U.S. patent application number 15/937942 was filed with the patent office on 2018-10-04 for selective catalytic reduction catalyst composition.
The applicant listed for this patent is FRIEDRICH-ALEXANDER-UNIVERSITAT ERLANGEN- NURNBERG, JOHNSON MATTHEY CATALYSTS (GERMANY) GMBH. Invention is credited to Juergen BAUER, Ralf DOTZEL, Joerg Werner MUENCH, Ralitsa PUROVA, Wilhelm SCHWIEGER, Thangaraj SELVAM, Ameen SHAHID.
Application Number | 20180280937 15/937942 |
Document ID | / |
Family ID | 58682555 |
Filed Date | 2018-10-04 |
United States Patent
Application |
20180280937 |
Kind Code |
A1 |
BAUER; Juergen ; et
al. |
October 4, 2018 |
SELECTIVE CATALYTIC REDUCTION CATALYST COMPOSITION
Abstract
A SCR catalyst composition comprises a SCR catalyst; and a
binder comprising a porous inorganic material, wherein the porous
inorganic material comprises a disordered arrangement of
delaminated layers, has a disordered porous structure, and has a
multimodal pore size distribution comprising at least a first modal
maximum having a macroporous or mesoporous pore size and a second
modal maximum having a microporous pore size. The SCR catalyst
composition can be manufactured using the method comprising the
steps of: (i) providing an inorganic material having a layered
structure; (ii) contacting the material with a cationic surfactant
to form a swollen material; (iii) agitating the swollen material to
form an agitated material; and (iv) calcining the agitated material
to recover a delaminated inorganic material, wherein an SCR
catalyst is mixed with the inorganic material prior to step
(iv).
Inventors: |
BAUER; Juergen; (Redwitz an
der Rodach, DE) ; DOTZEL; Ralf; (Redwitz an der
Rodach, DE) ; MUENCH; Joerg Werner; (Redwitz an der
Rodach, DE) ; PUROVA; Ralitsa; (Erlangen, DE)
; SCHWIEGER; Wilhelm; (Erlangen, DE) ; SELVAM;
Thangaraj; (Erlangen, DE) ; SHAHID; Ameen;
(Erlangen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNSON MATTHEY CATALYSTS (GERMANY) GMBH
FRIEDRICH-ALEXANDER-UNIVERSITAT ERLANGEN- NURNBERG |
Redwitz an der Rodach
Erlangen |
|
DE
DE |
|
|
Family ID: |
58682555 |
Appl. No.: |
15/937942 |
Filed: |
March 28, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 37/00 20130101;
B01J 23/30 20130101; B01D 2255/20769 20130101; B01J 37/0009
20130101; B01D 2255/20707 20130101; B01D 2255/40 20130101; B01J
29/763 20130101; B01D 2255/20738 20130101; F01N 13/16 20130101;
B01D 2255/30 20130101; B01J 29/049 20130101; B01J 35/04 20130101;
F01N 2610/02 20130101; B01D 2255/50 20130101; B01J 29/04 20130101;
B01J 23/72 20130101; F01N 3/2825 20130101; B01D 2255/20723
20130101; B01D 2255/9025 20130101; B01D 2255/20776 20130101; B01J
37/0207 20130101; B01J 37/08 20130101; B01J 21/16 20130101; B01J
37/343 20130101; B01D 53/9418 20130101; F01N 3/2066 20130101; B01J
37/04 20130101; B01D 2255/2096 20130101; B01J 21/18 20130101; B01D
53/8628 20130101 |
International
Class: |
B01J 23/30 20060101
B01J023/30; B01J 21/16 20060101 B01J021/16; B01J 35/04 20060101
B01J035/04; B01J 37/08 20060101 B01J037/08; B01J 37/04 20060101
B01J037/04; B01J 37/02 20060101 B01J037/02; B01J 37/00 20060101
B01J037/00; B01D 53/94 20060101 B01D053/94 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2017 |
GB |
1705241.6 |
Claims
1. A selective catalytic reduction (SCR) catalyst composition
comprising: a SCR catalyst; and a binder comprising a porous
inorganic material, wherein the porous inorganic material comprises
a disordered arrangement of delaminated layers, has a disordered
porous structure, and has a multimodal pore size distribution
comprising at least a first modal maximum having a macroporous or
mesoporous pore size and a second modal maximum having a
microporous pore size.
2. The SCR catalyst composition of claim 1, wherein the multimodal
pore size distribution is bimodal.
3. The SCR catalyst composition of claim 1, wherein a powder X-ray
diffraction pattern of the porous inorganic material obtained using
Cu K.alpha.radiation is devoid of peaks at 2.theta. values of
10.degree. or less.
4. The SCR catalyst composition of claim 1, wherein the first modal
maximum has a mesoporous and/or macroporous pore size.
5. The SCR catalyst of claim 1, wherein the delaminated layers are
delaminated silicate layers.
6. The SCR catalyst composition of claim 1, wherein the porous
inorganic material comprises one or more of: a clay mineral,
graphite, graphene, a layered silicate, a layered phosphate, a
layered zeolite, a layered double hydroxide, hydrotalcite, a
layered perovskite, attapulgite, sepiolite and vermiculite.
7. The SCR catalyst composition of claim 6, wherein the porous
inorganic material comprises a clay mineral comprising a
three-layered (2:1) clay mineral.
8. The SCR catalyst composition of claim 7, wherein the clay
mineral comprises bentonite.
9. The SCR catalyst composition of claim 1, wherein the porous
inorganic material is substantially non-pillared.
10. The SCR catalyst composition of claim 1, wherein the porous
inorganic material is functionalised with one or more of Cu, Fe,
Ce, Mn, V, Zn, Mo, Pt, Pd, Rh, Ir and Ni.
11. The SCR catalyst composition of claim 1, wherein the porous
inorganic material is functionalised with Cu and/or Fe.
12. The SCR catalyst composition of claim 1, wherein the SCR
catalyst comprises a zeolite.
13. The SCR catalyst composition of claim 1, wherein the SCR
catalyst comprises a titania and the porous inorganic material is
functionalised with V and/or Fe.
14. The SCR catalyst composition of claim 13, wherein the titania
comprises W, Si and/or Mo and the porous inorganic material is
functionalised with V.
15. The SCR catalyst composition of claim 1, wherein the porous
inorganic material comprises from 0.01 to 5 wt. % Fe.
16. The SCR catalyst composition of claim 1, wherein the SCR
catalyst composition is extrudable.
17. The SCR catalyst composition of claim 1 in the form of pellets
or a sheet or having a honeycomb structure.
18. An emission treatment system for treating a flow of a
combustion exhaust gas, the system comprising a source of
combustion exhaust gas in fluid communication with the SCR catalyst
composition of claim 1, and a source of nitrogenous reductant
arranged upstream of said SCR catalyst composition.
19. A method for the manufacture of a SCR catalyst composition, the
method comprising: (i) providing an inorganic material having a
layered structure; (ii) contacting the material with a cationic
surfactant to form a swollen material; (iii) agitating the swollen
material to form an agitated material; and (iv) calcining the
agitated material to recover a delaminated inorganic material,
wherein an SCR catalyst is mixed with the inorganic material prior
to step (iv).
20. The method of claim 19, wherein the cationic surfactant
comprises a carbon chain having at least 10 carbon atoms.
21. The method of claim 19, wherein step (ii) comprises mixing the
material and an aqueous solution of the cationic surfactant to form
a mixture, followed by storing the mixture for a period of from 1
to 3 days, wherein the storing is carried out at a temperature of
from 30 to 50.degree. C.
22. The method of claim 19, wherein the agitating comprises
sonication and/or the application of microwaves, wherein the
sonication comprises ultrasonication.
23. The method of claim 19, wherein step (iii) is carried out for a
period of from 1 to 4 hours, and/or at a temperature of from 15 to
35.degree. C.
24. The method of claim 19, further comprising contacting the
agitated material and/or delaminated inorganic material with a
solution of metal ions to incorporate at least some of the metal
ions into the agitated material and/or delaminated inorganic
material, the metal selected from one or more of Cu, Fe, Ce, Mn, V,
Zn, Mo, Pt, Pd, Rh, Ir and Ni.
25. The method of claim 19, further comprising forming the material
into a desired shape, wherein the forming comprises extrusion and
the desired shape comprises pellets or a sheet or a honeycomb
structure.
26. The method of claim 19, wherein the SCR catalyst composition
comprises a SCR catalyst; and a binder comprising a porous
inorganic material, wherein the porous inorganic material comprises
a disordered arrangement of delaminated layers, has a disordered
porous structure, and has a multimodal pore size distribution
comprising at least a first modal maximum having a macroporous or
mesoporous pore size and a second modal maximum having a
microporous pore size.
27. A method for the manufacture of a porous inorganic material,
the method comprising: (i) providing an inorganic material having a
layered structure; (ii) contacting the material with a cationic
surfactant to form a swollen material; (iii) agitating the swollen
material to form an agitated material; and (iv) calcining the
agitated material to recover a delaminated inorganic material.
28. A porous inorganic material comprising a disordered arrangement
of delaminated silicate layers, a disordered porous structure, a
pore size distribution comprising at least a first modal maximum
having a macroporous or mesoporous pore size and a second modal
maximum having a microporous pore size, the porous inorganic
material obtainable by the method of claim 27.
29. (canceled)
30. (canceled)
Description
[0001] The present invention relates to a selective catalytic
reduction (SCR) catalyst composition. In particular, the present
invention relates to a SCR catalyst composition having improved
catalytic activity.
[0002] Catalyst compositions typically comprise, inter alia,
particles of catalytic material held together with a binder.
Conventional binders may comprise, for example, a clay material.
The binder "binds" the catalyst composition together, and may serve
to hold the catalyst composition in a desired shape and/or provide
the catalyst composition with particular desired rheological
characteristics. As will be appreciated, the binder will affect the
overall characteristics of the catalyst composition. For example,
the porosity characteristics of the binder may affect the access of
gaseous species to catalytic sites within the catalyst composition.
One problem with conventional binders, such as conventional clays,
is that they exhibit limited, typically zero, catalytic activity.
Accordingly, when high levels of binder are required, the catalyst
composition may exhibit low catalytic activity per unit volume,
thereby requiring larger volumes of catalyst composition to provide
a desired catalytic effect or higher quantities of expensive
catalytically active components.
[0003] Hydrocarbon combustion in diesel engines, stationary gas
turbines, and other systems generates exhaust gas that must be
treated to remove nitrogen oxides (NO.sub.x), which comprises NO
(nitric oxide), NO.sub.2 (nitrogen dioxide) and N.sub.2O (nitrous
oxide), with NO being the majority of the NO.sub.x formed. NO.sub.x
is known to cause a number of health issues in people as well as
causing a number of detrimental environmental effects including the
formation of smog and acid rain. To mitigate both the human and
environmental impact from NO.sub.x in exhaust gas, it is desirable
to eliminate these undesirable components, preferably by a process
that does not generate other noxious or toxic substances.
[0004] Exhaust gas generated in lean-burn and diesel engines is
generally oxidative. Preferably, NO.sub.x needs to be reduced
selectively with a catalyst and a reductant in a process known as
selective catalytic reduction (SCR) that converts NO.sub.x into
elemental nitrogen (N.sub.2) and water. In an SCR process, a
gaseous reductant, typically anhydrous ammonia, aqueous ammonia, or
urea, is added to an exhaust gas stream prior to the exhaust gas
contacting the SCR catalyst. The reductant can be absorbed onto the
SCR catalyst and the NO.sub.x reduced as the gases pass through or
over the catalysed substrate.
[0005] Suitable catalysts for SCR known in the art include, for
example, V.sub.2O.sub.5/WO.sub.3 supported on TiO.sub.2 (see WO
99/39809) and transition metal exchanged zeolites (see U.S. Pat.
No. 4,961,917 and WO 2008/106519) or a mixture of the two (see WO
2014/027207). Active layered silicates, often referred to as
"pillared interlayered clays" (PILCs), have been investigated for
use as SCR catalysts (see, for example, EP 1727619, U.S. Pat. No.
6,521,559 and U.S. Pat. No. 5,415,850). PILCs are two-dimensional
zeolite-like materials with artificially configured layers that are
separated at controlled distances. PILCs are prepared by exchanging
the charge-compensating cations between clay layers with large
inorganic hydroxycations, which are polymeric or oligomeric hydroxy
metal cations formed by hydrolysis of metal oxides or salts. Upon
heating, the metal hydroxycations undergo dehydration and
dehydroxylation, forming stable clusters of metal oxides, or other
metal salts, which act as pillars keeping the thin silicate layers
separated. This may create interlayer space of molecular
dimensions. Oxides of metals such as, for example, titanium,
zirconium, aluminium, iron and chromium have been used as
"pillars". Due to their large pores and hydrothermal stability,
PILCs are considered to be potential replacements for zeolite SCR
catalysts. However, in comparison to conventional SCR catalysts,
such as zeolites, the SCR catalytic activity of PILCs is low.
[0006] Natkanski et al, Microporous and Mesoporous Materials 221
(2016) 212-219 describes methods for the manufacture of a PILC. The
methods are inefficient on an industrial scale, and also rely on
the use of the mineral laponite, which has only limited
availability.
[0007] U.S. Pat. No. 5,415,850 discloses certain pillared
interlayered clay (PILC) catalysts, specifically
Cr.sub.2O.sub.3-PILC, Fe.sub.2O.sub.3-PILC, TiO.sub.2-PILC,
ZrO.sub.2-PILC and Al.sub.2O.sub.3-PILC, for use in the selective
reduction (SCR) of nitrogen oxides (NO.sub.x) in exhaust gases in
the presence of ammonia. The catalysts are said to have a bimodal
pore structure for increased poison resistance and increased
reaction rates.
[0008] U.S. Pat. No. 6,475,944 discloses a V.sub.2O.sub.5/Ti-PILC
catalyst for removing NOx by using NH.sub.3 as a reducing agent in
the flue gas from an electric power plant and the like.
[0009] Accordingly, it is desirable to provide a SCR catalyst
composition exhibiting improved catalytic activity and which may be
manufactured more easily and/or to tackle at least some of the
problems associated with the prior art or, at least, to provide a
commercially useful alternative thereto.
[0010] According to a first aspect, there is provided a selective
catalytic reduction (SCR) catalyst composition comprising: [0011] a
SCR catalyst; and [0012] a binder comprising a porous inorganic
material, wherein the porous inorganic material comprises a
disordered arrangement of delaminated layers, has a disordered
porous structure, and has a multimodal pore size distribution
comprising at least a first modal maximum having a macroporous or
mesoporous pore size and a second modal maximum having a
microporous pore size.
[0013] The present disclosure will now be described further. In the
following passages different aspects/embodiments of the disclosure
are defined in more detail. Each aspect/embodiment so defined may
be combined with any other aspect/embodiment or aspects/embodiments
unless clearly indicated to the contrary. In particular, any
feature indicated as being preferred or advantageous may be
combined with any other feature or features indicated as being
preferred or advantageous. It is intended that the features
disclosed in relation to the product may be combined with those
disclosed in relation to the method and vice versa.
[0014] Furthermore, the term "comprising" as used herein can be
exchanged for the definitions "consisting essentially of" or
"consisting of". The term "comprising" is intended to mean that the
named elements are essential, but other elements may be added and
still form a construct within the scope of the claim. The term
"consisting essentially of" limits the scope of a claim to the
specified materials or steps and those that do not materially
affect the basic and novel characteristic(s) of the claimed
invention. The term "consisting of" closes the claim to the
inclusion of materials other than those recited except for
impurities ordinarily associated therewith.
[0015] In comparison to SCR catalyst compositions containing
conventional binders, it has been surprisingly found that the SCR
catalyst composition of the present invention may exhibit improved
SCR catalytic activity. Without being bound by theory, it is
considered that the improved catalytic activity is a result of
improved access to catalytic sites within the SCR catalyst
composition due to the porosity characteristics of the inorganic
material. Furthermore, the binder itself may exhibit SCR catalytic
activity. For example, the binder may exhibit increased catalytic
activity in comparison to a PILC. This may advantageously allow the
use of lower levels of SCR catalyst in comparison to conventional
SCR catalyst compositions to provide the same level of catalytic
activity.
[0016] In comparison to a PILC, the porous inorganic material may
have improved ability as a binder.
[0017] The SCR catalyst composition comprises a SCR catalyst and a
binder. The SCR catalyst composition may comprise, for example,
from 1 to 99 wt. % SCR catalyst and from 1 to 99 wt. % binder based
on the total amount of the SCR catalyst and binder, or from 10 to
90 wt. % SCR catalyst and from 10 to 90 wt. % binder, or from 60 to
80 wt. % SCR catalyst and from 20 to 40 wt. % binder. As will be
appreciated, the relative amounts of SCR catalyst and binder will
depend on the desired catalytic activity and rheology of the SCR
catalyst composition.
[0018] The SCR catalyst composition is typically in the form of a
blend of the SCR catalyst and binder.
[0019] The SCR catalyst composition may be in the form of, for
example, a washcoat. The washcoat may comprise, for example, one or
more fillers, and/or one or more processing aids, and/or water,
and/or one or more dopants.
[0020] Any suitable SCR catalyst may be employed. Suitable SCR
catalysts are known in the art.
[0021] The SCR catalyst and/or porous inorganic material may be in
the form of, for example, particles, e.g. a powder. The particles
(e.g. at least 95% of the particles) may have a longest dimension
of, for example, from 1 to 20 .mu.m. These longest dimensions refer
to the individual particles themselves rather than, for example,
agglomerates of particles. The longest dimension may be measured,
for example, using scanning electron microscopy (SEM). When the
particles are in the shape of a sphere, the longest dimension is
the diameter of the sphere.
[0022] The binder may function to hold the SCR catalyst composition
in a desired shape and/or to provide the SCR catalyst composition
with a desired rheology. The binder may advantageously render the
SCR catalyst composition extrudable. This may enable the SCR
catalyst composition to be more easily processed into a desired
shape, for example a honeycomb shape.
[0023] The porous inorganic material comprises a disordered
arrangement of delaminated layers, for example delaminated silicate
layers. This is in contrast to a PILC. In the porous inorganic
material, typically substantially all layers are delaminated. In
other words, typically the porous inorganic material does not
contain any stacked layers. The substantial absence of any stacked
layers may be observed, for example, via the use of powder X-ray
diffraction. The disordered arrangement of delaminated layers
contains substantially no long-range ordering of the layers. The
substantial absence of any long-range ordering of the layers may be
observed, for example, via the use of powder X-ray diffraction.
[0024] The porous inorganic material has a disordered pore
structure. This is in contrast to, for example, a zeolite or a
PILC, in which the pores are arranged in a repeating pattern. The
disordered pore structure means that the pores substantially do not
exhibit any long-range order. The substantial absence of any
long-range order may be observed, for example, via powder X-ray
diffraction.
[0025] The pore size distribution of the porous inorganic material
is determined using, for example, a nitrogen sorption technique or
mercury intrusion porosimetry (MIP). Such a technique is well known
in the art. The pore size distribution may have a number of peaks,
i.e. be multimodal, but at least has two peaks and preferably is
essentially a bimodal distribution, i.e. at least 80% (preferably
90%) by volume of the pores are associated with the two peaks.
Preferably substantially all of the pores are associated with the
two peaks. It is preferred that the first and second peaks are
relatively clearly defined, that is, the standard deviation from
the modal values (the highest points in each peak) is relatively
low. In relation to the pore size distribution, in accordance with
the IUPAC definition, the term "macroporous" means that the pore
diameter is greater than 50, the term "mesoporous" means that the
pore diameter is from 2 to 50 nm, and the term "microporous" means
that the pore diameter is less than 2 nm.
[0026] The porous inorganic material contains both macropores,
mesopores and micropores. The macropores, mesopores may be formed
between disordered delaminated layers, and the micropores may be
provided in the disordered delaminated layers themselves. Such a
structure is sometimes referred to as a "house of cards"
structure.
[0027] In a preferred embodiment, the multimodal pore size
distribution is bimodal. Substantially restricting the pores of the
porous inorganic material to being either: (i) macroporous,
mesoporous, or (ii) microporous may provide the SCR catalyst
composition with a high level of access to catalytic sites and a
high catalytic activity.
[0028] Preferably, the porous inorganic material is substantially
X-ray amorphous. By "X-ray amorphous" it is meant that a powder
X-ray diffraction pattern of the porous inorganic material obtained
using Cu K.alpha. radiation is devoid of peaks at 2.theta. values
of less than less than 20.degree. , typically less than 15.degree.
and preferably less than 10.degree. (e.g. from 2 to 10.degree.).
The powder X-ray diffraction pattern being "devoid" of such peaks
means that either such peaks cannot be observed in the powder X-ray
diffraction pattern, or that the intensity of such peaks is less
than 5% that of the most intense peak of the powder X-ray
diffraction pattern attributable to the porous inorganic material,
typically less than 1%. Without being bound by theory, it is
considered that such 2.theta. values may correspond to a large
d-spacing associated with a large unit cell derived from ordering
of layers. The powder X-ray diffraction pattern may, of course,
contain peaks at 2.theta. values of 10.degree. or higher, which may
be associated with, for example, order within the delaminated
layers themselves. In addition, a powder X-ray diffraction pattern
of the porous inorganic material may contain peaks corresponding to
impurities in the starting material. For example, when the starting
material is bentonite, the powder X-ray diffraction pattern may
contain peaks corresponding to impurities such as, for example,
quartz or cristobalite. When considering whether the powder X-ray
diffraction pattern of the porous inorganic material is "devoid" of
the peaks referred to above, it will be appreciated that peaks
corresponding to impurity phases are not counted.
[0029] The first modal maximum preferably has a macroporous and/or
mesoporous pore size. The presence of a high number of macropores
may increase the access of species to be treated (e.g. gaseous
species in an exhaust gas) to catalytic sites within the SCR
catalyst composition. A PILC cannot contain macropores and cannot
have a macroporous modal maximum.
[0030] The delaminated layers are preferably delaminated silicate
layers. Delaminated silicate layers are particularly suitable for
providing the above-mentioned pore size distribution.
[0031] The porous inorganic material preferably comprises one or
more of: a clay mineral, graphite, graphene, a layered silicate, a
layered phosphate, a layered zeolite, a layered double hydroxide,
(e.g. hydrotalcite), a layered perovskite, attapulgite, sepiolite
and vermiculite. Such species may be particularly suitable for
providing the above-mentioned pore size distribution and may be
particularly suitable for use as a binder.
[0032] The porous inorganic material preferably comprises a clay
mineral, more preferably a three-layered (2:1) clay mineral. In a
preferred embodiment, the clay mineral comprises bentonite. Such
materials may be particularly suitable for providing the
above-mentioned pore size distribution and may be particularly
suitable for use as a binder.
[0033] Preferably, the porous inorganic material is substantially
non-pillared. By "non-pillared" it is meant that the delaminated
layers are not separated by intercalated polymer chains or keggin
ions, for example via in situ polymerisation of monomers between
the layers (see, for example, Natkanski et al, Microporous and
Mesoporous Materials, 221 (2016) 212-219). The long-range order
provided by such pillars may be observed, for example, using powder
X-ray diffraction. In contrast to PILCs, the substantially
non-pillared porous inorganic material of the present invention may
be prepared more easily and at lower cost, since an in situ
polymerisation step is not required. Furthermore, the catalytic
activity, in particular SCR catalytic activity, may be increased in
comparison to PILCs. In addition, in comparison to PILCs, the
binding ability of the porous inorganic material may be improved.
Compared with a PILC, the porous inorganic material may have a
lower surface area and/or meso-/macro-porosity (a typical surface
area of .about.500 m.sup.2/g vs .about.150-200 m.sup.2/g). The
porous inorganic material may have a larger surface area and/or
meso-/macro-porosity in comparison to its corresponding parent clay
(typically .about.80-100 m.sup.2/g).
[0034] The porous inorganic material is preferably functionalised
with one or more of Cu, Fe, Ce, Mn, V, Zn, Mo, Pt, Pd, Rh, Ir and
Ni. By "functionalised" it is meant that one or more of these
elements have been incorporated into the porous inorganic material,
for example via ion exchange, impregnation or isomorphous
substitution. Functionalising the porous inorganic material with
such elements may serve to increase the catalytic activity of the
porous inorganic material.
[0035] In a preferred embodiment, the porous inorganic material is
functionalised with Cu and/or Fe. Such elements may serve to
increase the SCR catalytic activity of the porous inorganic
material. In this embodiment, the SCR catalyst preferably comprises
a zeolite, for example chabazite. The combination of a zeolite SCR
catalyst and a porous inorganic material functionalised with Cu
and/or Fe may result in the SCR catalyst composition exhibiting
particularly pronounced SCR catalytic activity.
[0036] The zeolite may be a small pore zeolite (a zeolite
containing a maximum ring size of 8 tetrahedral atoms) such as
chabazite (CHA). The zeolite may be a medium pore zeolite (a
zeolite containing a maximum ring size of 10 tetrahedral atoms)
such as ZSM-5 (MFI). The zeolite may be a large pore zeolite (a
zeolite having a maximum ring size of 12 tetrahedral atoms), such
as Beta (BEA). Small pore zeolites are preferred. The term
"zeolite" as used herein is intended to refer generally to a
molecular sieve rather than, for example, just an aluminosilicate
molecular sieve. In other words, the term "zeolite" may cover
materials other than aluminosilicates, such as, for example, SAPOs
and AIPOs. The zeolite (molecular sieve) is preferably selected
from the Framework Type Codes AEI, AFX, CHA, ERI, FER, BEA, MFI,
STT and LEV. AEI is particularly preferred. Such zeolites may
provide the composite material with high levels of SCR catalytic
activity. The zeolite is preferably an aluminosilicate zeolite.
Aluminosilicate zeolites are capable of undergoing favourable
levels of copper and iron exchange at the alumina sites.
Accordingly, following exchange such zeolites may provide the
composite material with high levels of SCR catalytic activity. The
term "aluminosilicate" as used herein may encompass zeolite
structures containing only alumina and silica. In addition, the
term "aluminosilicate" as used herein may encompass zeolite
structures containing species other than alumina and silica, for
example metals (e.g. iron).
[0037] In an alternative embodiment, the SCR catalyst comprises a
titania and the porous inorganic material is functionalised with V
and/or Fe. Such a combination may result in the SCR catalyst
composition exhibiting particularly pronounced SCR catalytic
activity. In this embodiment, preferably the titania comprises W,
Si and/or Mo and the porous inorganic material is functionalised
with V. This may serve to further improve the SCR catalytic
activity of the SCR catalyst composition.
[0038] In a preferred embodiment, the SCR catalyst composition
comprises a blend of both a titania functionalised with V and/or
Fe; and a zeolite (molecular sieve)-preferably an aluminosilicate
zeolite --functionalised with copper and/or iron as described in WO
2014/027207 A1.
[0039] The titania functionalised with V and/or Fe preferably
further comprises tungsten oxide. The iron is preferably present as
iron vanadate.
[0040] The SCR catalyst composition preferably comprises about 0.5
to about 5 wt. % of the vanadium calculated as V.sub.2O.sub.5 based
on the total weight of the first component and the second
component.
[0041] The porous inorganic material preferably comprises from 0.01
to 5 wt. % Fe, more preferably from 1 to 4 wt. % Fe. Such an Fe
level may provide the porous inorganic material with particularly
high SCR catalytic activity.
[0042] The SCR catalyst composition is preferably extrudable. This
may allow the SCR catalyst composition to be formed more easily
into a desired shape during manufacture.
[0043] The SCR catalyst composition is preferably in the form of
pellets or a plate or has a honeycomb structure. Such shapes may be
advantageous when the SCR catalyst composition is incorporated into
a SCR catalyst article.
[0044] In a second aspect, there is provided an emission treatment
system for treating a flow of a combustion exhaust gas, the system
comprising a source of combustion exhaust gas in fluid
communication with the SCR catalyst composition described herein,
and a source of nitrogenous reductant arranged upstream of said SCR
catalyst composition. Such an emission treatment may be, for
example, a vehicle emission treatment system, e.g. an automotive
vehicle diesel engine emission treatment system. The nitrogenous
reductant may comprise, for example, ammonia and/or urea.
[0045] The preferable features of the first aspect apply equally to
this second aspect.
[0046] In a third aspect, there is provided a method for the
manufacture of a SCR catalyst composition, the method comprising:
[0047] (i) providing an inorganic material having a layered
structure; [0048] (ii) contacting the material with a cationic
surfactant to form a swollen material; [0049] (iii) agitating the
swollen material to form an agitated material; and [0050] (iv)
calcining the agitated material to recover a delaminated inorganic
material, wherein an SCR catalyst is mixed with the inorganic
material prior to step (iv).
[0051] The SCR catalyst composition may be the SCR catalyst
composition of the first aspect of the invention. The preferable
features of the first aspect of the invention apply equally to this
third aspect.
[0052] The method is less complex in comparison to methods of
manufacturing a PILC.
[0053] The inorganic material having a layered structure may
comprise the inorganic materials referred to above in relation to
the first aspect, for example, a clay mineral, graphite, graphene,
a layered silicate, a layered phosphate, a layered zeolite, a
layered double hydroxide, hydrotalcite, a layered perovskite,
attapulgite, sepiolite and vermiculite. The inorganic material is
preferably microporous/mesoporous and can contain macropores (see
Examples). This may serve to provide a meso- and/or macroporous
modal maximum in the pore size distribution of the final SCR
catalyst composition. This is advantageous because the porosity of
the inorganic material can assist with gas mass transfer within the
SCR catalyst composition as a whole.
[0054] Contacting the material with a cationic surfactant to form a
swollen material is typically carried out in a liquid, for example
an aqueous liquid. The material and cationic surfactant may be
added to the liquid at the same time, or may be added sequentially.
Contacting the material with a cationic surfactant may result in a
mixture of the material and cationic surfactant. By "swollen
material" it is meant that the interlayer spacing of the layers of
the inorganic material is increased, typically as a result of the
cationic surfactant intercalating between the layers.
[0055] The SCR catalyst is mixed with the inorganic material prior
to step (iv), i.e. prior to step (ii), and/or with the swollen
material after step (ii) but prior to step (iii), and/or with the
swollen material during step (iii), and/or with the agitated
material after step (iii) but prior to step (iv). Such a "one pot"
manufacturing method, in which the SCR catalyst is mixed with the
inorganic material prior to calcination, may be simpler in
comparison to conventional SCR catalyst composition manufacturing
methods.
[0056] The cationic surfactant preferably comprises a carbon chain
having at least 10 carbon atoms, more preferably from 12 to 20
carbon atoms. Such surfactants may be particularly suitable for
increasing the interlayer spacing of the inorganic material.
[0057] Step (ii) preferably comprises mixing the material and an
aqueous solution of the cationic surfactant to form a mixture,
followed by storing the mixture for a period of from 1 to 3 days,
more preferably wherein the storing is carried out at a temperature
of from 30 to 50.degree. C.
[0058] Agitating the swollen material may be carried out, for
example, by the use of shear mixing and/or sonication and/or the
use of microwaves. The agitating preferably comprises sonication
and/or the application of microwaves. In a preferred embodiment,
the sonication comprises ultrasonication. Such forms of agitation
may be particularly suitable for causing delamination of the
inorganic material. Ultrasonication is particularly preferred
since, in contrast to chemical delamination methods (e.g.
[0059] involving a pH change or a concentration change), the
delamination tends to be irreversible.
[0060] Step (iii) is preferably carried out for a period of from 1
to 4 hours, and/or at a temperature of from 15 to 35.degree. C.
Such conditions may be particularly suitable for causing
delamination of the inorganic material.
[0061] The method preferably further comprises contacting the
agitated material and/or delaminated inorganic material with a
solution of metal ions to incorporate at least some of the metal
ions into the agitated material and/or delaminated inorganic
material, the metal selected from one or more of Cu, Fe, Ce, Mn, V,
Zn, Mo, Pt, Pd, Rh, Ir and Ni. Such "ion exchange" techniques are
known in the art.
[0062] When the inorganic material is an aluminosilicate, the metal
ions will typically ion exchange at the alumina site.
[0063] The method preferably comprises forming the material into a
desired shape, wherein the forming preferably comprises extrusion
and the desired shape preferably comprises pellets or a sheet or a
honeycomb structure.
[0064] The SCR catalyst composition may be the SCR catalyst
composition according to the first aspect.
[0065] In a fourth aspect, there is provided a method for the
manufacture of a porous inorganic material, the method comprising:
[0066] (i) providing an inorganic material having a layered
structure; [0067] (ii) contacting the material with a cationic
surfactant to form a swollen material; [0068] (iii) agitating the
swollen material to form an agitated material; and [0069] (iv)
calcining the agitated material to recover a delaminated inorganic
material.
[0070] The porous inorganic material may be the porous inorganic
material of the SCR catalyst composition according to the first
aspect of the invention. The preferable features of the first,
second and third aspects described hereinabove apply equally to
this fourth aspect.
[0071] In a fifth aspect, there is provided a porous inorganic
material comprising a disordered arrangement of delaminated
silicate layers, a disordered porous structure, a pore size
distribution comprising at least a first modal maximum having a
macroporous or mesoporous pore size and a second modal maximum
having a microporous pore size, the porous inorganic material
obtainable by the method of the previous aspect.
[0072] In a sixth aspect, there is provided use of the porous
inorganic material as described herein in a SCR catalyst
composition. In an alternative embodiment, the SCR catalyst
composition is an ammonia slip catalyst composition, and the SCR
catalyst is preferably a zeolite functionalised with platinum group
metal.
[0073] In a seventh aspect, there is provided use of the porous
inorganic material as described herein to increase the catalytic
activity of an SCR catalyst composition.
[0074] The present disclosure will now be described in relation to
the following non-limiting figures, in which:
[0075] FIG. 1 shows a flow chart of a method according to the
present invention;
[0076] FIG. 2 shows powder X-ray diffraction patterns of
Bentonite-U, Bentonite-S and Bentonite-DEL according to Example 1;
and
[0077] FIG. 3 shows a N.sub.2 sorption pore size distribution of
Bentonite-U and Bentonite-DEL according to Example 1.
[0078] Referring to FIG. 3, there is shown a method for the
manufacture of a SCR catalyst composition, the method comprising:
(i) providing an inorganic material having a layered structure;
(ii) contacting the material with a cationic surfactant to form a
swollen material; (iii) agitating the swollen material to form an
agitated material; and (iv) calcining the agitated material to
recover a delaminated inorganic material,
[0079] The present disclosure will now be described in relation to
the following non-limiting examples.
EXAMPLE 1
[0080] A number of binders comprising a porous inorganic material
were prepared. The starting material used was Bentonite-B
(Witgert), which is composed of:
Si.sub.4O.sub.10(Al.sub.3.84Mg.sub.0.49)(Fe.sub.1.84Ca.sub.0.21)Na.sub.0-
.03(OH).sub.2.xH.sub.2O.
[0081] Step 1 (steps (i) and (ii) in the claimed method): In the
first step, the small cations between the layers of the bentonite
were exchanged using hexadecyltrimethylammonium bromide (CTAB). To
this end, 30 g of CTAB and 13 g of tetrapropylammonium hydroxide
(TPAOH, 40% solution) were dissolved in 116 ml of water under
agitation (magnetic stirrer). Then, 5 g of bentonite were gradually
admixed. The mixing took 20 minutes. The exchange was then carried
out at 40.degree. C. under continuous, gentle stirring for a period
of 2 days.
[0082] Step 2 (steps (iii) and (iv) in the claimed method): In the
second step, delamination of the layered structure was initiated by
ultrasonication at room temperature. The treatment time was two
hours. Thereafter, the solid fraction was separated from the
dispersion by centrifugation and dried at 75.degree. C. for 12
hours. This drying step was followed by a calcination at
550.degree. C. in air for 5 hours. The heating rate for this was 1
K/min.
[0083] FIG. 2 shows powder X-ray diffraction patterns of the
untreated bentonite material (Bentonite-U), the swollen bentonite
after step 1 (Bentonite-S) and the delaminated clay after step 2
(Bentonite-DEL). It can be observed that a number of peaks decline
in intensity after ultrasonication especially peaks from 2.degree.
to 10.degree. 2Theta, indicating a disordered arrangement of
delaminated layers. A powder X-ray diffraction pattern of the
bentonite material after swelling was also measured, from which the
change in layer spacing on swelling could be observed.
[0084] FIG. 3 shows pore size distributions obtained from nitrogen
sorption measurements for the untreated bentonite (Bentonite-U) and
the delaminated bentonite (Bentonite-DEL). Compared to the
untreated clay two pronounced maxima, one maximum in the micropore
range and one maximum in the mesopore range, have been observed for
the delaminated clay. In Table 1 the derived specific surface area
and pore volume data are summarized showing an increase in meso-
and macropore volume and therefore a significantly higher total
pore volume and specific surface area for the delaminated bentonite
material.
TABLE-US-00001 TABLE 1 Porosity characteristics by N.sub.2-sorption
measurement Micropore Mesopore Macropore BET Total pore volume
volume volume (m.sup.2/g) volume (cm.sup.3/g) (cm.sup.3/g)
(cm.sup.3/g) (cm.sup.3/g) Bent-U 107 0.174 0.041 0.110 0.023 Bent-
165 0.342 0.025 0.283 0.034 DEL
EXAMPLE 2
[0085] The following SCR catalyst compositions were prepared:
[0086] 1. 100 wt. % Cu-CHA zeolite (according to WO 2008/132452;
comparative example); [0087] 2. 80 wt. % V--Ti--W/ 20 wt. %
delaminated bentonite (present invention), 80 wt. % Cu-CHA+20 wt. %
Bentonite-U (comparative example); [0088] 3. 80 wt. % Cu-CHA+20 wt.
% Bentonite-DEL; and [0089] 4. 80 wt. % Cu-CHA+20 wt. %
Fe-Bentonite-DEL.,
[0090] Composition 4 was prepared by functionalising Bentonite-DEL
with 2 wt. % Fe (using Fe(NO.sub.3)3 as source of Fe) by wet ion
exchange. The Fe-Bentonite-DEL material was then mixed with the
Cu-CHA SCR catalyst.
[0091] The NOx conversion activity of powder samples of each of
compositions 1-4 were tested in a laboratory synthetic catalytic
activity test (SCAT) apparatus using a gas mixture of 500 ppm NO,
550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest N.sub.2 and the
results are shown in Table 2. No N.sub.2O was detected. The results
indicate higher NOx conversion with delaminated bentonite than
non-delaminated bentonite, even higher conversion with the sample
containing the Fe-Bentonite-DEL material. Composition 4 has nearly
the same activity level as composition 1 (100 wt. % Cu-CHA).
TABLE-US-00002 TABLE 2 NOx conversion for SCR catalyst composition
1-4 (500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest
N.sub.2; volume flux = 1000 ml min.sup.-1; sample mass = 0.05 g)
NOx Conversion (%) 200.degree. C. 300.degree. C. 400.degree. C.
500.degree. C. 1. 100% Cu-CHA 46 100 100 94 2. 80% Cu-CHA + 20%
Bentonite- 26 74 91 92 U 3. 80% Cu-CHA + 20% Bentonite- 30 92 98 82
DEL 4. 80% Cu-CHA + 20% 45 100 100 91 Fe-Bentonite-DEL
EXAMPLE 3
[0092] The following four SCR catalyst compositions were prepared:
[0093] 5. 100 wt. % V--Ti--W (according to U.S. Pat. No. 4,085,193;
comparative example); [0094] 6. 70 wt. % V--Ti--W +30 wt. %
Bentonite-U (comparative example); and [0095] 7. 70 wt. % V--Ti--W
+30 wt. % Fe-Bentonite-DEL delaminated bentonite* functionalised
with Fe *As explained in Example 2, composition 3 was prepared by
addition of 2 wt. % Fe to the delaminated clay prior mixing with
V--Ti--W SCR catalyst.
[0096] NO x conversion testing of powder samples of compositions
5-7 was carried out using a SCAT apparatus (Reaction conditions:
500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest
N.sub.2) and the results are shown in Table 3. No N.sub.2O was
detected. Composition 7 shows higher NOx conversion compared to
Composition 6 at high temperatures and nearly the same level of
conversion at 500.degree. C. compared to composition 5 (100%
V--Ti--W SCR catalyst).
TABLE-US-00003 TABLE 3 NOx conversion for SCR catalyst composition
5-7 (500 ppm NO, 550 ppm NH.sub.3, 8% O.sub.2, 10% H.sub.2O, rest
N.sub.2; volume flux = 1000 ml min.sup.-1; sample mass = 0.05 g).
NOx Conversion [%] 200.degree. C. 300.degree. C. 400.degree. C.
500.degree. C. 5. 100% V--Ti--W 7 49 79 70 6. 70% V--Ti--W + 30% 5
38 53 50 Bentonite-U 7. 70% V--Ti--W + 30% Fe- 5 37 60 65
DEL-Bentonite
[0097] The foregoing detailed description has been provided by way
of explanation and illustration, and is not intended to limit the
scope of the appended claims. Many variations in the presently
preferred embodiments illustrated herein will be apparent to one of
ordinary skill in the art, and remain within the scope of the
appended claims and their equivalents.
[0098] For the avoidance of doubt, the entire contents of all
documents acknowledged herein are incorporated herein by
reference.
* * * * *