U.S. patent application number 14/336751 was filed with the patent office on 2015-03-12 for steam reforming of hydrocarbonaceous fuels over a ni-alumina spinel catalyst.
This patent application is currently assigned to UTI Limited Partnership, By Its General Partner, University Technologies International Inc. (UTI). The applicant listed for this patent is UTI Limited Partnership, By Its General Partner, University Technologies International Inc. (UTI). Invention is credited to Nicolas Abatzoglou, Jasmin Blanchard, Clemence Fauteux-Lefebvre, Francois Gitzhofer.
Application Number | 20150069300 14/336751 |
Document ID | / |
Family ID | 43606507 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150069300 |
Kind Code |
A1 |
Abatzoglou; Nicolas ; et
al. |
March 12, 2015 |
STEAM REFORMING OF HYDROCARBONACEOUS FUELS OVER A NI-ALUMINA SPINEL
CATALYST
Abstract
A process for steam reforming of a hydrocarbonaceous fuel
includes the steps of: providing a reactant mixture comprising
H.sub.2O and the hydrocarbonaceous fuel; and contacting the
reactant mixture with a Al.sub.2O.sub.3-yttria-stabilized ZrO.sub.2
(YSZ)-supported NiAl.sub.2O.sub.4 spinel catalyst under conditions
wherein the reactant gas mixture is at least partially steam
reformed into a product gas mixture including H.sub.2 and CO. The
synthesis gas (H.sub.2 and CO) produced can be used as feed
material for fuel cells. The catalyst includes a NiAl.sub.2O.sub.4
spinel-based catalytically active material; and a support material
comprising: Al.sub.2O.sub.3 and ZrO.sub.2. The
Al.sub.2O.sub.3-YSZ-supported NiAl.sub.2O.sub.4 catalyst can be
used in steam reforming of a liquid hydrocarbonaceous fuel.
Inventors: |
Abatzoglou; Nicolas;
(Sherbrooke, CA) ; Fauteux-Lefebvre; Clemence;
(Sherbrooke, CA) ; Blanchard; Jasmin; (Sherbrooke,
CA) ; Gitzhofer; Francois; (Sherbrooke, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UTI Limited Partnership, By Its General Partner, University
Technologies International Inc. (UTI) |
Calgary (Alberta) |
|
CA |
|
|
Assignee: |
UTI Limited Partnership, By Its
General Partner, University Technologies International Inc.
(UTI)
Calgary (Alberta)
CA
|
Family ID: |
43606507 |
Appl. No.: |
14/336751 |
Filed: |
July 21, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13391578 |
Jul 2, 2012 |
|
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PCT/CA2010/001284 |
Aug 19, 2010 |
|
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14336751 |
|
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61235835 |
Aug 21, 2009 |
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Current U.S.
Class: |
252/373 |
Current CPC
Class: |
B01J 23/83 20130101;
C01B 2203/1247 20130101; C01B 2203/1082 20130101; C10J 3/72
20130101; B01J 23/755 20130101; C01B 2203/1229 20130101; C10J
2300/1853 20130101; B01J 35/023 20130101; B01J 35/002 20130101;
C01B 2203/1223 20130101; B01J 21/066 20130101; B01J 37/0201
20130101; B01J 23/005 20130101; B01J 37/08 20130101; C01B 3/40
20130101; C10J 2200/06 20130101; B01J 37/04 20130101; C01B 3/326
20130101; C01B 2203/1217 20130101; C01B 2203/0233 20130101; C01B
2203/1058 20130101; Y02P 20/52 20151101; C01B 2203/066
20130101 |
Class at
Publication: |
252/373 |
International
Class: |
C10J 3/72 20060101
C10J003/72 |
Claims
1. A process for steam reforming of a hydrocarbonaceous fuel,
comprising the steps of: providing a reactant mixture comprising
H.sub.2O and the hydrocarbonaceous fuel; and contacting the
reactant mixture with a Al.sub.2O.sub.3-yttria-stabilized ZrO.sub.2
(YSZ)-supported NiAl.sub.2O.sub.4 spinel catalyst under conditions
wherein the reactant gas mixture is at least partially steam
reformed into a product gas mixture including H.sub.2 and CO, and
the Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel
catalyst is substantially free of metallic nickel and nickel
oxide.
2. A process according to claim 1, wherein: the reactant mixture is
in gaseous state when contacted with the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst;
the hydrocarbonaceous fuel in liquid state at ambient temperature
and atmospheric pressure; the hydrocarbonaceous fuel is selected
from the group consisting of: at least one hydrocarbon, at least
one oxygen-containing fuel, at least one biofuel, at least one
fossil fuel, at least one synthetic fuel and a mixture thereof; the
hydrocarbonaceous fuel is selected from the group consisting of:
gasoline, diesel, biodiesel, commercial fossil-derived diesel,
synthetic diesel, jet fuel, methanol, ethanol, bloethanol, methane,
alcohol, and mixture thereof; the reactant mixture comprises
H.sub.2O in a liquid state and the hydrocarbonaceous fuel in a
liquid state; said providing further comprises heating the reactant
mixture to provide a gaseous reactant mixture; and said contacting
comprises contacting the gaseous reactant mixture with the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst;
or said contacting is carried out at a temperature between
500.degree. C. and 900.degree. C.
3. The process according to claim 1, further comprising at least
one of atomizing and vaporizing the H.sub.2O and the
hydrocarbonaceous fuel to form an emulsion before contacting the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst;
and optionally further comprising adding a surfactant to the
H.sub.2O and the hydrocarbonaceous fuel before atomizing or
vaporizing the H.sub.2O and the hydrocarbonaceous fuel to form the
emulsion.
4. The process according to claim 1, wherein: the hydrocarbonaceous
fuel comprises carbon and the reactant mixture has a
H.sub.2O:carbon molar ratio between 2.3 and 3; the contacting is
carried out with a gas hourly space velocity ranging between 300
cm.sup.3g.sup.-1h.sup.-1 and 200 000 cm.sup.3g.sup.-1h.sup.-1; the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst
has a ratio Al.sub.2O.sub.3/YSZ ranging between 1/5 and 5/1; the
Al.sub.2O.sub.3--YSZ support consists essentially of
Al.sub.2O.sub.3 and YSZ and comprises between 1 w/w % to 2 w/w % of
yttria and the catalyst comprises an active phase consisting
essentially of the NiAl.sub.2O.sub.4 spinel; the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst
comprises a molar ratio of Ni/Al.sub.2O.sub.3 smaller or equal to
1; or the Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel
catalyst comprises between 1 and 10 w/w % of nickel.
5. A process according to claim 1, wherein: the hydrocarbonaceous
fuel is in liquid state at ambient temperature and atmospheric
pressure and the reactant mixture is in gaseous state when
contacted with the Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4
spinel catalyst; the hydrocarbonaceous fuel is selected from the
group comprising: at least one hydrocarbon, at least one biofuel,
at least one oxygen-containing fuel, at least one fossil fuel, at
least one synthetic fuel and a mixture thereof; or the reactant
mixture comprises H.sub.2O in a liquid state and the
hydrocarbonaceous fuel in the liquid state; said process further
comprises heating the reactant mixture to provide a gaseous
reactant mixture; and said contacting comprises contacting the
gaseous reactant mixture with the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst.
6. The process according to claim 1, wherein said submitting
comprises at least one of atomizing and vaporizing the H.sub.2O and
the hydrocarbonaceous fuel to form an emulsion before contacting
the Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel
catalyst; and optionally further comprising adding a surfactant to
the H.sub.2O and the hydrocarbonaceous fuel before atomizing or
vaporizing the H.sub.2O and the hydrocarbonaceous fuel to form the
emulsion.
7. The process according to claim 1, wherein: said contacting is
carried out at a temperature between 500.degree. C. and 900.degree.
C., with a H .sub.2O:carbon molar ratio between 2.3 and 3, and a
gas hourly space velocity ranging between 300
cm.sup.3g.sup.-1h.sup.-1 and 200 000 cm.sup.3g.sup.-1h.sup.-1; the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst is
substantially free of metallic nickel and nickel oxide, comprises
between 1 w/w % to 2 w/w % of yttria, and has a ratio
Al.sub.2O.sub.3/YSZ ranging between 1/5 and 5/1; or the
Al.sub.2O.sub.3--YSZ support consists essentially of
Al.sub.2O.sub.3 and YSZ and comprises between 1 and 10 w/w % of
nickel, the catalyst comprises an active phase consisting
essentially of the NiAl.sub.2O.sub.4 spinel, and the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst
comprises a molar ratio of Ni/Al.sub.2O.sub.3 smaller or equal to
1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/391,578, filed Jul. 2, 2012, which is a 371 national
stage application of PCT/CA2010/001284, filed Aug. 19, 2010, which
claims priority from U.S. provisional patent application No.
61/235,835 filed on Aug. 21, 2009, all of which are hereby
incorporated herein by reference in their entireties.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to steam reforming of
hydrocarbonaceous fuels and, more particularly, to steam reforming
of hydrocarbonaceous fuels over a Ni-Alumina spinel catalyst. It
also relates to new catalysts for steam reforming of
hydrocarbonaceous fuels.
BACKGROUND
[0003] Gaseous hydrogen (H.sub.2) can be used as feed for Solid
Oxide Fuel Cells (SOFC). Furthermore, it can be used altogether
with carbon monoxide (CO) to produce synthesis gas, syngas, without
harming the SOFC. Thus, the SOFC can use a mixture of H.sub.2 and
CO as co-fuel,
[0004] H.sub.2 can be obtained from hydrocarbons reforming either
by catalytic partial oxidation (see reaction 1 below), steam
reforming (see reaction 2 below) or autothermal reforming.
C.sub.nH.sub.m+n/2O.sub.2.fwdarw.nCO/m/2H.sub.2(.DELTA.H<0)
(1)
C.sub.nH.sub.m+nH.sub.2O.fwdarw.nCO+(n+m/2)H.sub.2(.DELTA.H>0)
(2)
[0005] Steam reforming (reaction 2) is advantageous for producing
higher H.sub.2 concentration in the product mixture (or reaction
products) compared to catalytic partial oxidation (reaction 1)
since there is no H.sub.2 associated with the oxidant in partial
oxidation reactions (see lbarreta and Sung (2006). Optimization of
Jet-A fuel reforming for aerospace applications. Int. J. Hydrogen
Energy, Vol. 31, n.degree. 8, p. 1066-1078). In addition, partial
oxidation is an exothermic reaction and hot spots at the catalytic
bed are a usual technical nuisance, which leads to higher catalyst
aging rates (lbarreta and Sung, 2006).
[0006] Transition metals are commonly used as catalysts for
reforming reactions. However, they typically deactivate during
hydrocarbon reforming reactions due to (a) sintering, (b) sulphur
poisoning or (c) coking. Sintering is mainly caused by the surface
mobility of the active metals at high reaction temperatures.
Sulphur poisoning is caused by organic sulphur contained in fossil
fuels which, under the reforming conditions, is converted to
S.sup.-2 thatreacts with the active metals at the catalyst surface.
The so formed sulphides are catalytically inactive, because they
prevent reactants from being adsorbed on the catalytic surface.
Coking is the term used for carbon-rich compounds formation and
deposition. There are two main undesirable reactions that cause
carbon deposition: the Boudouard reaction (CO disproportionation to
C and CO.sub.2) and the hydrocarbons cracking. The deactivation
through coking is different in non-noble and noble metals. Namely,
metallic nickel allows for carbon diffusion and dissolution which
leads to the formation of whisker carbon (Alvarez-Galvan, M. C., R.
M. Navarro, F. Rosa, Y. Briceno, F. Gordillo Alvarez and J. L. G.
Fierro (2008). Performance of La,Ce-modified alumina-supported Pt
and Ni catalysts for the oxidative reforming of diesel
hydrocarbons. Int. J. Hydrogen Energy, Vol. 33, n.degree. 2, p.
652-663). On the opposite, noble metals do not dissolve
significantly carbon; thus leading to less carbon formation and to
different carbon deposition mechanisms (Alvarez-Galvan et al.,
2008).
[0007] In diesel or other hydrocarbons reforming reactions, the
catalyst is usually deactivated within 100 hours of use
(Cheekatamarla, P. K. and A. M. Lane (2005). Catalytic autothermal
reforming of diesel fuel for hydrogen generation in fuel cells: I.
Activity tests and sulfur poisoning. J. Power Sources, Vol. 152,
n.degree. 1-2, p. 256-263; Rosa, F., E. Lopez, Y. Briceno, D.
Sopena, R. M. Navarro, M. C. Alvarez-Galvan, J. L. G. Fierro and C.
Bordons (2006). Design of a diesel reformer coupled to a PEMFC.
Catal. Today, Vol. 116, n.degree. 3, p. 324-333; Strohm, J. J., J.
Zheng and C. Song (2006). Low-temperature steam reforming of jet
fuel in the absence and presence of sulfur over Rh and Rh--Ni
catalysts for fuel cells. J. Catal., Vol. 238, n.degree. 2 p.
309-320). Depending upon the catalyst and reaction severity (mainly
sufficiently low space velocities), concentrations close to the
theoretical thermodynamic equilibrium can be reached. Strohm et al.
(2006) studied the steam reforming of simulated jet fuel without
sulphur and reported constant H.sub.2 concentrations of 60% vol for
80 hours using a Ceria-Alumina-supported Rhodium (Rh) catalyst. The
reactions took place at temperatures below 520.degree. C. and a
steam-to-carbon molar ratio (H.sub.2O/C) of 3, i.e. there is a
steam excess of 300%. When they added 35 ppm of sulphur in the
feed, the catalyst was deactivated within 21 hours.
[0008] With an Al.sub.2O.sub.3-supported bimetallic noble metal
with a metal loading <1.5% catalyst, Ming et al. (Steam
reforming of hydrocarbon fuels. Catal. Today, Vol. 77, n.degree.
1-2, p. 51-64, 2002) reported constant H.sub.2 concentrations of
70% over a 73 hours steady state operation for hexadecane steam
reforming. The H.sub.2O/C molar ratio was 2.7 with an operating
temperature of 800.degree. C. When no-noble metal s are used, there
is deactivation within 8 hours with less H.sub.2 in the products in
most reaction severities (Alvarez-Galvan et al, 2008; Gardner, T.
H., D. Shekhawat, D. A. Berry, M. W. Smith, M. Salazar and E. L.
Kugler (2007). Effect of nickel hexaaluminate mirror cation on
structure-sensitive reactions during n-tetradecane partial
oxidation. Appl. Catal. A, Vol. 323, p. 1-8.; Gould, B. D., A. R.
Tadd and J. W. Schwank (2007). Nickel-catalyzed autothermal
reforming of jet fuel surrogates: n-Dodecane, tetralin, and their
mixture. J. Power Sources, Vol. 164, n.degree. 1, p. 344-350). Kim
et al. (Steam reforming of n-hexadecane over noble metal-modified
Ni-based catalysts, Catal. Today, Vol. 136, p. 228-234, 2008))
obtained H.sub.2 concentrations of 72% to 65% over a 53 hours of
steady state operation with a Magnesia-Alumina-supported Nickel
catalyst (Ni/MgO--Al.sub.2O.sub.3). This was obtained at
temperature of 900.degree. C., GHSV of 10 000 h.sup.-1 and a
H.sub.2O/C molar ratio of 3. They also reported lower deactivation
rates when noble metal (Rh) was added to the catalyst.
[0009] There is thus a need for a reforming process and a catalyst
that lower the catalyst deactivation rate while maintaining high
H.sub.2 concentration in the product mixture and high conversion
rates of the hydrocarbonaceous fuel.
SUMMARY
[0010] It is therefore an aim of the present invention to address
the above mentioned issues.
[0011] According to a general aspect, there is provided a process
for steam reforming of a hydrocarbonaceous fuel, comprising the
steps of: providing a reactant mixture comprising H.sub.2O and the
hydrocarbonaceous fuel; and contacting the reactant mixture with a
Al.sub.2O.sub.3-yttria-stabilized ZrO.sub.2 (YSZ)-supported
NiAl.sub.2O.sub.4 spinel catalyst under conditions wherein the
reactant gas mixture is at least partially steam reformed into a
product gas mixture including H.sub.2 and CO.
[0012] In an embodiment, the reactant mixture is in gaseous state
when contacted with the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst.
[0013] In an embodiment, the hydrocarbonaceous fuel in liquid state
at ambient temperature and atmospheric pressure.
[0014] The hydrocarbonaceous fuel can be selected from the group
comprising: at least one hydrocarbon, at least one biofuel, at
least one fossil fuel, at least one synthetic fuel and a mixture
thereof. The hydrocarbonaceous fuel can be selected from the group
consisting of: gasoline, diesel, biodiesel, commercial
fossil-derived diesel, synthetic diesel, jet fuel, methanol,
ethanol, bioethanol, methane, and mixture thereof.
[0015] In an embodiment, the reactant mixture comprises H.sub.2O in
a liquid state and the hydrocarbonaceous fuel in the liquid state;
providing further comprises heating the reactant mixture to provide
a gaseous reactant mixture; and contacting comprises contacting the
gaseous reactant mixture with the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst.
[0016] In an embodiment, the process further comprises at least one
of atomizing and vaporizing the H.sub.2O and the hydrocarbonaceous
fuel to form a fine droplet emulsion before contacting the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst.
The process can further comprise adding a surfactant to the
H.sub.2O and the hydrocarbonaceous fuel before atomizing or
vaporizing the H.sub.2O and the hydrocarbonaceous fuel to form the
emulsion.
[0017] In an embodiment, the contacting is carried out at a
temperature between 500.degree. C. and 900.degree. C.
[0018] In an embodiment, the hydrocarbonaceous fuel comprises
carbon and the reactant mixture has a H.sub.2O:carbon ratio between
2.3 and 3.
[0019] In an embodiment, the contacting is carried out with a gas
hourly space velocity ranging between 300 cm.sup.3g.sup.-1h.sup.-1
and 200 000 cm.sup.3g.sup.-1h.sup.-1.
[0020] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst is substantially free of metallic
nickel and nickel oxide.
[0021] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst has a ratio Al.sub.2O.sub.3/YSZ
ranging between 1/5 and 5/1.
[0022] In an embodiment, the Al.sub.2O.sub.3--YSZ support consists
essentially of Al.sub.2O.sub.3 and YSZ and comprises between 1 w/w
% to 2 w/w % of yttria. In an embodiment, the catalyst comprises an
active phase consisting essentially of the NiAl.sub.2O.sub.4
spinal.
[0023] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst has a molar ratio of
Ni/Al.sub.2O.sub.3 smaller or equal to 1.
[0024] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst comprises between 1 and 10 w/w %
of nickel.
[0025] In an embodiment, the Al.sub.2O.sub.3-YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst is dispersed in quartz wool.
[0026] According to a general aspect, there is provided a synthesis
gas for fuel cells obtained by the process described above.
[0027] According to another general aspect, there is provided a
process for the production of H.sub.2 comprising the steps of:
submitting a reactant mixture including a hydrocarbonaceous fuel
and H.sub.2O under steam reforming conditions; and contacting the
reactant mixture under steam reforming conditions with a
Al.sub.2O.sub.3--YSZ-supported Ni--Al.sub.2O.sub.4 spinel
catalyst.
[0028] In an embodiment, the reactant mixture is in gaseous state
when contacted with the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst and the hydrocarbonaceous fuel in
liquid state at ambient temperature and atmospheric pressure.
[0029] The hydrocarbonaceous fuel can be selected from the group
comprising: at least one hydrocarbon, at least one biofuel, at
least one fossil fuel, at least one synthetic fuel and a mixture
thereof.
[0030] In an embodiment, the reactant mixture comprises H.sub.2O in
a liquid state and the hydrocarbonaceous fuel in the liquid state;
the process further comprises heating the reactant mixture to
provide a gaseous reactant mixture; and contacting comprises
contacting the gaseous reactant mixture with the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel
catalyst.
[0031] In an embodiment, the submitting comprises at least one of
atomizing and vaporizing the H.sub.2O and the hydrocarbonaceous
fuel to form an emulsion before contacting the
Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4 spinel
catalyst.
[0032] In an embodiment, the process can further comprise adding a
surfactant to the H.sub.2O and the hydrocarbonaceous fuel before
atomizing or vaporizing the H.sub.2O and the hydrocarbonaceous fuel
to form the emulsion.
[0033] In an embodiment, the contacting is carried out at a
temperature between 500.degree. C. and 900.degree. C., with a
H.sub.2O:carbon ratio between 2.3 and 3, and a gas hourly space
velocity ranging between 300 cm.sup.3g.sup.-1h.sup.-1 and 200 000
cm.sup.3g.sup.-1h.sup.-1.
[0034] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst is substantially free of metallic
nickel and nickel oxide, comprises between 1 w/w % to 2 w/w % of
yttria, and has a ratio Al.sub.2O.sub.3/YSZ ranging between 1/5 and
5/1.
[0035] In an embodiment, the Al.sub.2O.sub.3--YSZ support consists
essentially of Al.sub.2O.sub.3 and YSZ, the catalyst comprises an
active phase consisting essentially of the NiAl.sub.2O.sub.4
spinel, and the molar ratio of Ni/Al.sub.2O.sub.3 in the entire
(total) catalyst is smaller than 1.
[0036] According to a further general aspect, there is provided a
catalyst for steam reforming of a hydrocarbonaceous fuel, the
catalyst comprising: a NiAl.sub.2O.sub.4 spinel-based catalytically
active material; and a support material comprising: Al.sub.2O.sub.3
and ZrO.sub.2.
[0037] In an embodiment, the ZrO.sub.2 of the support material
comprises yttria-stabilized zirconia (YSZ) and the catalyst
comprises a Al.sub.2O.sub.3-YSZ-supported NiAl.sub.2O.sub.4.
[0038] In an embodiment, Y.sub.2O.sub.3 is present in YSZ at about
1 w/w % to 2 w/w %.
[0039] In an embodiment, the catalyst is substantially free of
metallic nickel and nickel oxide.
[0040] In an embodiment, the catalyst has a ratio
Al.sub.2O.sub.3/YSZ ranging between 1/5 and 5/1.
[0041] In an embodiment, the support material consists essentially
of Al.sub.2O.sub.3 and YSZ and the catalytically active material
consists essentially of the NiAl.sub.2O.sub.4 spinel.
[0042] In an embodiment, the molar ratio of Ni I Al.sub.2O.sub.3 is
smaller or equal to 1.
[0043] In an embodiment, the catalyst comprises between 1 and 10
wlw % of nickel.
[0044] The Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4
catalyst described above can be used in steam reforming of a liquid
hydrocarbonaceous fuel.
[0045] According to a general aspect, there is provided a method
for the preparation of a Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst, comprising the steps of:
mechanical mixing Al.sub.2O.sub.3 and yttria-stabilized zirconia
(YSZ) powders to form a mixed powder; wet impregnation of the mixed
powder with an acquous nitrate solution to form an impregnated
powder; and submitting the impregnated powder under conditions to
allow decomposition of nitrate and formation of
NiAl.sub.2O.sub.4.
[0046] In an embodiment, the Al.sub.2O.sub.3 and YSZ powders are
mixed in a ratio of 1/1.
[0047] In an embodiment, the acquous nitrate solution comprises
Ni(NO.sub.3).sub.2.6H.sub.2O.
[0048] In an embodiment, the Al.sub.2O.sub.3 and YSZ powders
comprise particulate materials smaller than about 40 .mu.m.
[0049] In an embodiment, submitting is carried out at a temperature
ranging between 850.degree. C. and 1200.degree. C. for 1 to 8
hours. In an embodiment , the submitting is carried under
conditions to obtain the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst substantially free of metallic
nickel and nickel oxide.
[0050] In an embodiment, Y.sub.2O.sub.3 is present in YSZ at about
1 w/w % to 2 w/w %.
[0051] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst has a ratio Al.sub.2O.sub.3/YSZ
ranging between 1/5 and 5/1.
[0052] In an embodiment, the molar ratio of Ni/Al.sub.2O.sub.3 is
smaller or equal to 1.
[0053] In an embodiment, the Al.sub.2O.sub.3--YSZ-supported
NiAl.sub.2O.sub.4 spinel catalyst comprises between 1 and 10 w/w %
of nickel.
[0054] In this specification, the term "hydrocarbonaceous fuel" is
intended to mean compounds comprising carbon and hydrogen including
hydrocarbons (e.g. methane, propane, hexane, benzene, hexadecane,
tetralin, etc.), oxygen-containing fuels (i.e. alcohols such as
methanol, ethanol, propanol, butanol, etc.) and fuels (e.g. fossil
fuels, biofuels, diesel, biodiesel, etc.). The hydrocarbonaceous
fuel can either be solid, liquid or gaseous at room temperature and
atmospheric pressure.
[0055] In this specification, the term "hydrocarbon" is intended to
mean organic compounds, such as methane, propane, hexane, benzene,
hexadecane, tetralin, that contain only carbon and hydrogen.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] Further features and advantages of the present invention
will become apparent from the following detailed description, taken
in combination with the appended drawings, in which:
[0057] FIG. 1 is scanning electron microscopic (SEM) pictures of
the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ catalyst before steam
reforming;
[0058] FIGS. 2A and 2B are SEM-EDXS (scanning electron
microscopy-energy-dispersive X-ray spectroscopy) graphs and
pictures of the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ catalyst for
an alumina particle (FIG. 2A) and zirconia particle (FIG. 2B),
before steam reforming;
[0059] FIG. 3 is an XRD analysis of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ catalyst before reforming,
showing an XRD pattern that is dominated by YSZ. The other features
of the XRD pattern are constituted by weak and broad peaks which
are likely assigned to the mixture of low crystallinity
.gamma.-Al.sub.2O.sub.3.
[0060] FIG. 4 is a schematic view of a reactor for steam reforming
of hydrocarbonaceous gases;
[0061] FIG. 5 is a graph showing the gaseous concentrations of the
product mixture over time for propane steam reforming using a
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst;
[0062] FIG. 6 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst before propane
steam reforming;
[0063] FIG. 7 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst after 12 hours of
propane steam reforming;
[0064] FIG. 8 is a graph showing the gaseous concentrations of the
product mixture over time for hexadecane steam reforming without
catalyst;
[0065] FIG. 9 is a graph showing the gaseous concentrations of the
product mixture over time for hexadecane steam reforming with the
NiAl.sub.2O.sub.41Al.sub.2O.sub.3--YSZ-1 catalyst at different
temperatures and GHSV and a H.sub.2O/C molar ratio of 2.5;
[0066] FIG. 10 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst after 22 hours of
hexadecane steam reforming;
[0067] FIG. 11 is a graph showing the yield of the product mixture
components over time for hexadecane steam reforming with a
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst at a reaction
temperature of 710.degree. C., GHSV of 5 000
cm.sup.3g.sup.-1h.sup.-1, and a H2O/C molar ratio of 2.5
(experiment A);
[0068] FIG. 12 is a graph showing the yield of the product mixture
components over time for hexadecane steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst at a reaction
temperature of 670 .degree. C., GHSV of 4 800
cm.sup.3g.sup.-1h.sup.-1, and a H2O/C molar ratio of 2.5
(experiment B);
[0069] FIG. 13 is a graph showing the yield of the product mixture
components over time for hexadecane steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst at a reaction
temperature of 670.degree. C., GHSV of 12 800
cm.sup.3g.sup.-1h.sup.-1, and a H2O/C molar ratio of 2.5
(experiment C);
[0070] FIG. 14 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst after hexadecane
steam reforming for experiment A;
[0071] FIG. 15 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst after hexadecane
steam reforming for experiment C;
[0072] FIGS. 16A and 16B are SEM-EDXS graphs and pictures of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst for an alumina
particle (FIG. 16A) and zirconia particle (FIG. 16B) after
hexadecane steam reforming for experiment A;
[0073] FIGS. 17A and 17B are SEM-EDXS graphs and pictures of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst for an alumina
particle (FIG. 17A) and zirconia particle (FIG. 17B) after
hexadecane steam reforming for experiment B;
[0074] FIGS. 18A and 18B are SEM-EDXS graphs and pictures of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst for an alumina
particle (FIG. 18A) and zirconia particle (FIG. 18B) after
hexadecane steam reforming for experiment C;
[0075] FIG. 19 is SEM-EDXS graphs and pictures of a
Ni/Al.sub.2O.sub.3--YSZ-2 catalyst after hexadecane steam
reforming;
[0076] FIG. 20 is a graph showing the yield of the product mixture
components over time for tetralin steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst at a reaction
temperature of 705.degree. C., GHSV of 4 800
cm.sup.3g.sup.-1h.sup.-1, and a H2O/C molar ratio of 2.3;
[0077] FIGS. 21A and 21B are SEM-EDXS graphs and pictures of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst for an alumina
particle (FIG. 21A) and zirconia particle (FIG. 21B) after tetralin
steam reforming;
[0078] FIG. 22 is a graph showing the equilibrium concentrations of
the gaseous product mixture as a function of the reaction
temperature for hexadecane steam reforming with a H.sub.2O/C molar
ratio of 2.5;
[0079] FIG. 23 is a graph showing the comparison of equilibrium and
experimental concentrations for hexadecane steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst;
[0080] FIG. 24 is a graph showing the comparison of equilibrium and
experimental concentrations for tetralin steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst;
[0081] FIGS. 25A and 25B are graphs showing the experimental versus
theoretical concentrations in biodiesel reforming product mixtures;
and
[0082] FIG. 26 is a SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ catalyst after run B for
biodiesel reforming.
[0083] It will be noted that throughout the appended drawings, like
features are identified by like reference numerals.
DETAILED DESCRIPTION
[0084] Catalysts have been developed for steam reforming of
hydrocarbonaceous fuels. The catalysts are nickel-based and
alumina/yttria (Y.sub.2O.sub.3)-stabilized zirconia (ZrO.sub.2)
(YSZ) supported and, more particularly, they are Ni-alumina spinel
catalysts and Al.sub.2O.sub.3/YSZ supported (or
Al.sub.2O.sub.3/YSZ--supported NiAl.sub.2O.sub.4 spinel catalysts).
Reforming converts a reactant mixture including hydrocarbonaceous
fuels, such as propane, hexadecane, diesel, and biodiesel,
oxygen-containing fuels, into a product mixture, mainly composed of
H.sub.2 and CO, i.e. synthesis gas. The reactant mixture in gaseous
state contacts the catalyst under conditions for steam reforming of
the hydrocarbonaceous fuel for generating a gaseous product mixture
including CO and H.sub.2.
[0085] The Ni-alumina spinel catalyst is substantially free of
metallic Ni and nickel oxide to reduce its tendency for carbon
formation and deposition during the steam reforming process. In an
embodiment, the nickel spinel is substantially pure and supported
on the Al.sub.2O.sub.3--YSZ substrate. As it will be shown below,
it has been found that Ni-spinels are stable and have a high
resistance to coke formation.
[0086] The ceramic support Al.sub.2O.sub.3--YSZ includes a mixture
of Al.sub.2O.sub.3 and zirconia (ZrO.sub.2). In an embodiment, the
zirconia is stabilized by yttria. For instance, the zirconia can be
stabilized by the addition of 1 w/w % to 2 w/w % of yttria. The
ratio Al.sub.2O.sub.3/YSZ can range between 1/5 and 5/1. In an
embodiment, the ratio Al.sub.2O.sub.3/YSZ ranges between 1/2 and
2/1 and, in a particular embodiment, the ratio Al.sub.2O.sub.3/YSZ
is about 1/1.
[0087] The ceramic support Al2O3-YSZ can be obtained by
mechanically mixing together Al2O3 and YSZ powders, as it will be
described below in more details. The particle size can range
between 50 nm and 40 .mu.m, preferentially between 1 and 40
.mu.m.
[0088] The ceramic support Al.sub.2O.sub.3--YSZ can include other
elements such as and without being limitative MgO,
MgAl.sub.2O.sub.4, Cr.sub.2O.sub.3, La.sub.2O.sub.3, SiO.sub.2,
CaO, K.sub.2O, and TiO.sub.2. For instance and without being
limitative, the ceramic support could be Al.sub.2O.sub.3--YSZ doped
with MgO.
[0089] The catalytically active phase includes a nickel spinel.
Spinets are any of a class of minerals of general formulation
A.sup.2+B.sub.2.sup.3+O.sub.4.sup.2-. The catalyst spinel is of the
form NiAl.sub.2O.sub.4.
[0090] In an embodiment, the nickel represents about between 1 and
10 w/w % of the final catalyst formulation (including the ceramic
support). In a particular embodiment, the nickel represents about 5
w/w % of the final, dry catalyst formulation. The ratio
Ni/Al.sub.2O.sub.3 of the entire (total catalyst) should be equal
or inferior to 1 to avoid metallic Ni and nickel oxide in the
catalyst, as it will be described in more details below. The ratio
Ni/Al.sub.2O.sub.3 of the spinel should be equal or inferior to 1
and, in a particular embodiment, the molar ratio is
Ni/Al.sub.2O.sub.3 (spinel) is about 1/4. In the catalyst, the
spinel is distributed as nanometric grains in the ceramic support
and the major part of the spinel is physically associated with the
Al.sub.2O.sub.3 particles rather than YSZ particles.
[0091] The catalytically active phase NiAl.sub.2O.sub.4 can contain
other elements such as and without being limitative CuO, MoO.sub.3,
and WO.sub.3. In an embodiment, the catalytically active phase
NiAl.sub.2O.sub.4 is substantially free of other elements, i.e. it
contains no other elements except inevitable impurities.
[0092] The main products of hydrocarbonaceous fuel reforming, such
as propane, hexadecane, diesel, and biodiesel reforming, are
H.sub.2, carbon monoxide (CO), and carbon dioxide (CO.sub.2).
Equation (3) is the core reaction of steam reforming and equation
(4) is the water gas shift (WGS), a secondary reaction.
C.sub.nH.sub.m+nH.sub.2O.fwdarw.nCO+(n+m/2)H.sub.2(.DELTA.H>0)
(3)
CO+H.sub.2O.fwdarw.CO.sub.2+H.sub.2(.DELTA.H>0) (4)
[0093] Catalyst Preparation
[0094] The Al2O3-YSZ-supported NiAl2O4 catalyst tested was prepared
by a wet impregnation method. An Al2O3 (mixture of amorphous and
.gamma.-Al2O3) and YSZ (Y2O3-ZrO2--about between 1 w/w % and 2 w/w
% of yttria) support was prepared by mechanically mixing equal
quantities of the two powders together. Two Al2O3 powder sizes were
studied: NiAl2O4/Al2O3-YSZ-1 at 20 nm to 40 nm and
NiAl2O4/Al2O3-YSZ-2 at 40 .mu.m. YSZ powder size distribution had
an upper limit at 20.mu.m. The Al2O3 and YSZ powder mixture was
impregnated with a Ni(NO3)2.6H2O aqueous solution, targeting a 5
w/w % nickel (Ni) load in the final formulation. Water was
evaporated, and the resulting impregnated powder was dried
overnight at 105-110.degree. C. The resulting powder was
crushed-comminuted and calcined at 900.degree. C. for 6 hours to
form the NiAl2O4 spinel. This procedure leads to nitrates
decomposition and formation of the spinel phase. All nickel should
be converted to its spinel form; there must remain substantially no
residual metallic nickel or free Ni oxides.
[0095] One skilled in the art will appreciate that the process for
preparing the Al.sub.2O.sub.3--YSZ-supported NiAl.sub.2O.sub.4
catalyst can vary. Moreover, the above-described embodiment for
preparing the catalyst can also vary. For instance and without
being limitative, the sintering temperature and time can change.
For instance, the sintering temperature can be carried out between
900.degree. C. to 1 200.degree. C. during few minutes to several
hours. The sintering process can also be carried out by plasma or
by any other appropriate technique.
[0096] The catalysts were analyzed by scanning electron microscopy
(SEM) Hitachi S-4700 field emission gun and energy-dispersive X-ray
spectroscopy (EDXS) Oxford EDXS detector with an ultra-thin ATW2
window. Both fresh and used catalysts were subjected to Philips
X'Pert Pro X-ray diffractometry (XRD), employing a monochromator
with radiation Cu K.alpha.1, 40 mA current and voltage of 45 kVs.
Chemical surface analysis was completed by X-ray photoelectron
spectroscopy (XPS) in an Axis Ultra DLD of Kratos Analytical
Equipement with Al Ka monochromatic X-ray source. Calibration of
the curve was based on the contaminant carbon.
[0097] The catalyst formulation was analyzed using XPS surface
analysis, XRD analysis, and SEM analysis. The targeted catalyst
form is a NiAl.sub.2O.sub.4 spinel on the surface of an alumina
support without any metallic nickel or nickel oxide, i.e. the
catalyst is substantially free of metallic nickel and nickel oxide,
i.e. it contains no metallic nickel and nickel oxide except
inevitable impurities.
[0098] Surface SEM and SEM-EDXS analyses of the fresh catalyst are
shown in FIGS. 1 and 2. FIG. 1 shows that a spinel catalyst support
is composed of two types of distinct particles (grains) with
distinct size distribution, those rich in alumina and those rich in
YSZ. The smaller particles typically smaller than 20 .mu.m are
identified as the YSZ component, as confirmed by the EDX spectra
(FIG. 2b). The larger particles are assigned to the alumina-bearing
phase (typically 40-50 .mu.m). SEM-EDXS analysis of these two types
of grains presented in FIG. 2 with the corresponding SEM
micrographs revealed that Ni was confined exclusively to alumina
grains.
[0099] The route to build NiAl.sub.2O.sub.4 in the catalyst
includes a NiO formation step, as shown in equations (5) and
(6).
xNi(NiO.sub.3).sub.2.6H.sub.2O+yAl.sub.2O.sub.3.fwdarw.xNiO+yAl.sub.2O.s-
ub.3+Gas (5)
xNiO+yAl .sub.2O.fwdarw.xNiAl.sub.2O+yAl.sub.2O.sub.3 (6)
[0100] It was important to ensure that reaction 6 was completed and
the resulting catalyst is substantially free of NiO. Two simple
tests were used to rule out the existence of NiO. First, NiO is
green, while the catalyst gives a blue tint to the white
Al.sub.2O.sub.3/YSZ mixture; this is typical to NiAl.sub.2O.sub.4.
Second, the catalyst is resistant to chlorhydric (HCL) and nitric
(HNO.sub.3) acid solutions while NiO is completely digested
(dissolved) by these strong acids.
[0101] The XRD pattern shown in FIG. 3 is dominated by the YSZ. The
absence of NiO peaks is another indication that NiO is not formed.
The other features of the XRD pattern are constituted by weak and
broad peaks which are likely assigned to the mixture of low
crystallinity .gamma.-Al.sub.2O.sub.3 (FIG. 3).
.gamma.-Al.sub.2O.sub.3 and NiAl.sub.2O.sub.4 both share the same
Bravais lattice with similar lattice parameters making them
difficult to differentiate; especially when the diffraction lines
are broadened.
[0102] The formation of the NiAl.sub.2O.sub.4 is confirmed from the
analysis of the Ni L.sub.23 edge obtained from the XPS of the
catalyst formulation. The main features (L.sub.3 peak position,
L.sub.2-L.sub.3 energy separation, position of satellite peaks) are
consistent with typical Ni L.sub.23 edges associated to
NiAl.sub.2O.sub.4 (Rivas, M. E., Fierro, J. L. G., Guil-Lopez, R.,
Pena, M. A., La Parole, V, and Goldwsser, M. R. (2008). Preparation
and characterization of nickel-based mixed-oxides and their
performance for catalytic methane decomposition. Catalysis Today
133-135: 367-373; Osaki, T. and Mori T. (2009). Characterization of
nickel-alumina aerogels with high thermal stability. Journal of
Non-Crystalline Solids: 1590: 1596.). Furthermore, the position of
the Ni 2p3/2 peak for NiO is found at a typically lower binding
energy (around 855 eV). This confirms the absence of formation of
NiO from the spinel catalyst.
[0103] Reactor Design
[0104] A schematic representation of the reactor 20 is presented at
FIG. 4. The reactor 20 is a lab-scale isothermal differential
packed & fixed bed reactor. The reactant mixture 22 and an
inert gas 24 enter the reactor 20 into a pre-heating zone 26
located in the upper section of the housing. During steam
reforming, the pre-heating zone 26 is characterized by a
pre-heating temperature (T.sub.P-H). The pre-heating zone 26
ensures mixing of the reactant mixture prior to its entrance in the
lower section of the reaction zone 28. The catalyst is disposed in
the catalytic zone 30 which is located in the reaction zone 28. The
reaction zone 28, including the catalytic zone 30, is characterized
by a reaction temperature (T.sub.R). The product mixture 31 exits
the reactor 20 and is directed to and analyzed with a Varian
CP-3800 gas chromatograph 32. The exit gaseous flow rate was
measured using a mass flow rate mass meter (Omega FMA-700A). In the
embodiment used, the reactor diameter was 46 mm and the catalytic
bed was 60 mm.
[0105] The catalyst in powder from was dispersed in quartz wool.
The quartz wool was then compacted in the reactor 20 to form a
catalytic bed of quartz fibre containing catalyst particulates.
Since the reactant mixture gas flow entering the bed comes from an
injecting device, it is highly turbulent and does not have enough
time to become fully developed. This configuration prevents
channelling issues and helps obtaining a uniform catalytic bed with
the small amount of catalyst used.
[0106] The reactor design should allow an as complete as possible
mixing of the reactant mixture, i.e. hydrocarbonaceous fuels and
water, prior to the entrance in the reaction zone 28. It should
also allow liquid preheating/vaporization/gas preheating of the
reactant mixture 22 in conditions to minimize undesirable carbon
forming cracking reactions.
[0107] Since hydrocarbons are not miscible with water and if the
above mentioned constraints are not respected, hydrocarbons
pyrolysis takes place prior to the reaction in the preheating
section (Liu, D., M. Krumpelt, H. Chien and S. Sheen (2006).
Critical issues in catalytic diesel reforming for solid oxide fuel
cells. J. Mater. Eng. Perform., Vol. 15, n.degree. 4, p.
442-444.).
[0108] The reactor can be fed by vaporization or atomization.
Atomization typically limits thermal cracking. Furthermore, by
decreasing the size, and therefore increasing the surface of each
droplet, a better water/hydrocarbons mixing is obtained prior to
heating and a better pre-mixing of the reactant mixture lowers the
thermal cracking reactions occurrence (Liu et at., 2006). This can
be carried out, for instance and without being limitative, with
ultrasons-enhanced or other commercial diesel engines injectors
(Kang, I., J. Bae, S. Yoon and Y. Yoo (2007). Performance
improvement of diesel autothermal reformer by applying ultrasonic
injector for effective fuel delivery. J. Power Sources, Vol. 172,
n.degree. 2, p. 845-852; Liu et at., 2006).
[0109] In the below described examples, the reactions are carried
out at atmospheric pressure.
[0110] Conversion Calculations
[0111] Overall conversion was calculated for hydrocarbonaceous fuel
reforming based on the total amount of carbon fed in the reactor.
Hydrocarbonaceous fuels were considered to be converted when they
were transformed into gaseous product mixture (CO, CO.sub.2 or
CH.sub.4). Carbon found in the reactor after the experiment was
therefore not considered as converted hydrocarbon (or
hydrocarbonaceous fuel).
[0112] The experimental conversion (X) was calculated (7):
X = N CO out + N CO 2 out + N CH 4 out N C m H n in xm + N
surfactan t in xY ( 7 ) ##EQU00001##
[0113] With N.sub.i being the total number of moles of component i
at the reactor exit or inlet, Y being the number of carbon atoms in
the surfactant.
[0114] For the different reforming reactions, the reactor exit
concentrations of H.sub.2, CO, CO.sub.2, CH.sub.4 were compared to
the theoretical thermodynamic equilibrium concentrations, in order
to determine if the equilibrium was reached. Thermodynamic
equilibrium concentrations calculations were calculated with
FactSage software on the basis of Gibbs energy minimization.
[0115] Measurement Errors
[0116] Errors associated with concentration data obtained by gas
chromatography are presented in Table 1. They were calculated by
using an external standard.
[0117] In addition to the GC concentrations measurements errors,
the mass flow meter used to measure the exit gas flow introduces a
second error in the conversion calculations. The accuracy of the
mass flow meter is 1 mol %.
[0118] Maximum and minimum values were therefore calculated for
each conversion, using the extreme values for concentrations and
flow rate based on the known error and accuracy.
TABLE-US-00001 TABLE 1 Gaseous concentrations measurement errors.
Absolute error (on % Standard gaseous concentration of the Gas
concentration (mol %) standard) Relative error (%) H.sub.2 55.16
0.46 0.83 CO 19.70 0.21 1.05 CO.sub.2 6.96 0.38 5.45 CH.sub.4 2.08
0.04 1.87 Ar 16.10 0.22 1.37
[0119] Propane Reforming
[0120] Using the above described reactor and Ni--Al.sub.2O.sub.4
spinel catalyst, propane (C.sub.3H.sub.8) reforming was first
performed. Propane was chosen because it is the simpler saturated
hydrocarbon containing carbon linked chemically with two other
carbon atoms.
[0121] Gaseous propane was mixed with 110.degree. C. steam before
entering the pre-heating zone, which was maintained at 750.degree.
C. The te mperature just before the catalyst bed was between
30.degree. C. and 45.degree. C. below the reaction te mperature,
depending on the operating parameters. Argon served as inert
diluent and internal standard for liquid hydrocarbonaceous fuel
steam reforming. It is appreciated that other inert gases can be
used.
[0122] Propane was reformed in the packed-bed reactor (PBR) 20. The
reactor was heated to the desired temperature under an argon (Ar)
blanket. The argon flow was switched off prior to feeding the
reactant mixture. The reaction temperatures tested were 750.degree.
C. and 700.degree. C., pressure was atmospheric or s lightly higher
due to the pressure loss along the PBR set-up, and the
steam-to-carbon (H.sub.2O/C) molar ratio was 3, i.e. there was a
steam excess of 300 mol %. The gas hourly space velocity (GHSV) was
between 2 900 and 5 950 cm.sup.3.sub.reacg.sup.-12cath.sup.-1 under
reaction conditions.
[0123] Hexadecane and Tetralin Reforming
[0124] Hexadecane reforming and tetralin reforming were performed
to test the Ni-alumina spinel catalyst with paraffin and aromatic
compounds. Hexadecane was chosen as a surrogate of diesel's
paraffinic compounds and because it represents the average fossil
diesel composition. Tetralin was selected as a representative of
diesel's naphthenic and aromatic part.
[0125] For hexadecane and tetralin reforming, an emulsion, as
explained below, entered at room temperature and was rapidly heated
in the pre-heating zone maintained at a temperature between
400.degree. C. and 500.degree. C.
[0126] The method chosen to enhance the hydrocarbonaceous
fuel/water mixing for hexadecane and tetralin reforming was the
formation of an emulsion of two immiscible reactants in a
surfactant-aided protocol.
[0127] In an embodiment, the emulsion was obtained by (1)
magnetically stirring together oleic acid (90%, Alfa Aesar.RTM.),
pentanol (99%, Fisher Scientific.TM.), and the hydrocabonaceous
fuel. (2) A solution of ammonium hydroxide (30%) was mixed with
water. This solution (1) was added drop by drop to the mixture (2)
whilst continuing magnetic stirring. When the entire water and
ammonium hydroxide solution was integrated in the hydrocabonaceous
fuel, stirring was maintained for few minutes.
[0128] Table 2, below, shows the percentage of the components used
to prepare the emulsion. Depending on the hydrocarbonaceous fuel
used, emulsions with H2O/C ratio ranging between 2 and 2.5 can be
obtained.
TABLE-US-00002 TABLE 2 Emulsion components. Component Concentration
(w/w %) Oleic acid (90%) 5.2 Pentanol (99%) 2.6 Ammonium hydroxide
solution (30%) 0.7 Water 21.9 Hydrocarbonaceous fuel 69.6
[0129] This emulsion was heated and vaporized in the preheating
zone before reaching the catalyst. The surfactant-stabilized
emultion of hydrocarbonaceous fuel and steam was employed to
maximize reactant mixing and prevent cracking reactions that lower
reforming efficiency.
[0130] The PBR described above in reference to FIG. 4 with the
catalyst dispersed in quartz wool was used for hexadecane and
tetralin reforming. The H.sub.2O/C ratio was 2.5 for hexadecane
reforming and 2.3 for tetralin reforming. The reaction temperatures
were between 630.degree. C. and 720.degree. C. with GHSV ranging
from 1 900 to 12 000 cm.sup.3g.sub.reacg.sup.-1.sub.cath.sup.-1 at
atmospheric pressure.
[0131] Results
[0132] Propane Catalytic Steam Reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst
[0133] The results of propane steam reforming using
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst are shown in FIG.
5. During the first 10 hours of reaction, the reaction temperature
was kept constant at 750.degree. C. For the last two hours, the
reaction temperature was decreased to 700.degree. C. The observed H
.sub.2 concentration was constant at 70 vol % for the 12 hours of
operation, and methane concentration was below 1 vol % for the
entire reaction time. There was no deactivation of the catalyst.
The shift in the carbon monoxide (CO) and carbon dioxide (CO.sub.2)
concentrations with the decrease in temperature follows the
predictions of the theoretical thermodynamic equilibrium
calculations.
[0134] SEM pictures of the catalyst before and after the 12 hours
of reaction are shown respectively in FIGS. 6 and 7. No carbon
deposition on the catalyst was evident. The somewhat larger
catalyst grains observed in FIG. 7 were explained by some sintering
activity which was not, nevertheless, sufficient to lower the
activity under reaction conditions. These results being positive,
the catalyst was then tested on hexadecane steam reforming.
[0135] Hexadecane Catalytic Steam Reforming without a catalyst
[0136] The results of a blank experiment are illustrated in FIG. 8.
This blank experiment was performed without catalyst but with
quartz wool as inert bed in the PBR, at a temperature of
710.degree. C., a flow rate of 22 700 cm.sup.3 h.sup.-1, and a
H.sub.2O/C molar ratio of 2.5. The concentrations corresponded to
cracking, and no reforming reaction took place in the reactor
without the catalyst. A major part of hexadecane was transformed
into coke in the reactor, and conversion, as defined in Eq. 7, was
only 25 w/w %.
[0137] In addition to this blank experiment, an experiment at
650.degree. C. has been done aimed at measuring the concentration
of the gas just before entering the catalytic zone. The
concentrations of the gaseous product mixture (at 25.degree. C.)
are presented in Table 3. The conversion as defined by Eq. 7 was
only of 6 w/w %. The hexadecane conversion including the ethane,
ethylene, propane and butane in the calculation was 42 w/w %. The
rest of the reactant mixture was collected as condensed liquid
phase at the exit of the reactor.
TABLE-US-00003 TABLE 3 Thermal cracking of hexadecane with a
H.sub.2O/C molar ratio = 2.5:Gasproduct mixture composition at
25.degree. C. Product mixture Gaseous concentration (% mole)
CO.sub.2 1.4 CO 3.2 H.sub.2 8.1 CH.sub.4 19.7 C.sub.2H.sub.4 46.2
C.sub.2H.sub.6 4.5 C.sub.3H.sub.8 15.4 C.sub.4H.sub.10 1.5
[0138] Hexadecane Catalytic Steam Reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst
[0139] The results of hexadecane steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst are shown in FIG.
9. The catalyst was used for 22 hours under different GHSV and
three different temperatures. 720.degree. C., 675.degree. C., a nd
630.degree. C., with a H.sub.2O/C molar ratio of 2.5.
[0140] Surface SEM analysis of the catalyst is shown in FIG. 10. As
in the propane reforming test, there was no carbon deposition. The
extent of the sintering seemed higher. This could be linked to
longer test durations (22 hours instead of 12 hours for propane),
but since the temperature was lower, it is rather difficult to draw
safe conclusions based only on these preliminary qualitative
findings. However, no deactivation of the catalyst was due to this
small extent of sintering.
[0141] Hexadecane Catalytic Steam Reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 Catalyst
[0142] The results of three experiments on hexadecane steam
reforming with the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2
catalyst are shown in FIGS. 11 to 13. The catalyst was tested under
three different sets of operating conditions reported in Table
4.
TABLE-US-00004 TABLE 4 Operating conditions for hexadecane steam
reforming with the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3-YSZ-2
catalyst. Run A B C GHSV (cm.sup.3g.sup.-1h.sup.-1) 5 000 4 800 12
000 Entrance temperature (.degree. C.) 655 648 645 Reaction
temperature (.degree. C.) 710 670 670 H.sub.2O/C ratio (mol/mol)
2.5 2.5 2.5
[0143] It can be observed from experiments A-C that the
concentrations of the product gas mixture were stable and
consequently there was no catalyst deactivation observed. However,
there was a slight difference in the concentrations of experiments
B and C, even if they were performed at the same temperature. This
indicates that an increase of the GHSV from 5 000
cm.sup.3.sub.reactg.sub.cat.sup.-1h.sup.-1 to 12 000
cm.sup.3.sub.reactg.sub.cat.sup.-1h.sup.-1 at a temperature of
670.degree. C. had an effect on the reaction. In addition,
conversion decreased at the higher GHSV. The calculated conversions
are presented in Table 5. The difference in calculated conversions
between experiments A and B is of the order of magnitude of the
systematic error associated with the measurements precision. The
confidence intervals show that the conversion is statistically the
same for both experiments. Moreover, as explained in more details
below, concentrations are at equilibrium. Finally, the decrease of
temperature by 40.degree. C. does not have a significant impact on
conversion (comparison of experiments A and B).
TABLE-US-00005 TABLE 5 Calculated conversions for hexadecane steam
reforming with the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3-YSZ-2
catalyst. Run A B C Conversion 0.94 (0.908-0.970) 0.97
(0.938-0.996) 0.86 (0.839-0.889)
[0144] SEM pictures of the catalyst after its use in experiments A
and C are shown in FIGS. 14 and 15, respectively. There is no
apparent change in the morphology of the support and no sintering
was observed. SEM-EDXS analyses with the associated SEM picture of
the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst after its use
in the three hexadecane experiments are shown in FIGS. 16 to 18.
Small quantities of graphitic carbon appear to be deposited only on
the catalyst used in experiment C; no carbon nanofibers were
observed.
[0145] FIG. 19 presents the SEM-EDXS analysis of a catalyst made of
metallic nickel deposited on the same substrate instead of the
spinal. The mass compositions of the two catalysts were the same
and the experiment took place at lower GHSV but all other operation
conditions of experiment C were kept identical. The conversion was
lower (0.76) and FIG. 19 shows that there is a significant amount
of carbon deposit on the catalyst including carbon nanofibers. This
is a significant proof of the spinel improved capacity to steam
reform without favoring carbon formation and deposition.
[0146] Table 6 presents the BET analysis of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst before and after
experiment C. After the experiment, the catalyst was mechanically
sorted out of its quartz wool matrix; however, some quartz wool
remained with the catalyst. The quartz wool contribution in the BET
analysis is insignificant (BET analysis of the quartz wool sample
shows no measurable specific surface), but it is part of the mass
of the sample. The results show that there is a relatively
significant increase of the BET surface in the used catalyst. This
leads to the conclusion that there is no measurable sintering; this
fact is supported by the SEM analysis. At least a part of the BET
specific surface increase can be attributed to catalyst grains
breakage, also observed by SEM. Another part could be associated
with the experimental error due to the possibility of having
different quartz wool mass percentages in the measured samples.
TABLE-US-00006 TABLE 6 BET surface area analysis of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3-YSZ-2 catalyst. Catalyst BET
(m.sup.2 g.sup.-1) Fresh 35.0 After experiment C 44.8
[0147] Tetralin catalytic steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst
[0148] The results obtained for tetralin steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst are shown in FIG.
20. The catalyst was used under a GHSV of 4800
cm.sup.3.sub.reactg.sub.cat.sup.-1h.sup.-1, an entrance temperature
of 670.degree. C., a reaction temperature of 705.degree. C. with a
H.sub.2O/C molar ratio of 2.3. The conversion obtained was 0.69
(0.668-0.715), explained by the higher refractory behavior of
cyclic/aromatic compounds in reforming reactions. Gaseous
concentrations at the reactor exit were, however, stable, with no
deactivation of the catalyst. The BET surface of the catalyst after
the experiment was 40.0 m.sup.2 g.sup.-1, which is consistent with
the observed behavior in hexadecane reforming.
[0149] SEM-EDXS analysis with the associated SEM picture of the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst is shown in FIG.
21. There is no significant carbon deposition and the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2 catalyst after use in the
tetralin experiment results are similar to those obtained with the
hexadecane reforming at similar conditions (experiment B).
[0150] Discussion
[0151] For hexadecane steam reforming with the
NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-1 catalyst, and for the
entire duration of the reaction, the concentrations of H.sub.2, CO,
CO.sub.2 and CH.sub.4 were all near the values predicted from
theoretical thermodynamic equilibrium calculations. Product
concentrations were still close to equilibrium, even if lower
temperatures decreased the rate of reforming reactions and
thermodynamically favored carbon formation and deposition through
the Boudouard reaction. The equilibrium concentrations for
hexadecane steam reforming appear in FIG. 22. Comparisons between
theoretical equilibrium concentrations and experimental
concentrations are shown in FIG. 23 for hexadecane and FIG. 24 for
tetralin with the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ-2
catalyst. It can be seen that the experimental concentrations were
similar to theoretical equilibrium concentrations. For experiment
C, at higher GHSV, the concentrations were slightly different;
these conditions were thus considered as the limit to operate
within equilibrium conditions.
[0152] Biodiesel Reforming
[0153] Biodiesel reforming can be represented by the following
global reaction (8):
C.sub.18H.sub.36O.sub.2+16H.sub.2O.fwdarw.18CO+34H.sub.2(.DELTA.H>0)
(8)
[0154] As mentioned before, an emulsion-in-water technique was
adopted for biodiesel injection. This method was chosen to enhance
hydrocarbonaceous fuel/water mixing. The two immiscible reactants
were emulsified according to the surfactant-aided protocol
described above. The reactant mixture entered at room temperature
and was rapidly heated and vaporized in the pre-heating zone 26
(FIG. 4) maintained at 550.degree. C. The temperature just before
the catalyst bed was between 30.degree. C. and 45.degree. C. below
the reaction temperature, depending on operating parameters. Argon
served as inert diluent and internal standard for liquid
hydrocarbonaceous fuel steam reforming.
[0155] The water to steam molar (H.sub.2O/C) ratio was varied
between 1.9 and 2.4. Reaction temperatures were 700.degree. C. and
725.degree. C. with GHS V ranged from 5 500 and 13 500
cm.sup.3.sub.reactg.sub.cat.sup.-1h.sup.-1 at atmospheric pressure.
Biodiesel, from used vegetable oil, was produced by a
transesterification process developed by Biocarburant PL
(Sherbrooke, Qc, Canada; www.biocarburantpl.ca).
[0156] The same packed-bed reactor, as described above, was used
for carrying out the steam reforming.
[0157] Table 7 lists the conditions for three different biodiesel
reforming test runs with the associated overall conversion
calculated.
TABLE-US-00007 TABLE 7 Biodiesel reforming test runs description
Run A B C Temperature (.degree. C.) 700 725 725 Catalyst weight (g)
5.0 3.0 3.0 Run time (h) 3 4 2 GHSV (cm.sup.3g.sup.-1h.sup.-1) 8
700 5 500 13 500 H.sub.2O/C* (mol/mol) 1.9 1.9 2.4 Conversion
(.+-.3%) 88 100 85 *Steam-to-carbon (H.sub.2O/C) molar ratio
calculated, including surfactant
[0158] Dry gaseous concentrations in product mixture are presented
in FIG. 25. Concentrations were stable for the entire reaction time
with no catalyst deactivation noted.
[0159] With a temperature increase and flow rate decrease, 100%
conversion can be reached. Furthermore, an increase of GHSV
decreases conversion, even at a higher H.sub.2O/C molar ratio. This
reduction of conversion was associated with concentrations not
being exactly at equilibrium. FIG. 25 compares the theoretical
equilibrium and experimental concentrations of the dry gas at the
reactor exit.
[0160] These data are indicative of the ability of the
Al.sub.2O.sub.3/YSZ-supported NiAl.sub.2O.sub.4 spinel catalyst to
efficiently steam reform commercial biodiesel. The catalyst is not
poisoned by sulfur since the latter is not present in biodiesel in
detectable quantities, and since carbon formation is insignificant,
the only remaining catalyst deactivation mechanism is sintering.
Thus, the expected life cycle of the NiAl.sub.2O.sub.4 catalyst is
considerably longer than any other metallic Ni-based
formulation.
[0161] High GHSV, which gave complete biodiesel conversion, are
indicative of a rather surface reaction kinetics-controlled
process.
[0162] Concentrations for run B were equal to those at chemical
thermodynamic equilibrium. In run A, even if the conversion was not
complete, the concentrations were near equilibrium. It should be
noted that for biodiesel reforming below 700.degree. C.,
theoretical equilibrium concentrations predict the presence of
significant amounts of methane and coke formation if the H.sub.2O/C
molar ratio in the reactant mixture is not higher than
stoichiometric ratio.
[0163] The used catalyst was also analyzed by SEM. SEM pictures
proved that there were not significant carbon deposits on the
surface. Some carbon whiskers were found on less than 5% of the
surface; this was, however, expected because local
nanoheterogeneities and the possibility that some NiO on the
surface was not transformed into NiAl.sub.2O.sub.4 which could form
Ni during SR reactions. FIG. 26 shows the SEM micrograph of an
Al.sub.2O.sub.3 particulate of the NiAl.sub.2O.sub.4 catalyst
employed in run B of the biodiesel reforming test.
[0164] The Al.sub.2O.sub.3/YSZ-supported NiAl.sub.2O.sub.4 catalyst
has been tested efficiently in biodiesel steam reforming. 100%
conversion was obtained at relatively low severity conditions.
Increasing GHSV above 10 000 (cm.sup.3g.sup.-1h.sup.-1) decreased
conversion, but dry concentrations of the exit gas were still near
equilibrium. No catalyst deactivation was encountered. There was no
observable carbon on the surface of the catalyst used in these
conditions, event with a H.sub.2O/C molar ratio lower than 2.
[0165] Conclusion
[0166] A Ni-alumina spinel supported on an Al.sub.2O.sub.3--YSZ
ceramic matrix was developed as a catalyst for steam reforming of
carbonaceous fuels including hydrocarbons, diesels, and the
like.
[0167] Reactants feeding as a stabilized hydrocarbon-water emulsion
proved to be efficient and prevented undesired pre-cracking.
[0168] Nickel-based catalysts offer a low-cost, effective option
for steam reforming. Compared to conventional nickel catalysts
which deactivate rapidly mainly due to coking, the spin&
catalyst NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ is stable, i.e. it
has an improved resistance to carbon formation and therefore a
longer catalyst lifetime. Furthermore, the results showed that the
spinel catalyst is efficient for steam reforming of
hydrocarbonaceous fuel(s). There was no significant coking on the
active part of the catalysts, even at high reaction seventies.
[0169] With the reactor design used and the above-described method
for feeding the reactant mixture, conversion rates as high as 100 %
were achieved with high H.sub.2 concentration as summarized in
Table 8 below. Moreover, the product mixture concentrations are
close to equilibrium and constant over time for durations up to
about 20 hours. Regarding the operating conditions, the GHSV for
reaching equilibrium are equal or higher than those found in the
literature at equal or higher reaction severities
(temperature).
TABLE-US-00008 TABLE 8 Steam reforming parameters in the presence
of the NiAl.sub.2O.sub.4/Al.sub.2O.sub.3--YSZ catalyst. Carbon
Conver- formation T Ratio GHSV sion H.sub.2 observed Fuel (.degree.
C.) H.sub.2O/C (cm.sup.3g.sup.-1h.sup.-1) (%) (%) by SEM Propane
700-750 3 2 500-5 950 100 70 None Hexa- 670-710 2.5 4 800-12 000
86-97 65-70 None decane Tetralin 630-720 2.3 1 900-12 000 69 60-70
Minimal Biodiesel 710 1.9-2.4 5 500-13 500 85-100 60-70 Minimal
Diesel 695-710 1.9 4 500-52 000 79-93 63-70 None
[0170] The above-described catalysts and process can be used for
steam reforming of biodiesel, a renewable energy carrier.
[0171] The catalysts and the steam reforming processes using same
can be used for the production of high concentrations of H.sub.2.
The H.sub.2 produced can be used, for instance and without being
limitative, for refineries and petrochemical processes (e.g. fossil
fuels processing, ammonia production) and SOFCs targeting stable,
clean, chemical-to-electrical energy conversion applications.
[0172] The product gas mixture mainly composed of H.sub.2 and CO
(synthesis gas) can be used directly as SOFC fuel.
[0173] The reaction conditions, including and without being
limitative, the temperature, the pressure, the steam-to-carbon
ratio (H.sub.2O/C ratio), and gas hourly space velocity (GHSV), can
be optimized for the steam reformed hydrocarbons such as methane,
propane, hexadecane, tetradecane, diesel, and the like.
[0174] Several alternatives can be foreseen. For instance and
without being limitative, the reaction temperature for the steam
reforming process can range between 500.degree. C. and 900.degree.
C., in an embodiment, they can range between 600.degree. C. and
750.degree. C.; and in a particular embodiment, they can range
between 630.degree. C. and 720.degree. C. The reactant mixture has
a H.sub.2O:carbon molar ratio between 2.3 and 3; in an embodiment
between 2.3 and 2.8, and in a particular embodiment about 2.5. The
steam reforming process is carried out with a gas hourly space
velocity (GHSV) ranging between 300 cm.sup.3g.sup.-1h.sup.-1 and
200 000 cm.sup.3g.sup.-1h.sup.-1 and in an embodiment between 900
cm.sup.3g.sup.-1h.sup.-1and 52 000 cm.sup.3g.sup.-1h.sup.-1.
[0175] Several alternative embodiments and examples have been
described and illustrated herein. The embodiments of the invention
described above are intended to be exemplary only. A person of
ordinary skill in the art would appreciate the features of the
individual embodiments, and the possible combinations and
variations of the components. A person of ordinary skill in the art
would further appreciate that any of the embodiments could be
provided in any combination with the other embodiments disclosed
herein. It is understood that the invention may be embodied in
other specific forms without departing from the spirit or central
characteristics thereof. The present examples and embodiments,
therefore, are to be considered in all respects as illustrative and
not restrictive, and the invention is not to be limited to the
details given herein. Accordingly, while the specific embodiments
have been illustrated and described, numerous modifications come to
mind without significantly departing from the spirit of the
invention. The scope of the invention is therefore intended to be
limited solely by the scope of the appended claims.
* * * * *
References