U.S. patent application number 11/273038 was filed with the patent office on 2006-04-13 for process for the production of hydrogen.
Invention is credited to Laszlo T. Nemeth, Anil R. Oroskar, Christine M. Rayner, Kurt M. Vanden Bussche.
Application Number | 20060076535 11/273038 |
Document ID | / |
Family ID | 36101902 |
Filed Date | 2006-04-13 |
United States Patent
Application |
20060076535 |
Kind Code |
A1 |
Oroskar; Anil R. ; et
al. |
April 13, 2006 |
Process for the production of hydrogen
Abstract
A process and apparatus are disclosed for the generation of
hydrogen from hydrogen rich compounds. The process uses hydrogen
peroxide as an oxidizer with a hydrogen rich compound forming a
mixture such that when the mixture is exposed to a catalyst forming
a hydrogen rich gas.
Inventors: |
Oroskar; Anil R.; (Oakbrook,
IL) ; Vanden Bussche; Kurt M.; (Lake in the Hills,
IL) ; Nemeth; Laszlo T.; (Barrington, IL) ;
Rayner; Christine M.; (Des Plaines, IL) |
Correspondence
Address: |
JOHN G TOLOMEI, PATENT DEPARTMENT;UOP LLC
25 EAST ALGONQUIN ROAD
P O BOX 5017
DES PLAINES
IL
60017-5017
US
|
Family ID: |
36101902 |
Appl. No.: |
11/273038 |
Filed: |
November 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10395319 |
Mar 21, 2003 |
|
|
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11273038 |
Nov 14, 2005 |
|
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Current U.S.
Class: |
252/188.25 |
Current CPC
Class: |
C01B 2203/0244 20130101;
C01B 2203/1288 20130101; C01B 2203/0838 20130101; C01B 2203/0844
20130101; C01B 2203/1229 20130101; C01B 2203/044 20130101; C01B
3/323 20130101; C01B 13/0214 20130101; C01B 2203/0283 20130101;
C01B 2203/0866 20130101; C01B 2203/0233 20130101 |
Class at
Publication: |
252/188.25 |
International
Class: |
C01B 3/00 20060101
C01B003/00 |
Claims
1. A fuel suitable for the generation of a gas comprising at least
5 weight percent hydrogen comprising: an oxygenate wherein the
oxygenate concentration is greater than 20 weight percent; and an
oxidizer wherein the oxidizer concentration is greater than 15
weight percent.
2. The fuel of claim 1 further comprising a diluent wherein the
diluent concentration is greater than 2 weight percent of the
fuel.
3. The fuel of claim 2 wherein the diluent has a concentration of
at least 25 weight percent.
4. The fuel of claim 1 wherein the oxygen concentration is at least
33 weight percent.
5. The fuel of claim 1 wherein the oxygenate concentration is
between about 30 weight percent and about 70 weight percent.
6. The fuel of claim 1 wherein the oxidizer concentration is
between about 30 weight percent and about 70 weight percent.
7. The fuel of claim 1 wherein the oxygenate is selected from the
group consisting of alcohols, diols, triols, ethers, ketones,
diketones, esters, sugars, and mixtures thereof.
8. The fuel of claim 7 wherein the oxygenate is selected from the
group consisting of methanol, ethanol, n-propanol, isopropanol,
1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol,
3-pentanol, tert-amyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol,
dimethylether, diethylether, isopropylether, methyl tert-butyl
ether, methyl tert-amyl ether, glucose, sorbitol and mixtures
thereof.
9. The fuel of claim 1 wherein the oxidizer is selected from the
group consisting of hydrogen peroxide, organic peroxides,
hydroperoxides, and mixtures thereof.
10. The fuel of claim 9 wherein the oxidizer is hydrogen peroxide.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a Division of copending application Ser.
No. 10/395,319 filed Mar. 21, 2003, the contents of which are
hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to fuels and processes for the
production of hydrogen. In particular, this invention relates to a
fuel mixture, which when used in conjunction with a catalyst
generates a hydrogen rich gas through autothermal reforming.
BACKGROUND OF THE INVENTION
[0003] The production of hydrogen (H.sub.2) is a very important
process. It is used in oil refineries, the production of fine
chemicals, and energy applications. One method of producing
hydrogen is the steam reforming process, wherein hydrocarbons are
catalytically reacted with steam at high temperature to produce
hydrogen and oxides of carbon. This is the most common method of
producing hydrogen, or hydrogen and carbon oxide mixtures.
Currently, natural gas predominates as a feedstock over other
hydrocarbons, e.g., naphtha, LPG, refinery gases. The catalytic
steam reforming process in tubular furnaces was invented by BASF,
and was used in the United States in the early 1930s. The principal
purposes were to produce hydrogen from natural gas for
hydrogenation purposes and to synthesize ammonia. The process was
initially carried out at low pressures (0.4-1 MPa) and temperatures
close to 800.degree. C., and subsequently higher pressures (up to 4
MPa) and temperatures (up to 950.degree. C.) are used today.
[0004] A special type of steam reforming is autothermal reforming,
and is also called catalytic partial oxidation. This process
differs from catalytic steam reforming in that the heat is supplied
by the partial internal combustion of the feedstock with oxygen or
air, and not supplied from an external source.
[0005] Modification of the process, using air as the oxidizer was
developed for ammonia synthesis, and recently, oxygen based
gasification has been introduced into methanol synthesis.
SUMMARY OF THE INVENTION
[0006] The present invention is a process for generating hydrogen
for use in chemical processes, or for use as a fuel for fuel cells.
The invention comprises mixing an oxygenate and an oxidizer in the
presence of an initiator. In one embodiment, the oxygenate is
selected from alcohols, diols, triols, ethers, ketones, diketones,
esters, carbonates, dicarbonates, oxalates, sugars, and mixtures
thereof. In another embodiment the oxidizer is selected from
hydrogen peroxide, organic peroxides, hydroperoxides, and mixtures
thereof. In a preferred embodiment, the initiator comprises a
catalyst.
[0007] In a preferred embodiment, the process comprises flowing a
mixture of an oxygenate and hydrogen peroxide over an initiator.
The preferred initiator is a catalyst mixture that comprises a
first catalyst for decomposing the hydrogen peroxide and a second
catalyst for catalytic autothermal reforming of the oxygenate.
[0008] An aspect of the present invention is an apparatus for
generating hydrogen from a fuel mixture of an oxygenate and an
oxidizer. In one embodiment, the apparatus comprises a housing for
holding a catalyst bed and having an inlet for admitting the fuel
and an outlet for directing a product stream rich in hydrogen gas.
In one embodiment the catalyst bed comprises a mixture of catalysts
with a first catalyst for decomposing the oxidizer and a second
catalyst for reforming the oxygenate.
[0009] Another aspect of the invention is a liquid fuel for
generating hydrogen. The liquid fuel comprises an organic compound
and an oxidizer. In one embodiment the organic compound is an
oxygenate and preferably an alcohol and the oxidizer is hydrogen
peroxide.
[0010] Other objects, advantages and applications of the present
invention will become apparent to those skilled in the art after
the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a schematic of the process for generating a
hydrogen rich gas;
[0012] FIG. 2 is a graph depicting the mole fractions of hydrogen
and oxygen in desired fuel compositions;
[0013] FIG. 3 is one embodiment of the apparatus for generating a
hydrogen rich gas; and
[0014] FIG. 4 is an alternate design of the apparatus for
generating a hydrogen rich gas.
DETAILED DESCRIPTION OF THE INVENTION
[0015] Hydrogen production is important for chemical processes and
energy applications. A combination of catalytic steam reforming and
autothermal reforming is an efficient means for converting a
hydrocarbon to a hydrogen (H.sub.2) rich gas. A process and fuel
that utilizes autothermal reforming and produces hydrogen on demand
can be useful for intermittent processes.
[0016] One use for intermittent hydrogen production is for fuel
cells, where hydrogen is needed for variable demand. An example of
the needs for automotive applications is shown in Table 1.
TABLE-US-00001 TABLE 1 Alternate fuel for automotive applications
Automotive Applications -Alternate Fuel Required Range 300 miles
Average Speed 50 mph Average Propulsion Power Needed 14 kW Cell to
Wheel Efficiency 0.81 Density of Storage Means 0.9 kg/litre H.sub.2
Capacity of Storage Means 7 wt. % H.sub.2 Fuel Cell Performance 1
0.7 V Fuel Cell Performance 2 600 mA/cm.sup.2 Overall Energy
Required 373 MeJ Overall Hydrogen Required 5.5 kg Mass of Storage
Means Required 79 kg Volume of Storage Means Required 88 litres 23
gallons CO.sub.2 Emission Reduction Factor 2.30 Fuel Cost 1.30
$/gallon (20 /lb H.sub.2O.sub.2; 1.35 $/gallon EtOH) Cost per mile
to consumer 0.10 $/mile Traditional Fuel Cost per mile 0.07
$/mile
[0017] The present invention is a process and a fuel for generating
hydrogen. The process comprises mixing an oxygenate and oxidizer in
the presence of an initiator. It is preferable that the oxygenate
and oxidizer are liquids, or that a mixture of the oxygenate and
oxidizer form a substantially liquid mixture at normal
environmental temperatures, i.e., from about -40.degree. C. to
about 50.degree. C. or over a portion of this temperature range,
especially, from about 0.degree. C. to about 40.degree. C. When
this mixture is brought into contact with an initiator, the
oxidizer decomposes and generates heat, oxygen and water. The
mixture may be mixed as the mixture is brought into contact with
the initiator, or the mixture may be pre-mixed and subsequently
brought into contact with the initiator. The resulting heat and
water concurrently causes steam reforming of the oxygenate,
according to: ##STR1##
[0018] An initiator can be any means for starting the decomposition
of the oxidizer, and includes, but is not limited to, heat, a
chemical additive, and a catalyst. Heat as an initiator can be
provided by a heated wire through electrical resistance, or
combustion of a portion of the fuels. A chemical additive when
mixed with the fuel reacts with the oxidizer to generate heat and
oxygen can be an appropriate initiator. An example of a chemical
initiator is potassium permanganate (KMnO.sub.4). Preferably, the
initiator can be a catalyst, wherein the catalyst is one selected
to decompose the oxidizer and generate heat and oxygen.
[0019] Using thermodynamic data from an HYSYS.TM., by Hyprotech,
Ltd., Calgary Canada, the reaction of ethanol and hydrogen peroxide
showed the reaction was preferred to produce carbon monoxide and
hydrogen. The results of the reaction are shown in Table 2 for the
reaction: C.sub.2H.sub.5OH(g)+H.sub.2O.sub.2(g).fwdarw.2 CO(g)+3
H.sub.2(g)+H.sub.2O(g) (eqn. 2)
[0020] TABLE-US-00002 TABLE 2 Thermodynamics of ethanol oxidation
with hydrogen peroxide T .DELTA.H .DELTA.S .DELTA.G C Kcal Cal/K
Kcal K Log(K) 0.000 -22.421 108.483 -52.053 4.482E+041 41.652
100.000 -20.837 113.457 -63.174 1.008E+037 37.003 200.000 -19.698
116.182 -74.670 3.113E+034 34.493 300.000 -18.941 117.644 -86.369
8.637E+032 32.936 400.000 -18.493 118.371 -98.174 7.526E+031 31.877
500.000 -18.265 118.689 -110.030 1.274E+031 31.105 600.000 -18.187
118.786 -121.905 3.276E+030 30.515 700.000 -18.230 118.741 -133.782
1.115E+030 30.047 800.000 -18.375 118.599 -145.650 4.617E+029
29.664 900.000 -18.609 118.391 -157.500 2.206E+029 29.344 1000.000
-18.922 118.135 -169.326 1.172E+029 29.069 Molecular wt. Amount
Amount Volume Formula g/mol Conc. wt-% mol g l or ml
C.sub.2H.sub.5OH(g) 46.069 57.526 1.000 46.069 22.414
H.sub.2O.sub.2(g) 34.015 42.474 1.000 34.015 22.414 g/mol wt-% mol
g l or ml CO(g) 28.010 69.953 2.000 56.021 44.827 H.sub.2(g) 2.016
7.551 3.000 6.047 67.241 H.sub.2O(g) 18.015 22.496 1.000 18.015
22.414
[0021] This indicates a significant energy release in the
production of hydrogen when using hydrogen peroxide as an oxidizer.
Experiments were conducted in lab scale quantities to verify that
sufficient heat is generated to reform a mixture of alcohol and
water without adding additional heat.
EXAMPLE 1
[0022] Pure ethanol was mixed with 30% aqueous hydrogen peroxide
under atmospheric conditions. The mixture was oxidized using the
catalyst MnO.sub.2. The test consisted of mixing 2 gm of pure
ethanol with 2 gm of 30% hydrogen peroxide. The reaction was very
exothermic, and a large amount of gas was produced. The gas product
composition comprised about 30 volume percent of H.sub.2, about 22
volume percent of CO.sub.2, and a small amount of CO; and the
liquid product composition included ethoxy-acetic acid, and
2-propanol based on gas chromatography-mass spectroscopy
(GC-MS).
[0023] The process is as shown in FIG. 1. A fuel comprising, for
example, a mixture of ethanol and hydrogen peroxide enters a
reactor 10 through an inlet port 12. Reactor 10 comprises a
catalyst bed holding a decomposition catalyst for decomposing the
hydrogen peroxide. The operating conditions are at ambient pressure
and at a temperature from about -20.degree. C. to about 50.degree.
C. The decomposition reaction decomposes the hydrogen peroxide and
generates heat and a first product stream 14, including water and
oxygen. The product streams 14 is directed to a second reactor 20
comprising a second catalyst bed holding a reforming catalyst. The
reforming catalyst is chosen to reform the ethanol and water to
form a second product stream 22, which includes a gas comprising
hydrogen, carbon dioxide, and carbon monoxide. The reforming
reaction is endothermic and requires the addition of heat. The heat
from the decomposition reaction is transferred to the second
catalyst bed via an appropriate heat transfer means 26. The second
reactor 20 is operated at ambient pressure and at a temperature
between about 200.degree. C. and about 1100.degree. C.
[0024] Optionally, the second product stream 22 is directed to a
third reactor 30 comprising a third catalyst bed. The third
catalyst bed holds a water gas shift (WGS) catalyst for performing
the water gas shift reaction. The WGS reactor is operated at
ambient pressure and at temperatures between about 180.degree. C.
and about 300.degree. C. This produces additional hydrogen while
converting carbon monoxide to carbon dioxide in a third product
stream 32.
[0025] The process also provides for optional preheating of the
fuel to the decomposition catalyst with a heat exchanger 34 when
excess heat is generated in the process.
[0026] The process requires an oxidizer that is a compound that
gives up its oxygen readily, and generates heat in the process of
giving up its oxygen for further chemical reaction. Oxidizers
include, but are not limited to, hydrogen peroxide, organic
peroxides, hydroperoxides, and mixtures thereof. Preferably, the
oxidizer is a liquid, or is readily soluble in a liquid to form a
liquid phase at normal environmental conditions. A preferred
oxidizer is hydrogen peroxide, or hydrogen peroxide in water. When
the hydrogen peroxide is in water, it is preferred that the aqueous
hydrogen peroxide concentration be less than 90 weight percent,
with a more preferred hydrogen peroxide concentration of less than
50 weight percent.
[0027] The determination of an appropriate mixture for the fuel
includes whether there is adequate hydrogen and adequate oxygen in
the mixture. However, an initial look at possible fuel mixtures can
be analyzed from an overall composition. Specifically, looking at
the ratios of hydrogen (H), oxygen (O), and carbon (C). One method
is by graphing the positions of fuel compositions on a triangular
graph showing the overall compositions of H, O and C. Components of
potential fuels and fuels are listed in Table 3 and plotted on FIG.
2 in atomic ratios. TABLE-US-00003 Fuel or Fuel Approximate Atomic
Ratio of Compound H C O Graph Symbol Biomas 2 1 1 B Ethanol 3 1 0.5
E Methanol 4 1 1 M Glycol 3 1 1 G Fuel 1 5 1 2 F1 Fuel 2 8 1 3 F2
Fuel 3 6 1 3 F3 Fuel 4 7 1 3 F4
[0028] Aspects of the compositions are that for increasing oxygen
(O) content, activation is lower and therefore reforming
temperature is lower; and for increasing hydrogen (H) content more
H.sub.2 is generated from reforming.
[0029] From FIG. 2, a preferred atomic concentration of hydrogen in
the mixture of organic compound and oxidizer is in the range of 0.5
atomic fraction to about 0.8 atomic fraction with a more preferred
range from about 0.6 atomic fraction to about 0.68 atomic fraction;
and a preferred atomic concentration of oxygen in the mixture is
from about 0.1 atomic fraction to about 0.5 atomic fraction with a
more preferred concentration from about 0.15 atomic fraction to
about 0.35 atomic fraction.
[0030] The process requires an organic compound. An organic
compound of choice is an oxygenate, that is, a hydrocarbon compound
that has been altered with the addition of at least one oxygen atom
to the hydrocarbon compound. Oxygenates include, but are not
limited to, alcohols, diols, triols, ethers, ketones, diketones,
esters, carbonates, dicarbonates, oxalates, organic acids, sugars,
and mixtures thereof. The oxygenates of choice will be compounds
that are generally in a liquid state at normal environmental
conditions, or are soluble in a liquid to form a liquid solution at
normal environmental conditions. Suitable oxygenates include, but
are not limited to, alcohols having 12 or fewer carbons, ketones
having 12 or fewer carbons, esters having 12 or fewer carbons,
diols having 12 or fewer carbons, triols having 12 or fewer
carbons, ethers having 12 or fewer carbons, carbonates having 12 or
fewer carbons, dicarbonates having 12 or fewer carbons, oxalates
having 12 or fewer carbons, organic acids having 12 or fewer
carbons, sugars having 12 carbons or less, and mixtures
thereof.
[0031] Preferably, the oxygenates are alcohols, including diols and
triols, having 8 or less carbons, and ethers having 8 or less
carbons. Examples of preferred oxygenates are methanol and ethanol.
Other oxygenates that are preferred include propanols, butanols,
amyl alcohols, hexanols, dimethyl ether, isopropylether,
dimethoxymethane, and sorbitols.
[0032] The oxygenate and oxidizer are mixed in the presence of an
initiator to generate a hydrogen rich gas. Preferably the initiator
is a catalyst. The catalyst can comprise one or more metals
selected from calcium (Ca), scandium (Sc), titanium (Ti), vanadium
(V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel
(Ni), copper (Cu), zinc (Zn), strontium (Sr), yttrium (Y),
zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc),
ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium
(Cd), barium (Ba), lanthanum (La), hafnium (Hf), tantalum (Ta),
tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum
(Pt), gold (Au), and mercury (Hg). The catalyst can include oxides
of the metal, sulfides and other sulfur compounds of the metal and
sols comprising the metal. Preferred catalysts comprise one or more
metals from vanadium, iron, cobalt, ruthenium, copper, nickel,
manganese, molybdenum, platinum, gold, silver, palladium, rhodium,
rhenium, osmium, and iridium, with the more preferred catalyst
comprising iron, cobalt, nickel and manganese.
[0033] The catalyst can be deposited on a support for increasing
the surface area of the catalyst when reacting the mixture of
oxygenate and oxidizer. Materials suitable for supports include,
but are not limited to, inorganic oxides such as silicas, aluminas,
titania, zirconia, yttria, and molecular sieves. Other supports
include, but are not limited to, carbon, silicon carbide,
diatomaceous earth, and clays.
[0034] When mixing the oxygenate and oxidizer, there must be
sufficient oxidizer to generate heat sufficient to heat the mixture
to a reforming temperature, and there must be sufficient oxygenate
to be reformed and generate a hydrogen rich gas having at least 2
weight percent hydrogen as hydrogen gas (H.sub.2), and preferably
at least 5 weight percent, and more preferably at least 7 weight
percent. In order to achieve this hydrogen concentration, the mass
ratio of oxygenate to oxidizer needs to be between about 0.25 and
about 9.75. Preferably, the mass ratio is between about 0.7 and
about 3.
[0035] The process autothermally reforms the oxygenate with water
and heat from the decomposition of the oxidizer, and in the
presence of a catalyst generates a gas that is rich in hydrogen,
i.e. a gas having at least 5 weight percent hydrogen (H.sub.2).
When the oxidizer is hydrogen peroxide, the reaction is very
vigorous, and the reaction can be lessened with a moderator or
diluent. An appropriate diluent is water, wherein the water is at
least partially consumed in the reforming of the oxidizer, as shown
in equation 1. The water can be added separately, or be mixed in
with the oxidizer by using an aqueous solution of hydrogen
peroxide. By using an aqueous solution of hydrogen peroxide, the
process uses an oxidizer that is cheaper and easier to produce.
[0036] The process can comprise multiple catalysts. A first, or
decomposition catalyst can be used for the decomposition of the
oxidizer and a second, or reforming catalyst can be used for the
autothermal reforming of the oxygenate. The process comprises
flowing a mixture of oxygenate and oxidizer over the first
catalyst, wherein the first catalyst exothermally decomposes the
oxidizer to heat the mixture. The resulting mixture comprises the
oxygenate and oxygen, and can also include steam generated from the
decomposition of the oxidizer. The mixture subsequently flows over
a second catalyst, wherein the heated mixture undergoes reformation
to generate a hydrogen rich gas.
[0037] The first catalyst for decomposition of the oxidizer is
preferably a catalyst comprising at least one metal selected from
vanadium, iron, cobalt, ruthenium, copper, nickel, manganese,
molybdenum, platinum, gold, silver, palladium, rhenium, rhodium,
osmium, and iridium. The compound can be an oxide, sulfide, or
other compound of the metal. A more preferred compound is manganese
oxide (MnO.sub.2).
[0038] The second catalyst for reforming the oxygenate is
preferably a catalyst comprising at least one metal selected from
chromium, gold, zinc, copper, platinum, silver, palladium, rhodium,
rhenium, osmium, ruthenium, and iridium. The compound can be an
oxide, sulfide, or other compound of the metal, with a more
preferred compound comprising zinc oxide (ZnO).
[0039] The process comprises using the heat generated by the
decomposition of the oxidizer to heat the oxygenate, water, and
oxygen to facilitate reforming the oxygenate over a catalyst. The
process may comprise the use of separate catalyst beds with a first
catalyst bed holding the decomposition catalyst for the
decomposition step, and a second catalyst bed for the reformation
step. One embodiment using separate catalyst beds comprises flowing
the mixture in a countercurrent method, wherein the mixture of
oxygenate and oxidizer first flows over the first catalyst bed, and
then reversed direction to flow over a second catalyst bed in
thermal communication with the first catalyst bed. The catalyst
beds may be disposed in an apparatus comprising an inner tube
holding the second catalyst bed, and an outer tube holding the
first catalyst bed and surrounding the inner tube.
[0040] In an alternative embodiment, the process flows the
oxygenate and oxidizer concurrently over the first and second
catalysts. The decomposition and reforming catalysts can be
commingled in a single catalyst bed, where the catalysts are heated
with the decomposition, and reformation occurs in the presence of
the heated mixture, generating a reformate gas.
[0041] Optionally, the process includes a water-gas shift
processing step. The water-gas shift processing step comprises
flowing the reformate gas over a third catalyst in the presence of
steam at an elevated temperature. The carbon monoxide and steam
react to form hydrogen and carbon dioxide, as shown in equation 3.
##STR2##
[0042] The third, or watergas shift catalyst comprises at least one
metal selected from iron, cobalt, nickel, copper, zinc, yttrium,
zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,
palladium, silver, cadmium, lanthanum, hafnium, tantalum, tungsten,
rhenium, osmium, iridium, platinum, gold, and mercury. Preferably,
the watergas shift is deposited on a support. Supports include
inorganic oxides listed above, and the process for depositing a
catalyst metal on a support are known to one skilled in the
art.
[0043] The process may optionally include an oxidation step for the
selective oxidation of carbon monoxide in the reformate gas stream
to carbon dioxide. The oxidation step comprises flowing the
hydrogen rich reformate gas over a fourth catalyst, wherein the
fourth catalyst comprises at least one metal selected from
ruthenium, platinum, gold, and palladium.
[0044] An aspect of the present invention is an apparatus for
performing the process. The apparatus includes a housing for
holding catalyst beds for the fuel to flow over. The housing has an
inlet for admitting a feedstream, where the feedstream is a fuel
comprising a mixture of at least one organic compound and at least
one oxidizer. The apparatus includes a first catalyst bed having an
inlet in fluid communication with the housing inlet, and an outlet
for a first product stream. The first catalyst bed comprises a
decomposition catalyst for decomposing the oxidizer and is as
described above. The apparatus further includes a second catalyst
bed having an inlet in fluid communication with the first catalyst
bed outlet, and an outlet for a second product stream. The second
catalyst bed comprises a reforming catalyst for reformulating the
fuel and is as described above.
[0045] In one embodiment, the apparatus further comprises a third
catalyst bed. The third catalyst bed includes a catalyst for
performing the water gas shift reaction: ##STR3## Suitable
catalysts for the water gas shift reaction comprise at least one
metal selected from iron, cobalt, nickel, copper, zinc, yttrium,
zirconium, niobium, molybdenum, technetium, ruthenium, rhodium,
palladium silver, cadmium, lanthanum, hafnium, tantalum, tungsten,
rhenium, osmium, iridium, platinum, gold, and mercury. Preferably
the catalyst comprises at least one metal selected from cobalt,
iron, ruthenium, copper, and nickel. A preferred catalyst for the
water gas shift reaction includes copper (Cu) and zinc oxide
(ZnO)
[0046] One embodiment of the present invention is an apparatus as
shown in FIG. 3. The apparatus comprises a housing 40 having a
cylindrical configuration. Inside the housing 40 a first catalyst
bed 42 is disposed having a generally toroidal configuration. The
fuel enters an inlet port 44 flows over the first catalyst bed 42,
and exits a first bed outlet port 46. The first bed outlet port 46
in fluid communication with a second catalyst bed inlet port 48.
The product stream from the first catalyst bed 42 flows over a
second catalyst bed 50 and exits a second catalyst bed outlet port
52. The heat generated in the first catalyst bed 42 provides a heat
source to the second catalyst bed 52 which is absorbed due to the
endothermic reaction of the reforming reaction in the second
catalyst bed 50.
[0047] An alternate embodiment of the apparatus includes a third
catalyst bed 54 as shown in FIG. 4. The third catalyst bed
comprises a catalyst for performing the water gas shift reaction,
wherein the second catalyst outlet port 52 is in fluid
communication with the third catalyst bed inlet port 56. The
product stream flows over the catalyst bed 54 and exits the third
catalyst bed outlet port 58 with a hydrogen rich gas stream.
[0048] The invention is intended to include alternate
configurations, including layering of the catalyst beds with fluid
flow traversing back and forth through alternating beds. It is also
intended to include, as an alternate embodiment, a commingling of
the first and second catalyst beds to provide concurrent
decomposition of the oxidizer and reformation of the alcohol, or
other oxygenate.
[0049] Optional features that may be included in the design include
heat conducting fins within the catalyst bed to facilitate heat
transfer from one catalyst bed to another.
[0050] In an alternate embodiment, the present invention includes a
housing for holding a catalyst bed, and having an inlet for
admitting a feedstream and an outlet for delivering a product
stream. The catalyst bed comprises a catalyst that is a mixture of
catalysts for combining the process of decomposing the oxidizer and
reformulating the organic compound using the energy generated by
the decomposition of the oxidizer to drive the reformulation
reaction.
[0051] Fuels are typically composed of a substantially pure
component, or a mixture of components comprising individual
constituents wherein each constituent can be a fuel, and wherein
when the fuel is mixed with an oxidizing agent combustion occurs.
Oxidizer and fuel are generally kept separate usually because the
oxidizer is cheap, such as air, and does not need to be stored, and
can be mixed with the fuel as needed. For example, in the case of
the automobile internal combustion engine, the oxidizer (air) is
mixed in a carburetor or in the fuel injector. Other circumstances
that necessitate separation of oxidizer and fuel includes
hypergolic fuels that combust upon contact with the oxidizer. A
feature of the present invention is that the fuel and oxidizer are
mixed for the production of H.sub.2 and not for combustion and
optionally the fuel and oxidizer are premixed and from a stable
mixture.
[0052] Increasingly, specialized fuels are needed for specialized
functions. An important aspect of a fuel is its ability to be
readily stored and transported. For example, a fuel in a liquid
form at standard environmental temperatures (-40.degree. C. to
50.degree. C.) is easily transported and stored. This provides for
convenience of use with the delivery of the fuel to an appropriate
device for using the fuel, such as an engine. A fuel that can be
used to generate hydrogen as a single mixture provides considerable
convenience for many purposes, such as, for example, supplemental
hydrogen for petrochemical processes, hydrogen for PEM fuel cells,
etc. It is preferred that the fuel be a pre-mixed composition
having the necessary composition such that when passed over a
catalyst generates a hydrogen rich gas. Preferably, the fuel is in
a liquid state in the temperature range over which the fuel is
normally exposed, and is comprised of chemicals having a relatively
low toxicity.
[0053] Such a fuel, for use in hydrogen production instead of
combustion, wherein the hydrogen is then consumed to generate
power, is one that is a mixture of a organic compound and an
oxidizer. The term fuel used hereinafter refers to a mixture of an
organic compound and an oxidizer. A fuel suitable for the
generation of hydrogen, when the fuel is mixed with an initiator,
has an oxygenate concentration of at least 20 weight percent, and
an oxidizer with a concentration of at least 15 weight percent. The
fuel has hydrogen that is readily produced upon reformation, and
has a hydrogen concentration of at least 5 weight percent.
Preferably, the hydrogen concentration in the fuel is at least 7
weight percent, and more preferably at least 9 weight percent. In
addition, the fuel has oxygen in the mixture with a concentration
of at least 20 weight percent. Preferably, the oxygen concentration
is greater than 40 weight percent, and more preferably greater than
50 weight percent.
[0054] In one preferred embodiment, the organic compound comprises
an oxygenate. Suitable oxygenates are compounds that have a
substantially liquid phase at normal environmental conditions, or
are substantially soluble in an appropriate liquid at normal
environmental conditions. Normal environmental conditions would be
typically from about 0.degree. C. to about 40.degree. C., but could
include temperatures as low as -40.degree. C. and as high as about
65.degree. C. Suitable oxygenates include, but are not limited to,
alcohols, diols, triols, ethers, ketones, diketones, esters,
carbonates, dicarbonates, oxalates, and carbohydrates such as
sugars. Preferably, the oxygenates are selected from cheap
chemicals such as methanol, ethanol, propanols and butanols. The
oxygenates may also include mixtures of oxygenates. The oxygenate
has a concentration from about 20 weight percent to about 91 weight
percent of the fuel.
[0055] The fuel also comprises an oxidizer. Suitable oxidizers are
either substantially liquid at normal environmental conditions, or
remains in a substantially liquid phase when mixed with an
appropriate liquid, such as an oxygenate, or water. Oxidizers that
are suitable include, but are not limited to, hydrogen peroxide,
organic peroxides, and hydroperoxides, with a preferred oxidizer
being hydrogen peroxide. The oxidizer in the fuel has a
concentration from about 20 weight percent to about 90 weight
percent.
[0056] The oxygenate and oxidizer are mixed in a mass ratio from
about 0.25 to about 9.8, and preferably from about 0.45 to about
4.0.
[0057] Optionally, the fuel includes a diluent, wherein the diluent
is a compound that provides stability to the fuel when stored, and
contributes to the production of hydrogen from the fuel when the
fuel is processed to generate a hydrogen rich gas. A suitable
diluent is water. Water provides stability to the mixture, as well
as a source of hydrogen during a water-gas shift reaction.
[0058] The fuel may be further blended with appropriate organic
compounds for controlling mixture properties, such as for example
lowering mixture freezing points or raising mixture boiling
points.
[0059] When the oxygenate comprises a solid, it is desirable that
the oxygenate be soluble in the diluent or oxidizer so as to form a
liquid solution. An example would be a sugar in a water and
hydrogen peroxide solution.
[0060] As an example, ethanol was used as the preferred oxygenate,
hydrogen peroxide as the oxidizer, and water as the diluent,
computations were performed for determining the amount of hydrogen
(H.sub.2) produced. Table 4 lists the amount of hydrogen for
varying composition of the three components. TABLE-US-00004 TABLE 4
Mass Fraction of Hydrogen Produced Mass Flow Rate lb/hr Mass
Fraction H.sub.2 Produced Water Ethanol Hydrogen Peroxide Without
Energy With Energy lb./hr. lb./hr. lb./hr. Recycle Recycle 10 40 33
0.0910 0.0954 10 40 34 0.0925 0.0956 10 40 35 0.0935 0.0945 10 40
36 0.0932 0.0933 10 40 37 0.0920 0.0920 15 25 22 0.0748 0.0751 15
25 23 0.0779 0.0797 15 25 24 0.0790 0.0795 15 25 25 0.0774 0.0774
15 25 26 0.0754 0.0754 23 5 10 0.0125 -- 23 6 10 0.0130 -- 23 7 10
0.0131 -- 23 8 10 0.0131 -- 23 9 10 0.0129 --
[0061] The results show that a diluent content can be substantial,
and with a diluent content as high as 24 weight percent, a gas
having at least 7 weight percent H.sub.2 can be generated. The
diluent has a concentration of less than about 40 weight percent.
The amount of diluent will depend on the choice and relative ratios
of oxygenate and oxidizer. The diluent can provide water for the
reformation reaction, added stability to the fuel mixture, or other
enhancements of selected physical properties, such as, for example,
a fuel's boiling point.
[0062] In addition the diluent helps bring the fuel mixture to a
value in a more stable range. Preferably, the concentration of
oxygenate is in the range from about 30 weight percent to about 70
weight percent, and the oxidizer has a concentration in the range
from about 30 weight percent to about 70 weight percent.
[0063] In an alternate embodiment, the organic compound comprises a
hydrocarbon. The hydrocarbons are preferably paraffins. Suitable
hydrocarbons include, but are not limited to methane, ethane,
propanes, butanes, pentanes, hexanes, heptanes, octanes, nonanes,
decanes, dodecanes, and mixtures thereof.
[0064] Preferably, the hydrocarbons have a substantially liquid
phase, or are substantially soluble in a liquid phase at normal
environmental conditions.
[0065] A comparison of hydrogen production of various organic
compounds with hydrogen peroxide as the oxidizer water as a diluent
are listed in Tables 5 and 6. In addition to hydrocarbons, and
alcohols, other compounds are possible, including sugars (glucose)
dissolved in a solution of water and hydrogen peroxide.
TABLE-US-00005 TABLE 5 Comparison of organic compounds properties.
Steam reformability at 90% conversion Temper- L or V + Toxicity H
Content ature Mole Ratio Contact Time Pressure to LD50 (mg/kg) LC50
(mg/liter) Formula wt. % .degree. C. water:fuel or GHSV Catalyst
Liquify (psi) Oral-Rat Inhalation-Rat Methanol CH.sub.3OH 12.58 280
1.8:1 300 msec Unavailable L 5628 Ethanol C.sub.2H.sub.5OH 13.13
615 13:1 5000/hour V.sub.2O.sub.5 L 7060 Isopropanol
C.sub.3H.sub.7OH 13.42 L 5045 Butanol C.sub.4H.sub.9OH 13.60 L 790
Methane CH.sub.4 25.13 790 1.1:1 27600/hour NiO--CaO V, >10000
>5 Ethane C.sub.2H.sub.6 20.11 V, 610.9 Propane C.sub.3H.sub.8
18.29 600 3:1 1000/hour Pt--Sn V, 139.0 Butane C.sub.4H.sub.10
17.34 660 3:1 10 msec Unavailable V, 35.2 658 for 4 hours Pentane
C.sub.5H.sub.12 16.76 L >2000 Hexane C.sub.6H.sub.14 16.37 L
28710 Dodecane C.sub.12H.sub.26 15.38 L Dimethylether
C.sub.2H.sub.6O 13.13 L Isopropylether C.sub.6H.sub.14O 13.81 L
8470 Dimethoxymethane C.sub.3H.sub.8O.sub.2 10.60 L Glucose
C.sub.6H.sub.12O.sub.6 6.71 630 93:1 30 sec Unavailable L 25800
Sorbitol C.sub.6H.sub.14O.sub.6 7.75 L 15900
[0066] TABLE-US-00006 TABLE 6 Comparison of organic compounds
H.sub.2 content of gas produced. H Content Mass Flow Rate lb/hr H
Content after Temperature Fuel Formula wt. % Renewable Water
H.sub.2O.sub.2 Fuel reaction (wt %) .degree. C. Conversion Methanol
CH.sub.3OH 12.58 Y/N 0.0 1.0 2.15 10.11 339.7 98.7 Ethanol
C.sub.2H.sub.5OH 13.13 Y 0.0 1.0 1.16 9.66 645.5 99.7 Isopropanol
C.sub.3H.sub.7OH 13.42 N 0.02 1.0 0.94 9.46 704.1 99.7 Butanol
C.sub.4H.sub.9OH 13.60 N 0.02 1.0 0.88 9.46 705.6 99.8 Methane
CH.sub.4 25.13 Y/N 0.02 1.0 0.47 10.80 1289.5 97.7 Ethane
C.sub.2H.sub.6 20.11 N 0.02 1.0 0.55 10.81 1047.4 99.7 Propane
C.sub.3H.sub.8 18.29 N 0.02 1.0 0.58 10.39 961.7 99.9 Butane
C.sub.4H.sub.10 17.34 N 0.02 1.0 0.60 10.12 902.3 99.6 Pentane
C.sub.5H.sub.12 16.76 N 0.02 1.0 0.61 9.97 879.0 99.7 Hexane
C.sub.6H.sub.14 16.37 N 0.02 1.0 0.60 9.79 856.0 99.8 Dodecane
C.sub.12H.sub.26 15.38 N 0.02 1.0 0.61 9.49 829.7 100.0
Dimethylether C.sub.2H.sub.6O 13.13 N 0.02 1.0 1.66 10.37 465.8
99.6 Isopropylether C.sub.6H.sub.14O 13.81 N 0.02 1.0 0.82 9.44
697.0 99.8 Dimethoxymethane C.sub.3H.sub.8O.sub.2 10.60 Y/N -- --
-- -- -- -- Glucose C.sub.6H.sub.12O.sub.6 6.71 Y -- -- -- -- -- --
Sorbitol C.sub.6H.sub.14O.sub.6 7.75 Y 0.02 1.0 2.31 7.08 267.0
100.0
* * * * *