U.S. patent application number 14/320197 was filed with the patent office on 2015-01-29 for engine exhaust catalysts containing copper-ceria.
The applicant listed for this patent is Shubin, Inc.. Invention is credited to Juan CAI, Xianghong HAO.
Application Number | 20150031530 14/320197 |
Document ID | / |
Family ID | 44143605 |
Filed Date | 2015-01-29 |
United States Patent
Application |
20150031530 |
Kind Code |
A1 |
HAO; Xianghong ; et
al. |
January 29, 2015 |
ENGINE EXHAUST CATALYSTS CONTAINING COPPER-CERIA
Abstract
An emission control catalyst includes copper-ceria to boost low
temperature CO oxidation performance, generate exothermic heat
during the process, and reduce HC and NO.sub.x emissions. As a
result, system performance is boosted at equal catalyst cost or
maintained at a reduced catalyst cost. In one embodiment, an engine
exhaust catalyst includes a first washcoat layer having at least
one of a platinum-based catalyst, a palladium-based catalyst, and
combinations thereof; and a second washcoat layer having
copper-ceria.
Inventors: |
HAO; Xianghong; (Kingwood,
TX) ; CAI; Juan; (Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Shubin, Inc. |
Los Altos |
CA |
US |
|
|
Family ID: |
44143605 |
Appl. No.: |
14/320197 |
Filed: |
June 30, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12964624 |
Dec 9, 2010 |
8765625 |
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14320197 |
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61285498 |
Dec 10, 2009 |
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Current U.S.
Class: |
502/304 |
Current CPC
Class: |
B01J 35/023 20130101;
B01D 53/944 20130101; B01J 37/0248 20130101; B01D 2258/012
20130101; B01D 2255/1023 20130101; B01J 29/106 20130101; B01J
37/0246 20130101; B01D 2255/106 20130101; B01J 29/80 20130101; B01D
2255/2065 20130101; B01D 2255/9025 20130101; B01J 37/0203 20130101;
B01J 37/0244 20130101; B01D 2255/1021 20130101; B01D 2255/20761
20130101; B01J 23/894 20130101; B01J 29/42 20130101; B01D 2255/50
20130101 |
Class at
Publication: |
502/304 |
International
Class: |
B01J 23/89 20060101
B01J023/89 |
Claims
1. An engine exhaust catalyst comprising: a first washcoat layer
having a platinum-based catalyst; a second washcoat layer; and a
copper ceria catalyst in at least one of the first and second
layers.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments of the present invention are directed to engine
exhaust catalysts and more particularly to engine exhaust catalysts
containing copper-ceria.
[0003] 2. Description of the Related Art
[0004] Copper or copper oxide on cerium oxide, which are referred
to as copper-ceria catalysts have been employed in various
applications, such as total oxidation of carbon monoxide and
methane, methanol, the water-gas shift reaction, and oxidation of
phenol.
[0005] In U.S. Pat. No. 3,819,535, an improved catalyst for
oxidation of hydrocarbons and carbon monoxide present in engine
exhaust gases is disclosed where the catalyst is prepared by
depositing copper oxide and ceria on an alumina support that has
been stabilized against shrinkage. The improved catalyst according
to U.S. Pat. No. 3,819,535 provides high activity for carbon
monoxide combustion as well as sufficient activity to oxidize
hydrocarbons. Other advantages that are cited in the patent include
a low ignition temperature for carbon monoxide and maintaining high
activity even after extended exposure to high temperatures.
[0006] In U.S. Pat. No. 4,996,180, a catalyst containing an
intimate mixture of copper oxide and ceria that is suitable for
oxidation or reduction of chemical feedstocks, low temperature
water gas shift, methanol synthesis, and controlling engine exhaust
emissions is disclosed. A key feature of this catalyst is that the
weight of the copper oxide is less than the weight of the ceria.
Experiments disclosed in U.S. Pat. No. 4,996,180 show inferior
oxidation and reduction performance when the copper content is very
high.
[0007] U.S. Pat. No. 7,220,692 shows copper-ceria applied to
selective catalyst reduction (SCR). This patent teaches the
addition of ceria as a stabilizing oxide to zeolite-based materials
in SCR applications as a way to combat the loss of catalytic
activity of the zeolite-based materials under wet conditions.
According to U.S. Pat. No. 7,220,692, the addition of ceria to
zeolite-based materials, in particular Cu-ZSM-5, improves
hydrothermal stability of Cu-ZSM-5 so that the catalytic activity
of Cu-ZSM-5 is sustained even under wet conditions.
[0008] Copper-ceria catalysts have also been employed in cigarette
filters to catalyze the oxidation of carbon monoxide at low
temperatures and reduce the amount of carbon monoxide in cigarette
smoke. In U.S. Pat. No. 6,857,431, copper oxide nanoparticles
and/or copper nanoparticles are combined with ceria nanoparticles
to reduce the amount of carbon monoxide in cigarette smoke. This
patent recognizes the application of such catalysts to vehicle
exhaust emissions systems of automobiles and diesel engines and
cold starting systems of automobile engines.
[0009] As has been recognized in the art, copper-ceria catalysts
are attractive because they are cost effective relative to catalyst
containing precious metals such as platinum (Pt), palladium (Pd),
and the like, and are good oxidation catalysts at low temperatures.
Despite these advantages, their use in automotive applications has
been very limited. An investigation of most commercial emission
control systems of today will reveal that copper-ceria is not
employed as a catalytically active component.
SUMMARY OF THE INVENTION
[0010] Embodiments of the present invention leverage the advantages
of copper-ceria catalysts by applying copper-ceria to emission
control systems as a way to boost system performance at equal cost
or maintain system performance at a reduced cost, relative to
alternatives that are currently available.
[0011] In a first embodiment of the present invention, copper-ceria
is contained in a middle layer of a three-layer engine control
catalyst. In a second embodiment of the present invention,
copper-ceria is contained in a bottom layer of a two-layer engine
control catalyst. In a third embodiment of the present invention,
copper-ceria is physically mixed with a platinum-containing
catalyst and zeolites in a single layer engine control catalyst. In
all of the embodiments, copper-ceria boosts low temperature carbon
monoxide ("CO") oxidation performance, generates exothermic heat
during the process, and reduces hydrocarbon ("HC") and nitrogen
oxide ("NO.sub.x") emissions during cold starts.
[0012] In another embodiment, an engine exhaust catalyst includes a
first washcoat layer having a platinum-based catalyst; a second
washcoat layer; a third washcoat layer includes a palladium-gold
catalyst; and a copper ceria catalyst in at least one of the first,
second, and third layers. In one or more of the embodiments
described herein, the copper ceria is in the second washcoat layer.
In one or more of the embodiments described herein, the catalyst
further includes a substrate, wherein the third washcoat layer
directly contacts the substrate and the second washcoat layer is
disposed between the first and third washcoat layers. In one or
more of the embodiments described herein, the copper ceria is
included in another washcoat layer.
[0013] In another embodiment, an engine exhaust catalyst includes a
first washcoat layer having at least one of a platinum-based
catalyst, a palladium-based catalyst, and combinations thereof; and
a second washcoat layer having copper-ceria. In one or more of the
embodiments described herein, the catalyst includes a substrate,
wherein the second washcoat layer directly contacts the substrate.
In one or more of the embodiments described herein, the catalyst
includes a third washcoat layer.
[0014] In another embodiment, an engine exhaust catalyst includes a
copper ceria; a platinum-based catalyst, a palladium-based
catalyst, and combinations thereof; and a zeolite. In one or more
of the embodiments described herein, the zeolites include HY
zeolites and ZSM5 zeolites.
[0015] In another embodiment, an engine exhaust catalyst includes a
first zone having at least one of a platinum-based catalyst, a
palladium-based catalyst, and combinations thereof; and a second
zone having copper-ceria. In yet another embodiment, the engine
exhaust catalyst further includes one or more washcoat layers
having a metal catalyst. In still yet another embodiment, the
engine exhaust catalyst further includes a washcoat layer having
copper ceria.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0017] FIGS. 1A-1D are schematic representations of different
engine exhaust systems in which embodiments of the present
invention may be used.
[0018] FIG. 2 is an illustration of a catalytic converter with a
cut-away section that shows a substrate onto which emission control
catalysts according to embodiments of the present invention are
coated.
[0019] FIGS. 3A-3D illustrate different configurations of a
substrate for an emission control catalyst.
DETAILED DESCRIPTION
[0020] In the following, reference is made to embodiments of the
invention. However, it should be understood that the invention is
not limited to specific described embodiments. Instead, any
combination of the following features and elements, whether related
to different embodiments or not, is contemplated to implement and
practice the invention. Furthermore, in various embodiments the
invention provides numerous advantages over the prior art. However,
although embodiments of the invention may achieve advantages over
other possible solutions and/or over the prior art, whether or not
a particular advantage is achieved by a given embodiment is not
limiting of the invention. Thus, the following aspects, features,
embodiments and advantages are merely illustrative and are not
considered elements or limitations of the appended claims except
where explicitly recited in the claims. Likewise, reference to "the
invention" shall not be construed as a generalization of any
inventive subject matter disclosed herein and shall not be
considered to be an element or limitation of the appended claims
except where explicitly recited in the claims.
[0021] FIGS. 1A-1Dare schematic representations of different engine
exhaust systems in which embodiments of the present invention may
be used. The combustion process that occurs in an engine 102
produces harmful pollutants, such as CO, various hydrocarbons,
particulate matter, and nitrogen oxides (NO.sub.x), in an exhaust
stream that is discharged through a tail pipe 108 of the exhaust
system.
[0022] In the exhaust system of FIG. 1A, the exhaust stream from an
engine 102 passes through a catalytic converter 104, before it is
discharged into the atmosphere (environment) through a tail pipe
108. The catalytic converter 104 contains supported catalysts
coated on a monolithic substrate that treat the exhaust stream from
the engine 102. The exhaust stream is treated by way of various
catalytic reactions that occur within the catalytic converter 104.
These reactions include the oxidation of CO to form CO.sub.2,
burning of hydrocarbons, and the conversion of NO to NO.sub.2.
[0023] In the exhaust system of FIG. 1B, the exhaust stream from
the engine 102 passes through a catalytic converter 104 and a
particulate filter 106, before it is discharged into the atmosphere
through a tail pipe 108. The catalytic converter 104 operates in
the same manner as in the exhaust system of FIG. 1A. The
particulate filter 106 traps particulate matter that is in the
exhaust stream, e.g., soot, liquid hydrocarbons, generally
particulates in liquid form. In an optional configuration, the
particulate filter 106 includes a supported catalyst coated thereon
for the oxidation of NO and/or to aid in combustion of particulate
matter.
[0024] In the exhaust system of FIG. 1C, the exhaust stream from
the engine 102 passes through a catalytic converter 104, a
pre-filter catalyst 105 and a particulate filter 106, before it is
discharged into the atmosphere through a tail pipe 108. The
catalytic converter 104 operates in the same manner as in the
exhaust system of FIG. 1A. The pre-filter catalyst 105 includes a
monolithic substrate and supported catalysts coated on the
monolithic substrate for the oxidation of NO. The particulate
filter 106 traps particulate matter that is in the exhaust stream,
e.g., soot, liquid hydrocarbons, generally particulates in liquid
form.
[0025] In the exhaust system of FIG. 1D, the exhaust stream passes
from the engine 102 through a catalytic converter 104, a
particulate filter 106, a selective catalytic reduction (SCR) unit
107 and an ammonia slip catalyst 110, before it is discharged into
the atmosphere through a tail pipe 108. The catalytic converter 104
operates in the same manner as in the exhaust system of FIG. 1A.
The particulate filter 106 traps particulate matter that is in the
exhaust stream, e.g., soot, liquid hydrocarbons, generally
particulates in liquid form. In an optional configuration, the
particulate filter 106 includes a supported catalyst coated thereon
for the oxidation of NO and/or to aid in combustion of particulate
matter. The SCR unit 107 is provided to reduce the NO.sub.x species
to N.sub.2. The SCR unit 107 may be ammonia/urea based or
hydrocarbon based. The ammonia slip catalyst 110 is provided to
reduce the amount of ammonia emissions through the tail pipe 108.
An alternative configuration places the SCR unit 107 in front of
the particulate filter 106.
[0026] Alternative configurations of the exhaust system includes
the provision of SCR unit 107 and the ammonia slip catalyst 110 in
the exhaust system of FIG. 1A or 1C, and the provision of just the
SCR unit 107, without the ammonia slip catalyst 110, in the exhaust
system of FIG. 1A, 1B or 1C. As a further alternative, a NO.sub.x
storage reduction (NSR) catalyst may be used in place of the SCR
unit 107.
[0027] As particulates get trapped in the particulate filter within
the exhaust system of FIG. 1B, 1C or 1D, it becomes less effective
and regeneration of the particulate filter becomes necessary. The
regeneration of the particulate filter can be either passive or
active. Passive regeneration occurs automatically in the presence
of NO.sub.2. Thus, as the exhaust stream containing NO.sub.2 passes
through the particulate filter, passive regeneration occurs. During
regeneration, the particulates get oxidized and NO.sub.2 gets
converted back to NO. In general, higher amounts of NO.sub.2
improve the regeneration performance, and thus this process is
commonly referred to as NO.sub.2 assisted oxidation. However, too
much NO.sub.2 is not desirable because excess NO.sub.2 is released
into the atmosphere and NO.sub.2 is considered to be a more harmful
pollutant than NO. The NO.sub.2 used for regeneration can be formed
in the engine during combustion, from NO oxidation in the catalytic
converter 104, from NO oxidation in the pre-filter catalyst 105,
and/or from NO oxidation in a catalyzed version of the particulate
filter 106.
[0028] Active regeneration is carried out by heating up the
particulate filter 106 and oxidizing the particulates. At higher
temperatures, NO.sub.2 assistance of the particulate oxidation
becomes less important. The heating of the particulate filter 106
may be carried out in various ways known in the art. One way is to
employ a fuel burner which heats the particulate filter 106 to
particulate combustion temperatures. Another way is to increase the
temperature of the exhaust stream by modifying the engine output
when the particulate filter load reaches a pre-determined
level.
[0029] The present invention provides catalysts that are to be used
in the catalytic converter 104 shown in FIGS. 1A-1D, or generally
as catalysts in any vehicle emission control system, including as a
diesel oxidation catalyst, a diesel filter catalyst, an
ammonia-slip catalyst, an NSR catalyst, an SCR catalyst, or as a
component of a three-way catalyst. The present invention further
provides a vehicle emission control system, such as the ones shown
in FIGS. 1A-1D, comprising an emission control catalyst comprising
a monolith and a supported catalyst coated on the monolith.
[0030] FIG. 2 is an illustration of a catalytic converter with a
cut-away section that shows a substrate 210 onto which supported
metal catalysts are coated. The exploded view of the substrate 210
shows that the substrate 210 has a honeycomb structure comprising a
plurality of channels into which washcoats containing supported
metal catalysts are flowed in slurry form so as to form coating 220
on the substrate 210.
[0031] In one embodiment of the present invention, a single layer
of washcoat containing one or more supported metal catalysts is
coated on substrate 210. FIGS. 3A-3D illustrate multi-layered,
multi-zoned, and multi-brick embodiments of the present invention.
In the embodiment of FIG. 3A, coating 220 comprises two washcoat
layers 221, 223 on top of substrate 210. Washcoat layer 221 is the
bottom layer that is disposed directly on top of the substrate 210.
Washcoat layer 223 is the top layer that is in direct contact with
the exhaust stream. Based on their positions relative to the
exhaust stream, washcoat layer 223 encounters the exhaust stream
before washcoat layer 221.
[0032] In the embodiment of FIG. 3B, coating 220 comprises three
washcoat layers 221, 222, 223 on top of substrate 210. Washcoat
layer 221 is the bottom layer that is disposed directly on top of
the substrate 210. Washcoat layer 223 is the top layer that is in
direct contact with the exhaust stream. Washcoat layer 222 is the
middle layer that is disposed in between washcoat layers 221, 223.
The middle layer is also referred to as a buffer layer. Based on
their positions relative to the exhaust stream, washcoat layer 223
encounters the exhaust stream before washcoat layers 221, 222, and
washcoat layer 222 encounters the exhaust stream before washcoat
layer 221.
[0033] In the embodiment of FIG. 3C, the substrate 210 is a single
monolith that has two coating zones 210A, 210B. A first washcoat is
coated onto a first zone 210A and a second washcoat is coated onto
a second zone 210B. In the embodiment of FIG. 3D, the substrate 210
includes first and second monoliths 231, 232, which are physically
separate monoliths. A first washcoat is coated onto the first
monolith 231 and a second washcoat is coated onto the second
monolith 232.
[0034] All of the embodiments of the present invention include a
copper-ceria catalyst in one or more of the washcoats. The
copper-ceria catalyst that is included is synthesized based on the
procedure disclosed in Tang, et al., "CuO/CeO.sub.2 Catalysts:
Redox Features and Catalytic Behaviors," Applied Catalysis A:
General, Vol. 288, pp. 116-125 (2005), which is incorporated by
reference herein. The present invention, however, is not limited to
copper-ceria catalyst synthesized in this manner, and may cover
copper-ceria catalyst synthesized according to other methods known
in the art.
[0035] The synthesis to produce 4% Cu supported on CeO.sub.2 is as
follows. First, mix 6 g of ceria into 50 ml de-ionized water. Then,
add 0.786 g of Cu(CH.sub.3COO).sub.2 into it, while keeping the
reaction temperature at 70.degree. C., and stir for 0.5 hours.
Prepare 0.25 M of Na.sub.2CO.sub.3, gradually add to the mixture
until pH is about 9. The resulting mixture is aged for 1 hour at a
temperature of 44.degree. C. After aging, the precipitate is
filtered, washed with 300 mL of water, dried for about 5 hours at
140.degree. C., and calcined for 2 hours at 500.degree. C.
[0036] Steady state core tests were conducted to demonstrate the
performance-enhancing benefits or cost-reduction benefits of using
copper-ceria as part of an engine exhaust catalyst. The different
configurations that were tested are shown in Table 1-3. Pt--Pd
samples were synthesized according to methods disclosed in Example
11 of U.S. Patent Application Publication No. 2008/0119353, which
is incorporated by reference herein, and have indicated weight
ratios. Pd--Au samples were synthesized according to Example 1 of
U.S. Pat. No. 7,709,407, which in incorporated by reference herein
and have indicated weight ratios. Zeolites that were used include
ZSM-5 zeolite and HY zeolite. Other types of zeolites that can be
used which include beta zeolite, mordenite, ferrierite, etc. The
zeolites can be mixtures in any weight ratio. In some embodiments,
ceria (CeO.sub.2) and alumina (Al.sub.2O.sub.3) are added as
components. Example 1 is the comparative sample. Examples 1-5
employ three layers. Examples 6-10 employ two layers. Examples
11-13 employ only a single layer.
Example 1
[0037] Tri-layer: PtPd (at 62.2 g/ft.sup.3) 1.sup.st layer, Zeolite
mixture 2.sup.nd layer, PdAu (at 95.8 g/ft.sup.3) 3.sup.rd
layer
[0038] The supported PtPd catalyst powder (3.0% Pt, 1.5% Pd) was
prepared as follows. To 10 L of de-ionized H.sub.2O was added 1940
g of La-stabilized alumina (having a BET surface area of .about.200
m.sup.2 g.sup.-1) followed by stirring for 30 minutes at room
temperature. To this slurry was added 490.6 g of Pt(NO.sub.3).sub.2
solution (12.23% Pt(NO.sub.3).sub.2 by weight), followed by
stirring at room temperature for 60 minutes. Acrylic acid (750 mL,
99% purity) was then added into the system over 12 minutes and the
resulting mixture was allowed to continue stirring at room
temperature for 2 hours. The solid La-doped alumina supported Pt
catalyst was separated from the liquid via filtration, dried at
120.degree. C. for 2 hours, ground into a fine powder, and calcined
in air for 2 hours at a temperature of 500.degree. C. (heated at
8.degree. C. min.sup.-1) to give a 3% Pt material.
[0039] To 9.25 L of de-ionized H.sub.2O was added 1822 g of the
above 3% Pt material followed by stirring for 20 minutes at room
temperature. To this slurry was added 194.4 g of Pd(NO.sub.3).sub.2
solution (14.28% Pd(NO.sub.3).sub.2 by weight), followed by
stirring at room temperature for 60 minutes. An aqueous ascorbic
acid solution (930 g in 4.5 L of de-ionized H.sub.2O) was then
added over 25 minutes followed by stirring for 60 minutes. The
solid La-doped alumina supported PtPd catalyst was separated from
the liquid via filtration, dried at 120.degree. C. for 2 hours,
ground into a fine powder, and calcined in air for 2 hours at a
temperature of 500.degree. C. (heated at 8.degree. C. min.sup.-1)
to give a 3% Pt, 1.5% Pd material.
[0040] The resulting PtPd catalyst powder was made into a washcoat
slurry via addition to de-ionized water, milling to an appropriate
particle size (typically with d.sub.50 range from 3 to 7 .mu.m),
and pH adjustment to give an appropriate viscosity for washcoating.
The washcoat slurry was coated onto a round cordierite monolith,
dried at 120.degree. C. and calcined at 500.degree. C. to give the
first layer of the multi-layer coated monolith, such that the PtPd
loading was .about.62.2 g/ft.sup.3.
[0041] Then Y zeolite and ZSM-5 zeolite, copper ceria were made
into a washcoat slurry via addition to de-ionized water, milling to
an appropriate particle size (typically with a d.sub.50 range from
3 to 7 .mu.m), and pH adjustment to give an appropriate viscosity
for washcoating. The zeolite and copper ceria slurry were coated
onto the cordierite monolith, dried at 120.degree. C. and calcined
at 500.degree. C. to give the second layer of the multi-layer
coated monolith.
[0042] Then supported PdAu catalyst powder (1.7% Pd, 2.0% Au) was
prepared as follows. Add 3.853 g of alumina powder to 15 mL of
de-ionized water and stir for 10 minutes. Add in 3.2 mL of 1 M NaOH
to mixture and increase the temperature to 368 K. After the mixture
reaches 368 K, dropwise add solutions containing 0.667 mL of 100
mg/mL Pd(NO.sub.3).sub.3 in 2.5 mL of de-ionized water and 0.80 mL
of 100 mg/mL HAuCl.sub.4 in 2.5 mL of de-ionized water, to the
mixture simultaneously. During this step, the pH of the mixture is
maintained to be greater than 7.5 by adding additional 1 mL of 1 M
NaOH to the mixture. Then, stir the mixture for 3 hours while
keeping the mixture at 368 K. The mixture is then filtered and
washed with de-ionized water at 323 K to separate out the supported
catalyst. The supported catalyst is dried at 393 K for 3 hours, and
ground to a fine powder using a mortar and pestle. The powder is
calcined in air at 773 K for 2 hours using a heating ramp rate of 8
K/min.
[0043] The resulting PdAu catalyst powder was made into a washcoat
slurry via addition to de-ionized water, milling to an appropriate
particle size (typically with d.sub.50 range from 3 to 7 .mu.m),
and pH adjustment to give an appropriate viscosity for washcoating.
The washcoat slurry was coated onto a round cordierite monolith,
dried at 120.degree. C. and calcined at 500.degree. C. to give the
third layer of the multi-layer coated monolith, such that the PdAu
loading was .about.95.8 g/ft.sup.3.
Example 2-5
[0044] Examples 2-5 represent various tri-layer configurations
containing copper ceria. The samples in Examples were prepared
using a procedure similar to Example 1. If a layer in a sample
contains a combination of catalysts, then the catalysts for the
layer were mixed before the milling step.
Example 6
[0045] Double-layer: zeolite mixture and PdAu (at 63.0 g/ft.sup.3)
1.sup.st layer, Copper Ceria at the 2.sup.nd layer
[0046] The supported PdAu catalyst powder (1.7% Pd, 2.0% Au)
prepared as shown in Example 1 was made into a washcoat slurry via
addition to de-ionized water, then add HY zeolite and ZSM-5
zeolite, milling to an appropriate particle size (typically with
d.sub.50 range from 3 to 7 .mu.m), and pH adjustment to give an
appropriate viscosity for washcoating. The washcoat slurry was
coated onto a round cordierite monolith, dried at 120.degree. C.
and calcined at 500.degree. C. to give the first layer of the
multi-layer coated monolith, such that the PdAu loading was
.about.63.0 g/ft.sup.3.
[0047] Copper Ceria catalyst powder prepared as described was made
into a washcoat slurry via addition to de-ionized water, milling to
an appropriate particle size (typically with d.sub.50 range from 3
to 7 .mu.m), and pH adjustment to give an appropriate viscosity for
washcoating. The washcoat slurry was coated onto a round cordierite
monolith, dried at 120.degree. C. and calcined at 500.degree. C. to
give the second layer of the multi-layer coated monolith, such that
the copper ceria loading was .about.1.2 g/in.sup.3.
Example 7-10
[0048] Examples 7-10 represent various double-layer configurations
containing copper ceria. The samples in Examples were prepared
using a procedure similar to Example 6. If a layer in a sample
contains a combination of catalysts, then the catalysts for the
layer were mixed before the milling step.
Example 11
[0049] Single-layer: zeolite mixture and PtPd (at 78 g/ft.sup.3)
and copper ceria in one layer
[0050] The supported PtPd catalyst powder (3% Pt, 1.5% Pd) prepared
as shown in Example 1 was made into a washcoat slurry via addition
to de-ionized water, then add HY zeolite and ZSM-5 zeolite, copper
ceria, milling to an appropriate particle size (typically with
d.sub.50 range from 3 to 7 .mu.m), and pH adjustment to give an
appropriate viscosity for washcoating. The washcoat slurry was
coated onto a round cordierite monolith, dried at 120.degree. C.
and calcined at 500.degree. C. to give the layer of the
single-layer coated monolith, such that the PtPd loading was
.about.78.0 g/ft.sup.3 and copper ceria was .about.1.2
g/in.sup.3.
Examples 12-15
[0051] Examples 12-15 represent various single-layer configurations
containing copper ceria. The samples in Examples were prepared
using a procedure similar to Example 11. If a layer in a sample
contains a combination of catalysts, then the catalysts for the
layer were mixed before the milling step.
[0052] For easy reference, the copper-ceria component is indicated
in boldface. Also, the cost reduction (CR) relative to the cost of
Example 1 is provided for all the examples. The cost calculations
assume the cost basis for Pt:Pd:Au to be 5:1:2. The cost basis of
Pd:Cu is assumed to be about 100:1. It is calculated with the
formula:
(cost of example 1-cost of sample X)/cost of example 1.
[0053] T-50 numbers indicate the temperature that reactants reach
50% conversion. For instance: CO T-50 at 148.degree. C. means that
50% CO has been converted at 148.degree. C. Lower T-50 is normally
desired for better conversion efficiency. All the test are in the
condition of 1000 ppm CO, 105 ppm C.sub.3H.sub.8, 245 ppm
C.sub.3H.sub.6, 120 ppm O-Xylene, 150 ppm NO, 10% O.sub.2. Gas
Hourly Space Velocity (GHSV) is 60,000 h.sup.-1 unless indicated
otherwise. During the run, the gas mixtures were flowed at
40.degree. C. for 15 minutes and then their temperatures were
increased from 40.degree. C. to 250.degree. C. at a rate of
5.degree. C./min. Samples were aged in 10% H.sub.2O at 750.degree.
C. for 20 hours before testing. Grams per cubic inch ("g/in.sup.3")
units are used herein and in the claims to express the quantity of
relatively plentiful components such as the copper ceria, ceria,
alumina, zeolite catalytic materials, and grams per cubic foot
("g/ft.sup.3") units are used to express the quantity of the
sparingly-used ingredients, such as the Platinum, Palladium, Gold
metals.
TABLE-US-00001 TABLE 1 Tri-layer configurations and performance
Fresh Propene Aged Aged Fresh T- CO Propene Middle Bottom CO 50
T-50 T-50 Top Layer Layer Layer CR % T-50 (.degree. C.) (.degree.
C.) (.degree. C.) (.degree. C.) Example 1 Pt--Pd (3.0%, HY Zeolite
Pd--Au 0 148 172 158 181 1.5% by (0.2 g/in.sup.3) (1.7%, weight) at
62.2 g/ft.sup.3 ZSM-5 2.0% by Zeolite (0.1 g/in.sup.3) weight) at
Ceria (0.2 g/in.sup.3) 95.8 g/ft.sup.3 Example 2 Pt--Pd (3.0%, HY
Zeolite Pd--Au 21.7 155 177 158 184 1.5% by (0.15 g/in.sup.3)
(1.7%, weight) at 62.2 g/ft.sup.3 ZSM-5 2.0% by Zeolite weight) at
(0.15 g/in.sup.3) 44.4 g/ft.sup.3 Copper Ceria (1.2 g/in.sup.3)
Example 3 Pt--Pd (3.0%, HY Zeolite Pd--Au 21.7 167 192 158 193 1.5%
by (0.15 g/in.sup.3) (1.7%, weight) at 62.2 g/ft.sup.3 ZSM-5 2.0%
by Zeolite weight) at (0.15 g/in.sup.3) 44.4 g/ft.sup.3 Ceria (0.2
g/in.sup.3) Copper Ceria (1.2 g/in.sup.3) Example 4 Pt--Pd (3.0%,
HY Zeolite Pd--Au 21.7 157 182 154 185 1.5% by (0.15 g/in.sup.3)
(1.7%, weight) at 62.2 g/ft.sup.3 ZSM-5 2.0% by Copper Zeolite
weight) at Ceria (1.2 g/in.sup.3) (0.15 g/in.sup.3) 44.4 g/ft.sup.3
Ceria (0.2 g/in.sup.3) Example 5 Pt--Pd (3.0%, HY Zeolite Pd--Au 0
151 176 155 185 1.5% by (0.15 g/in.sup.3) (1.7%, weight) at 62.2
g/ft.sup.3 ZSM-5 2.0% by Zeolite weight) at (0.15 g/in.sup.3) 95.8
g/ft.sup.3 Copper Ceria (0.2 g/in.sup.3)
TABLE-US-00002 TABLE 2 Double-layer configurations and performance
Fresh Fresh Aged Aged CO Propene CO Propene T-50 T-50 T-50 T-50 Top
Layer Bottom Layer CR % (.degree. C.) (.degree. C.) (.degree. C.)
(.degree. C.) Example 6 HY Zeolite (0.15 g/in.sup.3) Copper Ceria
73.9 164 210 162 213 ZSM-5 Zeolite (0.15 g/in.sup.3) (1.2
g/in.sup.3) Pd--Au (1.7%, 2.0% by weight) at 63.0 g/ft.sup.3
Example 7 HY Zeolite (0.15 g/in.sup.3) Copper Ceria 41.6 141 171
152 186 ZSM-5 Zeolite (0.15 g/in.sup.3) (1.2 g/in.sup.3) Pt--Pd
(3%, 1.5% by weight) at 60.0 g/ft.sup.3 Example 8 HY Zeolite (0.15
g/in.sup.3) Pd--Au (1.7%, 73.9 167 214 177 209 ZSM-5 Zeolite (0.15
g/in.sup.3) 2.0% by Copper Ceria (1.2 g/in.sup.3) weight) at 63.0
g/ft.sup.3 Alumina (0.7 g/in.sup.3) Example 9 HY Zeolite (0.15
g/in.sup.3) Copper Ceria 37.7 148 170 181 202 ZSM-5 Zeolite (0.15
g/in.sup.3) (1.2 g/in.sup.3) Pt--Pd (2%, 2% by weight) at 78.0
g/ft.sup.3 Example HY Zeolite (0.15 g/in.sup.3) Copper Ceria 24.2
136 168 172 212 10 ZSM-5 Zeolite (0.15 g/in.sup.3) (1.2 g/in.sup.3)
Pt (3% by weight) at 57.0 g/ft.sup.3
TABLE-US-00003 TABLE 3 Single-layer configurations and performance
Fresh Fresh Aged Aged CO Propene CO Propene T-50 T-50 T-50 T-50
Layer composition CR % (.degree. C.) (.degree. C.) (.degree. C.)
(.degree. C.) Example HY Zeolite (0.15 g/in.sup.3) 37.7 157 181 167
191 11 ZSM-5 Zeolite (0.15 g/in.sup.3) Pt--Pd (2%, 2% by weight) at
78.0 g/ft.sup.3 Copper Ceria (1.2 g/in.sup.3) Example HY Zeolite
(0.15 g/in.sup.3) 24.2 142 165 182 205 12 ZSM-5 Zeolite (0.15
g/in.sup.3) Pt (3% by weight) at 57.0 g/ft.sup.3 Copper Ceria (1.2
g/in.sup.3) Example HY Zeolite (0.15 g/in.sup.3) -37.9 155 180 210
230 13 ZSM-5 Zeolite (0.15 g/in.sup.3) Pt (3% by weight) at 57.0
g/ft.sup.3 Example HY Zeolite (0.15 g/in.sup.3) -16.8 167 183 175
185 14 ZSM-5 Zeolite (0.15 g/in.sup.3) Pt--Pd (3%, 1.5% by weight)
at 120 g/ft.sup.3 Example Copper Ceria (1.2 g/in.sup.3) 99 150 n/a
155 n/a 15
[0054] The T50 temperatures presented in the tables above show the
benefits of adding copper-ceria. In the three-layer configurations,
the inventors have discovered that Example 2, which has
copper-ceria in the middle layer, exhibits comparable performance
to Example 1, even though Example 2 uses lesser amount of Pd--Au
catalyst in the bottom layer. The performance of Example 2 is
expected to improve even more if the same amount of Pd--Au catalyst
is used in the bottom layer as in Example 1. Thus, the benefits of
using Example 2 are reduction of about 20% in cost for the same
performance or improvement in performance for the same cost. In
addition, T50 temperatures presented in the tables above show that
the performances of Examples 2, 6, and 10 do not degrade
significantly upon aging. This shows that the copper-ceria
introduced in these example catalysts are stable under our
conditions.
[0055] In general, the inventors have discovered through the
application of copper-ceria in engine exhaust treatment systems
that copper-ceria is a good low temperature CO oxidation catalyst
that generates exothermic heat during catalysis and reduces HC and
NO.sub.x emissions especially during cold start. In addition,
copper-ceria adds little cost to the whole system, and is stable
under our aging conditions.
[0056] The weight loading of copper in the embodiments of the
present invention is 0.1% to 10%, preferably 1% to 5%. Support
metal oxides in the embodiments of the present invention include
functioning metal oxides, such as CeO.sub.2, CeZrO.sub.x,
TiO.sub.2, and the like. Washcoat loading of copper-ceria in the
embodiments of the present invention is greater than 0.2
g/in.sup.3, preferably 0.4 g/in.sup.3 to 2.0 g/in.sup.3, more
preferably 0.7 g/in.sup.3 to 1.7 g/in.sup.3. The total weight
loading of platinum-palladium in the embodiments of the present
invention is 0.5% to 10%, preferably 0.5% to 6%. Washcoat loading
of platinum-palladium in the embodiments of the present invention
is greater than 0.2 g/in.sup.3, preferably 0.2 g/in.sup.3 to 2
g/in.sup.3, more preferably 0.5 g/in.sup.3 to 1.5 g/in.sup.3. The
total weight loading of palladium in the embodiments of the present
invention is 0.2% to 10%, preferably 0.5% to 6%. Washcoat loading
of palladium-gold in the embodiments of the present invention is
greater than 0.2 g/in.sup.3, preferably 0.2 g/in.sup.3 to 2
g/in.sup.3, more preferably 0.5 g/in.sup.3 to 1.5 g/in.sup.3.
[0057] In one embodiment, the engine exhaust catalyst may include
three washcoat layers disposed on a substrate. Each layer may
include one or more metals of copper ceria, platinum based
catalysts, and palladium based catalysts. For example, the first
layer may include a platinum based catalyst such as
platinum-palladium, platinum bismuth, platinum, and combinations
thereof. The weight ratio of the platinum to palladium may be from
4:1 to 1:4, preferably, from 3:1 to 1:2. The second layer may
include copper-ceria. The third layer may include a palladium based
catalyst such as palladium-gold, palladium, and combinations
thereof. The weight ratio of the palladium to gold may be from 3:1
to 1:3, preferably, from 2:1 to 1:2. These layers may be arranged
in any order relative to the substrate. For example, the palladium
based layer is in direct contact with the substrate, while the
copper ceria layer is disposed between the platinum based layer and
the palladium based layer. In an exemplary embodiment, the washcoat
loading of the copper-ceria is higher than the washcoat loading of
the platinum based layer or the palladium based layer. In another
example, at least two of the catalysts may be disposed on the same
layer. The copper ceria may be combined with the palladium based
catalyst or the platinum-based catalyst, or the palladium-based
catalyst may be combined with the platinum-based catalyst. In yet
another example, the same metal may be included on more than one
layer.
[0058] In another embodiment, the engine exhaust catalyst may
include two washcoat layers disposed on a substrate. The first
layer may include a platinum based catalyst such as
platinum-palladium, platinum bismuth, platinum, and combinations
thereof, and/or a palladium based catalyst such as palladium-gold
or palladium, and combinations thereof. The weight ratio of the
platinum to palladium may be from 4:1 to 1:4, preferably, from 3:1
to 1:2. The weight ratio of the palladium to gold may be from 3:1
to 1:3, preferably, from 2:1 to 1:2. The second layer may include
copper-ceria. These layers may be arranged in any order relative to
the substrate. For example, the platinum based layer is in direct
contact with the substrate, while the copper ceria layer is
disposed exterior to the platinum based layer. In an exemplary
embodiment, the washcoat loading of the copper-ceria is higher than
the washcoat loading of the platinum based catalyst or the
palladium based catalyst. In yet another example, the same metal
may be included on more than one layer. For example, any one of the
metal catalyst such as copper ceria may on both layers. In another
example, copper ceria may be combined with the palladium based
catalyst or the platinum-based catalyst.
[0059] In another embodiment, the engine exhaust catalyst may
include a washcoat layer containing copper-ceria disposed on a
substrate. The washcoat layer may additionally include a platinum
based catalyst such as a platinum-palladium catalyst; and/or
platinum bismuth or platinum, a palladium based catalyst such as
palladium-gold or palladium, and combinations thereof. The weight
ratio of the platinum to palladium may be from 4:1 to 1:4,
preferably, from 3:1 to 1:2. The weight ratio of the palladium to
gold may be from 3:1 to 1:3, preferably, from 2:1 to 1:2. In an
exemplary embodiment, the washcoat loading of the copper-ceria is
higher than the washcoat loading of the platinum based catalyst or
the palladium based catalyst.
[0060] In the embodiments described herein, the engine exhaust
catalyst may optionally include one or more zeolites such as ZSM5
zeolite, HY zeolite, beta zeolite, mordenite, ferrierite, and
combinations thereof. In some embodiments, ceria (CeO.sub.2) and
alumina (Al.sub.2O.sub.3) may be added as components. The zeolites
and other components may be included in one or more of the washcoat
layers.
[0061] Embodiments of the present invention include providing the
copper ceria in one or more zones of the substrate. Therefore, the
description herein with respect to washcoat layers applies equally
to providing metal particles such copper ceria zones. In one
embodiment, instead of the coating the monolith with the supported
catalysts in washcoat layers, the catalysts may be coated on the
monolith using two or more coating zones, as shown in FIGS. 3C and
3D. For example, instead of three layers, the monolith may be
coated with three zones of catalysts. In yet another embodiment,
the monolith may be coated with a combination of zones and layers
of different catalyst formulations. If desired, the zones and/or
layers may overlap to provide even more flexibility for the
catalyst design.
[0062] In an exemplary embodiment of coating a monolith in zones,
the zone of the monolith to be coated is partially immersed in the
coating liquid which fills the dip pan. The liquid is raised up to
the desired coating profile level through a combined effect of
capillary forces and vacuum applied to the top face of the zone.
The amount of coating liquid per zone is controlled through the
depth of immersion. The monolith is immersed into the coating media
to a depth L (about 6-12 mm), that ensures a suitable volume of the
liquid above the immersed end of the substrate. A complete two-zone
coating process is performed by coating of one end followed by
drying and then coating of the other end followed by drying and
calcination.
[0063] In another embodiment, an engine exhaust catalyst includes a
first washcoat layer having a platinum-based catalyst; a second
washcoat layer; a third washcoat layer includes a palladium-gold
catalyst; and a copper ceria catalyst in at least one of the first,
second, and third layers.
[0064] In one or more of the embodiments described herein, the
copper ceria is in the second washcoat layer.
[0065] In one or more of the embodiments described herein, the
catalyst further includes a substrate, wherein the third washcoat
layer directly contacts the substrate and the second washcoat layer
is disposed between the first and third washcoat layers.
[0066] In one or more of the embodiments described herein, the
first washcoat layer encounters an engine exhaust flow before the
second and third washcoat layers.
[0067] In one or more of the embodiments described herein, the
second washcoat layer further includes zeolites.
[0068] In one or more of the embodiments described herein, the
platinum-based catalyst is a platinum-palladium catalyst, a
platinum-bismuth catalyst, or combinations thereof.
[0069] In one or more of the embodiments described herein, the
weight loading of copper in the copper-ceria is 1% to 10%.
[0070] In one or more of the embodiments described herein, the
weight loading of the copper-ceria in the second washcoat layer is
0.2 g/in.sup.3 to 2.0 g/in.sup.3.
[0071] In one or more of the embodiments described herein, the
copper ceria is included in another washcoat layer.
[0072] In one or more of the embodiments described herein, the
third washcoat layer is above the first and second washcoat
layers.
[0073] In one or more of the embodiments described herein, the
second washcoat layer is above the first and third washcoat
layers
[0074] In another embodiment, an engine exhaust catalyst includes a
first washcoat layer having at least one of a platinum-based
catalyst, a palladium-based catalyst, and combinations thereof; and
a second washcoat layer having copper-ceria.
[0075] In one or more of the embodiments described herein, the
second washcoat layer is above the first washcoat layer.
[0076] In one or more of the embodiments described herein, the
second washcoat layer includes one or more zeolites.
[0077] In one or more of the embodiments described herein, the
catalyst includes a substrate, wherein the second washcoat layer
directly contacts the substrate.
[0078] In one or more of the embodiments described herein, the
first washcoat layer encounters an engine exhaust flow before the
second washcoat layer.
[0079] In one or more of the embodiments described herein, the
first washcoat layer further includes zeolites.
[0080] In one or more of the embodiments described herein, the
palladium-based catalyst is a palladium-gold catalyst.
[0081] In one or more of the embodiments described herein, the
second layer further includes one a platinum-based catalyst, a
palladium-based catalyst, and combinations thereof.
[0082] In one or more of the embodiments described herein, the
platinum-based catalyst comprises platinum-bismuth.
[0083] In one or more of the embodiments described herein, the
weight loading of copper in the copper-ceria is 1% to 10%.
[0084] In one or more of the embodiments described herein, the
weight loading of the copper-ceria in the second washcoat layer is
0.2 g/in.sup.3 to 2.0 g/in.sup.3.
[0085] In one or more of the embodiments described herein, the
catalyst includes a third washcoat layer.
[0086] In another embodiment, an engine exhaust catalyst includes a
copper ceria; a platinum-based catalyst, a palladium-based
catalyst, and combinations thereof; and a zeolite.
[0087] In one or more of the embodiments described herein, the
zeolites include HY zeolites and ZSM5 zeolites.
[0088] In one or more of the embodiments described herein, the
weight loadings of the platinum-based catalyst and the copper-ceria
are approximately the same.
[0089] In one or more of the embodiments described herein, wherein
the platinum-based catalyst is a platinum-palladium catalyst.
[0090] In one or more of the embodiments described herein, the
weight loading of copper in the copper-ceria is 1% to 10%.
[0091] In one or more of the embodiments described herein, wherein
the weight loading of the copper-ceria is 0.2 g/in.sup.3 to 2.0
g/in.sup.3.
[0092] In another embodiment, an engine exhaust catalyst includes a
first zone having a platinum-based catalyst; a second zone; a third
zone having a palladium-gold catalyst; and a copper ceria catalyst
in at least one of the first, second, and third zones. In yet
another embodiment, the engine exhaust catalyst further includes
one or more washcoat layers having a metal catalyst.
[0093] In another embodiment, an engine exhaust catalyst includes a
first zone having at least one of a platinum-based catalyst, a
palladium-based catalyst, and combinations thereof; and a second
zone having copper-ceria. In yet another embodiment, the engine
exhaust catalyst further includes one or more washcoat layers
having a metal catalyst. In still yet another embodiment, the
engine exhaust catalyst further includes a washcoat layer having
copper ceria.
[0094] In one or more of the embodiments described herein, the
catalyst includes a substrate, and the second zone is in front of
the first zone.
[0095] In one or more of the embodiments described herein, one or
more zeolites is provided in at least one of the first zone and the
second zone.
[0096] In one or more of the embodiments described herein, the
first zone encounters an engine exhaust flow before the second
zone.
[0097] In one or more of the embodiments described herein, the
palladium-based catalyst is a palladium-gold catalyst.
[0098] In one or more of the embodiments described herein, the
second layer further includes one a platinum-based catalyst, a
palladium-based catalyst, and combinations thereof.
[0099] In one or more of the embodiments described herein, the
platinum-based catalyst is one of platinum-palladium,
platinum-bismuth, and combinations thereof.
[0100] In one or more of the embodiments described herein, the
weight loading of copper in the copper-ceria is 1% to 10%.
[0101] In one or more of the embodiments described herein, the
weight loading of the copper-ceria in the second zone is 0.2
g/in.sup.3 to 2.0 g/in.sup.3.
[0102] In one or more of the embodiments described herein, the
catalyst includes a third zone.
[0103] In one or more of the embodiments described herein, the
first zone includes a plurality of washcoat layers. In another
embodiment, the first zone includes at least two layers and at
least one of the washcoat layers includes copper ceria. In yet
another embodiment, the second zone includes a plurality of
washcoat layers.
[0104] In one or more of the embodiments described herein, the
second zone includes two washcoat layers. In another embodiment,
the second zone includes a first washcoat layer having at least one
of a platinum-based catalyst, a palladium-based catalyst, and
combinations thereof; and a second washcoat layer having
copper-ceria.
[0105] While particular embodiments according to the invention have
been illustrated and described above, those skilled in the art
understand that the invention can take a variety of forms and
embodiments within the scope of the appended claims.
* * * * *