U.S. patent application number 11/987350 was filed with the patent office on 2008-07-24 for compositions and methods for hydrogen generation.
Invention is credited to Michael T. Kelly, Alexander MacLachan, Kevin W. McNamara, Xiaolei Sun.
Application Number | 20080172932 11/987350 |
Document ID | / |
Family ID | 39639883 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080172932 |
Kind Code |
A1 |
Kelly; Michael T. ; et
al. |
July 24, 2008 |
Compositions and methods for hydrogen generation
Abstract
Hydrogen storage fuel compositions comprising a mixture of at
least one chemical hydride compound and at least one compound,
polymer, carboxylic acid or salt that acts as a water surrogate
source, and methods for thermally initiated hydrogen generation
from fuel compositions, are disclosed. The water surrogate
source/chemical hydride compositions are preferably solids, and may
be powders, caplets, tablets, pellets or granules, for example. The
water surrogate source/chemical hydride compositions may comprise
alternating layers of the chemical hydride and of the water
surrogate source.
Inventors: |
Kelly; Michael T.;
(Plainsboro, NJ) ; McNamara; Kevin W.; (Red Bank,
NJ) ; Sun; Xiaolei; (Chandler, AZ) ;
MacLachan; Alexander; (Wilmington, DE) |
Correspondence
Address: |
DICKSTEIN SHAPIRO LLP
1825 EYE STREET NW
Washington
DC
20006-5403
US
|
Family ID: |
39639883 |
Appl. No.: |
11/987350 |
Filed: |
November 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11524446 |
Sep 21, 2006 |
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11987350 |
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60718748 |
Sep 21, 2005 |
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60718749 |
Sep 21, 2005 |
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60748598 |
Dec 9, 2005 |
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60748599 |
Dec 9, 2005 |
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Current U.S.
Class: |
44/500 ;
44/550 |
Current CPC
Class: |
Y02E 60/36 20130101;
C01B 3/065 20130101; Y02E 60/362 20130101 |
Class at
Publication: |
44/500 ;
44/550 |
International
Class: |
C10L 5/00 20060101
C10L005/00 |
Claims
1. A solid fuel composition comprising at least one chemical
hydride and at least one carboxylic acid.
2. The fuel composition of claim 1, wherein the at least one
carboxylic acid comprises at least one hydroxyl group.
3. The fuel composition of claim 2, wherein the carboxylic acid is
selected from the group consisting of malic acid, tartaric acid,
fumaric acid and citric acid.
4. The fuel composition of claim 1, wherein the at least one
carboxylic acid is fumaric acid.
5. The fuel composition of claim 1, wherein the chemical hydride is
a boron hydride selected from the group consisting of borohydride
salts [M(BH.sub.4).sub.n], triborohydride salts
[M(B.sub.3H.sub.8).sub.n], decahydrodecaborate salts
[M.sub.2(B.sub.10H.sub.10).sub.n], tridecahydrodecaborate salts
[M(B.sub.10H.sub.13).sub.n], dodecahydrododecaborate salts
[M.sub.2(B.sub.12H.sub.12).sub.n], and octadecahydroicosaborate
salts [M.sub.2(B.sub.20H.sub.18).sub.n], where M is an alkali metal
cation, alkaline earth metal cation, aluminum cation, zinc cation,
ammonium cation, alkyl ammonium cation, dialkyl ammonium cation,
triakyl ammonium cation, tetraalkyl ammonium cation, or phosphonium
cation, and n is equal to the charge of the cation.
6. The fuel composition of claim 5 further comprising a
stabilizer.
7. The fuel composition of claim 1, wherein the chemical hydride
comprises a borane compound.
8. The fuel composition of claim 7, wherein the borane compound is
selected from the group consisting of decaborane(14)
(B.sub.10H.sub.14), ammonia borane compounds of formula
NH.sub.xBH.sub.y, and NH.sub.xRBH.sub.y, wherein x and y are
independently selected from 1 to 4, and wherein R is a methyl or
ethyl group.
9. The fuel composition of claim 1, wherein the chemical hydride is
a hydride salt selected from the group consisting of hydrides of
alkali metals and alkaline earth metals.
10. The fuel composition of claim 1, wherein the chemical hydride
is an aluminum hydride selected from the group consisting of alane
(AlH.sub.3) and aluminum hydride salts.
11. The fuel composition of claim 10, wherein the aluminum hydride
salts have the formula M(AlH.sub.4).sub.n, where M is an alkali
metal cation, alkaline earth metal cation, aluminum cation, zinc
cation, or ammonium cation, and n is equal to the charge of the
cation.
12. The fuel composition of claim 1, wherein the composition is in
a form selected from the group consisting of granules, pellets,
gel, tablets and powder, or a combination thereof.
13. The fuel composition of claim 1, wherein the composition is in
the form of a composite comprising at least one layer of the at
least one chemical hydride and at least one layer of the carboxylic
acid.
14. The fuel composition of claim 1, further comprising a
hydrolysis catalyst.
15. The fuel composition of claim 14, wherein the hydrolysis
catalyst comprises a material selected from the group consisting of
chloride salts of cobalt, chloride salts of nickel, chloride salts
of ruthenium, chloride salts of rhodium, chloride salts of
platinum, and chloride salts of copper.
16. A solid fuel composition, comprising: at least one chemical
hydride; at least one carboxylic acid; and a hydrolysis
catalyst.
17. The fuel composition of claim 16, wherein the hydrolysis
catalyst is a metal salt.
18. The fuel composition of claim 17, wherein the metal salt is
selected from the group consisting of chloride salts of cobalt,
chloride salts of nickel, chloride salts of ruthenium, chloride
salts of rhodium, chloride salts of platinum, and chloride salts of
copper.
19. The fuel composition of claim 16, wherein the at least one
carboxylic acid is selected from the group consisting of malic
acid, tartaric acid, fumaric acid, and citric acid.
20. A process for generating hydrogen, comprising: providing a
mixture of at least one chemical hydride and at least one
carboxylic acid; and heating the mixture to generate hydrogen.
21. The process of claim 20, wherein the at least one chemical
hydride comprises sodium borohydride, lithium borohydride, lithium
hydride, or combinations thereof.
22. The fuel composition of claim 20, wherein the carboxylic acid
is selected from the group consisting of malic acid, tartaric acid,
fumaric acid, and citric acid.
23. The process of claim 20 further comprising heating the mixture
to a temperature of between about 40 to about 350.degree. C.
24. The process of claim 20 further comprising heating the mixture
to a temperature above about 100.degree. C.
25. The process of claim 20 further comprising heating the mixture
to a temperature above about 130.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S.
application Ser. No. 11/524,446, filed Sep. 21, 2006, which in turn
claims the benefit of U.S. Provisional Application Ser. No.
60/718,748, filed Sep. 21, 2005, of U.S. Provisional Application
Ser. No. 60/718,749, filed Sep. 21, 2005, of U.S. Provisional
Application Ser. No. 60/748,598, filed Dec. 9, 2005, and of U.S.
Provisional Application Ser. No. 60/748,599, filed Dec. 9, 2005,
the entire disclosures of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to hydrogen storage fuel
compositions comprising a mixture of at least one chemical hydride
compound and at least one compound, polymer, carboxylic acid, or
salt that acts as a water surrogate source. The invention also
relates to methods for thermally initiated hydrogen generation from
fuel compositions.
BACKGROUND OF THE INVENTION
[0003] Hydrogen is the fuel of choice for fuel cells; however, its
widespread use is complicated by the difficulties in storing the
gas. Various nongaseous hydrogen carriers, including hydrocarbons,
metal hydrides, and chemical hydrides, are being considered as
hydrogen storage and supply systems. In each case, systems need to
be developed to release the hydrogen from its carrier, either by
reformation as in the case of hydrocarbons, desorption from metal
hydrides, or catalyzed hydrolysis of chemical hydrides.
DETAILED DESCRIPTION OF THE INVENTION
[0004] The invention provides hydrogen storage compositions
comprising at least one chemical hydride and at least one water
surrogate source. The invention also provides heat-activated
methods of hydrogen generation in which hydrogen is generated by
the hydrolysis reaction of a chemical hydride, which reaction may
be initiated by the application of heat to a mixture comprising at
least one chemical hydride compound and at least one water
surrogate source. Chemical hydride compounds undergo a reaction
with the water surrogate to generate hydrogen, wherein the
stoichiometry is determined by the number of water molecules
necessary for oxidation of the chemical hydride compound. The rate
of hydrogen generation can be accelerated with the application of
heat, or a catalyst, or both.
[0005] Water surrogate sources useful in the invention can be
characterized as "chemical water" or "bound water" defined below. A
mixture of water surrogate sources may be used to control
activation temperature, pH, reaction conditions, and product
properties.
[0006] The term "chemical water" as used in the present invention
encompasses a compound, polymer, or salt that generates water
equivalents via intramolecular or intermolecular reactions that
occur upon warming to a temperature preferably above ambient.
Chemical water species do not contain molecular water in the form
of H.sub.2O molecules. Preferably, the chemical water species
releases the water equivalents at a temperature between about
40.degree. C. to about 350.degree. C., preferably between about
70.degree. C. to about 250.degree. C., and most preferably above
about 100.degree. C.
[0007] Chemical water species can release water equivalents via a
chemical reaction such as dehydration of a compound containing
hydroxyl groups. In this sense, water is not simply water molecules
present in the lattice of a salt, but the water equivalent is a
product of a thermally initiated chemical reaction. Classes of
compounds which undergo such thermal dehydration include, for
example, carbohydrates, borates, carboxylic acids, and allylic
alcohols. It is important to note that, although some compounds and
classes (for example, carbohydrates, sodium metaborate dihydrate,
and magnesium borate trihydrate) contain the term "hydrates" in
their name, they do not necessarily contain free water in the form
of H.sub.2O molecules within their structures. Rather, the water
equivalent is present as hydrogen and oxygen atoms, for example, in
hydroxyl and hydrogen groups, within such compounds or salts.
[0008] The term "bound water" as used in the present invention
encompasses water molecules contained within the structure of a
compound, polymer, or salt, that can be released upon warming to a
temperature above ambient. The water may be released from the bound
water species by various processes, including, but not limited to,
melting, decomposition, or polymorph conversion. Preferably, the
bound water species releases the water at a temperature between
about 40.degree. C. to about 350.degree. C., preferably between
about 40.degree. C. and 250.degree. C., preferably above about
100.degree. C.
[0009] Bound water species include hydrated salts wherein water
molecules are contained in the crystal lattice of a salt. At room
temperature the hydrated salt is in the solid state, but at
elevated temperature "free" water is available for reaction. Many
hydrated salts are polyhydrates and will lose sequential water
molecules at different temperatures. For example, a first water of
hydration can be lost at a temperature T.sub.1, a second water of
hydration can be lost at a second temperature T.sub.2. Bound water
species further include gelled water stored in a hydrated polymer,
some of which can store significant amounts of water. For example,
hydrated polyacrylate has the capability to store a large amount of
water, up to 300 times its own weight.
[0010] Suitable chemical hydrides include, but are not limited to,
boron hydrides, ionic hydride salts, and aluminum hydrides.
Suitable boron hydrides include, without intended limitation, the
group of borohydride salts [M(BH.sub.4).sub.n], triborohydride
salts [M(B.sub.3H.sub.8).sub.n], decahydrodecaborate salts
[M.sub.2(BH.sub.4).sub.n], tridecahydrodecaborate salts
[M(B.sub.3H.sub.8).sub.n], dodecahydrododecaborate salts
[M.sub.2(B.sub.12H.sub.12).sub.n], and octadecahydroicosaborate
salts [M.sub.2(B.sub.20H.sub.18).sub.n], where M is an alkali metal
cation, alkaline earth metal cation, aluminum cation, zinc cation,
ammonium cation, or phosphonium cation, and n is equal to the
charge of the cation; and neutral borane compounds, such as
decaborane(14) (B.sub.10H.sub.14), ammonia borane compounds of
formula NH.sub.xBH.sub.y, wherein x and y independently=1 to 4 and
do not have to be the same, and NH.sub.xRBH.sub.y, wherein x and y
independently=1 to 4 and do not have to be the same, and R is a
methyl or ethyl group. These chemical hydrides may be utilized in
mixtures or individually. As used herein, the term "ammonium
cation" includes unsubstituted (e.g., NH.sub.4.sup.+) and alkyl
substituted (e.g., mono-, di-, tri-, or tetra-alkyl) ammonium
cations.
[0011] Ionic hydrides include, without intended limitation, the
hydrides of alkali metals and alkaline earth metals such as lithium
hydride, sodium hydride, magnesium hydride, and calcium hydride.
Aluminum hydrides include, for example, alane (AlH.sub.3) and
aluminum hydride salts including, without intended limitation,
salts with the general formula M(AlH.sub.4).sub.n, where M is an
alkali metal cation, alkaline earth metal cation, aluminum cation,
zinc cation, or ammonium cation, and n is equal to the charge of
the cation.
[0012] An optional component of any water surrogate source/chemical
hydride system as described above is a metal salt, where the metal
salt can be reduced to a hydrolysis catalyst on exposure to a
chemical hydride, such as, for example, a borohydride. Preferably,
for the greatest storage efficiency, the catalyst precursor is also
a hydrated salt, though non-hydrated salts are suitable.
Nonlimiting examples of metal salts include the chloride salts of
cobalt, nickel ruthenium, rhodium, platinum, and copper, among
others. Examples of hydrated salts include, without intended
limitation, CoCl.sub.2.6H.sub.2O, NiCl.sub.2.6H.sub.2O,
RuCl.sub.3.H.sub.2O, RhCl.sub.3.H.sub.2O, PtCl.sub.4.5H.sub.2O, and
CuCl.sub.2.2H.sub.2O. The borohydride or other suitable chemical
hydride will react with the transition metal salt to form a
metal-based hydrolysis catalyst. The catalyst helps promote the
reaction even in a basic environment.
[0013] Optionally, the boron or other chemical hydride fuel
component may be combined with a stabilizer agent. Stabilized fuel
compositions comprising borohydride and hydroxide salts are
disclosed in co-pending U.S. patent application Ser. No. 11/068,838
entitled "Borohydride Fuel Composition and Methods" and filed on
Mar. 2, 2005, the disclosure of which is incorporated by reference
herein in its entirety.
[0014] The water surrogate source/chemical hydride compositions are
preferably solids, and may be powders, caplets, tablets, pellets or
granules, for example. In some embodiments, the water surrogate
source/chemical hydride compositions are liquid or gelatinous. For
example, the admixture of certain hydrated salts and chemical
hydride compounds may produce a eutectic, e.g., a mixture of two or
more components which has a lower melting point than any of its
constituents, and the resultant mixture is in the liquid state at
ambient temperature. The individual components may be physically
mixed together and/or held in close contact. The water surrogate
source and chemical hydride components may be combined into a
pellet, caplet, gel, or tablet comprising at least two components.
Alternatively, the water surrogate source and chemical hydride may
be held in close contact as separate layers in, for example, a
composite. The water surrogate source and chemical hydride are
combined in proportions ranging from a 4-fold molar excess of the
stoichiometric ratio of water equivalent to a 4-fold excess of the
stoichiometric ratio of chemical hydride based on the
stoichiometric ratio required by the hydrolysis reaction.
Preferably, the water surrogate source and chemical hydride are
combined in proportions equivalent to the stoichiometric ratio of
water equivalent to chemical hydride required by the hydrolysis
reaction. As used herein, molar water equivalent means the number
of moles of water a water surrogate source provides.
[0015] Hydrogen is generated from the water surrogate
source/chemical hydride mixtures when heat is applied to the
mixture. Heating elements suitable for use in the invention
include, but are not limited to, resistance heaters,
nickel-chromium resistance wires, and heat exchangers. The heating
can be achieved, for example, by placing the materials in a reactor
and heating the reactor, or by bringing a heating element in
contact with the water surrogate source/chemical hydride
mixture.
[0016] In one embodiment of the invention, fuel compositions
comprise a mixture of at least one carbohydrate with at least one
chemical hydride. For the purposes of determining stoichiometry,
the carbohydrates can be written as, for example,
C.sub.x(H.sub.2O).sub.y compounds or C.sub.xH.sub.2(H.sub.2O).sub.y
compounds where x and y are integers; other stoichiometric ratios
can be determined using the teachings herein. For example, one mole
of C.sub.6H.sub.12O.sub.6 has a molar water equivalent of 6 when
written as C.sub.6(H.sub.2O).sub.6, wherein the water may be
obtained by a dehydration mechanism such as that illustrated in
Equation (1) for a monosaccharide. The disaccharides and
polysaccharides undergo dehydration of the hydroxyl groups in a
similar fashion.
C.sub.6H.sub.12O.sub.6.fwdarw.6C+6H.sub.2O (1)
[0017] The class of carbohydrates includes monosaccharides such as
the hexoses (e.g., glucose, fructose, mannose, and galactose), the
pentoses (e.g., ribose, and xylose), the tetroses (e.g. erythrose);
disaccharides such as sucrose; polysaccharides such as starch,
cellulose, and glycogen; and sugar alcohols such as mannitol,
sorbitol, xylitol, inositol, and glycerol. In the carbohydrate
case, both aldoses and ketoses are suitable.
[0018] In a second embodiment of the invention, fuel compositions
comprise a mixture of at least one carboxylic acid with at least
one chemical hydride. Preferably, the carboxylic acid contains at
least one hydroxyl group (i.e., is a hydroxyacid) or at least two
carboxyl groups (i.e., is a dicarboxylic acid). Carboxylic acids
will undergo intermolecular or intramolecular condensation
reactions to form anhydrides with the generation of at least one
water equivalent. Hydroxyacids can undergo an intermolecular or an
intramolecular dehydration reaction to yield at least one water
equivalent. The following are non-limiting examples of carboxylic
acids suitable for use as water surrogates: malic acid (an
.alpha.-hydroxy acid with formula
CO.sub.2H(CH)(OH)CH.sub.2CO.sub.2H) will dehydrate to yield fumaric
acid (CO.sub.2H(CH).sub.2CO.sub.2H) at around 130.degree. C. with
the loss of one water equivalent, and maleic anhydride at around
180.degree. C. with the loss of a second water equivalent; citric
acid will decompose at temperatures above about 175.degree. C. to
yield carbon dioxide and water; and tartaric acid will undergo
dehydration which may be accompanied with decarboxylation to
produce an anhydride, acetic acid, or pyruvic acid at temperatures
between about 100 and 200.degree. C. preferably between about 120
to 180.degree. C.
[0019] In another embodiment of the present invention, fuel
compositions according to the present invention may comprise
mixtures of at least one chemical hydride with at least one
hydrated salt. Suitable hydrated salts include, without intended
limitation, borates, chlorides, phosphates, carbonates, bisulfates,
and sulfates, wherein the cation is an alkali metal ion, an
alkaline earth metal ion, zinc ion, aluminum ion, or ammonium ion,
or a combination thereof as in a double salt. Representative
examples of hydrated salts include, without intended limitation,
magnesium sulfate heptahydrate (MgSO.sub.4.7H.sub.2O, a molar water
equivalent of 7), magnesium chloride hexahydrate
(MgCl.sub.2.6H.sub.2O, a molar water equivalent of 6), trisodium
phosphate (Na.sub.3PO.sub.4.12H.sub.2O, a molar water equivalent of
12), calcium sulfate dihydrate (CaSO.sub.4.2H.sub.2O, a molar water
equivalent of 2), sodium carbonate decahydrate
(Na.sub.2CO.sub.3.10H.sub.2O), aluminum sulfate octadecahydrate
(Al.sub.2(SO.sub.4).sub.3.18H.sub.2O), sodium aluminum sulfate
(NaAl(SO.sub.4).sub.2.12H.sub.2O, a molar water equivalent of 12),
and potassium aluminum sulfate (KAl(SO.sub.4).sub.2.12H.sub.2O);
the molar water equivalent of such salts is determined by the moles
of water contained within a mole of hydrate. Salts can be chosen
for use in fuel compositions according to the teachings herein by
consideration of the weight fraction of water in the hydrated
solid, the temperature of water-release, the presence of a cation
and anion that cannot be reduced by the chemical hydride, and
molecular weight.
[0020] In a further embodiment of the present invention, fuel
compositions may comprise mixtures of at least one chemical hydride
with at least one borate salt. Many of the borate salts contain a
portion of their water as waters of hydration and a portion as
hydroxyl groups, and can be written in the format j
M.sub.2O.sub.n.k B.sub.2O.sub.3.XH.sub.2O, wherein n is equal to
the charge of the metal cation M. The molar water equivalent of
such salts is represented by XH.sub.2O.
[0021] Representative examples of borates useful as water
surrogates in the embodiments described above, include, without
intended limitation, sodium tetraborate decahydrate
(Na.sub.2B.sub.4O.sub.7.10H.sub.2O,
Na.sub.2O.2B.sub.2O.sub.3.10H.sub.2O); sodium tetraborate
pentahydrate (Na.sub.2B.sub.4O.sub.7.5H.sub.2O, or
Na.sub.2O.2B.sub.2O.sub.3.5H.sub.2O); sodium metaborate
tetrahydrate (NaBO.sub.2.4H.sub.2O, or
1/2Na.sub.2O.2B.sub.2O.sub.3.4H.sub.2O), disodium tetraborate
tetrahydrate (Na.sub.2B.sub.4O.sub.7.4H.sub.2O, or
Na.sub.2O.2B.sub.2O.sub.3.4H.sub.2O), ulexite
(NaCaB.sub.5O.sub.9.8H.sub.2O, or
1/2Na.sub.2O.CaO.5/2B.sub.2O.sub.3.8H.sub.2O), probertite
(NaCaB.sub.5O.sub.95H.sub.2O, or
1/2Na.sub.2O.CaO.5/2B.sub.2O.sub.3.5H.sub.2O), lithium pentaborate
pentahydrate (LiB.sub.5O.sub.8.5H.sub.2O, or
1/2Li.sub.2O.5/2B.sub.2O.sub.3.5 H.sub.2O), potassium tetraborate
tetrahydrate (K.sub.2B.sub.4O.sub.7.4H.sub.2O, or
K.sub.2O.2B.sub.2O.sub.3.4H.sub.2O); ammonium pentaborate
octahydrate (NH.sub.4B.sub.5O.sub.8.4H.sub.2O, or
(NH.sub.4).sub.2O.5B.sub.2O.sub.3.8H.sub.2O), zinc borate
heptahydrate (2ZnO.3B.sub.2O.sub.3.7 to 7.5H.sub.2O), zinc borate
nonahydate (2ZnO.3B.sub.2O.sub.3.9H.sub.2O), sodium metaborate
dihydrate (NaB(OH).sub.4, or
1/2Na.sub.2O.1/2B.sub.2O.sub.3.2H.sub.2O), sodium pentaborate
pentahydrate (NaB.sub.5O.sub.8.5H.sub.2O, or
1/2Na.sub.2O.5/2B.sub.2O.sub.3.5H.sub.2O), and pinnoite
(MgB.sub.2O.sub.4.3H.sub.2O, or MgO.B.sub.2O.sub.3.3H.sub.2O).
Disodium tetraborate tetrahydrate
(Na.sub.2B.sub.4O.sub.7.4H.sub.2O, or
Na.sub.2O.2B.sub.2O.sub.3.4H.sub.2O), sodium metaborate dihydrate
(NaB(OH).sub.4, or 1/2Na.sub.2O.1/2B.sub.2O.sub.3.2H.sub.2O), and
pinnoite (MgB.sub.2O.sub.4.3H.sub.2O, or
MgO.B.sub.2O.sub.3.3H.sub.2O) do not contain any waters of
hydration; the application of heat to such compounds produces a
water equivalent and a boron oxide compound.
[0022] In another embodiment, fuel compositions according to the
present invention may comprise mixtures of at least one chemical
hydride with gelled water stored in a hydrated polymer such as
polyacrylic acid [PAA], polyacrylamide, poly(2-hydroxyethyl
methacrylate) [poly-HEMA], poly(iso-butylene-co-maleic acid),
poly(acrylic acid-co-acrylamide). The cation and degree of
cross-linking of the polymer can be varied to change the water
uptake properties and alter physical and chemical characteristics
such as viscosity. The molar water equivalents of such hydrated
polymers are determined by the amount of water carried by the gel.
We have demonstrated that it is possible to make a stable gel by
mixing poly-HEMA powder with an aqueous alkaline sodium borohydride
solution to produce a gel that produces hydrogen when heat is
applied.
[0023] In another embodiment of the present invention, fuel
compositions may comprise mixtures of at least one chemical hydride
with at least one bicarbonate salt, wherein the cation is an alkali
metal ion, an alkaline earth metal ion, zinc ion, aluminum ion, or
ammonium ion. The bicarbonate salts contain hydroxyl groups that
can be converted to oxides and water. For example, sodium
bicarbonate is converted to sodium carbonate, carbon dioxide, and
water at temperatures between about 50 to about 100.degree. C., as
illustrated in Equation (2).
2NaHCO.sub.3.fwdarw.Na.sub.2CO.sub.3+H.sub.2O+CO.sub.2 (2)
[0024] The following examples further describe and demonstrate
features of the present invention. The examples are given solely
for the purpose of illustration and are not to be construed as a
limitation of the present invention.
EXAMPLE 1
[0025] A mixture of sodium borohydride and D-fructose
(C.sub.6H.sub.12O.sub.6, 6 molar water equivalent) was combined in
a ratio of 1 mole sodium borohydride to 1 mole of fructose
(alternatively described as a ratio of 1 mole of sodium borohydride
to 6 molar water equivalents), and loaded into a Parr autoclave
reactor. The reaction temperature was stepped from room temperature
to about 70.degree. C. and then to about 250.degree. C. Hydrogen
generation was initiated at about 70.degree. C., with complete
conversion of borohydride to hydrogen at about 250.degree. C. The
amount of hydrogen generated was equivalent to 3.7 wt-% of the
reactants' weight.
EXAMPLE 2
[0026] A mixture of sodium borohydride and magnesium chloride
hexahydrate (MgCl.sub.2. 6H.sub.2O, 6 molar water equivalent) was
loaded into a Parr autoclave reactor. As the reactor temperature
increased to about 110.degree. C., limited hydrogen gas pressure in
the reactor was observed with about 21% borohydride conversion to
hydrogen. Borohydride conversion increased from about 21% to about
74%, as the reactor temperature was increased to about 150.degree.
C. in about 100 minutes. The amount of hydrogen generated was
equivalent to 4.6% of the reactants' weight.
EXAMPLE 3
[0027] A mixture of sodium borohydride and borax decahydrate
(Na.sub.2B.sub.4O.sub.7.10H.sub.2O, 10 molar water equivalent) in a
ratio of 2 moles sodium borohydride to 1 mole borax decahydrate
(or, alternatively described as a ratio of 2 moles of sodium
borohydride to 10 molar water equivalents) was loaded into a
cylindrical glass reactor with 2 wt-% CoCl.sub.2.6H.sub.2O
catalyst. The reaction was carried out in a semi-batch mode. The
generated hydrogen was measured through a mass flow meter. The
reactor was heated by using an oil bath. Hydrolysis of borohydride
was initiated at 70.degree. C., and the hydrogen generation rate
reached 600 standard cubic centimeters (sccm). The amount of
hydrogen generated was equivalent to a hydrogen storage density of
3.5 wt-% of the combined weight of reactants.
EXAMPLE 4
[0028] At room temperature, poly (2-hydroxyethyl methacrylate)
[poly(2-HEMA)] (Mv=1,000,000) was added in 3:1 ratio by weight to a
fuel solution comprising 20 wt-% sodium borohydride and 3 wt-%
sodium hydroxide. After the addition of poly (2-HEMA), the liquid
fuel turned into gel. Thermogravimetric analysis (TGA) of the poly
(2-HEMA)/fuel mixture indicated that water was released from the
gel at elevated temperature. With a 10.degree. C./min heating rate
starting from room temperature, hydrolysis of sodium borohydride
and hydrogen generation was observed at a temperature of about
150.degree. C.
EXAMPLE 5
[0029] A mixture of lithium hydride and D-fructose
(C.sub.6H.sub.12O.sub.6, 6 molar water equivalent) was combined in
a ratio of 12 moles of lithium hydride to 1 mole of fructose and
loaded into a Parr autoclave reactor. The reaction temperature was
stepped every 50.degree. from room temperature to 300.degree. C.
Hydrogen generation was initiated at about 70.degree. C. with about
50% of the hydride converted to hydrogen. The amount of hydrogen
generated was equivalent to about 4.0% of the reactants'
weight.
[0030] While the present invention has been described with respect
to particular disclosed embodiments, it should be understood that
numerous other embodiments are within the scope of the present
invention. It is not intended that the present invention be limited
to the illustrated embodiments. Any modification of the present
invention that comes within the spirit and scope of the following
claims should be considered part of the present invention.
* * * * *