer
diameter of 75 mm.
[0057]
[Example 2]
To 23.7 kg of raw Ti-W-V composite oxide obtained as
described above, added were 1.02 kg of lanthanum nitrate
hexahydrate, 1.28 kg of yttrium nitrate hexahydrate, 1.25 kg of
glass fiber, 2.10 kg of a 25%-by-mass ammonia water and
additional water, 125 g of polyethylene glycol (PEG-20000, from
DKS Co., Ltd.), and 125 g of crystalline cellulose (Ceolus TG-
101). The mixture was kneaded in a mixer so as to adjust the
water content to 30% by mass, and then extruded into a honeycomb
extrusion. The extrusion was dried under the drying conditions
same as described in Example 1, and then calcined at 500°C for 3
hours, to obtain a honeycomb-like catalyst having a thickness of
partition of 0.50 mm, an aperture of 3.20 mm, and an outer
diameter of 75 mm.
[0058]
[Example 3]
To 22.7 kg of raw Ti-Mo-Si composite oxide obtained as
described above, added were 4.52 kg of a 50%-by-mass aqueous
manganese nitrate solution, 1.89 kg of cerium (III) nitrate
hexahydrate, 1.25 kg of activated clay, 2.10 kg of a 25%-by-mass
ammonia water and additional water, 125 g of polyethylene glycol
(PEG-20000, from DKS Co., Ltd.), and 125 g of crystalline
25
cellulose (Ceolus TG-101). The mixture was kneaded in a mixer
so as to adjust the water content to 30% by mass, and then
extruded into a honeycomb extrusion. The extrusion was dried
under the drying conditions same as described in Example 1, and
then calcined at 500°C for 3 hours, to obtain a honeycomb-like
catalyst having a thickness of partition of 0.50 mm, an aperture
of 3.20 mm, and an outer diameter of 75 mm.
[0059]
[Example 4]
A catalyst was obtained in the same way as described in
Example 1, except that again 22.7 kg of raw Ti-Si composite
oxide was used.
[0060]
[Comparative Example 2]
The mixture was extruded into a honeycomb extrusion in the
same way as in Example 2, and the obtained extrusion was dried
in an environment whose humidity was rapidly reduced from 90%
down to 30% in one day (equivalent to a dehumidifying speed of
2.5%/hr), and whose temperature was rapidly elevated from 40°C
up to 60°C in one day. The resultant honeycomb extrusion was
found to produce a lot of cracks, and could not yield a sample.
[0061]
[Test Example 1] Measurement of Specific Surface Area by
Mercury Intrusion Porosimetry
The individual catalysts obtained in Examples and
Comparative Examples were analyzed for specific surface area by
26
mercury intrusion porosimetry over a pore diameter range from 5
nm to 5400 nm.
Mercury intrusion porosimeter for measuring specific surface
area: PoreMaster, from Quantachrome Instruments
Measurement conditions for specific surface area using mercury
intrusion porosimeter: Pretreatment at 300°C for 1 hour, mercury
intrusion angle = 130°, surface tension = 473 erg/cm2
[0062]
From the entire distribution patterns of the specific
surface area of the individual catalysts measured by mercury
intrusion porosimetry over the pore diameter range from 5 nm to
5400 nm, those corresponding to the pore diameter range from 5
nm to 500 nm were extracted and shown in FIG. 1 to FIG. 5.
There were no identifiable peak of specific surface area beyond
500 nm.
[0063]
[Test Example 2] Accelerated Degradation Test of Catalyst using
CaCl2 Solution Spray and Ammonium Sulfate
Each of the catalysts obtained in Examples and Comparative
Examples was cut into a size of four cells × four cells × 107 mm
(length) (thickness = 0.50 mm, aperture = 3.20 mm), set in a
quartz reaction tube, and the denitration performance of
catalyst in the fresh state was measured. Now the denitration
ratio may be determined by the equation below, using the
contents of nitrogen oxides (NOx) in the gas before and after
brought into contact with the catalyst. The NOx contents were
27
measured using a chemiluminescent NOx analyzer (ECL-88AO, from
Anatec Yanaco Corporation).
Denitration Ratio (%) = {(NOx in uncontacted gas (ppm by volume)
– NOx in contacted gas (ppm by volume))/NOx in uncontacted gas
(ppm by volume)} × 100
The calculated initial denitration ratio was denoted as
η0(%). Also reaction rate constant k0 (= ― AV × ln(1-η0/100)) was
calculated.
A nozzle for spraying a CaCl2 solution was then attached to
the quartz reaction tube, and the CaCl2 solution was applied to
the catalyst from the upstream thereof. The nozzle was located
300 mm away from the upstream end face of the quartz reaction
tube. The CaCl2 solution had a concentration of 0.1% by mass,
and sprayed for 48 hours. After spraying the CaCl2 solution, the
denitration performance of the catalyst was measured again.
Using the thus determined degraded denitration ratio η(%), k =
―AV × ln(1-η/100) was calculated. k/k0 was then calculated and
used for comparison of denitration performance with the fresh
catalyst. Both of measurement of the performance and spraying
of the CaCl2 solution were conducted at 130°C. Measurement
conditions are listed below.
Conditions for Measuring Activity
Reaction temperature = 130°C, SV = 3000 (1/h), gas flow
rate = 0.075 (Nm3/h), AV = 3.30 (Nm3/m2h), NO = 180 (ppm by
volume), NH3 = 180 (ppm by volume), SO2 = 40 (ppm by volume), O2
= 7% by volume, H2O = 10% by volume, N2 = balance
Conditions for Accelerated Degradation Test
28
SV = 3000 (1/h), gas flow rate = 0.075 (Nm3/h), AV = 3.30
(Nm3/m2h), NO = 0 (ppm by volume), NH3 = 0 (ppm by volume), SO2 =
1000 (ppm by volume), O2 = 7% by volume, H2O = 10% by volume (as
CaCl2 solution), N2 = balance
[0064]
Results are shown in Table 1. As compared with the
catalyst of Comparative Example 1, the catalysts of Examples 1
to 4 were found to retain high levels of activity even after
being sprayed with the CaCl2 solution.
[0065]
[Test Example 3] Low Temperature Denitration Test
Each of the catalysts obtained in Examples and Comparative
Examples was cut into a size of four cells × four cells × 107 mm
(length) (thickness = 0.50 mm, aperture = 3.20 mm), set in a
quartz reaction tube, and low-temperature denitration
performance was measured.
The denitration ratio was determined by the equation
described above, using NOx contents in the gas before and after
brought into contact with the catalyst. The NOx contents were
measured using a chemiluminescent NOx analyzer (ECL-88AO, from
Anatec Yanaco Corporation).
[0066]
Conditions for measuring low–temperature denitration
performance are listed below.
Reaction temperature = 110°C, superficial velocity (SV) =
3000 hr-1
29
Model gas composition: NOX = 180 ppm by volume, NH3 = 180
ppm by volume, O2 = 7% by volume, H2O = 10% by volume, N2 =
balance
[0067]
[Test Example 4] Denitration Test
Each of the catalysts obtained in Examples and Comparative
Examples was cut into a size of four cells × four cells × 272 mm
(length) (thickness = 0.50 mm, aperture = 3.20 mm), set in a
quartz reaction tube, and denitration performance was measured.
The denitration ratio was determined by the equation
described above, using NOx contents in the gas before and after
brought into contact with the catalyst. The NOx contents were
measured using a chemiluminescent NOx analyzer (ECL-88AO, from
Anatec Yanaco Corporation).
[0068]
Conditions for measuring low-temperature denitration
performance are listed below.
Reaction temperature = 350°C, superficial velocity (SV) =
29300 hr-1
Model gas composition: NOX = 180 ppm by volume, NH3 = 180
ppm by volume, O2 = 7% by volume, H2O = 10% by volume, N2 =
balance
[0069]
Results are shown in Table 1.
[0070]
[Table 1]
30
Unit Example 1 Comparative
Example 1 Example 2 Example 3 Example 4 Comparative
Example 2
TiO2-(1) % 88 0 0 0 0 42
TiO2-(2) % 0 96 0 0 0 0
TiO2-5%WO3-8%V2O5 % 0 0 92 0 0 50
TiO2-5%MoO3-10%SiO2 % 0 0 0 88 0 0
TiO2-20%SiO2 % 0 0 0 0 88 0
Si-Ca % 5
Glass fiber 0 5
Glass fiber
5
Activated clay
5
Glass fiber
5
Glass fiber
Active species 1 % 4
V2O5
4
V2O5
1.5
La2O3
4
MnO2
4
V2O5
1.5
La2O3
Active species 2 % 3
MoO3 0 1.5
Y2O3
3
CeO2
3
MoO3
1.5
Y2O3
Total SA(Hg): SAtotal m2/g 41.0 18.6 39.3 34.0 39.3 -
Peak position in pore
diameter distribution: X nm 24.1 27.7 28.7 39.1 27.7 -
Peak SA(Hg): SAx m2/g 27.4 11.7 30.2 25.1 34.6 -
SAx/SAtotal - 0.668 0.627 0.768 0.739 0.881 -
Exposure test (relative
activity) k/ko - 0.35 0.20 0.54 0.67 0.69 -
Denitration performance
at 110°C % 67.31 59.94 75.9 73.33 79.31 -
Denitration performance
at 350°C % 91.62 89.97 92.03 92.52 91.50 -
Remark -
Cracked due to
rapid drying.
Sampling not
possible.
[0071]
According to this invention, it becomes possible to
provide an exhaust gas treating catalyst capable of
demonstrating a high denitration performance even when used for
purification of exhaust gases at low temperatures (70 to 250°C
or around), and less likely to be inactivated even when used for
exhaust gases rich in poisoning components containing alkali
metal or alkali earth metal (calcium, in particular), and
ammonium sulfate.
31
It is apparent that this invention is not limited to the
above embodiment, and may be modified and changed without
departing from the scope and spirit of the invention.

CLAIMS
WHAT IS CLAIMED IS:
1. An exhaust gas treating catalyst satisfying conditions
(i) to (iii) below:
(i) having a specific surface area A (SAHg) of 25 to 50
m2/g when measured by mercury intrusion porosimetry over a
pore diameter range from 5 nm to 5400 nm;
(ii) showing a maximum peak within the range from 20 to 50
nm in the pore diameter distribution; and
(iii) when letting X denote the pore diameter (nm) at the
maximum peak, SAX denote specific surface area of pores
whose diameters range from X × 10-0.25 to X × 10+0.25 nm, and
SAtotal denote the total specific area of the catalyst, then
showing ratio SAX/SAtotal in the range from 0.65 to 0.90,
and,
the exhaust gas treating catalyst comprising a support, a
structure directing agent and an active metal component, and,
the support being composed of inorganic single oxide
and/or inorganic composite oxide, which is at least one species
selected from the group comprising of titanium oxide and
titanium composite oxide.
2. The exhaust gas treating catalyst according to Claim 1,
wherein the support comprises the inorganic single oxide
composed of TiO2, and/or the inorganic composite oxide composed
33
of Ti, and at least one species selected from the group
comprising of W, Mo, Si and V.
3. The exhaust gas treating catalyst according to Claim 1
or 2, wherein the active metal component is at least one species
selected from the group comprising of vanadium, molybdenum,
manganese, lanthanum, yttrium and cerium.
4. The exhaust gas treating catalyst according to any one
of Claims 1 to 3, wherein the structure directing agent is a
compound containing silicon and/or calcium.
5. A method of manufacturing the exhaust gas treating
catalyst described in any one of Claims 1 to 4, the method
comprising:
(a) dehydrating and then calcining a Ti-containing slurry,
or a slurry containing Ti, and at least one species selected
from the group comprising of W, Mo, Si and V, to obtain a raw
inorganic single oxide composed of TiO2, or, a raw inorganic
composite oxide composed of Ti, and at least one species
selected from the group comprising of W, Mo, Si and V; and
(b) mixing the raw inorganic single oxide and/or raw
inorganic composite oxide obtained in (a) with a compound
containing silicon and/or calcium and an active metal component,
and then extruding, drying and calcining the mixture.
34
6. The method of manufacturing the exhaust gas treating
catalyst according to Claim 5,
wherein, in step (b) and subsequent to extruding of the
mixture, the mixture is dried while reducing the humidity of
environment from 90% or above, down to 30%, at a dehumidifying
speed of 0.20 to 0.97%/hr.
7. A method of treating exhaust gas using the exhaust gas
treating catalyst described in any one of Claims 1 to 4.