U.S. patent application number 14/566906 was filed with the patent office on 2015-06-18 for enhanced methane formation in reforming catalysts.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. The applicant listed for this patent is Tilman Wolfram Beutel, John Francis Brody, Eugine Choi, Keith Robert Hajkowski, Chris Esther Kliewer, Paul Dmitri Madiara, Michael Anthony Marella, Partha Nandi, Sumathy Raman, George Skic, Karl Gottlieb Strohmaier, Brian Michael Weiss, Walter Weissman. Invention is credited to Tilman Wolfram Beutel, John Francis Brody, Eugine Choi, Keith Robert Hajkowski, Chris Esther Kliewer, Paul Dmitri Madiara, Michael Anthony Marella, Partha Nandi, Sumathy Raman, George Skic, Karl Gottlieb Strohmaier, Brian Michael Weiss, Walter Weissman.
Application Number | 20150167588 14/566906 |
Document ID | / |
Family ID | 52282935 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150167588 |
Kind Code |
A1 |
Beutel; Tilman Wolfram ; et
al. |
June 18, 2015 |
ENHANCED METHANE FORMATION IN REFORMING CATALYSTS
Abstract
Catalyst compositions suitable for use in the exhaust gas
recycle stream of an internal combustion engine are provided. Such
catalyst compositions typically provide significant amounts of
methane in addition to syngas. A reformer incorporating such a
catalyst for use in an exhaust gas recycle portion of an internal
combustion engine powertrain is described. A powertrain
incorporating such a reformer, a method of increasing the octane
rating of an exhaust gas recycle stream, and and a method of
operating an internal combustion engine using methane-assisted
combustion are also described.
Inventors: |
Beutel; Tilman Wolfram;
(Neshanic Station, NJ) ; Weiss; Brian Michael;
(Bridgewater, NJ) ; Strohmaier; Karl Gottlieb;
(Port Murray, NJ) ; Marella; Michael Anthony;
(Easton, PA) ; Hajkowski; Keith Robert; (Somerset,
NJ) ; Weissman; Walter; (Basking Ridge, NJ) ;
Choi; Eugine; (Marlton, NJ) ; Skic; George;
(Lambertville, NJ) ; Kliewer; Chris Esther;
(Clinton, NJ) ; Brody; John Francis; (Bound Brook,
NJ) ; Madiara; Paul Dmitri; (Bethlehem, PA) ;
Raman; Sumathy; (Annandale, NJ) ; Nandi; Partha;
(Bridgewater, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Beutel; Tilman Wolfram
Weiss; Brian Michael
Strohmaier; Karl Gottlieb
Marella; Michael Anthony
Hajkowski; Keith Robert
Weissman; Walter
Choi; Eugine
Skic; George
Kliewer; Chris Esther
Brody; John Francis
Madiara; Paul Dmitri
Raman; Sumathy
Nandi; Partha |
Neshanic Station
Bridgewater
Port Murray
Easton
Somerset
Basking Ridge
Marlton
Lambertville
Clinton
Bound Brook
Bethlehem
Annandale
Bridgewater |
NJ
NJ
NJ
PA
NJ
NJ
NJ
NJ
NJ
NJ
PA
NJ
NJ |
US
US
US
US
US
US
US
US
US
US
US
US
US |
|
|
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
52282935 |
Appl. No.: |
14/566906 |
Filed: |
December 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61915555 |
Dec 13, 2013 |
|
|
|
Current U.S.
Class: |
48/105 ; 123/1A;
48/213; 502/66; 60/273 |
Current CPC
Class: |
B01J 23/10 20130101;
B01J 23/63 20130101; Y02T 10/30 20130101; C10L 2230/22 20130101;
C01B 2203/1247 20130101; C01B 2203/1082 20130101; F02M 26/05
20160201; B01J 29/44 20130101; F02B 61/02 20130101; C01B 2203/0238
20130101; C01B 2203/1241 20130101; C10L 3/00 20130101; Y02P 20/141
20151101; Y02T 10/126 20130101; C01B 2203/107 20130101; C01B
2203/1064 20130101; F02B 51/02 20130101; B01J 29/70 20130101; F02M
27/02 20130101; B01J 29/85 20130101; C01B 2203/1047 20130101; F02B
2043/103 20130101; B01J 29/80 20130101; F02M 26/20 20160201; B01J
21/04 20130101; B01J 29/068 20130101; B01J 29/743 20130101; C10L
3/10 20130101; Y02T 10/12 20130101; C10L 2290/24 20130101; C01B
2203/0233 20130101; F02M 21/0227 20130101; Y02P 20/52 20151101;
C10L 2290/06 20130101; C10L 2290/02 20130101; B01J 21/08 20130101;
C01B 3/40 20130101; F01N 3/20 20130101; F02B 43/12 20130101; Y02P
20/142 20151101; F02B 37/013 20130101; F02M 26/36 20160201; B01J
2523/00 20130101; B01J 29/005 20130101; C10L 3/08 20130101; C01B
2203/84 20130101; C10L 2270/02 20130101; F02M 26/35 20160201; Y02T
10/32 20130101; B01J 23/464 20130101; B01J 2523/00 20130101; B01J
2523/31 20130101; B01J 2523/3706 20130101; B01J 2523/3712 20130101;
B01J 2523/48 20130101; B01J 2523/822 20130101 |
International
Class: |
F02M 21/02 20060101
F02M021/02; F02B 43/12 20060101 F02B043/12; F02M 27/02 20060101
F02M027/02; C10L 3/00 20060101 C10L003/00; B01J 29/80 20060101
B01J029/80; B01J 29/74 20060101 B01J029/74; B01J 29/44 20060101
B01J029/44; F02B 51/02 20060101 F02B051/02; F01N 3/20 20060101
F01N003/20 |
Claims
1. A method of increasing the octane rating of an internal
combustion engine exhaust gas stream, said method comprising: (a)
providing an exhaust gas-containing mixture to an exhaust gas
recycle reformer, the exhaust gas-containing mixture comprising
engine exhaust gas and a first hydrocarbon-containing fuel, said
engine exhaust gas having an initial octane rating, and (b)
converting under reforming conditions at least a portion of the
exhaust gas-containing mixture in the presence of a
hydrocarbon-reforming catalyst composition comprising at least
about 0.25 wt % of a hydrocarbon-reforming catalyst selected from
Co, Ru, Pt, Pd, Ni, Ir, Rh, Zn, Re, and mixtures thereof, and at
least about 10 wt % of a small pore molecular sieve to form a
reformed gaseous mixture, the reformed gas mixture comprising
H.sub.2, CO, CO.sub.2, H.sub.2O, N.sub.2, and greater than about
1.0 mol % CH.sub.4 based on the total moles of gas in the reformed
gaseous mixture.
2. The method of claim 1, wherein the small pore molecular sieve is
a molecular sieve having the framework type AEI, AFT, AFX, ATT,
DDR, EAB, EPI, ERI, KFI, LEV, LTA, MER, MON, MTF, PAU, PHI, RHO, or
SFW.
3. The method of claim 1, wherein the small pore molecular sieve is
chabazite, a CHA framework type molecular sieve, or a combination
thereof.
4. The method of claim 1, wherein the hydrocarbon-reforming
catalyst comprises Rh.
5. The method of claim 4, wherein the hydrocarbon-reforming
catalyst composition further comprises about 0.25 wt % to about 10
wt % of an additional metal selected from the group consisting of
Co, Ru, Pt, Pd, Ni, Ir, Zn, Re, and mixtures thereof, a total
weight of Rh and the additional metal being about 20 wt % or
less.
6. The method of claim 1, wherein said converting supplies heat
sufficient to maintain the reformer at an average reformer
temperature above about 450.degree. C.
7. The method of claim 1, wherein the hydrocarbon-reforming
catalyst composition further comprises a metal oxide composition
selected from aluminum oxides, silicon oxides, rare-earth metal
oxides, Group IV metal oxides, and mixtures thereof.
8. The method of claim 7, wherein the metal oxide composition
comprises a mixture of an aluminum-containing oxide and a
cerium-containing oxide.
9. The method of claim 1, wherein the hydrocarbon-reforming
catalyst composition further comprises about 5 wt % to about 50 wt
% of one or more additional molecular sieves having a largest ring
size of a 10-member ring, the one or more additional molecular
sieves optionally being ZSM-5, MCM-68, or a combination
thereof.
10. The method of claim 1, wherein the reformed gaseous mixture has
an octane rating (RON) from about 100 to about 125.
11. The method of claim 1, further comprising: introducing the
reformed gaseous mixture and a second hydrocarbon-containing fuel
into the engine, wherein said second hydrocarbon-containing fuel
may be the same or different from the first hydrocarbon-containing
fuel; combusting the reformed gaseous mixture and second
hydrocarbon-containing fuel in the engine to form an exhaust gas;
and passing the exhaust gas through a first heat exchanger to
extract heat from the exhaust gas.
12. The method of claim 11, further including prior to introducing
the reformed gaseous mixture into the internal combustion engine,
cooling the gaseous mixture by passing the gaseous mixture through
the first heat exchanger or a second heat exchanger.
13. The method of claim 1, further comprising pre-combusting a
portion of exhaust gas-containing mixture prior to providing the
exhaust gas-containing mixture to the exhaust gas recycle reformer,
the exhaust gas recycle reformer having a reformer inlet
temperature of about 525.degree. C. to about 625.degree. C.
14. The method of claim 1, wherein the reformed gaseous mixture
comprises from 2.0 mol % to 5.0 mol % CH.sub.4, the reformed
gaseous mixture has a CH.sub.4:H.sub.2 ratio (mol/mol) of at least
about 0.05 to 1.0, or a combination thereof.
15. A method of increasing the octane rating of an internal
combustion engine exhaust gas stream, said method comprising: (a)
providing an exhaust gas-containing mixture to an exhaust gas
recycle reformer, the exhaust gas-containing mixture comprising
engine exhaust gas and a first hydrocarbon-containing fuel, said
engine exhaust gas having an initial octane rating, and (b)
converting under reforming conditions at least a portion of the
exhaust gas-containing mixture in the presence of a
hydrocarbon-reforming catalyst composition comprising at least
about 0.25 wt % Rh and at least about 10 wt % of a CHA framework
type molecular sieve to form a reformed gaseous mixture, the
reformed gas mixture comprising H.sub.2, CO, CO.sub.2, H.sub.2O,
N.sub.2, and greater than about 1.0 mol % CH.sub.4 based on the
total moles of gas in the reformed gaseous mixture.
16. A hydrocarbon-reforming catalyst composition comprising about
0.25 wt % to about 10 wt % Rh, about 10 wt % to about 99.5 wt % of
a CHA framework type molecular sieve, and about 0.25 wt % to about
10 wt % of one or more additional molecular sieves having a largest
ring size of a 10-member ring.
17. The hydrocarbon-reforming catalyst composition of claim 16,
wherein the one or more additional molecular sieves comprise ZSM-5,
MCM-68, or a combination thereof.
18. A reformer for use in an exhaust gas recycle portion of an
internal combustion engine powertrain, said reformer comprising a
catalyst composition configured to convert a mixture comprising an
internal combustion engine exhaust gas and a hydrocarbon-containing
fuel to a gaseous mixture comprising H.sub.2, CO, CO.sub.2,
H.sub.2O, N.sub.2, and greater than about 1.0 mol % CH.sub.4 based
on the total moles of gas in the gaseous mixture, the catalyst
composition comprising at least about 0.25 wt % of a
hydrocarbon-reforming catalyst selected from Co, Ru, Pt, Pd, Ni,
Ir, Rh, Zn, Re, and mixtures thereof, and at least about 10 wt % of
a small pore molecular sieve.
19. The reformer of claim 18, further comprising an internal
combustion engine having an exhaust manifold comprising an exhaust
gas recycle unit and a fuel intake manifold, the reformer being
fluidly connected to the exhaust manifold and the fuel intake
manifold, the fuel intake manifold being configured to provide a
reformed fuel mixture from the exhaust gas recycle unit and a
second hydrocarbon-containing fuel to the internal combustion
engine for combustion, wherein the first and second
hydrocarbon-containing fuels may be the same or different.
20. The reformer of claim 18, further comprising at least a first
heat exchanger in fluid communication with the reformer; said first
heat exchanger configured to extract heat from the reformed gaseous
mixture.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of provisional U.S.
Application No. 61/915,555, filed on Dec. 13, 2013, the entirety of
which is incorporated herein by reference.
FIELD OF THE INVENTION
[0002] Embodiments of the invention relate to catalytic reforming
of an internal combustion engine exhaust gas. In particular,
embodiments of the invention relate to catalytic reforming of such
engine exhaust gas that produces an amount of methane sufficient to
sustain the formation of CO (and/or CO.sub.2) and H.sub.2 in the
reformer.
BACKGROUND
[0003] Conventional internal combustion engine designs can
typically include a single fuel for combustion within the engine
cylinders. This can require careful selection of an appropriate
fuel, so that the fuel has appropriate combustion properties, such
as a suitable Research Octane Number or a suitable flame speed.
This can limit the selection of fuels, as some compositions that
may be suitable from an energy content standpoint can lack
appropriate combustion properties.
[0004] In addition to naphtha boiling range (gasoline) and
distillate boiling range (kerosene or diesel) fuels, some
alternative types of fuels are available for use in internal
combustion engines. For example, an engine can be configured for
use with natural gas as a fuel.
SUMMARY OF THE INVENTION
[0005] In one aspect, a method of increasing the octane rating of
an internal combustion engine exhaust gas stream is provided, the
method including: (a) providing an exhaust gas-containing mixture
to an exhaust gas recycle reformer, the exhaust gas-containing
mixture comprising engine exhaust gas and a first
hydrocarbon-containing fuel, said engine exhaust gas having an
initial octane rating, and (b) converting under reforming
conditions at least a portion of the exhaust gas-containing mixture
in the presence of a hydrocarbon-reforming catalyst composition
comprising at least about 0.25 wt % of a hydrocarbon-reforming
catalyst selected from Co, Ru, Pt, Pd, Ni, Ir, Rh, Zn, Re, and
mixtures thereof, and at least about 10 wt % of a small pore
molecular sieve to form a reformed gaseous mixture, the reformed
gas mixture comprising H.sub.2, CO, CO.sub.2, H.sub.2O, N.sub.2,
and greater than about 1.0 mol % CH.sub.4 based on the total moles
of gas in the reformed gaseous mixture.
[0006] In another aspect, a method of increasing the octane rating
of an internal combustion engine exhaust gas stream is provided,
the method including: (a) providing an exhaust gas-containing
mixture to an exhaust gas recycle reformer, the exhaust
gas-containing mixture comprising engine exhaust gas and a first
hydrocarbon-containing fuel, said engine exhaust gas having an
initial octane rating, and (b) converting under reforming
conditions at least a portion of the exhaust gas-containing mixture
in the presence of a hydrocarbon-reforming catalyst composition
comprising at least about 0.25 wt % Rh and at least about 10 wt %
of a CHA framework type molecular sieve to form a reformed gaseous
mixture, the reformed gas mixture comprising H.sub.2, CO, CO.sub.2,
H.sub.2O, N.sub.2, and greater than about 1.0 mol % CH.sub.4 based
on the total moles of gas in the reformed gaseous mixture.
[0007] In still another aspect, a reformer for use in an exhaust
gas recycle portion of an internal combustion engine powertrain is
provided, the reformer comprising a catalyst composition configured
to convert a mixture comprising an internal combustion engine
exhaust gas and a hydrocarbon-containing fuel to a gaseous mixture
comprising H.sub.2, CO, CO.sub.2, H.sub.2O, N.sub.2, and greater
than 1.0 mol % CH.sub.4 based on the total moles of gas in the
gaseous mixture, the catalyst composition comprising at least about
0.25 wt % of a hydrocarbon-reforming catalyst selected from Co, Ru,
Pt, Pd, Ni, Ir, Rh, Zn, Re, and mixtures thereof, and at least
about 10 wt % of a small pore molecular sieve.
[0008] In yet another aspect, a hydrocarbon-reforming catalyst
composition is provided, the composition including about 0.25 wt %
to about 10 wt % Rh, about 10 wt % to about 99.5 wt % of a CHA
framework type molecular sieve, and about 0.25 wt % to about 10 wt
% of one or more additional molecular sieves having a largest ring
size of a 10-member ring, the CHA framework type molecular sieve
optionally being chabazite, the one or more additional molecular
sieves optionally being ZSM-5, MCM-68, or a combination
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic representation of an embodiment of a
powertrain.
[0010] FIG. 2 is a schematic representation of another embodiment
of a powertrain.
[0011] FIG. 3 is a graph of the amounts of hydrogen, methane, and
carbon monoxide produced versus propane conversion for an
embodiment of the present invention.
[0012] FIG. 4 is a graph of the amount of heat required to maintain
an example reformer at constant temperature.
[0013] FIG. 5 is a graph showing ratios of methane to hydrogen
versus n-heptane conversion.
[0014] FIG. 6 is a graph showing heptane conversion versus
residence time.
[0015] FIGS. 7A and 7B show reforming and methane formation rates
for various catalysts.
[0016] FIGS. 8A and 8B show reforming rates and methane formation
rates for various catalysts.
[0017] FIG. 8C shows product formation selectivities for various
catalysts.
[0018] FIG. 9 shows methane formation rates for catalysts in the
presence of syngas and n-heptane.
[0019] FIG. 10 shows methane formation rates for catalysts in the
presence of syngas and a multi-component naphtha feed.
[0020] FIG. 11 shows product formation selectivities for various
catalysts.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0021] In the following description, all numbers disclosed herein
are approximate values, regardless whether the word "about" or
"approximate" is used in connection therewith. They may vary by 1%,
2%, 5%, and sometimes, 10 to 20%. Whenever a numerical range with a
lower limit, R.sup.L and an upper limit, R.sup.U, is disclosed, any
number falling within the range is specifically disclosed. In
particular, the following numbers within the range are expressly
disclosed: R=R.sup.L+k*(R.sup.U--R.sup.L), wherein k is a variable
ranging from 1% to 100% with a 1% increment, i.e., k can be 1%, 2%,
3%, 4%, 5%, . . . , 50%, 51%, 52%, . . . , 95%, 96%, 97%, 98%, 99%,
or 100%. Moreover, any numerical range defined by two R numbers as
defined in the above is also expressly disclosed. It is noted that
for listings of R.sup.L or R.sup.U that begin with "about, e.g.,"
the presence of about prior to each number is expressly included,
but the term about is provided only once in the interest of
clarity.
[0022] As used herein the terms "substantially free of an
oxygen-containing gas" or "does not substantially include providing
an oxygen containing gas" mean that an oxygen-containing gas other
than the exhaust gas of the internal combustion engine is not
purposely provided to the catalytic reforming unit. Additionally or
alternatively, these terms can mean that not more than about 0.5
mol % (e.g., not more than about 0.2 mol %, not more than about 0.1
mol %, not more than about 0.05 mol %, or not more than about 0.01
mol %) of the total amount of gas supplied to the reforming unit is
an oxygen-containing gas other than the exhaust gas of the internal
combustion engine.
[0023] Octane ratings described herein generally refer to the
Research Octane Number (RON), unless otherwise specified. RON is
determined by running the fuel in a test engine with a variable
compression ratio under controlled conditions, and comparing the
results with those for mixtures of iso-octane and n-heptane.
Overview
[0024] The invention is based in part on discovery of a catalyst
composition that can effectively convert an internal combustion
engine exhaust stream in the presence of a hydrocarbon-containing
fuel to a mixture comprising H.sub.2, CO.sub.2, CO, H.sub.2O,
N.sub.2, and a relatively large amount of methane, CH.sub.4. Such a
mixture can have the desired properties of high octane, due to the
high methane content, along with a high H.sub.2 content that can
enable a flame speed high enough to maintain fuel combustion at the
desired engine conditions. The invention is further based in part
on discovery of a catalyst composition that can enhance the
formation of methane. The catalyst composition can produce
sufficient amounts of methane in the exothermic methanation
reaction to sustain the reformer temperatures for the syngas
producing endothermic reforming reaction, such that relatively
little or no other heat may need to be added to the reformer to
sustain the reforming reaction.
[0025] In various aspects, the catalyst can comprise rhodium (Rh)
supported on chabazite and/or a molecular sieve having the CHA
framework type. Optionally but preferably, the chabazite can be
bound and/or physically mixed with another oxide, so that at least
a portion of the Rh is supported on the other oxide. The oxide can
be a single metal oxide or can contain one or more metal oxides,
such as a mixed metal oxide containing a plurality of metal oxides.
Optionally, the catalyst can further comprise one or more
additional molecular sieves, such as additional zeolites.
Optionally, the catalyst can further comprise one or more
additional metals. The Rh (and/or the optional one or more
additional metals) can be incorporated into the catalyst as a metal
or as a metal-containing compound. The Rh (and/or the optional one
or more additional metals) can be incorporated into the catalyst by
any convenient method, such as by ion exchange, impregnation, by
incorporation into the synthesis mixture for forming the zeolite,
or a combination thereof.
[0026] The catalyst composition can be capable of catalyzing
hydrocarbon reforming and methane formation. The formation of
CH.sub.4 is typically exothermic, and the heat it produces may be
used to supply heat to and/or to sustain a reforming reaction to
produce synthesis gas or "syngas" that includes hydrogen and carbon
monoxide. To improve the overall efficiency of the systems,
catalysts may be optimally chosen to accomplish each reaction.
Thus, in some embodiments, there may be a first catalyst
composition for catalyzing a hydrocarbon reforming reaction for
converting a hydrocarbonaceous feed into CO.sub.2, CO, H.sub.2O,
and H.sub.2, and a second catalyst composition capable of forming
methane, whether directly from the unconverted hydrocarbonaceous
feed or from the converted/reformed products. The first and second
catalyst compositions may be mixed or they may be segregated within
the reformer according to design parameters, e.g., to efficiently
distribute and/or transfer heat within the reformer. In some
embodiments, the first and second catalyst compositions can be
similar or identical (such that effectively a single composition
effectively catalyzes both reactions).
[0027] In some aspects, the catalyst can include Rh, optionally one
or more additional metals, a zeolite (or other molecular sieve)
having the chabazite framework structure, and optionally one or
more additional molecular sieves. In such aspects, the CHA
framework type molecular sieve and optional additional molecular
sieves can comprise all of the support material for the catalyst,
so that the weight of the Rh (plus optional additional metals) and
the weight of the chabazite (plus optional additional molecular
sieves) correspond to the total catalyst weight. In certain
aspects, the catalyst can further include one or more metal oxide
components as support materials.
[0028] Use of a catalyst composition with activity for reforming
and enhanced activity for methanation can provide advantages when
reforming hydrocarbons. In particular, a catalyst composition with
increased activity for methanation can reduce or minimize the need
to provide additional heat to a reforming process.
[0029] Hydrocarbons and hydrocarbonaceous compounds (such as
alcohols) can be reformed, such as by steam reforming, to produce
syngas under appropriate conditions in the presence of a reforming
catalyst. In an engine or power train environment, reforming can be
used to convert hydrocarbon or hydrocarbonaceous compounds with low
octane ratings into CO and H.sub.2. The CO and H.sub.2 provide a
somewhat higher octane rating than some components in a typical
naphtha boiling range fuel such as C5+n-alkanes. Additionally, if
the reforming catalyst also has activity for forming methane from
CO and H.sub.2, the methane can serve as a still higher octane
rating component in the reformed fuel stream.
[0030] Steam reforming is typically an endothermic process, so that
additional heat must be provided to the reforming process to
maintain the temperature of the reaction environment. Equation 1
shows the enthalpy of reaction for steam reforming of n-heptane,
with the enthalpy expressed per mole of carbon in the fuel.
C.sub.7H.sub.16+7H.sub.2O.fwdarw.7CO+15H.sub.2.DELTA.H(500.degree.
C.).apprxeq.167 kJ/mol.degree. C. (1)
[0031] For reforming processes in an engine or power train
environment, additional heat can be provided by combustion of fuel,
but this decreases the overall efficiency of the engine. As an
alternative, formation of methane from CO and H.sub.2 is an
exothermic process, as shown in Equation 2.
CO+3H.sub.2.fwdarw.CH.sub.4+H.sub.2O.DELTA.H(500.degree.
C.).apprxeq.-221 kJ/mol.degree. C. (2)
[0032] As shown in Equation 2, converting CO and H.sub.2 in the
reforming environment into CH.sub.4 can provide a method for
reducing or minimizing the amount of additional heat that needs to
be supplied to the reforming reaction zone. As a result, a catalyst
composition that is effective for both reforming of hydrocarbons
while having improved activity for conversion of the resulting
syngas to methane can be desirable.
Catalyst Composition
[0033] In this discussion, unless specifically noted otherwise,
references to CHA framework type zeolites are understood to
generally refer to any zeolite (or other molecular sieve) having
the chabazite framework type. The chabazite framework type is
designated as framework type code CHA in the International Zeolite
Association database of zeolite structures. Other zeolites having
the CHA framework type can include AlPO-34, MCM-2, MeAPO-44,
MeAPO-47, SAPO-34, SAPO-47, SSZ-13, SSZ-62, and/or ZK-14. Chabazite
can refer to a naturally occurring or a synthetic form of
chabazite. Unless otherwise specified, a reference to chabazite, is
understood to generally refer to the zeolite chabazite (natural or
synthetic), optionally containing any of the potential various
counterions and/or additional metals that can be present.
[0034] While rhodium supported on CHA framework type molecular
sieve of the present invention can effectively enhance the
formation of methane, additional hydrocarbon-reforming catalysts
supported multi-dimensional small pore molecular sieves can also be
effective. Suitable small pore molecular sieves include those
having the AEI, AFT, AFX, ATT, DDR, EAB, EPI, ERI, KFI, LEV, LTA,
MER, MON, MTF, PAU, PHI, RHO, and SFW framework types. Suitable
hydrocarbon-reforming catalysts, as described in more detail
herein, include Rh, Ru, Ir, Co, Pt, Pd, Ni, Zn, Re, and
combinations thereof.
[0035] An additional or alternative option for characterizing small
pore molecular sieves can be based on the ring structures in the
molecular sieves. Some suitable small pore molecular sieves can
include molecular sieves having an 8-member ring channel as the
largest pore size for the molecular sieve.
[0036] Still another additional or alternative option for
characterizing small pore molecular sieves can be based on the
effective size of the pore channels. Some typical small pore
molecular sieves can include molecular sieves with a largest pore
channel having a maximum dimension of about 5.0 Angstroms or less.
A molecular sieve having elliptical pores with a slightly larger
maximum dimension of about 5.1 Angstroms or about 5.2 Angstroms
along the major axis may still correspond to a small pore molecular
sieve, e.g., particularly if the minor axis has a dimension of
about 4.0 Angstroms or less. In still other additional or
alternative embodiments, characterization of small pore molecular
sieves can be based on the effective size of the pore channels. In
some aspects, a suitable small pore molecular sieve can include a
largest pore channel that has a maximum dimension of about 4.8
Angstroms or less, e.g., about 4.7 Angstroms or less, about 4.6
Angstroms or less, about 4.5 Angstroms or less, about 4.4 Angstroms
or less, or about 4.3 Angstroms or less. In such a molecular sieve,
the largest pore channel can also have a minimum dimension of at
least about 3.5 Angstroms, e.g., at least about 3.6 Angstroms or at
least about 3.7 Angstroms. In this discussion, the maximum and
minimum dimensions of a pore channel for a molecular sieve refer to
the size of a sphere that can diffuse through such a pore channel,
as reported in the Database of Zeolite Structures that is
maintained by the International Zeolite Association.
[0037] In various aspects, the weight of the CHA framework type
molecular sieve (or small pore molecular sieve) in the catalyst
composition, and/or the weight of chabazite in the catalyst
composition, can be from about 1.0 wt % to about 99.75 wt %, based
on the total weight of the catalyst composition. The lower limit on
the range of CHA framework type molecular sieve (or small pore
molecular sieve) content, and/or the lower limit on the chabazite
content, may be about, e.g., 1.0 wt %, 2.0 wt %, 5.0 wt %, 7.5 wt
%, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt
%, 25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt
%, 40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt
%, 55.0 wt %, 57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt
%, 70.0 wt %, 72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt
%, 85.0 wt %, 90.0 wt %, 92.5 wt %, 95.0 wt %, or 97.5 wt %. The
upper limit on the range of CHA framework type molecular sieve (or
small pore molecular sieve) content, and/or the lower limit on the
chabazite content, may be about, e.g., 2.0 wt %, 5.0 wt %, 7.5 wt
%, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt
%, 25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt
%, 40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt
%, 55.0 wt %, 57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt
%, 70.0 wt %, 72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt
%, 85.0 wt %, 90.0 wt %, 92.5 wt %, 95.0 wt %, 97.5 wt %, or 99.0
wt %, or 99.5 wt %, or 99.75 wt %. Combinations of such lower and
upper limits may be selected, e.g., from about 2.5 wt % to about
95.0 wt %, from about 5.0 wt % to about 80.0 wt %, from about 10.0
wt % to about 55.0 wt %, from about 20.0 wt % to about 40.0 wt %,
etc.
[0038] Optionally, the catalyst composition can further comprise
one or more additional molecular sieves, such as one or more
additional zeolites. Any convenient molecular sieve can be used for
the additional molecular sieve(s). For example, a zeolite with
cracking activity such as ZSM-5 or MCM-68 can also be beneficial in
some catalyst compositions. In some alternative aspects, instead of
including a aluminosilicate type molecular sieve to provide
cracking activity a silicoaluminophosphate molecular sieve or an
aluminophosphate molecular sieve can be included in the catalyst
composition.
[0039] The additional molecular sieve(s) can correspond to from
about 1.0 wt % to about 99.75 wt %, based on the total weight of
the catalyst composition. The lower limit on the range of the one
or more molecular sieves added to the catalyst composition may be
about, e.g., 1.0 wt %, 2.0 wt %, 5.0 wt %, 7.5 wt %, 10.0 wt %,
12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0 wt %,
27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0 wt %,
42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt %, 55.0 wt %,
57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt %, 70.0 wt %,
72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt %, 85.0 wt %,
90.0 wt %, 92.5 wt %, 95.0 wt %, or 97.5 wt %. The upper limit on
the range of the one or more molecular sieves added to the catalyst
composition may be about, e.g., 2.0 wt %, 5.0 wt %, 7.5 wt %, 10.0
wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0
wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0
wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt %, 55.0
wt %, 57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt %, 70.0
wt %, 72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt %, 85.0
wt %, 90.0 wt %, 92.5 wt %, 95.0 wt %, 97.5 wt %, or 99.0 wt %, or
99.5 wt %, or 99.75 wt %. Combinations of such lower and upper
limits may be selected and are expressly considered herein, e.g.,
from about 2.5 wt % to about 95.0 wt %, from about 5.0 wt % to
about 80.0 wt %, from about 10.0 wt % to about 55.0 wt %, from
about 20.0 wt % to about 40.0 wt %, etc.
[0040] When one or more additional molecular sieves different from
a CHA framework type zeolite are included in the catalyst
composition, the additional molecular sieve(s) can be at least one
medium pore aluminosilicate zeolite having a Constraint Index of
1-12 (as defined in U.S. Pat. No. 4,016,218). Suitable zeolites
include zeolites having an MFI or MEL framework, such as ZSM-5 or
ZSM-11. ZSM-5 is described in detail in U.S. Pat. Nos. 3,702,886
and RE 29,948. ZSM-11 is described in detail in U.S. Pat. No.
3,709,979. Preferably, the zeolite is ZSM-5. Another suitable
zeolite can be MCM-68, which is described in detail in U.S.
Published Patent Application 2014/0140921. Other useful medium pore
molecular sieves can include ZSM-12 (U.S. Pat. No. 3,832,449);
ZSM-22 (U.S. Pat. No. 4,556,477); ZSM-23 (U.S. Pat. No. 4,076,842);
ZSM-34 (U.S. Pat. No. 4,086,186) ZSM-35 (U.S. Pat. No. 4,016,245);
ZSM-48 (U.S. Pat. No. 4,397,827); and ZSM-57 (U.S. Pat. No.
4,873,067). Non-limiting examples of SAPO and AlPO molecular sieves
include one or a combination of SAPO-11, SAPO-31, SAPO-41, AlPO-11,
AlPO-31, AlPO-41, and PST-6. The additional molecular sieve(s) can
also be at least one large pore aluminosilicate, aluminophosphate,
or silicoaluminophosphate zeolite, such as containing 12-ring
pores. Suitable large pore molecular sieves include those having
AFI, AFS, ATO, ATS, *BEA, BEC, BOG, BPH, CAN, CON, EMT, EON, EZT,
FAU, GME, GON, IFR, ISV, -*ITN, IWR, IWW, LTL, MAZ, MEI, MOR, MOZ,
MSE, MTW, OFF, OKO, OSI, SAF, SAO, SEW, SFE, SFO, SSF, SSY, and/or
USI frameworks.
[0041] An additional or alternative option for characterizing a
zeolite (or other molecular sieve) is based on the nature of the
ring channels in the zeolite. The ring channels in a zeolite can be
defined based on the number of tetrahedral framework atoms included
in the ring structure that forms the channel. In some aspects, a
zeolite can include at least one ring channel based on a 10-member
ring. In such aspects, the zeolite preferably does not have any
ring channels based on a ring larger than a 10-member ring.
Examples of suitable framework structures having a 10-member ring
channel but not having a larger size ring channel can include EUO,
FER, HEU, IFW, ITH, IMF, LAU, MEL, MFI, MFS, MTT, MVY, MWW, NES,
PCR, PON, RRO, SFF, SFG, *SFV, STF, -SVR, STI, SZR, TON, TUN, MRE,
and combinations thereof.
[0042] Generally, a zeolite having the desired activity can have a
silicon to aluminum molar ratio of about 2 to about 300, such as
about 5 to about 100 or about 20 to about 40. For example, the
silicon to aluminum ratio can be at least about 2, such as at least
about 5, or at least about 10, or at least about 40, or at least
about 50, or at least about 60. Additionally or alternately, the
silicon to aluminum ratio can be about 300 or less, such as about
200 or less, or about 100 or less, or about 80 or less, or about 60
or less, or about 50 or less.
[0043] Additionally or alternately, an additional molecular sieve
in the catalyst composition can include and/or be enhanced by a
transition metal. The transition metal can be incorporated into the
zeolite by any convenient method, such as by impregnation or by ion
exchange. If the transition metal is added to the additional
molecular sieve prior to incorporating the additional molecular
sieve into the catalyst composition, the amount of transition metal
can be expressed as a weight percentage of the additional molecular
sieve, such as having at least about 0.1 wt % of transition metal,
or at least about 0.25 wt %, or at least about 0.5 wt %, or at
least about 0.75 wt %, or at least about 1.0 wt %. Additionally or
alternately, the amount of transition metal can be about 20 wt % or
less, such as about 10 wt % or less, or about 5 wt % or less, or
about 2.0 wt % or less, or about 1.5 wt % or less, or about 1.2 wt
% or less, or about 1.1 wt % or less, or about 1.0 wt % or
less.
[0044] Further additionally or alternately, the one or more
molecular sieves can include non-framework phosphorus and/or be
enhanced by phosphorus treatment. Including phosphorus in the
additional molecular sieve can potentially provide increased
stability for the molecular sieve(s) in the reaction conditions
present during reforming and/or methanation as described herein.
The weight of the phosphorus can be about 0.1 wt % to about 10.0 wt
% based on the weight of the additional molecular sieve. Thus, the
upper limit on the range of the phosphorus added to the one or more
molecular sieves may be 10.0 wt %, 9.0 wt %, 8.0 wt %, 7.0 wt %,
6.0 wt %, 5.0 wt %, 4.0 wt %, 3.0 wt %, 2.0 wt %, 1.0 wt %, or 0.1
wt %; and the lower limit on the range added to the additional
molecular sieve may be 10.0 wt %, 9.0 wt %, 8.0 wt %, 7.0 wt %, 6.0
wt %, 5.0 wt %, 4.0 wt %, 3.0 wt %, 2.0 wt %, 1.0 wt %, or 0.1 wt
%. Ranges expressly disclosed include combinations of any of the
above-enumerated upper and lower limits; e.g., 0.1 to 10.0 wt %,
0.1 to 8.0 wt %, 0.1 to 6.0 wt %, 0.1 to 5.0 wt %, 0.1 to 4.0 wt %,
0.1 to 3.0 wt %, 0.1 to 2.0 wt %, 0.1 to 1.0 wt %, 1.0 to 10.0 wt
%, 1.0 to 9.0 wt %, 1.0 to 8.0 wt %, 1.0 to 7.0 wt %, 1.0 to 6.0 wt
%, 1.0 to 5.0 wt %, 1.0 to 4.0 wt %, 1.0 to 3.0 wt %, etc. Of
course, these total weights of the phosphorus shall be understood
to exclude any phosphorus in the molecular sieve framework.
[0045] In aspects where the catalyst composition also includes one
or more metal oxides, the catalyst composition can include at least
a minimum amount of chabazite (and/or a CHA framework type zeolite)
such as any of the lower limit amounts described above. In such
aspects, the one or more metal oxide components may be selected
from any suitable metal oxide(s). Exemplary metal oxides can
include, but are not necessarily limited to, aluminum oxides (e.g.,
Al.sub.2O.sub.3, including .theta.-Al.sub.2O.sub.3 and/or
.gamma.-Al.sub.2O.sub.3), silicon oxides, rare-earth metal oxides,
Group IV metal oxides, SiO.sub.2, Y.sub.2O.sub.3, Sc.sub.2O.sub.3,
La.sub.2O.sub.3, CeO.sub.2, Pr.sub.2O.sub.3 Sm.sub.2O.sub.3
Eu.sub.2O.sub.3, Gd.sub.2O.sub.3, Tb.sub.2O.sub.3, Dy.sub.2O.sub.3,
Ho.sub.2O.sub.3, Er.sub.2O.sub.3, Tm.sub.2O.sub.3, Yb.sub.2O.sub.3,
Lu.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2, and mixtures
thereof. For example, embodiments of a metal oxide mixture suitable
for use in the catalyst compositions herein may include from about
1.0 wt % to about 99.0 wt %, based on the total weight of the
catalyst composition, of a first metal oxide. The lower limit on
the range of first metal oxide content may be about, e.g., 1.0 wt
%, 2.0 wt %, 5.0 wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %,
17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0 wt %, 27.5 wt %, 30.0 wt %,
32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0 wt %, 42.5 wt %, 45.0 wt %,
47.5 wt %, 50.0 wt %, 52.5 wt %, 55.0 wt %, 57.5 wt %, 60.0 wt %,
62.5 wt %, 65.0 wt %, 67.5 wt %, 70.0 wt %, 72.5 wt %, 75.0 wt %,
77.5 wt %, 80.0 wt %, 82.5 wt %, 85.0 wt %, 90.0 wt %, 92.5 wt %,
95.0 wt %, or 97.5 wt %. The upper limit on the range of first
metal oxide content may be about, e.g., 2.0 wt %, 5.0 wt %, 7.5 wt
%, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt
%, 25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt
%, 40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt
%, 55.0 wt %, 57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt
%, 70.0 wt %, 72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt
%, 85.0 wt %, 90.0 wt %, 92.5 wt %, 95.0 wt %, 97.5 wt %, or 99.0
wt %. Combinations of such lower and upper limits may be selected,
e.g., from about 2.5 wt % to about 95.0 wt %, from about 5.0 wt %
to about 80.0 wt %, from about 10.0 wt % to about 55.0 wt %, from
about 20.0 wt % to about 40.0 wt %, etc. A second metal oxide may
optionally be present in an amount from about 1.0 wt % to about
99.0 wt %. The lower limit on the range of second metal oxide
content may be about, e.g., 1.0 wt %, 2.0 wt %, 5.0 wt %, 7.5 wt %,
10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt %,
25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt %,
40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %, 52.5 wt %,
55.0 wt %, 57.5 wt %, 60.0 wt %, 62.5 wt %, 65.0 wt %, 67.5 wt %,
70.0 wt %, 72.5 wt %, 75.0 wt %, 77.5 wt %, 80.0 wt %, 82.5 wt %,
85.0 wt %, 90.0 wt %, 92.5 wt %, 95.0 wt %, or 97.5 wt %. The upper
limit on the range of second metal oxide content may be about,
e.g., 2.0 wt %, 5.0 wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt
%, 17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0 wt %, 27.5 wt %, 30.0 wt
%, 32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0 wt %, 42.5 wt %, 45.0 wt
%, 47.5 wt %, 50.0 wt %, 52.5 wt %, 55.0 wt %, 57.5 wt %, 60.0 wt
%, 62.5 wt %, 65.0 wt %, 67.5 wt %, 70.0 wt %, 72.5 wt %, 75.0 wt
%, 77.5 wt %, 80.0 wt %, 82.5 wt %, 85.0 wt %, 90.0 wt %, 92.5 wt
%, 95.0 wt %, 97.5 wt %, or 99.0 wt %. Combinations of such lower
and upper limits may be selected, e.g., from about 97.5 wt % to
about 5.0 wt %, from about 95.0 wt % to about 20.0 wt %, from about
90.0 wt % to about 45.0 wt %, from about 80.0 wt % to about 60.0 wt
%, etc.
[0046] In particular embodiments, the first metal oxide may itself
be a mixture of oxides disclosed herein. For example, in an
embodiment, the first metal oxide can comprise, consist essentially
of, or be a mixture of La.sub.2O.sub.3 and .gamma.-Al.sub.2O.sub.3.
For a mixture of La.sub.2O.sub.3 and .gamma.-Al.sub.2O.sub.3, or
more generally for a mixture of La.sub.2O.sub.3 and
Al.sub.2O.sub.3, the La.sub.2O.sub.3 can correspond to about 0.4 wt
% to about 20 wt % of the combined weight of La.sub.2O.sub.3 and
Al.sub.2O.sub.3. For example, the La.sub.2O.sub.3 can correspond to
at least about 0.4 wt % of the combined weight of La.sub.2O.sub.3
and .gamma.-Al.sub.2O.sub.3, or at least about 1.0 wt %, or at
least about 2.0 wt %, or at least about 5.0 wt %, or at least about
10.0 wt %, and/or about 20.0 wt % or less, or about 15.0 wt % or
less, or about 10.0 wt % or less, or about 5.0 wt % or less, or
about 2.0 wt % or less. It is noted that all combinations for the
upper and lower limit of the amount of La.sub.2O.sub.3 relative to
the combined amount of La.sub.2O.sub.3 and Al.sub.2O.sub.3 are
expressly contemplated herein. The amount of the La.sub.2O.sub.3
and .gamma.-Al.sub.2O.sub.3 together may be, for example, from
about 20.0 wt % to about 90.0 wt %, such as from about 30.0 wt % to
about 50.0 wt % or from about 32.5 wt % to about 37.5 wt %, based
on the total weight of the catalyst composition. Optionally, in
such embodiments, the second metal oxide may itself also be a
mixture of oxides disclosed herein. For example, the second metal
oxide may can comprise, consist essentially of, or be a combination
of CeO.sub.2 and ZrO.sub.2. The amount of the CeO.sub.2 and
ZrO.sub.2 together may be, for example, from about 10.0 wt % to
about 80.0 wt %, such as from about 15.0 wt % to about 70.0 wt % or
from about 20.0 wt % to about 65.0 wt %, or from about 30.0 wt % to
about 60.0 wt %, or from about 40.0 wt % to about 80.0 wt %, based
on the total weight of the catalyst composition. The Ce:Zr atomic
ratio may be about, e.g., 10:0.5, 7.5:0.5, 5.0:1.0, 4.0:1.0,
3.0:1.0, 2.0:1.0, 1.0:1.0, or the like, or anywhere
therewithin.
[0047] The amount of Rh in the catalyst composition may range from
about 0.1 wt % to about 50 wt %. The lower limit on the range of Rh
in the catalyst composition may be about, e.g., 1.0 wt %, 2.0 wt %,
5.0 wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %,
20.0 wt %, 22.5 wt %, 25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %,
35.0 wt %, 37.5 wt %, 40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %,
or 50.0 wt %. The upper limit on the range of Rh in the catalyst
composition may be about, e.g., 1.0 wt %, 5.0 wt %, 7.5 wt %, 10.0
wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0
wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0
wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %, 50.0 wt %. Combinations of
such lower and upper limits may be selected, e.g., from about 1.0
wt % to about 20.0 wt %, from about 2.5 wt % to about 17.5 wt %,
from about 5.0 wt % to about 15.0 wt %, from about 7.5 wt % to
about 10.0 wt %, from about 1.0 wt % to about 10.0 wt %, from about
2.0 wt % to about 9.5 wt %, from about 2.5 wt % to about 9.0 wt %,
from about 3.0 wt % to about 8.0 wt %, from about 4.0 wt % to about
7.7.wt %, etc., based on the total weight of the catalyst
composition.
[0048] In aspects where at least one additional metal or
metal-containing compound is present in the catalyst composition,
the at least one additional metal or metal-containing compound can
correspond to a metal-containing hydrocarbon reforming catalyst. It
is noted that Rh also serves as a hydrocarbon reforming catalyst,
in addition to the role Rh serves in combination with chabazite
with regard to enhancing methanation. Examples of suitable
additional hydrocarbon reforming catalysts can be selected from the
group consisting of Co, Ru, Pt, Pd, Fe, Ni, Ir, Zn, Re, and
mixtures thereof. It will be understood that reference to the
presence of such metals envisions their presence in elemental/and
or compound form. Thus, amounts of such compounds refer to the
total amount of metal, in the form of metal or in compound form,
based on the total weight of the catalyst composition. The amount
of total metal in the catalyst composition, including both Rh and
any additional metal-containing hydrocarbon reforming catalyst, may
range from about 1.0 wt % to about 50 wt %. The lower limit on the
range of total metal in the catalyst composition may be about,
e.g., 1.0 wt %, 2.0 wt %, 5.0 wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %,
15.0 wt %, 17.5 wt %, 20.0 wt %, 22.5 wt %, 25.0 wt %, 27.5 wt %,
30.0 wt %, 32.5 wt %, 35.0 wt %, 37.5 wt %, 40.0 wt %, 42.5 wt %,
45.0 wt %, 47.5 wt %, or 50.0 wt %. The upper limit on the range of
total metal in the catalyst composition may be about, e.g., 1.0 wt
%, 5.0 wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %,
20.0 wt %, 22.5 wt %, 25.0 wt %, 27.5 wt %, 30.0 wt %, 32.5 wt %,
35.0 wt %, 37.5 wt %, 40.0 wt %, 42.5 wt %, 45.0 wt %, 47.5 wt %,
50.0 wt %. Combinations of such lower and upper limits may be
selected, e.g., from about 1.0 wt % to about 20.0 wt %, from about
2.5 wt % to about 17.5 wt %, from about 5.0 wt % to about 15.0 wt
%, from about 7.5 wt % to about 10.0 wt %, from about 1.0 wt % to
about 10.0 wt %, from about 2.0 wt % to about 9.5 wt %, from about
2.5 wt % to about 9.0 wt %, from about 3.0 wt % to about 8.0 wt %,
from about 4.0 wt % to about 7.7.wt %, etc., based on the total
weight of the catalyst composition.
[0049] In aspects where Rh and at least one additional hydrocarbon
reforming catalyst are present in the catalyst composition, the
total amount of metals in the catalyst composition can correspond
to any convenient combination of an amount of Rh (and/or
Rh-containing compound) and an amount of the one or more additional
hydrocarbon reforming catalysts. For example, the catalyst
composition may include a non-zero amount up to about 20 wt %,
based on the total weight of the catalyst composition, of Rh and/or
an Rh-containing compound. The lower limit on the range of Rh
content may be about, e.g., 0.25 wt %, 0.50 wt %, 0.75 wt %, 1.0 wt
%, 2.0 wt %, 2.5 wt %, 3.0 wt %, 4.0 wt %, 5.0 wt %, 7.5 wt %, 10.0
wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, or 20.0 wt %. The upper
limit on the range of Rh content may be about, e.g., 0.50 wt %,
0.75 wt %, 1.0 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 4.0 wt %, 5.0 wt
%, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, or 20.0 wt
%. Combinations of such lower and upper limits may be selected,
e.g., from about 0.5 wt % to about 15 wt %, from about 1.0 wt % to
about 10 wt %, from about 2.0 wt % to about 7.5 wt %, from about
2.5 wt % to about 5.0 wt %, etc. The one or more additional
hydrocarbon reforming catalyst also may be present in an amount of
>0 to about 20.0 wt %, based on the total weight of the catalyst
composition. The lower limit on the range of additional hydrocarbon
reforming catalyst content may be about, e.g., 0.25 wt %, 0.50 wt
%, 0.75 wt %, 1.0 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 4.0 wt %, 5.0
wt %, 7.5 wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, or 20.0
wt %. The upper limit on the range of additional hydrocarbon
reforming catalyst content may be about, e.g., 0.50 wt %, 0.75 wt
%, 1.0 wt %, 2.0 wt %, 2.5 wt %, 3.0 wt %, 4.0 wt %, 5.0 wt %, 7.5
wt %, 10.0 wt %, 12.5 wt %, 15.0 wt %, 17.5 wt %, or 20.0 wt %.
Combinations of such lower and upper limits may be selected, e.g.,
from about 0.5 to about 15.0 wt %, from about 1.0 to about 10.0 wt
%, from about 2.0 to about 7.5 wt %, from about 2.5 to about 5.0 wt
%, from about 0.75 to about 2.0 wt %, etc. For example, in addition
to Rh or an Rh-containing compound, an additional hydrocarbon
reforming catalyst can include or be Pt, e.g., such that the
catalyst composition comprises from about 1.0 to about 6.0 wt % Rh,
from about 1.5 to about 5.0 wt %, from about 2.0 to about 4.5 wt %,
or from about 2.5 to about 4.0 wt % Rh and from about 0.5 to about
5.0 wt % Pt, from about 0.75 to about 3.0 wt %, or from about 1.0
to about 2.0 wt % Pt, based on the total weight of the catalyst
composition.
[0050] In some aspects, the catalyst composition comprising the
support (e.g., metal oxide(s)) and hydrocarbon reforming
catalyst(s), and optionally any molecular sieves, can comprise
>.about.80.0 wt % (e.g., >.about.82.5 wt %, >.about.85.0
wt %, >.about.87.5 wt %, >.about.90.0 wt %, >.about.92.5
wt %, >.about.95.0 wt %, from about 82.5 wt % to about 100.0 wt
%, from about 85.0 wt % to about 99.0 wt %, from about 87.5 wt % to
about 95.0 wt %) of particles having a size of 20-100 mesh (U.S.)
(e.g., 25-90 mesh, 30-85 mesh, or 35-80 mesh). A more particular
description for indicating particle size distribution using mesh
size can be to use+ and - designations. A "+" before the sieve mesh
indicates the particles are retained by the sieve, while a "-"
before the sieve mesh indicates the particles pass through the
sieve. This means that typically 90% or more (e.g., 95% or more,
96% or more, 97% or more, 98% or more, 99% or more, 99.5% or more,
or 99.9% or more) of the particles will have mesh sizes between the
two values. For instance, if the particle size of a material is
described as -80/+170, then 90% or more of the material will pass
through an 80 mesh sieve and be retained by a 170 mesh sieve. Thus,
in some embodiments, the catalyst composition may have a particle
size distribution of -20/+100 mesh, e.g., -25/+90 mesh, -30/+85
mesh, or -35/+80 mesh. It should be noted that the particle size
range specified above pertains to the particular test reactor that
was utilized for some of the catalytic test of catalysts described
herein. The preferred particle size range can change for different
reactors and/or converter embodiments used in a vehicle
application.
[0051] Another optional way of describing particle size
distribution refers to respective percentiles of log normal
particle size distribution determined by means of a Malvern.TM.
particle size analyzer using a hexane diluent. Thus, particles
having a D.sub.50 of, for example, 0.5 mm have a median particle
size of 0.5 mm. A D.sub.90 of 0.5 mm indicates that 90% of the
particles have a particle size of less than 0.5 mm, and a D.sub.10
of 0.5 mm indicates that 10% of the particles have a particle size
of less than 0.5 mm. The width or narrowness of a particle size
distribution can be given by its span. The span is defined as
(D.sub.90-D.sub.10)/(D.sub.50) and is therefore dimensionless. In
some embodiments, the catalyst composition may be characterized as
having a D.sub.50 from 0.15 mm to 1.0 mm (e.g., from 0.85 mm to
0.16 mm, from 0.60 mm to 0.17 mm, or from 0.50 mm to 0.20 mm)
and/or as having a span from about 0.5 to about 10, e.g., from 1.0
to 6.0, from 2.0 to 5.0, or from 3.0 to 4.0.
[0052] In certain aspects, a reforming and/or cracking and/or
methanation catalyst as described herein can be provided in a
reformer (or other reaction environment) in the form of a
washcoated monolithic converter. This type of catalyst embodiment
for providing a supported catalyst is commonly used for automotive
converters. In such an aspect, the catalyst composition can
deposited on or otherwise supported on a flow through substrate
with parallel or tortuous channels. The reactive gases enter a
plurality of channels at the front end of the converter and exit
the same channels at the rear end of the converter. In another
embodiment used, for example, for particulate filtration on diesel
engines, half of the channels of the monolith can be plugged on the
inlet side of the monolith and the alternate half of the channels
can be plugged on the outlet side of the substrate. In this
so-called wall flow substrate, the exhaust enters the portion of
the channel system that is open on the inlet side. At least a
portion of the exhaust then passes through the walls of the porous
substrate and exits the substrate through the other half of the
channel system. The monolith substrate can be made of, for example,
ceramic and/or metal. Ceramic substrate materials can include
cordierite, SiC, alumina, titania, and other oxides or mixtures of
oxides. The catalyst is typically supported on the substrate in the
form of a washcoat. An example of the preparation and application
washcoats for monolithic catalysts is described in the literature
"Catalytic Air Pollution" by Ronald M. Heck and Robert J. Farrauto,
published by Van Nostrand Reinhold, 1995. The preparation of a
monolith substrate typically includes the preparation of a slurry
containing the catalyst powder and typically a binder material
suspended in a liquid phase. The catalyst containing slurry can
then be washcoated onto the substrate. The washcoated substrate can
then be subsequently dried and calcined in air or annealed in
specified gas environments.
Reforming and Methanation in an Engine or Power Train
Environment
[0053] The catalyst composition can advantageously be suitable for
providing a sufficient amount of heat to sustain the reforming
reaction to produce syngas containing hydrogen. Typically, the
catalyst composition can provide, e.g., greater than about 1.0 mol
% CH.sub.4, such as from about 1.0 mol % to about 6.0 mol %
CH.sub.4, or from about 1.0 mol % to about 5.0 mol % CH.sub.4, or
from about 1.0 mol % to about 4.0 mol % CH.sub.4, or from about 1.0
mol % to about 3.5 mol % CH.sub.4, or from about 2.0 mol % to about
6.0 mol % CH.sub.4, or from about 2.0 mol % to about 5.0 mol %
CH.sub.4, or from about 1.0 mol % to about 4.0 mol % CH.sub.4, or
from about 1.0 mol % to about 3.5 mol % CH.sub.4, based on the
total moles of gas in the reformed gaseous mixture, thereby
optionally maintaining the average reformer temperature at or above
about 450.degree. C., e.g., above about 500.degree. C., above about
550.degree. C., above about 600.degree. C., above about 650.degree.
C., from about 450.degree. C. to about 650.degree. C., from about
500.degree. C. to about 650.degree. C., from about 550.degree. C.
to about 600.degree. C., from about 450.degree. C. to about
550.degree. C., or from about 475.degree. C. to about 525.degree.
C. In one embodiment, the inlet temperature can be about
550.degree. C. and the outlet temperature about 450.degree. C. In
certain aspects, the outlet temperature of the reformer can be at
least about 435.degree. C., or at least about 450.degree. C., or at
least about 465.degree. C., or at least about 475.degree. C.
Additionally or alternatively, the inlet temperature can be about
650.degree. C. or less, or about 600.degree. C. or less, or about
585.degree. C. or less, or about 575.degree. C. or less, or about
560.degree. C. or less, or about 550.degree. C. or less.
Maintaining a desired temperature for the reformer inlet can allow
for an effective amount of reforming while still maintaining a
desired reformer outlet temperature under adiabatic operation. The
catalyst composition may optionally be characterized as providing a
gaseous mixture having CH.sub.4:H.sub.2 ratio (mole/mole) of at
least about 0.075 to 1.0, or from 0.1:1 to 0.9:1, or from 0.1:1 to
0.75:1, or from 0.25:1 to 0.9:1, or from 0.25:1 to 0.75:1, e.g.,
wherein the mixture is substantially/essentially free of
oxygen-containing gas other than exhaust gas from the engine and
hydrocarbon-containing fuel.
[0054] One option for maintaining and/or increasing the temperature
of a reforming reactor can be to use pre-combustion of a portion of
the fuel as a source of heat for the reforming reactor.
Pre-combustion can allow the inlet temperature for the reforming
reactor to be varied without having to vary some other temperature
within the engine. Conventionally, pre-combustion of fuel to
provide heat for a reformer in an engine is not preferred, as any
fuel burned to heat the reformer represents fuel that cannot be
used to drive the powertrain. However, due to kinetic and or
thermodynamic limitations on the reforming reactions at low
temperature, using pre-combustion can allow increasing the amount
of conversion before the kinetic or thermodynamically limited
temperature is reached. For example, pre-combustion can allow the
inlet temperature of the reformer to be increased to a temperature
of about 525.degree. C. to about 650.degree. C., for example about
525.degree. C. to about 625.degree. C., about 525.degree. C. to
about 600.degree. C., about 550.degree. C. to about 650.degree. C.,
about 550.degree. C. to about 625.degree. C., or about 550.degree.
C. to about 600.degree. C. The resulting increase in enthalpy of
the product mix due to the reforming reaction can raise the heat of
combustion, which can essentially offset the loss in efficiency due
to the pre-combustion. This can be desirable up to point where
raising the feed temperature by pre-combustion would lead to
significant heat losses to the surrounding; e.g., a temperature
over about 650.degree. C. In some embodiments, the above amounts of
CH.sub.4 in the reformed gaseous mixture can be provided when the
mixture of exhaust gas and hydrocarbon-containing fuel introduced
into the reformer includes about 5.0 mol % or less of CH.sub.4, for
example about 4.0 mol % or less, about 3.0 mol % or less, about 2.0
mol % or less, or about 1.0 mol % or less. Additionally or
alternatively, the above amounts of CH.sub.4 in the reformed
gaseous mixture can be provided when the hydrocarbon-containing
fuel introduced into the reformer includes about 5.0 mol % or less
of CH.sub.4, for example about 4.0 mol % or less, about 3.0 mol %
or less, about 2.0 mol % or less, or about 1.0 mol % or less.
[0055] In some embodiments, the invention can include a reformer
for use in an exhaust gas recycle portion of an internal combustion
engine powertrain, said reformer comprising at least one catalyst
composition described herein. Such a reformer may be used in a
method of operating an internal combustion engine. This may be
accomplished, e.g., by providing an exhaust gas-containing mixture
to an exhaust gas recycle reformer. The exhaust gas-containing
mixture can typically comprise engine exhaust gas and a first
hydrocarbon-containing fuel. At least a portion of the exhaust
gas-containing mixture can be passed to the reformer and converted
by the catalyst composition in the presence of heat to a reformed
gaseous mixture (product) having an increased content of H.sub.2
relative to the mixture of exhaust gas and first
hydrocarbon-containing fuel. The reformed gaseous mixture and a
second hydrocarbon-containing fuel may be provided to the engine
for combustion. Typically, the second hydrocarbon-containing fuel
can be the same as the first hydrocarbon-containing fuel (i.e., it
can be convenient to draw both the first and second
hydrocarbon-containing fuels from a common source or tank, in some
embodiments), although this need not always be the case. Where
desired, the second hydrocarbon-containing fuel may be different
from the first hydrocarbon-containing fuel. The reformed gaseous
mixture and second hydrocarbon-containing fuel can then be
combusted in the engine to form an exhaust gas. The exhaust gas can
be passed through a first heat exchanger to extract heat therefrom.
The heat can be transferred to the reformer to aid in sustaining
the reforming reactions therein.
[0056] An important direction in future gasoline engines is use of
exhaust gas recycle (EGR). In some aspects, use of recycled exhaust
gas as part of the input fuel mixture to the engine can lower the
temperature for combustion. This can allow the engine to run at a
higher compression ratio without causing knocking, which can
provide increased efficiency. However, the compression ratio and
amount of exhaust gas recycle are limited conventionally by
practical concerns. Increasing the amount of exhaust gas recycle in
a conventional engine can cause the fuel delivered to the engine to
become too dilute, leading to problems with the fuel flame speed.
Additionally, the compression ratio can be limited by the fuel
octane rating, or resistance of a fuel to combustion prior to spark
ignition.
[0057] In various embodiments, use of exhaust gas recycle with
reforming of fuel prior to combustion can allow for increased use
of the exhaust gas recycle. For example, use of EGR can provide a
media with H.sub.2O and CO.sub.2 as reactants for reforming of
gasoline to produce H.sub.2 rich gas to raise flame speed and/or
methane to raise the octane. Typical ranges for EGR that can be
used for the engine in conjunction with reforming include about 20
vol % to about 50 vol % of the engine air/EGR mix. For example, the
amount of EGR can be at least about 20 vol % of the combined air
and exhaust gas delivered to the engine, or at least about 25 vol
%, or at least about 30 vol %, or at least about 35 vol %, and/or
about 50 vol % or less, or about 45 vol % or less, or about 40 vol
% or less, or about 35 vol % or less. It is noted that each of the
lower limits and upper limits for the amount of exhaust gas recycle
are explicitly contemplated in combination with each other. All or
a portion of this EGR can be fed in conjunction with the gasoline
(or other fuel) from tankage to the reformer. The desired amount of
EGR relative to feed to the reformer can depending on fuel input,
engine design and engine load points. A high level of EGR increases
the amount of H.sub.2O and CO.sub.2 available for reforming, which
can potentially mitigate the extent of temperature drop in the
reformer. Alternatively, lowering EGR can raise the fuel
concentration and thereby can enhance the kinetics for
conversion.
[0058] In some embodiments, the reforming reaction can be performed
in the presence of a reduced or minimized amount of water. During
conventional reforming, the ratio of the amount of water in the
reaction environment to the number of carbon atoms in the feed for
reforming can be at least about 3:1. It has been determined that,
by performing the reforming in the presence of a suitable catalyst,
the ratio of water to carbon atoms in the feed can be from about
0.3:1 to about 1:1, for example from about 0.5:1 to about 1:1 or
from about 0.3:1 to about 0.9:1. Operating the reforming with a
reduced amount of water can be beneficial, as this amount of water
can be provided by an exhaust gas recycle stream.
[0059] Thus, embodiments of the invention can include a reformer
for use in an exhaust gas recycle portion of an internal combustion
engine powertrain, said reformer comprising at least one catalyst
composition described herein. The catalyst composition can be
specifically configured to convert a mixture comprising an internal
combustion engine exhaust gas and a hydrocarbon-containing fuel to
a gaseous mixture comprising H.sub.2, CO.sub.2, CO, H.sub.2O,
N.sub.2, and greater than about 1.0 mol % CH.sub.4, based on the
total moles of gas in the gaseous mixture. It is noted that the
output from the reformer may often contain a variety of additional
components. For example, in aspects where the input flow to the
reformer contains aromatic compounds and/or longer chain aliphatic
compounds, the reformer output can typically include one or more
types of aromatic compounds. This can include benzene formed by
dealkylation of alkylated aromatics; aromatic compounds formed by
dehydrocyclization of aliphatic compounds; or other types of
aromatics, optionally including substituted aromatics. More
generally, the output flow from the reformer can include a mixture
of various aliphatic, cyclic, and/or aromatic compounds, optionally
including compounds containing heteroatoms other than C and H.
[0060] Such a reformer may be used in a method of operating an
internal combustion engine. The methane produced in the reformer
may be used for using methane-assisted combustion in the engine.
This may be accomplished, e.g., by providing an exhaust
gas-containing mixture to an exhaust gas recycle reformer. The
exhaust gas-containing mixture can typically comprise engine
exhaust gas and a first hydrocarbon-containing fuel. At least a
portion of the exhaust gas-containing mixture can be passed to the
reformer and converted by the catalyst composition in the presence
of heat to a reformed gaseous mixture (product) comprising
CH.sub.4, H.sub.2, CO.sub.2, CO, H.sub.2O, and N.sub.2, said
CH.sub.4 being present at a concentration greater than about 1.0
mol %, based on the total moles of gas in the reformed gaseous
mixture. The reformed gaseous mixture and a second
hydrocarbon-containing fuel may be provided to the engine for
combustion. Typically, the second hydrocarbon-containing fuel can
be the same as the first hydrocarbon-containing fuel (i.e., it can
be convenient to draw both the first and second
hydrocarbon-containing fuels from a common source or tank, in some
embodiments), although this need not always be the case. Where
desired, the second hydrocarbon-containing fuel may be different
from the first hydrocarbon-containing fuel. The reformed gaseous
mixture and second hydrocarbon-containing fuel can then be
combusted in the engine to form an exhaust gas. The exhaust gas can
be passed through a first heat exchanger to extract heat therefrom.
The heat can be transferred to the reformer (and/or to the input
feed passed into the reformer) to aid in sustaining the reforming
and methane-forming reactions therein.
[0061] The use of the catalyst compositions herein can serve to
provide an increase in the octane rating of an internal combustion
engine exhaust gas stream. An exhaust gas-containing mixture may be
provided to an exhaust gas recycle reformer including a catalyst as
described herein. The exhaust gas-containing mixture can typically
comprise engine exhaust gas and a first hydrocarbon-containing
fuel. The first hydrocarbon-containing fuel can typically have a
relatively low initial octane rating, e.g., <100 RON, <99
RON, <97 RON, <95 RON, <93 RON, <90 RON, <85 RON,
<80 RON, from about 65 RON to about 100 RON, from about 65 RON
to about 99 RON, from about 65 RON to about 97 RON, from about 65
RON to about 95 RON, from about 65 RON to about 93 RON, from about
65 RON to about 90 RON, from about 65 RON to about 85 RON, from
about 65 RON to about 80 RON, from about 70 RON to about 100 RON,
from about 70 RON to about 99 RON, from about 70 RON to about 97
RON, from about 70 RON to about 95 RON, from about 70 RON to about
93 RON, from about 70 RON to about 90 RON, from about 70 RON to
about 85 RON, from about 70 RON to about 80 RON, from about 75 RON
to about 100 RON, from about 75 RON to about 99 RON, from about 75
RON to about 97 RON, from about 75 RON to about 95 RON, from about
75 RON to about 93 RON, from about 75 RON to about 90 RON, from
about 75 RON to about 85 RON, from about 75 RON to about 80 RON,
from about 80 RON to about 100 RON, from about 80 RON to about 99
RON, from about 80 RON to about 97 RON, from about 80 RON to about
95 RON, from about 80 RON to about 93 RON, from about 80 RON to
about 90 RON, from about 80 RON to about 85 RON, from about 85 RON
to about 100 RON, from about 85 RON to about 99 RON, from about 85
RON to about 97 RON, from about 85 RON to about 95 RON, from about
85 RON to about 93 RON, or from about 85 RON to about 90 RON. The
catalyst composition in the reformer converts at least a portion of
the exhaust gas-containing mixture to a reformed gaseous mixture
having a second octane rating (RON) higher than the initial octane
rating of the first hydrocarbon-containing fuel. Typically, the
reformed gaseous mixture can comprise at least H.sub.2, CO.sub.2,
and greater than about 0.25 mol % CH.sub.4, or greater than about
0.4 mol % CH.sub.4, or greater than about 1.0 mol % CH.sub.4, or
greater than about 1.5 mol % CH.sub.4, or greater than about 2.0
mol % CH.sub.4, and up to about 5.0 mol % CH.sub.4, based on the
total moles of gas in the reformed gaseous mixture (and typically
also CO, H.sub.2O, and N.sub.2), and this total mixture can
advantageously have a second octane rating of >100, e.g., from
about 100 to about 125. The lower limit on the range of second
octane rating may be about, e.g., 100, 102, 105, 107, 110, 112,
115, 120, or 122. The upper limit on the range of the second octane
rating may be about, e.g., 102, 105, 107, 110, 112, 115, 120, 122,
or 125. Any combination of lower and upper limits may be provided
by such a method, e.g., from about 105 to about 125, from about 110
to about 125, from about 115 to about 125, or from about 120 to
about 125.
[0062] The reformer may also be incorporated into an internal
combustion engine powertrain. Many different variations of such
powertrains are known. One such powertrain envisioned can include
an internal combustion engine having an exhaust manifold and a fuel
intake manifold. A reformer comprising a catalyst composition as
described herein can fluidly connect a branch of the exhaust
manifold and the fuel intake manifold. The reformer and catalyst
composition can be specifically configured to convert an exhaust
gas-containing mixture from the exhaust manifold gas and a first
hydrocarbon-containing fuel to a reformed gaseous mixture
comprising H.sub.2, CO, and CH.sub.4, along with one or more
exhaust gas constituents--typically including N.sub.2, H.sub.2O,
CO.sub.2, trace quantities of minor species such as NO.sub.x and
SO.sub.x, and the like. The reformed gaseous mixture may be
characterized by one or more of the following: (i) a Research
Octane Number (RON) of >100, e.g., from about 100 to about 130,
or more typically from about 100 to about 125 (the lower limit on
the range of second octane rating may be about 100, about 102,
about 105, about 107, about 110, about 112, about 115, about 120,
or about 122; additionally or alternatively, the upper limit on the
range of the second octane rating may be about 102, about 105,
about 107, about 110, about 112, about 115, about 120, about 122,
or about 125; if a range is desired, the range can be, e.g., from
about 105 to about 125, from about 110 to about 125, from about 115
to about 125, or from about 120 to about 125); (ii) a CH.sub.4
content of greater than about 1.0 mol % (e.g., from about 1.0 mol %
to about 6.0 mol % CH.sub.4, from about 1.5 mol % to about 5.0 mol
% CH.sub.4, or from about 2.0 mol % to about 4.0 mol % CH.sub.4,
based on the number of moles of gas in the reformed fuel mixture);
and (iii) a mixture of H.sub.2, CO, CO.sub.2, H.sub.2O, and
CH.sub.4 (optionally also N.sub.2) characteristic of at least about
50% (e.g., at least about 80%, at least about 85%, at least about
90%, or at least about 95%) conversion in the reforming zone.
Conversion of a hydrocarbon feed should be understood to be
calculated solely by the ratio of the difference between the mass
(or number of moles) of hydrocarbon component of the feed entering
the inlet of the reforming zone and the mass (or number of moles)
of hydrocarbon component exiting the outlet of the reforming zone,
divided by the mass (or number of moles) of hydrocarbon component
of the feed entering the inlet of the reforming zone. Typically,
the intake manifold can be configured to provide a reformed fuel
mixture from the exhaust gas recycle unit and a second
hydrocarbon-containing fuel to the internal combustion engine for
combustion. As described above, the first and second
hydrocarbon-containing fuels may be the same or different.
[0063] Referring now to FIG. 1, there is shown a schematic
representation of an embodiment of such a powertrain. In FIG. 1,
air can be drawn into the powertrain by a compressor (1). The power
for compressor (1) can come from a turbine (2) that can expand the
exhaust gases (3) from the engine exhaust manifold. The compressed
air from the compressor can then be cooled in a cooler (4). The air
flow rate can be controlled by a throttle valve (5). The air can
then be mixed with the EGR stream (9) and delivered to the engine
intake manifold (6). A portion of the exhaust gas (3) from the
engine can be sent to an EGR stream where converter (7) and cooler
means (8) can treat the EGR portion of the engine exhaust prior to
reinjection to the engine, while the remaining exhaust gas can be
expanded in turbine (2) and vented to the atmosphere at (10).
[0064] Hydrocarbon-containing fuel can be supplied to the
powertrain in FIG. 1 by injection means (11) into the EGR stream.
The EGR stream can comprise substantially components from the
exhaust of the engine, which may represent a portion or
substantially all the exhaust from the engine. This EGR stream can
typically comprise N.sub.2, water vapor (H.sub.2O), CO.sub.2,
un-combusted hydrocarbons, and small amounts of CO and O.sub.2. The
hydrocarbon-containing fuel can be a conventional fuel, such as
gasoline, and may optionally be the primary fuel supplied to the
engine by direct injection into the engine. However, other fuels
can be used instead of or in combination with the conventional fuel
(gasoline). Other such fuels can include, but are not necessarily
limited to, LPG (liquefied petroleum gas), light ends,
C.sub.2-C.sub.12 paraffins, naphtha, kerosene, diesel, FCC off-gas,
oxygenated hydrocarbons (e.g., dialkyl ethers such as dimethyl
ether, diethyl ether, methyl ethyl ether, and the like, and
combinations thereof; C.sub.1-C.sub.12 alcohols such as methanol,
ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol,
a pentanol, a hexanol, and the like, and combinations thereof;
fatty acid alkyl esters, for instance from mono-, di-, and/or
tri-glyceride reaction with a C.sub.1-C.sub.4 alcohol, such as
represented by FAME, FAEE, and the like, and combinations thereof;
and the like; and combinations thereof), hydrocarbon-rich gas
overhead from a refinery process, hydrocarbon-rich off-gas from a
chemical process, or the like, or combinations thereof.
[0065] Whatever fuel is used as a feed in the methods described
herein, it can advantageously have one, two, or all of the
following characteristics: a relatively high paraffin content, no
more than a modest aromatics content, and a relatively small
content of polynuclear aromatics (PNAs, meaning compounds having
two or more aromatic rings in its structure, typically two or more
aromatic rings connected to each other, e.g., sharing two carbon
atoms between them). The overall aromatics content of the
hydrocarbon-containing fuel to be fed into the reforming zone can
advantageously be no more than about 35 wt % (e.g., no more than
about 30 wt %, no more than about 25 wt %, no more than about 20 wt
%, no more than about 15 wt %, or no more than about 10 wt %),
based on the weight of the hydrocarbon-containing fuel (optionally,
the fuel can additionally have some aromatics content, e.g., at
least about 0.1 wt %, at least about 0.5 wt %, at least about 1 wt
%, at least about 2 wt %, at least about 3 wt %, at least about 4
wt %, at least about 5 wt %, at least about 7 wt %, at least about
10 wt %, or at least about 15 wt %, based on the weight of the
hydrocarbon-containing fuel). Additionally or alternately, the PNA
content of the hydrocarbon-containing fuel to be fed into the
reforming zone can advantageously be no more than about 3 wt %
(e.g., no more than about 2 wt %, no more than about 1 wt %, no
more than about 0.5 wt %, or no more than about 0.1 wt %), based on
the weight of the hydrocarbon-containing fuel (though PNAs can
typically be undesirable for relatively high conversion in
reforming, the fuel may nonetheless optionally have some PNA
content, e.g., at least about 0.001 wt %, at least about 0.005 wt
%, at least about 0.01 wt %, at least about 0.03 wt %, at least
about 0.05 wt %, at least about 0.07 wt %, at least about 0.1 wt %,
at least about 0.2 wt %, at least about 0.3 wt %, or at least about
0.5 wt %, based on the weight of the hydrocarbon-containing fuel).
Further additionally or alternately, the paraffin content of the
hydrocarbon-containing fuel to be fed into the reforming zone can
advantageously be greater than about 50 wt % (e.g., at least about
55 wt %, at least about 60 wt %, at least about 65 wt %, at least
about 70 wt %, at least about 75 wt %, at least about 80 wt %, at
least about 85 wt %, at least about 90 wt %, at least about 95 wt
%, at least about 96 wt %, at least about 97 wt %, at least about
98 wt %, or at least about 99 wt %), based on the weight of the
hydrocarbon-containing fuel (though paraffinic hydrocarbons can
typically be very desirable for relatively high conversion in
reforming, the fuel may nonetheless optionally have some upper
limit on paraffin content, e.g., up to about 99.9 wt %, up to about
99.5 wt %, up to about 99 wt %, up to about 98 wt %, up to about 97
wt %, up to about 96 wt %, up to about 95 wt %, up to about 90 wt
%, up to about 85 wt %, up to about 80 wt %, up to about 75 wt %,
up to about 70 wt %, up to about 65 wt %, or up to about 60 wt %,
based on the weight of the hydrocarbon-containing fuel).
[0066] In FIG. 2, the fuel can be pre-heated and vaporized before
its injection into the EGR stream using waste heat in the engine
exhaust stream. The fuel and exhaust gas in the EGR stream can be
reacted in a reformer including a catalyst composition according to
embodiments of the invention to form syngas (CO/CO.sub.2 and
H.sub.2) and methane (CH.sub.4). Optionally, the reformer may also
be heated by combusting a hydrocarbon-containing fuel during cold
starts. The EGR stream leaving the reformer, i.e., the reformed
fuel stream, can optionally be cooled by passing it though a heat
exchanger. The reformed fuel stream may, upon cooling, be supplied
to the engine cylinders or co-mingled with a primary fuel delivered
to the engine by direct injection.
[0067] In one embodiment, the generation of hydrogen in the
powertrain of FIG. 1 can be accomplished by an initial endothermic
reaction to produce syngas. The syngas-containing hydrogen can then
be used to conduct the methane-producing exothermic reaction
described above, to thereafter sustain the temperature high enough
for the endothermic reforming processes of reactor during
operation. Alternatively, start-up hydrogen for the methane
formation reaction may be supplied by stored hydrogen (not shown),
which optionally may be replenished after start-up by operation of
the reforming reaction.
[0068] Referring now to FIG. 2, there is shown a schematic
representation of another embodiment of a powertrain having a
reformer of the present invention in the EGR loop. A feature of
this second embodiment is that two turbine-compressor systems are
used. In FIG. 2, air and exhaust gas from the EGR stream can be
mixed and compressed by compressor (20). The power for compressor
(20) can come from a turbine (21) that can expand the EGR stream.
The compressed mixture from (20) can be cooled in a cooler (24) and
compressed by a second compressor (22). The power for compressor
(22) can come from a turbine (23) that can expand the exhaust gas
vented to the atmosphere. The compressed air and EGR gas can be
cooled at (25) and then delivered to the engine (26). A portion of
the exhaust gas from the engine can be sent to an EGR stream (27),
while the remaining exhaust gas (28) can be expanded in turbine
(23), led over a three-way catalyst in a catalytic converter (32)
and vented to the atmosphere. Fuel can be provided from a fuel tank
(34), injected into the EGR stream (29), and the stream can then be
passed to reformer (30), substantially identical to that described
in the embodiment of the invention depicted in FIG. 1. The stream
exiting the reformer can be expanded in turbine (21), cooled in a
cooler (31), and finally mixed with the air stream supplying the
powertrain. Optionally, fuel may be preheated and/or vaporized
prior to injection into the EGR stream, e.g., by means of a heat
exchanger (33). Heat can be derived from the net exhaust by first
raising the exhaust temperature by combustion of residual
hydrocarbons and CO over a three-way catalyst. The heat transfer
from the three-way catalyst to the hydrocarbon feed is merely one
potential mechanism for heat integration. There are other ways of
attain heat integration than described in FIG. 2 that derive heat
from the net engine exhaust gas, and any one or more of them may be
used in tandem with the invention, in addition or alternatively to
the configuration shown in FIG. 2.
ADDITIONAL EMBODIMENTS
Embodiment 1
[0069] A method of increasing the octane rating of an internal
combustion engine exhaust gas stream, said method comprising: (a)
providing an exhaust gas-containing mixture to an exhaust gas
recycle reformer, the exhaust gas-containing mixture comprising
engine exhaust gas and a first hydrocarbon-containing fuel, said
engine exhaust gas having an initial octane rating, and (b)
converting under reforming conditions at least a portion of the
exhaust gas-containing mixture in the presence of a
hydrocarbon-reforming catalyst composition comprising at least
about 0.25 wt % of a hydrocarbon-reforming catalyst selected from
Co, Ru, Pt, Pd, Ni, Ir, Rh, Zn, Re, and mixtures thereof, and at
least about 10 wt % of a small pore molecular sieve to form a
reformed gaseous mixture, the reformed gas mixture comprising
H.sub.2, CO, CO.sub.2, H.sub.2O, N.sub.2, and greater than about
1.0 mol % CH.sub.4 based on the total moles of gas in the reformed
gaseous mixture.
Embodiment 2
[0070] The method of Embodiment 1, wherein the
hydrocarbon-reforming catalyst composition comprises about 0.25 wt
% to about 10 wt % of the hydrocarbon-reforming catalyst, or about
0.5 wt % to about 10 wt %, or wherein the hydrocarbon-reforming
catalyst composition comprises about 10 wt % to about 99.75 wt % of
the small pore molecular sieve, or about 10 wt % to about 75 wt %,
or about 10 wt % to about 50 wt %, or a combination thereof.
Embodiment 3
[0071] The method of any of the above embodiments, wherein the
small pore molecular sieve comprises a molecular sieve having the
framework type AEI, AFT, AFX, ATT, DDR, EAB, EPI, ERI, KFI, LEV,
LTA, MER, MON, MTF, PAU, PHI, RHO, or SFW, or wherein the small
pore molecular sieve comprises a molecular sieve having a largest
pore size corresponding to an 8-member ring.
Embodiment 4
[0072] The method of any of the above embodiments, wherein the
small pore molecular sieve is chabazite and/or has a CHA framework
type molecular sieve, and/or wherein the hydrocarbon-reforming
catalyst comprises Rh.
Embodiment 5
[0073] A method of increasing the octane rating of an internal
combustion engine exhaust gas stream, said method comprising: (a)
providing an exhaust gas-containing mixture to an exhaust gas
recycle reformer, the exhaust gas-containing mixture comprising
engine exhaust gas and a first hydrocarbon-containing fuel, said
engine exhaust gas having an initial octane rating, and (b)
converting under reforming conditions at least a portion of the
exhaust gas-containing mixture in the presence of a
hydrocarbon-reforming catalyst composition comprising at least
about 0.25 wt % Rh and at least about 10 wt % of a CHA framework
type molecular sieve to form a reformed gaseous mixture, the
reformed gas mixture comprising H.sub.2, CO, CO.sub.2, H.sub.2O,
N.sub.2, and greater than about 1.0 mol % CH.sub.4 based on the
total moles of gas in the reformed gaseous mixture.
Embodiment 6
[0074] The method of any of Embodiments 4-5, wherein the
hydrocarbon-reforming catalyst composition further comprises about
0.25 wt % to about 10 wt % of an additional metal selected from the
group consisting of Co, Ru, Pt, Pd, Ni, Ir, Zn, Re, and mixtures
thereof, a total weight of Rh and the additional metal being about
20 wt % or less.
Embodiment 7
[0075] The method of any of the above embodiments, wherein said
converting supplies heat sufficient to maintain the reformer at an
average reformer temperature above about 450.degree. C.
Embodiment 8
[0076] The method of any of the above embodiments, wherein said
exhaust gas-containing mixture is substantially free of
oxygen-containing gas other than the exhaust gas and the first
hydrocarbon-containing fuel.
Embodiment 9
[0077] The method of any of the above embodiments, wherein the
hydrocarbon-reforming catalyst composition further comprises a
metal oxide composition, the metal oxide composition optionally
comprising and/or being selected from aluminum oxides, silicon
oxides, rare-earth metal oxides, Group IV metal oxides, and
mixtures thereof, for example a mixture of an aluminum-containing
oxide and a cerium-containing oxide.
Embodiment 10
[0078] The method of any of the above embodiments, wherein the
hydrocarbon-reforming catalyst composition further comprises about
5 wt % to about 50 wt % of one or more additional molecular sieves,
the one or more molecular sieves optionally having a largest ring
size of a 10-member ring, and/or the one or more additional
molecular sieves optionally being ZSM-5, MCM-68, or a combination
thereof.
Embodiment 11
[0079] The method of any of the above embodiments, wherein the
reformed gaseous mixture has an octane rating (RON) from about 100
to about 125.
Embodiment 12
[0080] The method of any of the above embodiments, further
comprising: introducing the reformed gaseous mixture and a second
hydrocarbon-containing fuel into the engine, wherein said second
hydrocarbon-containing fuel may be the same or different from the
first hydrocarbon-containing fuel; combusting the reformed gaseous
mixture and second hydrocarbon-containing fuel in the engine to
form an exhaust gas; and passing the exhaust gas through a first
heat exchanger to extract heat from the exhaust gas, wherein, prior
to introducing the reformed gaseous mixture into the internal
combustion engine, the gaseous mixture can optionally be cooled by
passing the gaseous mixture through the first heat exchanger or a
second heat exchanger.
Embodiment 13
[0081] The method of any of the above embodiments, further
comprising pre-combusting a portion of exhaust gas-containing
mixture prior to providing the exhaust gas-containing mixture to
the exhaust gas recycle reformer, the exhaust gas recycle reformer
having a reformer inlet temperature of about 525.degree. C. to
about 625.degree. C.
Embodiment 14
[0082] The method of any of the above embodiments, wherein the
reformed gaseous mixture comprises from about 2.0 mol % to about
5.0 mol % CH.sub.4, the reformed gaseous mixture has a
CH.sub.4:H.sub.2 ratio (mol/mol) of at least about 0.05:1, or a
combination thereof.
Embodiment 15
[0083] A reformer for use in an exhaust gas recycle portion of an
internal combustion engine powertrain, said reformer comprising a
catalyst composition configured to convert a mixture comprising an
internal combustion engine exhaust gas and a hydrocarbon-containing
fuel to a gaseous mixture comprising H.sub.2, CO, CO.sub.2,
H.sub.2O, N.sub.2, and greater than 1.0 mol % CH.sub.4 based on the
total moles of gas in the gaseous mixture, the catalyst composition
comprising a hydrocarbon-reforming catalyst composition described
in any of Embodiments 1-14.
Embodiment 16
[0084] The reformer of Embodiment 15, further comprising an
internal combustion engine having an exhaust manifold comprising an
exhaust gas recycle unit and a fuel intake manifold, the reformer
being fluidly connected to the exhaust manifold and the fuel intake
manifold, the fuel intake manifold being configured to provide a
reformed fuel mixture from the exhaust gas recycle unit and a
second hydrocarbon-containing fuel to the internal combustion
engine for combustion, wherein the first and second
hydrocarbon-containing fuels may be the same or different.
Embodiment 17
[0085] A hydrocarbon-reforming catalyst composition comprising
about 0.25 wt % to about 10 wt % Rh, about 10 wt % to about 99.5 wt
% of a CHA framework type molecular sieve, and about 0.25 wt % to
about 10 wt % of one or more additional molecular sieves having a
largest ring size of a 10-member ring, the CHA framework type
molecular sieve optionally being chabazite, the one or more
additional molecular sieves optionally being ZSM-5, MCM-68, or a
combination thereof.
Embodiment 18
[0086] The hydrocarbon-reforming catalyst composition of Embodiment
17, wherein the hydrocarbon-reforming catalyst composition further
comprises 0.25 wt % to 10 wt % of an additional metal selected from
the group consisting of Co, Ru, Pt, Pd, Ni, Ir, Zn, Re, and
mixtures thereof.
Embodiment 19
[0087] The hydrocarbon-reforming catalyst composition of any of
Embodiments 17-18, wherein the hydrocarbon-reforming catalyst
composition further comprises a metal oxide composition, the metal
oxide composition optionally being selected from aluminum oxides,
silicon oxides, rare-earth metal oxides, Group IV metal oxides, and
mixtures thereof, or optionally comprising a mixture of an
aluminum-containing oxide and a cerium-containing oxide.
EXAMPLES
Catalyst Preparation Examples
[0088] Preparation of catalysts A and A':
[0089] Catalyst A included .about.3.5 wt % Rh supported on a mixed
metal oxide comprising La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3
(.about.40 wt % of total support) and CeO.sub.2--ZrO.sub.2
(.about.60 wt % of total support). Catalyst A' included .about.3.5
wt % Rh supported on a mixed metal oxide comprising
La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3 (.about.38.5 wt % of total
support) and CeO.sub.2--ZrO.sub.2 (.about.58 wt % of total
support). The La.sub.2O.sub.3--Al.sub.2O.sub.3 support was prepared
separately by impregnation of an aqueous La(NO.sub.3).sub.3
solution onto .gamma.-Al.sub.2O.sub.3, followed by drying and
calcination at .about.600.degree. C. The La:Al atomic ratio was
.about.1.5:100. CeO.sub.2--ZrO.sub.2 was co-precipitated from an
aqueous Ce(NO.sub.3).sub.4 and Zr(NO.sub.3).sub.4 solution onto the
La.sub.2O.sub.3--Al.sub.2O.sub.3 support using urea as base. The
Ce:Zr atomic ratio was .about.4:1. The
La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3--CeO.sub.2--ZrO.sub.2
support was calcined at .about.600.degree. C. prior to incipient
wetness impregnation with an aqueous solution containing
Rh(NO.sub.3).sub.3. After the precious metal impregnation, the
catalyst was calcined in air at .about.600.degree. C.
Preparation of Catalyst B:
[0090] Catalyst B included .about.3.5 wt % Rh supported on a mixed
metal oxide comprising La.sub.2O.sub.3 and .gamma.-Al.sub.2O.sub.3.
The La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3 support was prepared by
impregnation of an aqueous La(NO.sub.3).sub.3 solution onto
.gamma.-Al.sub.2O.sub.3, followed by drying and calcination at
.about.600.degree. C. The La:Al ratio was .about.1.5:100. The
calcined La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3 support was
subsequently impregnated with an aqueous solution of
Rh(NO.sub.3).sub.3. After the precious metal impregnation, the
catalyst was calcined in air at .about.600.degree. C.
Preparation of Catalyst C:
[0091] Catalyst C included .about.0.62 wt % Rh supported on zeolite
Chabazite. The zeolite was prepared from a synthesis mixture having
the stoichiometry: .about.3 SDAOH: .about.10
Na.sub.2O:Al.sub.2O.sub.3:.about.35 SiO.sub.2:.about.1000 H.sub.2O,
where SDAOH was N,N,N-trimethyl-adamantylammonium hydroxide. To a
.about.125 ml Teflon autoclave were added .about.8.86 g of
.about.25 wt % SDAOH, .about.0.70 g .about.50% NaOH, .about.21.0 g
of sodium silicate solution (.about.30% SiO.sub.2, .about.9%
Na.sub.2O), .about.42.3 g deionized water, and .about.2.1 g of USY
zeolite (Si/Al.about.2.5, 17% Al.sub.2O.sub.3), and the mixture was
heated for 4 days at .about.140.degree. C. in a tumbling oven at
.about.20 rpm. The product was recovered by vacuum filtration and
washed with de-ionized water. Phase analysis by powder X-ray
diffraction showed that the sample appeared to be pure chabazite
having a Si/Al ratio of .about.8 (ICP-AES analysis).
[0092] The Na-form of the chabazite was subsequently ion exchanged
with an aqueous solution of Rh(NH.sub.3).sub.5Cl.sub.3 for
.about.48 hours at .about.85.degree. C. using a .about.0.03 molar
Rh solution, .about.5 g dry zeolite, and a liquid/solid weight
ratio of .about.175:1. After the ion exchange, the slurry was
filtered, and the filter cake was washed with .about.500 ml of
deionized water. The washed Rh--CHA filter cake was subsequently
dried for .about.12 hours at .about.110.degree. C. and then
calcined for .about.2 hours at .about.500.degree. C. in air using a
ramp rate of .about.2.degree. C./min.
Preparation of Catalyst D:
[0093] Catalyst D included .about.1.37 wt % Rh supported on zeolite
CHA. A synthesis mixture was prepared having the stoichiometry:
.about.0.11 Rh: .about.1.4 K.sub.2O: Al.sub.2O.sub.3: .about.5.1
SiO.sub.2: .about.110 H.sub.2O. To a plastic beaker were added
.about.15.5 g deionized water, .about.1.94 g KOH.1/2H.sub.2O, and
.about.4.84 g of an amorphous silica-alumina gel (.about.22.5%
Al.sub.2O.sub.3, .about.67.5% SiO.sub.2). About 4.97 g of 10 wt %
Rh(en).sub.3Cl.sub.3.3H.sub.2O solution (en=ethylenediamine)
solution was added dropwise with stirring and then stirred for an
additional .about.20 mins. The mixture was transferred to a
.about.45 ml Teflon autoclave and then heated for .about.12 days at
.about.100.degree. C. in a tumbling oven at .about.25 rpm. The
product was recovered by vacuum filtration and washed with
de-ionized water. Phase analysis by powder X-ray diffraction showed
that the sample appeared to be pure chabazite. The sample was
finally calcined in air for .about.2 hours at .about.560.degree. C.
using a ramp rate of .about.4.5.degree. C./min.
Preparation of Catalyst E:
[0094] Catalyst E included .about.0.35 wt % Rh supported on zeolite
CHA. A reaction mixture having the stoichiometry: .about.0.064 Rh:
.about.3 SDAOH: .about.10 Na.sub.2O: Al.sub.2O.sub.3: .about.35
SiO.sub.2: 1000 H.sub.2O, where SDA was
N,N,N-trimethyladamantylammonium, was prepared by mixing the
following ingredients together in a Teflon liner of a .about.125 ml
autoclave: .about.9.49 g of .about.25% SDAOH, .about.0.46 g of
.about.50% NaOH .about.43.74 g deionized water, and .about.23.1 g
sodium silicate (.about.28.2% SiO.sub.2, .about.9.3% Na.sub.2O). A
.about.1.02 g solution of .about.10 wt %
Rh(en).sub.3Cl.sub.3.3H.sub.2O (en=ethylenediamine) was slowly
added while mixing with a magnetic stir bar. Then .about.2.18 g of
USY zeolite (.about.17.5% Al.sub.2O.sub.3,
Si/Al.apprxeq..about.2.5) was added and the mixture reacted for
.about.5 days at .about.140.degree. C. in a tumbling oven
(.about.40 rpm). The product was recovered by vacuum filtration,
washed with deionized water and then dried in a .about.115.degree.
C. oven. Phase analysis by powder X-ray diffraction showed the
sample to be pure chabazite. Analysis by X-ray fluorescence showed
the sample to contain about .about.0.35% Rh. The sample was finally
calcined in air for .about.2 hours at .about.560.degree. C. using a
ramp rate of .about.4.5.degree. C./min.
Preparation of Catalyst F:
[0095] Catalyst F included .about.1.31 wt % Rh encapsulated in
zeolite CHA. A synthesis mixture was prepared having the
stoichiometry: .about.0.2 Rh: .about.2.15 SDAOH: .about.7
Na.sub.2O: Al.sub.2O.sub.3: .about.25 SiO.sub.2: .about.715
H.sub.2O, where SDAOH was N,N,N-trimethyl-adamantylammonium
hydroxide. For preparation of the synthesis mixture, to a plastic
beaker were added .about.20.7 g sodium silicate (.about.28.2%
SiO.sub.2, .about.9.3% Na.sub.2O), .about.38.0 g deionized water,
.about.0.5 g .about.50% NaOH, and .about.8.8 g .about.25% SDAOH.
The mixture was stirred with a magnetic stirrer. About 4.14 g of
.about.10 wt % Rh(en).sub.3Cl.sub.3.3H.sub.2O solution
(en=ethylenediamine) solution was added drop wise with stirring and
then stirred until homogenous. The mixture was divided between
three .about.23 ml Teflon autoclaves and then .about.0.94 g of USY
zeolite (.about.60 wt % SiO.sub.2, .about.17 wt % Al.sub.2O.sub.3)
was mixed in each liner. The autoclaves were heated for .about.7
days at .about.140.degree. C. in a tumbling oven at .about.25 rpm.
The product was recovered by vacuum filtration and washed with
de-ionized water. Phase analysis by powder X-ray diffraction showed
that the sample appeared to be pure chabazite. The sample was
finally calcined in air for .about.3 hours at .about.560.degree. C.
using a ramp rate of .about.4.5.degree. C./min. Analysis by X-ray
fluorescence showed the sample contained .about.1.31 wt % Rh.
Preparation of Catalyst G:
[0096] A self-bound ZSM-5 sample (Si/Al.about.30) was contacted
with an aqueous solution of H.sub.3PO.sub.4 to the point of
incipient wetness. The impregnated material was dried overnight at
.about.121.degree. C. in stagnant air, and treated subsequently in
flowing dry air (.about.5 volumes air/volume solids/min) for
.about.3 hours at .about.538.degree. C. The calcined sample was
analyzed to contain .about.1.2 wt % P.
Preparation of Catalyst H:
[0097] Catalyst H was composed of a physical mixture of Catalyst A
and C, where equal amounts of Rh were supported on the support of
catalyst A (consisting of alumina, lanthana, ceria, zirconia) and
on the support of catalyst C (consisting of chabazite). Based on
the individual Rh loadings on catalyst components A and C, their
weight ratio in catalyst G was chosen to be .about.1 part by weight
of catalyst A and .about.5.6 parts by weight of catalyst C. This
resulted in a catalyst composition having about 1 wt % Rh, about 15
wt % of the mixed oxide support from catalyst A, and about 84 wt %
of chabazite.
Preparation of Catalyst I:
[0098] Catalyst I was composed of a physical mixture of Catalyst A
and D, where equal amounts of Rh were supported on the support of
catalyst A (consisting of alumina, lanthana, ceria, zirconia) and
on the support of catalyst D (consisting of chabazite). Based on
the individual Rh loadings on catalyst components A and D, their
weight ratio in catalyst H was chosen to be .about.1 part by weight
of catalyst A and .about.2.6 parts by weight of catalyst D. This
resulted in a catalyst composition of about 2 wt % Rh, about 28 wt
% of the mixed oxide support from catalyst A, and about 70 wt % of
chabazite.
Preparation of Catalyst J:
[0099] Catalyst J was composed of a physical mixture of Catalyst A
and E where equal amounts of Rh were supported on the support of
catalyst A (consisting of alumina, lanthana, ceria, zirconia) and
on the support of catalyst E (consisting of chabazite). Based on
the individual Rh loadings on catalyst components A and E, their
weight ratio in catalyst I was chosen to be .about.1 part by weight
of catalyst A and .about.10 parts by weight of catalyst E. This
resulted in a catalyst composition of about 0.6 wt % Rh, about 9 wt
% of the mixed oxide support from catalyst A, and about 90.4 wt %
of chabazite.
Preparation of Catalyst K:
[0100] Catalyst K was composed of a physical mixture of Catalyst A
and F, where equal amounts of Rh were supported on the support of
catalyst A (consisting of alumina, lanthana, ceria, zirconia) and
on the support of catalyst F (consisting of chabazite). Based on
the individual Rh loadings on catalyst components A and F, their
weight ratio in catalyst K was chosen to be .about.1 part by weight
of catalyst A and .about.2.7 parts by weight of catalyst F.
Preparation of Catalyst L:
[0101] Catalyst L was composed of a physical mixture of reforming
catalysts A and C and cracking catalyst G. Equal amounts of Rh were
supported on the support of catalyst A (consisting of alumina,
lanthana, ceria, zirconia) and on the support of catalyst C
(consisting of chabazite). Based on the individual Rh loadings on
catalyst components A and C, their weight ratio in catalyst L was
chosen to be .about.1 part by weight of catalyst A and .about.5.6
parts by weight of catalyst C. The amount of the cracking catalyst
G was chosen to be .about.1 part by weight.
Preparation of catalyst M:
[0102] Catalyst M included .about.3.75 wt % Rh and .about.1.25 wt %
Pt supported on a mixed metal oxide comprising
La.sub.2O.sub.3-.gamma.-Al.sub.2O.sub.3 (.about.40 wt % of total
support) and CeO.sub.2--ZrO.sub.2 (.about.60 wt % of total
support). The La.sub.2O.sub.3--Al.sub.2O.sub.3 support was prepared
separately by impregnation of an aqueous La(NO.sub.3).sub.3
solution onto .gamma.-Al.sub.2O.sub.3. The impregnated
.gamma.-Al.sub.2O.sub.3 was dried and calcined at
.about.600.degree. C. The La:Al atomic ratio was .about.1.5:100.
CeO.sub.2--ZrO.sub.2 was co-precipitated from an aqueous
Ce(NO.sub.3).sub.4 and Zr(NO.sub.3).sub.4 solution onto the
La.sub.2O.sub.3--Al.sub.2O.sub.3 support using urea as base. The
Ce:Zr atomic ratio was .about.4:1. The
La-.gamma.-Al.sub.2O.sub.3--CeO.sub.2--ZrO.sub.2 support was
calcined at .about.600.degree. C. prior to incipient wetness
impregnation with an aqueous solution containing Rh(NO.sub.3).sub.3
and Pt(NH.sub.3).sub.4(NO.sub.3).sub.2. After the precious metal
impregnation, the catalyst was calcined in air at
.about.600.degree. C.
Preparation of Catalyst N:
[0103] Catalyst N consisted of rhodium supported on .gamma.-alumina
A nominal metal loading of .about.2.0 wt % rhodium was attained.
For the preparation of catalyst N, an aqueous solution containing
Rh(NO.sub.3).sub.3 was impregnated onto the .gamma.-alumina support
in one step. The powder was dried after the impregnation for
.about.12 hours at .about.110.degree. C. in air. After drying, the
powder catalyst was calcined for .about.4 hours at
.about.450.degree. C. in air. After the calcination, the catalyst
powder was pelletized and reduced for .about.4 hours at
.about.350.degree. C. in a flow of .about.10% H.sub.2, balance
N.sub.2, followed by a .about.1 hour purge in a flow of pure
N.sub.2 gas at .about.350.degree. C.
[0104] Preparation of Catalyst O:
[0105] Catalyst O consisted of rhodium supported on silica. About
0.99 grams of an aqueous rhodium nitrate solution (.about.10 wt %
Rh), .about.1.35 grams of arginine, and about 6 drops of .about.60%
nitric acid were added to deionized water, so that the total
solution volume reached .about.10.0 cm.sup.3. The impregnated
solution was added onto .about.10.0 grams of a silica support
(Davisil.TM. 646) by incipient wetness. The catalyst was dried at
.about.100.degree. C. overnight (.about.8-16 hours). The catalyst
was calcined in air at .about.425.degree. C. for .about.4 hours.
The final Rh loading was about 1 wt %.
Preparation of Catalyst P
[0106] Catalyst P consisted of rhodium and ruthenium supported on
.gamma.-alumina. Nominal metal loadings of .about.3.5 wt % rhodium
and of .about.1.71 wt % ruthenium were attained. For the
preparation of catalyst P, an aqueous solution containing
Rh(NO.sub.3).sub.3 and Ru(NO)(NO.sub.3).sub.3 was impregnated onto
the .gamma.-alumina support in two steps. An incipient wetness
volume of .about.90% was achieved in the first impregnation step
and of .about.85% in the second impregnation step. Powders were
dried between impregnations and after the second impregnation for
.about.12 hours at .about.110.degree. C. in air. After drying, the
powder catalyst was calcined for .about.4 hours at
.about.450.degree. C. in air. After the calcination, the catalyst
powder was pelletized and reduced for .about.4 hours at
.about.350.degree. C. in a flow of .about.10% H.sub.2, balance
N.sub.2, followed by a .about.1 hour purge in a flow of pure
N.sub.2 gas at .about.350.degree. C.
TABLE-US-00001 TABLE 1 Composition of Catalysts A-P Catalyst
Support Rh loading, wt % Type A, A'
La.sub.2O.sub.3--Al.sub.2O.sub.3--CeO.sub.2--ZrO.sub.2 ~3.5
Reforming B La.sub.2O.sub.3--Al.sub.2O.sub.3 ~3.5 Reforming C CHA
~0.62 Reforming + Methanation D CHA ~1.37 Reforming + Methanation E
CHA ~0.35 Reforming + Methanation F CHA ~1.31 Reforming +
Methanation G P-ZSM-5 0.0 Acid Cracking Composite catalysts
Catalysts Catalyst wt ratio H A + C A:C .apprxeq. 1:5.6 Reforming +
Methanation I A + D .sup. A:D .apprxeq. 1:2.6 Reforming +
Methanation J A + E A:E .apprxeq. 1:10 Reforming + Methanation K A
+ F A:F .apprxeq. 1:2.7 Reforming + Methanation L A + C + G A:C:G
.apprxeq. 1:5.6:2 Reforming + Methanation + Cracking Additional Rh
(and other metals) catalysts Support loading, wt % M
La.sub.2O.sub.3--Al.sub.2O.sub.3 ~3.75 (+~1.25 Pt) Reforming N
.gamma.-alumina 2.0 Reforming O Silica 1.0 Reforming P
.gamma.-alumina .sup. ~3.5 (+~1.71 Ru) Reforming
Example 1
Propane Steam Reforming Test of Catalyst M
[0107] Propane was used as a model fuel compound for determining
reforming and methanation rates in the presence of a catalyst
composition with two hydrocarbon reforming catalysts (.about.3.75
wt % Ru, .about.1.25 wt % Pt). For the catalytic test, .about.0.08
grams of catalyst powder M sized to about .about.25-40 mesh was
diluted with silica at a ratio of .about.1:15. The diluted catalyst
was loaded into a vertically mounted cylindrical quartz plugged
flow reactor (.about.6 mm id.times..about.15 mm long), which was
heated by a furnace. The temperature was measured in the front
catalyst bed (.about.1/4'' from catalyst inlet) and in the rear
catalyst bed (.about.1/4'' from the catalyst outlet). The average
catalyst bed temperature was calculated from the catalyst bed
temperatures at the inlet and outlet. A feed gas comprising
.about.13.3 mol % propane, .about.27.4 mol % H.sub.2O, .about.26.6
mol % CO.sub.2, and N.sub.2 balance was fed over the catalyst to
achieve gas hourly space velocities of .about.26 khr.sup.-1 and
.about.52 khr.sup.-1. The conversion of propane and the
concentration of the reaction product methane were monitored by FID
(flame ionization detection), while the concentration of reaction
products, carbon monoxide, and hydrogen were detected by GC/TCD
(gas chromatography/thermal conductivity detector) analyzers.
[0108] FIG. 3 shows the amounts of H.sub.2 (31), CH.sub.4(32), and
CO (33) produced by the example reformer at various levels of fuel
conversion. The mole fraction of CH.sub.4 in the reformer product
appeared to increase from about 0.04 at .about.12% fuel conversion
to about 0.06 at .about.44% fuel conversion to about 0.13 at
.about.75% fuel conversion.
[0109] Referring now to FIG. 4, trace (41) shows the amount of heat
needed to maintain the reformer at about constant temperature when
the reforming catalyst produced substantially only syngas and no
methane. The heat requirement appeared to increase from about 1.5
kJ/g fuel at .about.12% fuel conversion to about 5.3 kJ/g fuel at
.about.44% conversion to about 9.1 kJ/g fuel at .about.75% fuel
conversion in this case. Trace (42) shows the amount of heat needed
to maintain the reformer at constant temperature when the reforming
catalyst produces the levels of methane shown in FIG. 3. The heat
requirement appeared to be much lower in this case, varying from
about 1.2 kJ/g fuel at .about.12% fuel conversion to about 2.8 kJ/g
fuel at .about.44% conversion to about 2.8 kJ/g fuel at .about.75%
fuel conversion.
[0110] As shown in FIG. 4, a reforming catalyst on a metal oxide
support can generate some methane under reforming conditions, so
that the amount of heat required for the reforming reaction can be
reduced. As a comparison, trace (43) shows the amount of heat
released by cooling the recycled exhaust gas by .about.100.degree.
C. and by combusting fuel with residual oxygen, present at about a
1% level in the exhaust gas. Trace (43) also shows that this amount
of heat appeared to be enough to supply the additional heat needed
for the reforming reactions. However, the additional fuel used to
supply heat for the reforming reactions can represent an additional
fuel debit against the overall efficiency of the engine.
Example 2
n-Heptane Steam Reforming Test
[0111] An n-heptane feed was used to for determining reforming and
methanation rates for a model feed based on a hydrocarbon that was
representative of a compound present in a typical naphtha boiling
range fuel. About 50 mg to about 1250 mg of catalysts K, N, O, and
P were sized to .about.40-60 mesh and blended with quartz sized to
.about.60-80 mesh to obtain .about.4 cm.sup.3 of catalyst-quartz
mixture. The catalyst diluent mixture was loaded into a stainless
steel reactor tube of .about.4'' length and .about.0.3'' inner
diameter. The reactor tube was heated by a furnace to maintain a
constant temperature of .about.450.degree. C., .about.500.degree.
C., or .about.550.degree. C. in the catalyst throughout the length
of the catalyst bed. A thermocouple in the bed was used to confirm
that all experiments were performed approximately isothermally. A
gas mixture comprising .about.2.5 mol % n-heptane, .about.13 mol %
H.sub.2O, .about.11 mol % CO.sub.2, and balance N.sub.2 was fed to
the catalyst at a pressure of .about.2 barg (.about.200 kPag) or
.about.4 barg (.about.400 kPag). The total gas flow rate was varied
between about 70 mL/min and about 400 mL/min to achieve different
levels of fuel conversion.
[0112] The ratio of methane and hydrogen as a function of
conversion at .about.500.degree. C. catalyst bed temperature was
measured for catalyst A'(71), N (72), O (73), and P (75) at
.about.2 barg (.about.200 kPag) pressure, as well as for catalyst O
(74) at .about.4 barg (.about.400 kPag) pressure. It was apparent
that catalysts N, O, and P appeared to exhibit a higher
CH.sub.4/H.sub.2 ratio compared to the reference catalyst K. The
CH.sub.4/H.sub.2 ratio also appeared to be higher when the pressure
was raised from .about.2 barg (.about.200 kPag) to .about.4 barg
(.about.400 kPag). These are shown in the graph at FIG. 5. The
catalyst and conditions in trace (74), corresponding to Catalyst O
at the higher pressure, appeared to be the most effective at
maintaining high catalyst temperatures.
[0113] FIG. 6 shows n-heptane conversion versus contact time for
(81) Catalyst A' at .about.550.degree. C., (82) Catalyst A' at
.about.500.degree. C., (83) Catalyst A' at .about.450.degree. C.,
(84) Catalyst N at .about.500.degree. C., (85) Catalyst O at
.about.500.degree. C., and (86) Catalyst P at .about.500.degree. C.
The conditions were .about.2.5 mol % n-heptane, .about.13 mol %
H.sub.2O, .about.11 mol % CO.sub.2, balance N.sub.2, at .about.2
barg (.about.200 kPag) pressure. Although Catalyst O was most
effective in producing a high ratio of CH.sub.4 to H.sub.2 (as
shown in FIG. 5), FIG. 6 shows that the conversion rate of Catalyst
O for reforming n-heptane appeared substantially slower than
Catalyst A', N, or P. This suggests that the high ratio of CH.sub.4
to H.sub.2 for Catalyst O may be related to a reduced level of
H.sub.2 production rather than an increased level of CH.sub.4
production.
Example 3
Reforming of n-Heptane and Methanation
[0114] Catalysts A and H were tested in a laboratory reactor in the
steam reforming reaction of n-heptane. For the tests,
.about.50-1250 mg of catalyst were sized to .about.40-60 mesh and
blended with quartz sized to .about.60-80 mesh to obtain .about.4
cm.sup.3 of catalyst-quartz mixture. The catalyst diluent mixture
was loaded into a stainless steel reactor tube of 4'' length and
0.3'' inner diameter. The reactor tube was heated by a furnace to
maintain a constant temperature of .about.500.degree. C. in the
catalyst throughout the length of the catalyst bed. A thermocouple
in the bed was used to confirm that experiments were performed
isothermally. A gas mixture comprising .about.2.5 mol % n-heptane,
.about.13 mol % H.sub.2O, and .about.11 mol % CO.sub.2 in N.sub.2
(balance of gas mixture) was fed to the catalyst at a pressure of
.about.2 barg (.about.200 kPag). The total gas flow rate was varied
between .about.70 ml/min and .about.400 ml/min to achieve different
levels of fuel conversion. Reaction products CO, CO.sub.2, H.sub.2,
were analyzed by GC-TCD, CH.sub.4 was analyzed by GC-FID. N-heptane
reforming rates were defined as mol fuel carbon converted/mol Rh/s.
Methane formation rates were defined as mol CH.sub.4 formed/mol
Rh/s. Tests were conducted at a residence time of .about.10 g
Rh*s/g fuel.
[0115] FIGS. 7A and 7B show the n-heptane conversion rates and the
methane formation rates, respectively, in the reforming reaction of
Example 3 for catalysts A and H. While catalysts A and H appeared
to display similar n-heptane conversion rates, the methane
formation rate was unexpectedly substantially higher over catalyst
H. Thus, catalyst H can provide both a desirable level of
conversion (reforming) of naphtha boiling range fuel components
like n-heptane, while also providing an improved amount of methane
formation.
Example 4
Reforming of Multi-Component Model Fuel and Methanation
[0116] Catalysts A, C, H, I, J, and K were tested on a surrogate
gasoline type fuel containing .about.45 vol % 3-methyl pentane,
.about.15 vol % n-hexane, .about.10 vol % 2,2,4-trimethyl pentane
(iso-octane), .about.20 vol % toluene, and .about.10 vol % ethanol.
The same reactor and procedures as described in Example 3 were used
for the multi-component model fuel reforming test. A gas mixture
comprising .about.1.4 mol % 3-methyl pentane, .about.0.46 mol %
n-hexane, .about.0.25 mol % 2,2,4 trimethyl pentane, .about.0.76
mol % toluene, .about.0.69 mol % ethanol, .about.13.1 mol %
H.sub.2O, and .about.12.6 mol % CO.sub.2 in N.sub.2 (balance of gas
mixture) was fed into a reactor at .about.2 barg (.about.200 kPag)
pressure and .about.500.degree. C. catalyst bed temperature.
Reaction products CO, CO.sub.2, H.sub.2, were analyzed by GC-TCD,
CH.sub.4 was analyzed by GC-FID. The global reforming rates were
defined as mol fuel carbon converted/mol Rh/s. Methane formation
rates were defined as mol CH.sub.4 formed/mol Rh/s. Tests were
conducted at a residence time of .about.10 g Rh*s/g fuel.
[0117] FIGS. 8A and 8B show the global multi component fuel
conversion rates and the methane formation rates, respectively, for
the reforming reaction of Example 4 for catalysts A, C, H, I, J,
and K. It was apparent that catalyst C showed a lower reforming
activity than catalyst A. It was unexpectedly found that catalyst
H, which was a physical mixture of catalysts A and C, had a similar
reforming activity to catalyst A alone. Catalyst J, which was a
physical mixture of catalysts A and E, also unexpectedly showed a
reforming activity comparable to catalyst A alone. Catalyst K,
which was a physical mixture of catalysts A and F, also
unexpectedly showed a reforming activity comparable to and possibly
greater than catalyst A alone.
[0118] Catalyst C showed a higher methanation activity than
catalyst A. It was unexpectedly found that catalyst H, which was a
physical mixture of catalyst A and C, showed a substantially higher
methane formation rate than its individual constituents A and C
alone. Catalyst I, which was a physical mixture of catalysts A and
D, also showed a higher methanation rate than catalyst A alone. It
was noted that Catalyst I was similar in Rh content to Catalyst H,
but had a lower concentration of the CHA framework type zeolite. As
shown in FIG. 8B, reducing the amount of CHA framework type zeolite
appeared to result in a reduced amount of methanation. By contrast,
Catalyst J, which was a physical mixture of catalysts A and E, and
Catalyst K, which was a physical mixture of catalysts A and F,
displayed the highest methanation rates. Catalyst J had an
increased amount of CHA framework type zeolite relative to Catalyst
H. Similar to catalyst I, catalyst K had a lower amount of CHA
framework type zeolite than catalyst H. However, unlike catalyst I,
catalyst K appeared to show a higher methane formation rate than H.
The methanation catalyst component in Catalyst K was formed by an
alternative method.
[0119] The product selectivities expressed as mol % carbon
converted into products COx (CO+CO.sub.2), benzene, and methane are
shown in FIG. 8C for the tests in Example 4. In FIG. 8C, the
CO.sub.x selectivity is shown as the left bar for each catalyst,
the benzene selectivity is the middle bar, and the methane
selectivity is the right bar. Catalyst C had higher COx
selectivity, lower benzene selectivity, and higher methane
selectivity compared to catalyst A. It was unexpectedly found that
mixing of catalysts A and C (such as to form catalyst H) resulted
in a significant reduction of COx selectivity and an increase in
methane selectivity relative to catalyst A. It was noted that, in
line with their high methane formation rates, catalysts J and K
also appeared to show the highest methane selectivity. Catalysts J
and K also appeared to show the lowest COx selectivities.
Example 5
CO Hydrogenation
[0120] The methanation rate was measured for various feed streams
containing CO and H.sub.2 over catalysts B and C. In a first test,
the methane formation rate for a feed containing just syngas
(H.sub.2, CO, CO.sub.2) was tested. The same reactor and procedure
as described for Example 1 was used for the CO hydrogenation test.
A gas mixture comprising .about.8.3 mol % CO, .about.15.9 mol %
H.sub.2, .about.5.7 mol % CO.sub.2 in N.sub.2 (balance of gas
mixture) was fed at .about.2 barg (.about.200 kPag) pressure and
.about.500.degree. C. catalyst bed temperature. Catalyst B
(Rh--LaAl.sub.2O.sub.3) was run at a residence time of .about.8.8 g
Rh*s/g CO, while catalyst C (Rh--CHA) was run at a residence time
of .about.11.1 g Rh*s/g CO. It was noted that water was not
included in the gas mixture. The absence of water in the initial
gas mixture was believed to reduce/minimize the opportunity for
steam reforming to occur in the reaction environment as a
complementary reaction.
[0121] The effect of n-heptane co-feed on the CO hydrogenation
activity was also tested. The same reactor and test procedure as
described above were used to test CO hydrogenation in the presence
of n-heptane. A gas mixture comprising .about.8.4 mol % CO,
.about.16 mol % H.sub.2, .about.5.3 mol % n-heptane, and .about.5.8
mol % CO.sub.2 in N.sub.2 (balance of gas mixture) was fed at
.about.2 barg (.about.200 kPag) pressure and .about.500.degree. C.
catalyst bed temperature. Catalyst B (Rh--LaAl.sub.2O.sub.3) was
run at a residence time of .about.3.9 g Rh*s/g heptane and
.about.8.8 g Rh*s/g CO.
[0122] The effect of a multi-component hydrocarbon fuel co-feed on
the CO hydrogenation activity was also tested. The same reactor and
test procedure as described above were used for the CO
hydrogenation test in the presence of the multi component
hydrocarbon fuel. A gas mixture comprising .about.8.1 mol % CO,
.about.15.6 mol % H.sub.2, .about.2.44 mol % 3-methyl pentane,
.about.0.81 mol % n-hexane, .about.0.43 mol % 2,2,4 tri-methyl
pentane, .about.1.32 mol % toluene, .about.1.2 mol % ethanol, and
.about.5.6 mol % CO.sub.2 in N.sub.2 (balance of gas mixture) was
fed at .about.2 barg (.about.200 kPag) pressure and
.about.500.degree. C. catalyst bed temperature. Catalyst C
(Rh--CHA) was run at a residence time of .about.5.0 g Rh*s/g fuel
and .about.11.1 g Rh*s/g CO.
[0123] FIG. 9 shows the methane formation rate from testing
catalyst B in the presence of the syngas feed (H.sub.2 and CO) and
the feed of syngas plus n-heptane. As shown in FIG. 9, the
n-heptane co-feed appeared to strongly deplete the ability of
catalyst B to convert syngas into methane. This indicated that
catalyst B had some activity for methanation. However, in an engine
environment, the goal of reforming can typically be to convert a
lower octane rating fuel to a higher octane fuel. Such lower octane
fuels can typically correspond to hydrocarbons, such as linear or
branched alkanes. FIG. 9 shows that low octane feed components
typically present in a naphtha boiling range fuel can substantially
reduce/minimize the methanation activity of Catalyst B.
[0124] FIG. 10 shows the methane formation rate from testing
Catalyst C in the presence of the syngas feed (H.sub.2 and CO) and
the feed of syngas plus the multi-component model fuel. As
described above, the multi-component model fuel includes a variety
of types of compounds that can be present in a fuel, including both
low octane components such as n-hexane and higher octane components
such as toluene. As shown in FIG. 10, Catalyst C actually had a
lower methane formation rate than Catalyst B for the syngas feed
without any additional fuel components. However, in the presence of
the fuel components of the multi-component model fuel, Catalyst C
unexpectedly showed a substantially higher methane formation
rate.
Example 6
Reforming, Methanation, and Cracking
[0125] In order to test the effect of an acid cracking catalyst on
reforming, a blend of catalysts H and G (corresponding to catalyst
L) was tested. The product selectivity of catalyst L for reforming
the multi-component fuel feed of Example 4 is shown in FIG. 11. The
product selectivity for catalyst H is also shown in FIG. 11 to
provide a comparison. As shown in FIG. 11, the addition of a
cracking function (such as P-ZSM-5 zeolite) appeared to decrease
the selectivity for COx and increase the selectivity for methane.
This result was unexpected, because no significant amounts of
methane were observed in fuel cracking experiments over the acid
cracking catalyst G alone. The methane selectivity for catalyst L,
as shown in FIG. 11, also appeared to be slightly greater than the
methane selectivity for catalyst J in FIG. 8C.
[0126] All patents, test procedures, and other documents cited
herein, including priority documents, are fully incorporated by
reference to the extent such disclosure is not inconsistent with
this invention and for all jurisdictions in which such
incorporation is permitted. Should the disclosure of any of the
patents and/or publications that are incorporated herein by
reference conflict with the present specification to the extent
that it might render a term unclear, the present specification
shall take precedence.
[0127] As should be apparent from the foregoing general description
and the specific embodiments, while forms of the invention have
been illustrated and described, various modifications can be made
without departing from the spirit and scope of the invention.
Accordingly, it is not intended that the invention be limited
thereby. Many variations will suggest themselves to those skilled
in this art in light of the above detailed description. All such
variations can be within the full intended scope of the appended
claims. Certain embodiments and features have been described using
a set of numerical upper limits and a set of numerical lower
limits. It should be appreciated that ranges from any lower limit
to any upper limit are contemplated unless otherwise indicated.
Certain lower limits, upper limits and ranges appear in one or more
claims below. All numerical values are "about" or "approximately"
the indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
* * * * *