U.S. patent application number 16/239185 was filed with the patent office on 2019-05-09 for porous ceramic body to reduce emissions.
The applicant listed for this patent is Corning Incorporated. Invention is credited to Mallanagouda Dyamanagouda Patil.
Application Number | 20190134614 16/239185 |
Document ID | / |
Family ID | 56507816 |
Filed Date | 2019-05-09 |
United States Patent
Application |
20190134614 |
Kind Code |
A1 |
Patil; Mallanagouda
Dyamanagouda |
May 9, 2019 |
POROUS CERAMIC BODY TO REDUCE EMISSIONS
Abstract
A porous ceramic honeycomb body including a substrate of
intersecting porous walls forming axial channels extending from a
first end face to a second end face. An active portion of the walls
include a zeolite catalyst disposed inside pores thereof and/or is
comprised of an extruded zeolite and a three way catalyst (TWC) is
disposed on wall surfaces of at least a portion of the active
portion.
Inventors: |
Patil; Mallanagouda
Dyamanagouda; (Corning, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Corning Incorporated |
Corning |
NY |
US |
|
|
Family ID: |
56507816 |
Appl. No.: |
16/239185 |
Filed: |
January 3, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15738434 |
Dec 20, 2017 |
10207258 |
|
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PCT/US2016/039710 |
Jun 28, 2016 |
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16239185 |
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62185874 |
Jun 29, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 35/1076 20130101;
B01D 2255/2061 20130101; F01N 2510/063 20130101; C04B 2111/0081
20130101; Y02T 10/22 20130101; F01N 3/0807 20130101; B01J 29/18
20130101; C04B 38/0051 20130101; F01N 3/2828 20130101; B01J 29/82
20130101; B01D 2255/912 20130101; B01J 29/08 20130101; B01J 29/7034
20130101; B01D 2255/9035 20130101; B01J 29/40 20130101; F01N
2370/04 20130101; B01J 29/084 20130101; F01N 13/0093 20140601; B01J
37/0009 20130101; B01D 53/9477 20130101; B01D 2255/50 20130101;
B01J 29/7007 20130101; B01J 35/04 20130101; B01J 37/0246 20130101;
B01D 2255/1023 20130101; B01J 29/7011 20130101; C04B 35/18
20130101; C04B 2235/3217 20130101; B01D 53/9486 20130101; C04B
35/447 20130101; B01D 2255/2065 20130101; B01D 2255/504 20130101;
B01J 37/0244 20130101; F01N 2330/06 20130101; B01J 23/63 20130101;
B01J 35/0026 20130101; B01D 2255/1021 20130101; B01D 2255/1025
20130101; B01D 2255/2063 20130101; C04B 2111/00793 20130101; B01D
2255/2092 20130101; C04B 2235/3205 20130101; B01J 35/0006 20130101;
B01J 2229/186 20130101; F01N 3/101 20130101; B01D 2255/20715
20130101; C04B 38/0006 20130101; Y02T 10/12 20130101; B01D 53/9445
20130101; B01J 29/70 20130101; C04B 38/0009 20130101; C04B 38/0006
20130101; C04B 35/18 20130101; C04B 35/447 20130101; C04B 38/0054
20130101; C04B 38/0074 20130101 |
International
Class: |
B01J 29/40 20060101
B01J029/40; B01J 29/82 20060101 B01J029/82; B01J 37/02 20060101
B01J037/02; B01J 23/63 20060101 B01J023/63; B01J 35/04 20060101
B01J035/04; B01J 37/00 20060101 B01J037/00; C04B 38/00 20060101
C04B038/00; F01N 3/10 20060101 F01N003/10; F01N 13/00 20060101
F01N013/00; B01D 53/94 20060101 B01D053/94; C04B 35/18 20060101
C04B035/18; C04B 35/447 20060101 C04B035/447; F01N 3/28 20060101
F01N003/28; B01J 35/10 20060101 B01J035/10; B01J 35/00 20060101
B01J035/00; B01J 29/08 20060101 B01J029/08; B01J 29/18 20060101
B01J029/18; B01J 29/70 20060101 B01J029/70 |
Claims
1. A method of manufacturing a ceramic article, comprising:
disposing zeolite catalyst inside pores in walls of a first portion
of walls of a porous ceramic body; and disposing three way catalyst
(TWC) on wall surfaces of at least a portion of the first portion
of the walls of the porous ceramic body.
2. The method of claim 1, wherein the TWC comprises at least one of
hydrocarbon oxidation, CO oxidation, and NOx reduction
catalysts.
3. The method of claim 1, wherein the walls of the porous ceramic
body define axial channels extending from a first end face to a
second end face of the porous ceramic body, and the first portion
of the walls extends at least partially from the first end face to
the second end face.
4. The method of claim 1, wherein the first portion of the walls is
spaced apart from the first end face by a second portion of the
walls.
5. The method of claim 4, wherein the second portion of the walls
is substantially free of zeolite catalyst inside pores of the
walls.
6. The method of claim 4, wherein the second portion of the walls
has a lower density than the first portion of the walls.
7. The method of claim 4, wherein the first portion of the walls is
spaced apart from the second end face by a third portion of the
walls.
8. The method of claim 7, wherein the third portion of the walls is
substantially free of zeolite catalyst inside pores of the
walls.
9. The method of claim 7, wherein the second portion of the walls
and the third portion of the walls are each substantially free of
zeolite catalyst inside pores of the walls.
10. A porous ceramic honeycomb body, comprising: a substrate of
porous walls forming channels extending from a first end face to a
second end face; and a three way catalyst (TWC) disposed on wall
surfaces of at least a portion of the walls, wherein the substrate
comprises an extruded zeolite catalyst.
11. A method of manufacturing a ceramic article, comprising:
extruding a zeolite catalyst porous ceramic body; and disposing
three way catalyst (TWC) on wall surfaces of the walls of the
porous ceramic body.
12. An exhaust system, comprising: a porous ceramic honeycomb body,
comprising: a substrate of porous walls forming channels extending
from a first end face to a second end face; an in wall zeolite
catalyst disposed inside pores of a first portion of the walls; and
a three way catalyst (TWC) disposed on wall surfaces of at least a
portion of the walls of the first portion of walls; and a housing,
comprising: an inlet configured to accept an exhaust gas stream to
be purified, an outlet configured to emit purified exhaust gas
stream, and a chamber between the inlet and outlet configured to
direct the exhaust gas stream to be purified into the first end
face of the substrate, wherein the substrate is disposed in the
chamber.
13. The system of claim 12, further comprising an engine configured
to generate and output an exhaust gas stream to the inlet of the
housing.
14. The system of claim 12, wherein the substrate mounted in the
chamber of the housing is close coupled to the engine.
15. The system of claim 12, further comprising at least one of a
filter and a selective catalytic reduction (SCR) catalyst
configured to purify the exhaust gas stream.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation application of U.S. patent
application Ser. No. 15/738,434 filed on Dec. 20, 2017, which
claims the benefit of priority to International Patent Application
Serial No. PCT/US2016/039710 filed on Jun. 28, 2016, and in turn
claims the benefit of priority to U.S. Provisional Patent
Application No. 62/185,874 filed on Jun. 29, 2015, the contents of
each are relied upon and incorporated herein by reference in their
entireties.
BACKGROUND
Field
[0002] Exemplary embodiments of the present disclosure relate to
porous ceramic bodies to reduce emissions, in particular porous
ceramic bodies having zeolite adsorber in wall and three way
catalyst (TWC) on wall to reduce hydrocarbons and volatile organic
components (HC/VOC) emissions, an exhaust gas system incorporating
the same, and methods of manufacturing the same.
Discussion of the Background
[0003] After-treatment of exhaust gas from internal combustion
engines may use catalysts supported on high-surface area substrates
and, in the case of diesel engines and some gasoline direct
injection engines, a catalyzed or non-catalyzed filter for the
removal of carbon soot particles. Porous ceramic flow-through
honeycomb substrates and wall-flow honeycomb filters may be used in
these applications.
[0004] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
disclosure and therefore it may contain information that does not
form any part of the prior art nor what the prior art may suggest
to a person of ordinary skill in the art.
SUMMARY
[0005] Exemplary embodiments of the present disclosure provide a
porous ceramic body having zeolite disposed inside pores of walls
of the porous ceramic body and three-way catalyst (TWC) disposed on
wall surfaces of the porous ceramic body.
[0006] Exemplary embodiments of the present disclosure also provide
a method of manufacturing a porous ceramic body having zeolite
disposed inside pores of walls of the porous ceramic body and
three-way catalyst (TWC) disposed on the wall surfaces of the
porous ceramic body.
[0007] Exemplary embodiments of the present disclosure also provide
an exhaust gas system including the porous ceramic body having
zeolite disposed inside pores thereof and TWC disposed on wall
surfaces thereof.
[0008] Additional features of the disclosure will be set forth in
the description which follows, and in part will be apparent from
the description, or may be learned by practice of the
disclosure.
[0009] An exemplary embodiment discloses a porous ceramic body
comprising a substrate of porous walls forming channels extending
from a first end face to a second end face. The porous ceramic
honeycomb body, comprises an in wall zeolite catalyst disposed
inside pores of a first portion of the walls, and a three way
catalyst (TWC) disposed on wall surfaces of the first portion of
the walls.
[0010] An exemplary embodiment also discloses a porous ceramic body
comprising a substrate of porous walls forming channels extending
from a first end face to a second end face. The porous ceramic
honeycomb body, comprises a three way catalyst (TWC) disposed on
wall surfaces of at least a portion of the walls, wherein the
substrate comprises an extruded zeolite catalyst.
[0011] An exemplary embodiment also discloses a method of
manufacturing a ceramic article. The method comprises extruding a
zeolite catalyst porous ceramic body and disposing three-way
catalyst (TWC) on wall surfaces of the walls of the porous ceramic
body.
[0012] An exemplary embodiment also discloses a method of
manufacturing a ceramic article. The method comprises disposing
zeolite catalyst inside pores in walls of a first portion of walls
of a porous ceramic body; and disposing three way catalyst (TWC) on
wall surfaces of at least a portion of the first portion of the
walls of the porous ceramic body.
[0013] An exemplary embodiment also discloses an exhaust gas
system. The exhaust gas system includes a housing having an inlet
configured to accept an exhaust gas stream to be purified, the
housing having a chamber configured to flow the exhaust gas stream
through a porous ceramic honeycomb body to purify the exhaust gas
stream, and the housing having an outlet configured to emit the
purified exhaust gas stream. The porous ceramic honeycomb body
disposed in the housing, comprises a substrate of porous walls
forming channels extending from a first end face to a second end
face. The porous ceramic honeycomb body comprises an in wall
zeolite catalyst disposed inside pores of walls of a first portion
of the walls and a three way catalyst (TWC) disposed on wall
surfaces of at least a portion of the walls of the first portion of
walls.
[0014] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the disclosure.
BRIEF DESCRIPTION OF THE FIGURES
[0015] The accompanying drawings, which are included to provide a
further understanding of the disclosure and are incorporated in and
constitute a part of this specification, illustrate exemplary
embodiments of the disclosure, and together with the description
serve to explain the principles of the disclosure.
[0016] FIG. 1A shows a schematic perspective view of a honeycomb
body comprising a skin on an outer periphery of a honeycomb core
according to exemplary embodiments of the disclosure. FIG. 1B is a
schematic cross section through the honeycomb body of FIG. 1A
according to these exemplary embodiments of the disclosure. FIG. 1C
is a schematic top view of the honeycomb body of FIG. 1A according
to these exemplary embodiments of the disclosure.
[0017] FIG. 2 is a graphical plot of cold start engine out HC
emissions in ppm carbon over time in seconds during an
Environmental Protection Agency (EPA) Federal Test Procedure-75
(FTP-75) cycle for a 3.8 L V6 engine in a vehicle.
[0018] FIG. 3 shows a graphical plot of cold start HC emissions in
ppm carbon over time in seconds before a zeolite adsorber and after
the zeolite adsorber.
[0019] FIG. 4 shows schematic cross sections through walls of the
conventional substrate having about 34% porosity and the fast
light-off, low mass, high porosity substrate having about 55%
porosity.
[0020] FIG. 5 shows schematic cross sections through walls of a
conventional substrate having about 34% porosity, the fast
light-off high porosity low mass substrate having about 55%
porosity, and the fast light-off high porosity low mass substrate
having zeolite disposed in the pores thereof according to exemplary
embodiments of the disclosure.
[0021] FIG. 6 schematically illustrates a process that shows HC
adsorption in zeolite in fast light-off high porosity low mass
substrate pores during cold start "CS" and desorption followed by
oxidation over TWC on fast light-off high porosity low mass
substrate channel wall surface once the substrate has reached a
higher temperature "HT" where TWC catalytic activity occurs
according to exemplary embodiments of the disclosure.
[0022] FIG. 7 illustrates a schematic cross section of a substrate
having a first portion of the cell channels having TWC disposed on
the walls, but no zeolite disposed in pores of the walls of the
first portion, and a second portion having zeolite disposed in the
pores of the walls and TWC disposed on the walls according to these
exemplary embodiments.
[0023] FIG. 8 shows a raw data plot of propylene concentration
(ppm) 802 and inlet temperature (.degree. C.) 804 as function of
time (sec) for a comparative example having on wall TWC only.
[0024] FIG. 9 shows a raw data plot of propylene concentration
(ppm) 902 and inlet temperature 904 (.degree. C.) as a function of
time (sec) for an example having on wall TWC and zeolite disposed
in wall according to exemplary embodiments of the disclosure.
[0025] FIG. 10 provides an overlap view of the data from FIGS. 8
and 9 showing the two light-off tests for TWC only in the
comparative example and ZSM-5 in pores and TWC on walls in the
example of the exemplary embodiment of the disclosure.
[0026] FIG. 11 shows exemplary embodiments of exhaust systems
including a porous ceramic honeycomb body comprising a zeolite
catalyst disposed in pores of the walls and a TWC disposed on
surfaces of the walls.
[0027] FIG. 12 is a schematic of exhaust systems when a sorbing
agent is disposed in a porous ceramic honeycomb body and a TWC is
disposed on surfaces of the walls of another porous ceramic
honeycomb body and there is no porous ceramic honeycomb body
comprising a sorbing agent disposed inside pores of at least a
portion of the walls and a TWC disposed on wall surfaces of the
portion of the walls.
DETAILED DESCRIPTION
[0028] The disclosure is described more fully hereinafter with
reference to the accompanying drawings, in which exemplary
embodiments of the disclosure are shown. This disclosure may,
however, be embodied in many different forms and should not be
construed as limited to the exemplary embodiments set forth herein.
Rather, these embodiments are provided so that this disclosure is
thorough, and will fully convey the scope of the disclosure to
those skilled in the art. In the drawings, the size and relative
sizes of layers and regions may be exaggerated for clarity.
[0029] It will be understood that when an element or layer is
referred to as being "on" or "connected to" another element or
layer, it can be directly on or directly connected to the other
element or layer, or intervening elements or layers may be present.
In contrast, when an element or layer is referred to as being
"directly on" or "directly connected to" another element or layer,
there are no intervening elements or layers present. It will be
understood that for the purposes of this disclosure, "at least one
of X, Y, and Z" can be construed as X only, Y only, Z only, or any
combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ,
ZZ).
[0030] In these exemplary embodiments, the disclosed article, and
the disclosed method of making the article provide one or more
advantageous features or aspects, including for example as
discussed below. Features or aspects recited in any of the claims
are generally applicable to all facets of the disclosure. Any
recited single or multiple feature or aspect in any one claim can
be combined or permuted with any other recited feature or aspect in
any other claim or claims.
[0031] While terms such as, top, bottom, side, upper, lower,
vertical, and horizontal are used, the disclosure is not so limited
to these exemplary embodiments. Instead, spatially relative terms,
such as "top", "bottom", "horizontal", "vertical", "side",
"beneath", "below", "lower", "above", "upper" and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. It will be understood that the
spatially relative terms are intended to encompass different
orientations of the device in use or operation in addition to the
orientation depicted in the figures. For example, if the device in
the figures is turned over, elements described as "below" or
"beneath" other elements or features would then be oriented "above"
the other elements or features. Thus, the exemplary term "below"
can encompass both an orientation of above and below. The device
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
interpreted accordingly.
[0032] "Include," "includes," or like terms means encompassing but
not limited to, that is, inclusive and not exclusive.
[0033] "About" modifying, for example, the quantity of an
ingredient in a composition, concentrations, volumes, process
temperature, process time, yields, flow rates, pressures,
viscosities, dimensions, and like values, and ranges thereof,
employed in describing the embodiments of the disclosure, refers to
variation in the numerical quantity that can occur, for example:
through typical measuring and handling procedures used for
preparing materials, compositions, composites, concentrates, or use
formulations; through inadvertent error in these procedures;
through differences in the manufacture, source, or purity of
starting materials or ingredients used to carry out the methods;
and like considerations. The term "about" also encompasses amounts
that differ due to aging of a composition or formulation with a
particular initial concentration or mixture, and amounts that
differ due to mixing or processing a composition or formulation
with a particular initial concentration or mixture.
[0034] The indefinite article "a" or "an" and its corresponding
definite article "the" as used herein means at least one, or one or
more, unless specified otherwise.
[0035] Abbreviations, which are well known to one of ordinary skill
in the art, may be used (e.g., "h" or "hr" for hour or hours, "g"
or "gm" for gram(s), "ml" for milliliters, and "RT" for room
temperature, "nm" for nanometers, and like abbreviations).
[0036] Specific values disclosed for components, ingredients,
additives, times, temperatures, pressures, and like aspects, and
ranges thereof, are for illustration only; they do not exclude
other defined values or other values within defined ranges. The
apparatus, and methods of the disclosure can include any value or
any combination of the values, specific values, and more specific
values described herein.
[0037] According to exemplary embodiments of this disclosure, an
active material is disposed inside the pores of a substrate and a
three-way catalyst (TWC) is disposed on the surfaces of the channel
walls of the substrate as will be described in more detail below.
In an exemplary embodiment, zeolite is disposed in the pores
directly on the pore surfaces and the TWC is disposed directly on
the wall surfaces.
[0038] An active material as used herein refers to material which
can modify a gaseous mixture, by reaction with the mixture
components, by catalytic activity, or by sorbing activity, or
desorbing activity. The active material is preferably sorbing
material and/or catalytic material. The sorbing material or sorbing
agents take up and hold substances by either absorption or
adsorption. In the present disclosure, a sorbing agent is present
in the substrate pores to take up or remove selected constituents
from a gaseous mixture under certain conditions. These constituents
can then desorb under certain conditions which are predetermined.
The term "sorbing material" or "sorbing agent" as used in the
present disclosure can refer to one or a plurality of sorbing
agents. Adsorption is the taking up of molecules by physical or
chemical forces, termed respectively, physical or chemical
adsorption. The term "adsorbing agent" according to the present
disclosure refers to at least one adsorbing agent. There can be
more than one type of adsorbing agent in the pores of the substrate
wall. The specific adsorbers can vary depending on the application.
Catalyst material according to the present disclosure refers to a
catalyst metal or catalyst metal oxide on a support. Catalyst
material includes also molecular sieves, such as zeolites when used
in conversions such as, e.g., in cracking of hydrocarbons or
oxidation, etc.
[0039] Example adsorbing agents that are suited for removal of
hydrocarbons are those that adsorb at relatively low temperatures
and desorb at relatively high temperatures. For example, adsorbing
agents that adsorb hydrocarbons at engine start-up temperatures
which are typically less than about 150.degree. C., and desorb at
engine operating temperatures which are typically greater than
about 150.degree. C. can be used. As disclosed in U.S. Pat. No.
5,260,035, hereby incorporated in its entirety as if fully set
forth herein, examples of adsorbing agents which can be used as
described herein without limitation are molecular sieves, activated
carbon, transition aluminas, activated silicas, and combinations of
these. Molecular sieves are crystalline substances having pores of
size suitable for adsorbing molecules. Some example types of
molecular sieves without limitation are carbon molecular sieves,
zeolites, aluminophosphates, metallophosphates,
silicoaluminophosphates, and combinations of these. Carbon
molecular sieves have well defined micropores made out of carbon
material.
[0040] In some embodiments, the active material can be without
limitation, a metal exchanged or impregnated zeolite, for example,
ZSM-5, beta-zeolites, mordenite, Y-zeolites, ultrastabilized
Y-zeolites, aluminum phosphate zeolites, gmelinite, mazzite,
offretite, ZSM-12, ZSM-18, Berryllophosphate-H, boggsite, SAPO-40,
SAPO-41, combinations thereof, and mixtures thereof.
[0041] The active material will be referred to herein as a zeolite
for convenience in the further detailed description. Zeolite,
zeolite adsorber, zeolite catalyst, zeolite-based catalyst, and the
like are used herein interchangeably for convenience according to
these exemplary embodiments of the disclosure.
[0042] The TWC can include noble metal oxidation catalysts such as
Pt, Rh, and/or Pd with a support such as alumina, ceria, titania,
lanthana, zirconia etc. The oxidation catalyst serves to oxidize
the hydrocarbons mainly, to innocuous products as carbon dioxide
and water, which are suitable for passing into the atmosphere. The
TWC can include a catalyst for conversion of NO.sub.x, CO, and
hydrocarbons to innocuous products. For example, the TWC can
include noble metal as e.g., Pt, Pd, Rh, or combinations thereof on
alumina, ceria, lanthana, zirconia, yttria, or combinations
thereof. The TWC suited to the practice of exemplary embodiments of
the present disclosure for stationary power plant exhaust
conversion can include SCR catalyst for NOx reduction such as
zeolite-based catalysts having transition metal or metals ion
exchanged. Some example catalysts are Fe mordenite, Cu mordenite,
ZSM-5 H.sup.+ form, and V.sub.2O.sub.5/TiO.sub.2. The TWC suited to
the practice of exemplary embodiments of the present disclosure for
auto exhaust conversion are, for example, Pt on ceria-alumina
combined with Rh on zirconia. The Pt-ceria-alumina and the
Rh-zirconia can be combined and applied at once, as in a single
coating or they can be applied in separate coatings. Another
suitable catalyst is Pt/Pd/Rh on gamma alumina with a rare earth
oxide such as ceria.
[0043] Improvements in engine efficiencies can lead to lower
exhaust gas temperatures. Lower temperatures may lead to lower
conversion of exhaust gas constituents on catalysts. Hybrid
electric vehicles (HEVs), engine starts and stops, other engine
cycling, and the like can lead to more cold start HC emissions. As
used herein, HC refers to hydrocarbons and volatile organic
components (HC/VOC). The disclosed zeolite disposed inside the
pores of a substrate and a three-way catalyst (TWC) disposed on the
surfaces of the channel walls of the substrate as described herein
can cost-effectively, efficiently, and passively reduce HC
emissions under these types of conditions.
[0044] FIG. 1A shows a honeycomb body 100 including a plurality of
intersecting walls 110 that form mutually adjoining cell channels
112 extending axially in direction "A" between opposing end faces
114, 116. FIG. 1B shows a schematic cross section through the
honeycomb body 100 of FIG. 1A. FIG. 1C shows a schematic top view
of the honeycomb body 100 of FIG. 1A. "Cell" is generally used
herein when referring to intersecting walls in cross section of the
honeycomb body and "channel" is generally used when referring to a
cell extending between the end faces 114, 116. Cell and channel may
be used interchangeably as well as "cell channel". The top face 114
refers to the first end face and the bottom face 116 refers to the
second end face of the honeycomb body 100 positioned in FIG. 1A,
otherwise the end faces are not limited by the orientation of the
honeycomb body 100. The top face 114 may be an inlet face and the
bottom face 116 may be an outlet face of the honeycomb body 100 or
the top face 114 may be an outlet face and the bottom face 116 may
be an inlet face of the honeycomb body 100.
[0045] Cell density can be between about 100 and 900 cells per
square inch (cpsi). Typical cell wall thicknesses can range from
about 0.025 mm to about 1.5 mm (about 1 to 60 mil). For example,
honeycomb body 100 geometries may be 400 cpsi with a wall thickness
of about 8 mil (400/8) or with a wall thickness of about 6 mil
(400/6). Other geometries include, for example, 100/17, 200/12,
200/19, 270/19, 300/4, 600/4, 400/4, 600/3, and 900/2. As used
herein, honeycomb body 100 is intended to include a generally
honeycomb structure but is not strictly limited to a square
structure. For example, hexagonal, octagonal, triangular,
rectangular or any other suitable cell shape may be used. Also,
while the cross section of the depicted cellular honeycomb body 100
is circular, it is not so limited, for example, the cross section
can be elliptical, square, rectangular, other polygonal shape, or
other desired shape, and a combination thereof.
[0046] As used herein, porous ceramic body can refer to a honeycomb
body, but is not so limited and can also refer to trough filters,
radial flow filters, and the like. Ceramic body compositions are
not particularly limited and can comprise major and minor amounts
of cordierite, aluminum-titanate, mullite, .beta.-spodumene,
silicon carbide, zeolite and the like, and combinations thereof. As
a further example, the ceramic honeycomb body can comprise an
extruded zeolite or other extruded catalyst.
[0047] The manufacture of porous ceramic honeycomb bodies may be
accomplished by the process of plasticizing ceramic powder batch
mixtures, extruding the mixtures through honeycomb extrusion dies
to form honeycomb extrudate, and cutting, drying, and firing the
extrudate to produce ceramic honeycomb bodies of high strength and
thermal durability having channels extending axially from a first
end face to a second end face. As used herein a ceramic honeycomb
body includes ceramic honeycomb monoliths and ceramic segmented
honeycomb bodies.
[0048] A co-extruded or an after-applied exterior skin may form an
outer peripheral surface extending axially from a first end face to
a second end face of the ceramic honeycomb bodies. Each channel of
the honeycomb bodies defined by intersecting walls (webs), whether
monolithic or segmented, can be plugged at an inlet face or an
outlet face to produce a filter. When some channels are left
unplugged a partial filter can be produced. The honeycomb body,
whether monolithic or segmented, can be catalyzed to produce a
substrate. A non-plugged honeycomb body is generally referred to
herein as a substrate. The catalyzed substrate can have an after
applied catalyst or comprise an extruded catalyst. Further, filters
and partial filters can be catalyzed to provide
multi-functionality. The ceramic honeycomb bodies thus produced are
widely used as catalyst supports, membrane supports, as wall-flow
filters, as partial filters, and the like or as combinations
thereof for cleaning fluids such as purifying engine exhausts.
[0049] When an internal combustion engine starts cold, a larger
amount of unburned hydrocarbons and carbon monoxide can be emitted
in the first minutes or less than when the internal combustion
engine is warm. Also the larger amount of unburned hydrocarbons and
carbon monoxide can pass through a cold catalyst without converting
to CO.sub.2, and H.sub.2O. Close coupling the catalyst to the
engine, for example, positioned within less than six inches (15.24
cm) of the engine exhaust manifold can reduce the un-burnt
hydrocarbons (HC) and carbon monoxide (CO) by more quickly warming
the catalyst. Nevertheless, cold start emissions can account for
greater than 80% of the total emissions, for example, for a vehicle
during a drive cycle. FIG. 2 illustrates the engine out cold start
HC emissions in ppm carbon 202 (dashed line) and the engine out
exhaust temperature 204 (solid line) over time in seconds during an
Environmental Protection Agency (EPA) Federal Test Procedure-75
(FTP-75) cycle for a 3.8 L V6 engine in a vehicle.
[0050] After the catalyst is warmed up, after about 20-30 seconds,
most of the emissions (HC, CO, NOx) get converted to CO.sub.2,
H.sub.2O, and N.sub.2 by the warm catalyst. To reduce catalyst
warming time, lower mass close coupled substrates having high
porosity and significantly lower density can be utilized. For
example, the density can be about 30% less than conventional porous
ceramic honeycomb substrates having similar cell density and wall
thickness. For example, when cordierite density is taken as about
2.5 g/cm.sup.3, a 400/6 conventional porous ceramic honeycomb
substrate of cordierite can have a density of about 0.41 g/cm.sup.3
with about 27 percent porosity (% P), whereas the 400/6 low mass
porous ceramic honeycomb substrate of cordierite can have a density
of about 0.31 g/cm.sup.3 with about 45% P, a density of about 0.25
g/cm.sup.3 with about 55% P, or a density of about 0.20 g/cm.sup.3
with about 65% P. For example, a 600/3 conventional porous ceramic
honeycomb substrate of cordierite can have a density of about 0.26
g/cm.sup.3 with about 27% P, whereas the 600/3 low mass porous
ceramic honeycomb substrate of cordierite can have a density of
about 0.20 g/cm.sup.3 with about 45% P, a density of about 0.16
g/cm.sup.3 with about 55% P, or a density of about 0.12 g/cm.sup.3
with porosity of 65%.
[0051] For another example, when the material is an aluminum
titanate composite, for example, about 70% aluminum titanate phase
having a density of about 3.7 g/cm.sup.3 and about 30% strontium
feldspar phase having a density of about 3.0 g/cm.sup.3 thus giving
the composite density of about 3.5 g/cm.sup.3, a 400/6 conventional
porous ceramic honeycomb substrate of aluminum titanate composite
can have a density of about 0.57 g/cm.sup.3 with about 27 porosity
(% P), whereas the 400/6 low mass porous ceramic honeycomb
substrate of aluminum titanate composite can have a density of
about 0.43 g/cm.sup.3 with about 45% P, a density of about 0.35
g/cm.sup.3 with about 55% P, or a density of about 0.28 g/cm.sup.3
with about 65% P. For example, a 600/3 conventional porous ceramic
honeycomb substrate of aluminum titanate composite can have a
density of about 0.36 g/cm.sup.3 with about 27% P, whereas the
600/3 low mass porous ceramic honeycomb substrate of aluminum
titanate composite can have a density of about 0.27 g/cm.sup.3 with
about 45% P, a density of about 0.22 g/cm.sup.3 with about 55% P,
or a density of about 0.17 g/cm.sup.3 with porosity of 65%.
[0052] Having faster light-off compared to standard substrates can
be provided by the lower mass substrates. These low mass high
porosity substrates can reduce engine out emissions. Testing has
shown that there is nearly a 10% HC reduction using such a low mass
high porosity substrate for a close coupled catalyst.
[0053] Another approach to reducing the cold start HC release
includes providing zeolites to adsorb this large amount of HC. The
low mass high porosity substrates provide pores that can
accommodate zeolites disposed therein. Zeolites adsorb HC at low
temperature and zeolites later release the HC at higher temperature
to allow conversion to CO.sub.2 and H.sub.2O by the warm catalyst.
FIG. 3 shows that a substantial amount of HC is adsorbed over the
zeolite catalyst. Curve 302 (dashed line) indicates HC before the
zeolite adsorber and curve 304 (dot-dashed line) indicates HC after
the zeolite adsorber. Curve 306 (solid line) indicates exhaust
temperature before the zeolite adsorber and curve 308 (double solid
line) indicates exhaust temperature after the zeolite adsorber.
[0054] For example, zeolite technology and zeolite coating can be
used for diesel oxidation catalysts (DOC) in diesel vehicles. In
such an application, it was found that zeolites adsorb >80% HC
from cold start emissions. Thus, it is beneficial to take advantage
of the properties of zeolites to adsorb HC to further reduce
emissions during cold start and during normal driving cycle on fast
light-off, low mass, high porosity substrates. The DOC catalysts
can have a porosity of less than about 40%, for example, less than
about 35%, a porosity of about 10% to about 30%, or even a porosity
of about 15% to about 20%. The DOC catalysts can have a median pore
size of about 7-10 .mu.m, and the density of the substrate can be
about 0.19-0.35 gm/cm.sup.3 at a 400/4 geometry.
[0055] The fast light-off, low mass, high porosity substrates, can
have a porosity of greater than about 40%, for example, greater
than about 45%, greater than about 50% and even greater than about
55%. For example, high porosity low mass substrates can have a
porosity between about 50% and 70%. The fast light-off high
porosity low mass substrate can have a mass of about 190 gm for an
about 4 inch (5.1 cm) diameter.times.about 4 inch (5.1 cm) length,
about 600/3 geometry with about 55% porosity. By comparison a
conventional substrate sample with about 34% porosity has a mass of
about 290 gm for about the same size and geometry.
[0056] FIG. 4 shows schematic cross sections through walls of the
conventional substrate having about 34% porosity and the fast
light-off high porosity low mass substrate having about 55%
porosity. The higher mass, lower porosity wall 402 is represented
by a darker shade than the lower mass, higher porosity wall
404.
[0057] Exemplary embodiments of the disclosure are directed to a
porous ceramic body having zeolite disposed in pores of walls of
the porous ceramic body and three-way catalyst (TWC) disposed on
wall surfaces of the porous ceramic body. In these exemplary
embodiments this concept includes zeolite coated exclusively inside
the pores of the substrate and TWC coated on the wall surfaces of
the channels. Zeolite coated inside the pores of the substrate is
referred to herein as "in wall" and TWC coated on the wall surfaces
is referred to herein as "on wall". Optionally, when the porous
ceramic body is an extruded zeolite, additional zeolite can be
coated inside the pores of the substrate, but need not be.
[0058] FIG. 5 shows schematic cross sections through walls of the
conventional substrate 502 having about 34% porosity, the high
porosity low mass substrate 504 having about 55% porosity, and the
high porosity low mass substrate 504 having zeolite 506 disposed in
the pores 508 thereof indicated by a cross hatch fill. The higher
mass, lower porosity wall 502 can have a larger median pore size
than the lower mass, higher porosity wall 504. For example, the
lower mass, higher porosity wall 504 can have a median pore size of
about 7 to 10 .mu.m. TWC 512 is coated on the channel walls 502,
504, and zeolite 506 is disposed in the pores 508 of the lower
mass, higher porosity wall 504 illustrated in FIG. 5 insert. "G"
represents the gas flow through the channels of the porous ceramic
substrate, including, for example, HC, CO, NOx, O.sub.2, etc.
[0059] Fast light-off high porosity low mass substrate 504 with
zeolite 506 disposed in the pores 508 and TWC 512 disposed on the
walls will adsorb HC in the zeolite 506 during cold start of the
cycle. As the TWC 512 catalyst gets heated these adsorbed HC desorb
from zeolite 506, which is also heated, to get oxidized over the
TWC 512 on the surface of the walls. There will be some temperature
gradient between the surface TWC 512 and zeolites 506 in the pores
508 due to wall thickness and mass. This process is schematically
illustrated in FIG. 6 that shows HC adsorption 602 in zeolite 506
in fast light-off high porosity low mass substrate pores 508 during
cold start "CS" and desorption 604 followed by oxidation 606 over
TWC 512 on high porosity low mass substrate 504 channel wall
surface once the substrate has reached a higher temperature "HT"
where TWC catalytic activity occurs. "CS" refers to colder
condition during adsorption 602, while "HT" represents hotter
substrate and catalyst during desorption 604 and oxidation cycle
606.
[0060] In these exemplary embodiments, the zeolite 506 disposed in
the pores 508 can adsorb HC during cold start at and below a
certain temperature and desorb HC above the certain temperature,
and the TWC 512 disposed on the walls can decompose at least a
portion of the desorbed HC in a temperature range having an upper
limit above the certain temperature. For example, the certain
temperature is a catalyst light-off temperature between about
100.degree. C. and about 300.degree. C., for example, a catalyst
light-off temperature between about 100.degree. C. and about
250.degree. C.
[0061] According to these exemplary embodiments of the disclosure,
zeolite can be in the pores and TWC can be disposed on the walls
throughout the entire length of the cell channels of the low mass,
high porosity substrate, alternatively zeolite can be disposed only
in pores of a portion of the cell channels of the low mass, high
porosity substrate. For example, a center portion extending axially
and spaced apart from at least one end face may have zeolite
disposed in pores of the channel walls. For example, a center
portion extending axially and spaced apart from an input end face
may have zeolite disposed in pores of the channel walls. In these
instances, the TWC can be disposed on the portion having the
zeolite disposed in the pores as well as the portion extending to
the at least one end face. Having no zeolite disposed in the
channels at an input end portion can provide low mass density
allowing the substrate and TWC in such a portion to heat up more
rapidly than if zeolite was present in the pores. Having no zeolite
disposed in the channels at an outlet end portion can provide, for
example, cost savings of catalyst material.
[0062] According to these exemplary embodiments of the disclosure,
zeolite can be disposed only in pores of a first portion of the
cell channels of the low mass, high porosity substrate and TWC can
be disposed on at least a portion of the walls of the first portion
of the cell channels of the low mass, high porosity substrate. For
example, in some of these exemplary embodiments, the first portion
of the walls can extend at least partially from the first end face
to the second end face. For example, in some of these exemplary
embodiments, the first portion of the walls can be spaced apart
from the first end face by a first distance, and the first end face
can be an inlet side of the porous ceramic honeycomb body. For
example, in some of these exemplary embodiments, a second portion
of the walls can extend from the first end face to the first
portion of the walls. For example, in some of these exemplary
embodiments, the walls extending between the first end face and the
first portion of the walls can have a lower density than the first
portion of the walls. For example, in some of these exemplary
embodiments, the first portion of the walls can be spaced apart
from the second end face by a second distance. For example, in some
of these exemplary embodiments, the first distance and the second
distance can be substantially the same or different. For example,
the first distance and/or the second distance can be about 5% of
the length of the low mass, high porosity substrate, for example,
about 10%, about 15%, about 20%, about 25%, about 30%, about 40%,
or even about 50% of the length of the low mass, high porosity
substrate, for example, between about 10% and 50% of the length of
the low mass, high porosity substrate depending on the catalyst
light off temperature and HC adsorption capacity. For example, in
some of these exemplary embodiments, a third portion of the walls
extends from the second end face to the first portion of the
walls.
[0063] The second and third portions can have no zeolite disposed
inside pores of the walls and have TWC disposed on at least a
portion of the second portion and/or the third portion.
[0064] FIG. 7 illustrates a schematic cross section of a substrate
700 having an input end face 702 and an output end face 704, a
first portion 706 of the cell channels having zeolite disposed in
the pores of the walls and second and third portions 708, 710 of
the cell channels having TWC disposed on the walls, but no zeolite
disposed in pores of the walls of the second and/or third portions
708, 710. The first portion 706 having zeolite disposed in the
pores of the walls can have TWC disposed on the walls according to
these exemplary embodiments of the disclosure. Such an arrangement
provides an advantage of keeping the mass density low in the
beginning, end or other desired section of the high porosity low
mass substrate. The first portion 706, second portion 708, and/or
third portion 710 design can be varied as needed to optimize HC
adsorption and desorption cycles and manage the desired heat
cycles.
EXAMPLES
[0065] Exemplary embodiments of the disclosure are further
described below with respect to certain exemplary and specific
embodiments thereof, which are illustrative only and not intended
to be limiting.
[0066] A high porosity, low mass honeycomb body was coated with
zeolite slurry comprising ZSM-5 and AL-20. The zeolite slurry was
disposed only in the wall pores. After drying, the high porosity,
low mass honeycomb body having zeolite disposed in wall was coated
with three-way catalyst (TWC) as a layer on the channel wall
surfaces. The sample was fired and tested for hydrocarbon (HC)
adsorption and desorption/oxidation using C.sub.3H.sub.6 in
accordance with exemplary embodiments of the disclosure.
C.sub.3H.sub.6 was adsorbed under CS conditions and a significant
portion was oxidized during heating cycle (HT). A comparative
sample was coated with TWC only and then similarly fired and tested
for hydrocarbon (HC) adsorption and desorption/oxidation.
[0067] The high porosity, low mass honeycomb body substrate having
dimensions of about 1 inch (2.54 cm) diameter by about 3 inch (7.62
cm) length was coated with TWC (about 0.1 g/cc) using a vacuum
coating process, without zeolite. An about 1 inch (2.5 cm) diameter
by about 1 inch (2.4 cm) length sample of this comparative
catalyzed sample was tested in a light off bench test with about
400 ppm propylene, 5000 ppm carbon monoxide, 500 ppm nitric oxide,
14% CO.sub.2, 10% steam (H.sub.2O), 1700 ppm hydrogen (H.sub.2),
balance nitrogen with space velocity of 90,000 ch/hr (ch refers to
volumetric changes so that ch/hr refers to volumetric changes per
hour herein) and a total flow of about 17.4 liters/min, using
Fourier transform infrared spectroscopy (FTIR) detector. FIG. 8
shows a raw data plot of propylene concentration (ppm) 802, and
catalyst on substrate inlet temperature (.degree. C.) 804 and
outlet temperature (.degree. C.) 806 as function of time (sec) for
the sample having on wall TWC. There was no removal of propylene
before the catalyst heats up as shown in Region "CS". Propylene was
oxidized at about 280 sec and the concentration decreased to less
than about 50 ppm as shown in region "HT". The spikes in the
propylene curve between about 0 and 100 sec and between about 100
and 200 sec are instrument anomalies caused by changing scale.
[0068] The same high porosity, low mass honeycomb body substrate
having dimensions of about 1 inch (2.5 cm) diameter by about 3 inch
(7.6 cm) length was coated with ZSM-5 zeolite at about 0.1 g/cc
loading in the pores followed by coating the same TWC as used in
the comparative example at about 0.1 g/cc loading on the channel
wall surfaces according to exemplary embodiments of the disclosure
as described herein. A sample of about 1 inch (2.4 cm) diameter by
about 1 inch (2.6 cm) length sample of this exemplary catalyzed
sample was tested in a light off bench test with 400 ppm propylene,
5000 ppm carbon monoxide, 500 ppm nitric oxide, 14% CO.sub.2,
H.sub.2O, 10% steam, 1700 ppm hydrogen, balance nitrogen with space
velocity of 90,000 ch/hr and 17.9 liter/min total flow, using
Fourier transform infrared spectroscopy (FTIR) detector as
explained above for the comparative example. FIG. 9 shows a raw
data plot of propylene concentration (ppm) 902, and inlet
temperature (.degree. C.) 904 and outlet temperature (.degree. C.)
910 as a function of time (sec) for the example having on wall TWC
and zeolite disposed in wall according to exemplary embodiments of
the disclosure. Referring to FIGS. 8 and 9, it can be seen that the
propylene concentration 902 is much lower at the beginning of the
test from about 15 second start time in the exemplary embodiment of
the disclosure indicating significant adsorption of propylene in
ZSM-5 zeolite coated in the high porosity, low mass honeycomb body
substrate pores. As the temperature heats up indicated by curve 904
and the catalyst gets heated the propylene concentration 902
decreases to zero indicating the oxidation reaction over TWC. In
cold start region CS, HC adsorption occurred as indicated by box
906 (See FIG. 10 area between curves 902 and 802). As the TWC
catalyst and zeolite were heated HC desorption and decomposition
occurred as indicated by ellipse 908 (See FIG. 10 shaded area
between curves 902 and 802). This example exothermic reaction shows
the adsorption of propylene (HC) on zeolite and desorption and
oxidation during heat up cycle over TWC on the surface.
[0069] FIG. 10 provides an overlap view of the data from FIGS. 8
and 9 showing the two light-off tests for TWC only in the
comparative example and ZSM-5 in pores and TWC on walls in the
example of the exemplary embodiment of the disclosure as described
herein. The Figure comparing the two examples shows that nearly
more than about 60% of the propylene is adsorbed and a small
fraction (<10%) of the propylene desorbed and the rest of the
hydrocarbon oxidized to CO.sub.2. These examples clearly
demonstrate the advantage of coating zeolite in pores of the fast
light-off, high porosity, low mass honeycomb body substrate having
TWC coated on wall to provide adsorption at low temperature
followed by desorption and oxidation of adsorbed propylene over the
TWC at high temperature.
[0070] Zeolites in automotive catalysts have been found by the
applicant to adsorb a broad range of HC, including, for example,
from C.sub.3 to C.sub.10 HC chains, alkanes, alkenes, aromatics,
and the like. The zeolites have been found to remain stable and
reliable for greater than about 100,000 miles (about 161,000 km).
Combining the zeolites with the fast light-off, high porosity, low
mass honeycomb body substrate deposited in the pores thereof and
the TWC deposited on the walls demonstrates the concepts of the
exemplary embodiments of the disclosure.
[0071] While not wishing to be bound by theory, the path of the HC
to be adsorbed by the zeolite disposed in pores of the walls can be
very short leading to rapid adsorption because the walls of the
fast light-off, high porosity, low mass honeycomb body substrate
are thin. As used herein, path simply refers to the path the gas
takes to penetrate the substrate walls. In addition, the path of
the desorbed HC to the TWC catalyst is also short for the same
reason leading to efficient adsorption at low temperature and
desorption and oxidation at high temperature. The TWC disposed on
wall tends to heat to catalytic temperature prior to mass in wall.
Thus, HC desorbed when the bulk of the wall heats up can be readily
oxidized by the heated catalyst leading to efficient adsorption at
low temperature and desorption and oxidation at high temperature.
Furthermore, the thin porous wall heats more easily than a thicker,
less porous wall such that the zeolite is efficiently utilized to
release adsorbed HC to be oxidized.
[0072] In an exemplary embodiment of a diesel oxidation catalyst
(DOC) having a lower porosity (% P), for example, in a range from
10% P to 35% P, according to this disclosure, zeolite can be
disposed in pores in the wall of the DOC and TWC can be disposed on
wall as described herein. In the instance of a DOC, the zeolite can
adsorb HC when the engine cycle runs at a cool temperature followed
by desorption and oxidation of HC as described and demonstrated
above when the engine cycle runs at a hot temperature.
[0073] In some of these exemplary embodiments, an exhaust system
for cleaning a fluid such as engine exhaust, can comprise the low
mass substrate having high porosity or lower porosity, with zeolite
disposed inside pores in wall and TWC disposed on wall of the
substrate as described herein. The substrate may be disposed in a
housing, which may be deployed in a fluid treatment system such as
an exhaust system. The housing may be referred to as a can, and the
process of disposing the ceramic honeycomb body in the can may be
referred to as canning.
[0074] FIG. 11 shows exemplary embodiments of exhaust systems
including a porous ceramic honeycomb body comprising a zeolite
catalyst disposed in pores of the walls and a TWC disposed on
surfaces of the walls. The system 3 according to some of these
embodiments can include an engine 5 or other source of fluid stream
"G", such as exhaust gas stream, to be purified, a housing 7 having
a chamber 8 to mount the substrate 9, a filter 11, and an outlet
pipe 13, such as a tail pipe or exhaust stack. The housing 7 can
have an inlet 12 to direct the gas stream G into the chamber 8 and
through the channels of the substrate 9 disposed in the housing
chamber 8 whereby the gas stream is purified as described above
with regard to some of the exemplary embodiments. The purified gas
stream G1 can exit the housing 7 through an outlet 14 and be
filtered as it passes through walls of a through-wall filter 11
having inlet and outlet channels sealed with plugs 20 at respective
outlet and inlet ends providing a purified and filtered gas stream
emission from tail pipe 13. The filter 11 can be a diesel
particulate filter or a gas particulate filter and can be upstream
or downstream of the substrate 9 according to some of these
exemplary embodiments. Furthermore, additional components of the
exhaust system may include, for example, a selective catalytic
reduction (SCR) catalyst and other compatible components.
[0075] In system 21, according to some of these exemplary
embodiments, the substrate is located further from the engine 10
and without a particulate filter 11 such that purified gas stream
G1 can directly exit the tail pipe 13. That is, in system 3, the
substrate may be close coupled to the engine 5 to provide fast
light-off as described above according to various exemplary
embodiments of the disclosure. Likewise, while the substrate 9 may
not be close-coupled to the engine 10 in the system 21, the system
21 may nevertheless include a filter, SCR catalyst, and the like,
and combinations thereof. When the substrate 9 has a low mass
density inlet portion as described above with reference to FIG. 7,
a sorbing agent to adsorb cold start and/or cold cycle emission
constituents and desorb the emission constituents at a temperature
near or above a three way catalyst (TWC) light-off temperature, and
such a TWC to decompose the desorbed emission constituents,
according to some of the exemplary embodiments described herein,
then the substrate may need not be so closely coupled to the
engine, providing more flexibility in system design where space is
limited, while still providing full drive cycle emissions below
target regulations.
[0076] Furthermore, components not having the sorbing agent and TWC
disposed according to these exemplary embodiments can lead to
inefficiencies. For example, as shown in FIG. 12, a sorbing agent
33 disposed closer to an engine 35 than a TWC 37 would adsorb
emission constituents in exhaust gas stream G, but the TWC 37 would
be delayed in heating up, even, perhaps, reaching light off
temperature after the sorbing agent desorbs the constituents at a
desorbing temperature. On the other hand, a TWC 37 closer to the
engine 35 would heat up faster, but would not be able to decompose
the desorbed constituents. Further, a TWC 37 closer to the engine
and an additional TWC 39 further from the engine than the sorbing
agent 33 would add additional components and weight and require
additional space.
[0077] It will be apparent to those skilled in the art that various
modifications and variations can be made in the present disclosure
without departing from the spirit or scope of the disclosure. Thus,
it is intended that the appended claims cover the modifications and
variations of this disclosure provided they come within the scope
of the appended claims and their equivalents.
* * * * *