U.S. patent application number 13/848573 was filed with the patent office on 2014-01-09 for hyrdrogen generator for fuel cells.
This patent application is currently assigned to Spawnt Private SarL. The applicant listed for this patent is Spawnt Private SarL. Invention is credited to Julius Pretterebner.
Application Number | 20140010717 13/848573 |
Document ID | / |
Family ID | 38941847 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140010717 |
Kind Code |
A1 |
Pretterebner; Julius |
January 9, 2014 |
HYRDROGEN GENERATOR FOR FUEL CELLS
Abstract
The invention relates to a hydrogen generator for fuel cells
based on silanes. A process for supplying a fuel cell with hydrogen
includes the steps: intermediate storage of (poly)silanes or
(poly)silane solutions; transfer of the (poly)silanes to a reaction
chamber; reaction or hydrolysis of the silanes or silane solutions
in the reaction chamber with an aqueous solution to liberate H2;
removal of the solid and/or liquid reaction products from the
reaction chamber; transfer of the H2 formed to the fuel cell.
Inventors: |
Pretterebner; Julius;
(Oppenweiler, DE) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Spawnt Private SarL; |
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|
US |
|
|
Assignee: |
Spawnt Private SarL
Luxembourg
LU
|
Family ID: |
38941847 |
Appl. No.: |
13/848573 |
Filed: |
September 25, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12364001 |
Feb 2, 2009 |
8435476 |
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13848573 |
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PCT/EP2007/006855 |
Aug 2, 2007 |
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12364001 |
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Current U.S.
Class: |
422/162 |
Current CPC
Class: |
Y02E 60/36 20130101;
Y02E 60/50 20130101; H01M 8/065 20130101; H01M 8/04216 20130101;
B01J 14/00 20130101; Y02E 60/32 20130101 |
Class at
Publication: |
422/162 |
International
Class: |
B01J 14/00 20060101
B01J014/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2006 |
DE |
10 2006 036 227.6 |
Aug 25, 2006 |
DE |
10 2006 039 869.6 |
Claims
1. A hydrogen generator for fuel cells comprising: an intermediate
storage facility for solutions selected from the group consisting
of fluid silanes, silane solutions and polysilane solutions; an
intermediate storage facility for an aqueous solution; a reaction
chamber having at least two fluid inlet pipes coming from the
intermediate storage facilities; and a separating device for
separating H.sub.2 gas from conversion products.
2. The hydrogen generator according to claim 1, characterized in
that the reaction chamber contains a device for mixing a solution
selected from the group consisting of fluid silane or silane
solution with the aqueous solution.
3. The hydrogen generator according to claim 1, characterized in
that the intermediate storage facility has an inlet pipe for the
water which is generated as conversion water in the fuel cell.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S.
application Ser. No. 12/364,001, filed on Feb. 2, 2009 and titled
"PROCESS FOR SUPPLYING A FUEL CELL WITH HYDROGEN BY MEANS OF
SILANES OR POLYSILANES", which is a continuation of International
Application No. PCT/EP2007/006855 filed on Aug. 2, 2007, which
claims the benefit of DE 10 2006 036 227.6, filed Aug. 3, 2006 and
DE 10 2006 039 869.6, filed Aug. 25, 2006. The disclosures of the
above applications are incorporated herein by reference.
FIELD
[0002] The invention concerns a process for supplying a fuel cell
with hydrogen, wherein solutions storable in liquid or solid form,
which split the hydrogen, are utilized as hydrogen carriers. It
concerns in particular the utilization of specific materials as
hydrogen storage material for supplying a fuel cell with
hydrogen.
BACKGROUND
[0003] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0004] The problem of storing fuel (hydrogen carrier or H.sub.2)
has still not been satisfactorily solved for the broad use of fuel
cells, for example, in motor vehicles. Different methods for the
storage of H.sub.2 are known:
[0005] Pressure storage of H.sub.2 in pressure vessels at up to 700
bar;
[0006] Pressureless storage as liquid H.sub.2 in cryogenic dewars
at temperatures of below -253.degree. C.;
[0007] Storage in metals or metal alloys that form
thermo-reversible intercalation compounds (metallic hydrides) with
H.sub.2;
[0008] Storage in form of hydrogen-rich organic compounds, such as,
for example, methane, methanol, benzene, etc., which are subjected
to a reformation reaction in order to release H.sub.2;
[0009] Storage in form of H.sub.2O, which is decomposed into
H.sub.2 with suitable metals (for example, Li, Na, K, Mg,
etc.);
[0010] Storage in form of salt-like metal hydrides (for example,
NaH, LiH, etc.), which are decomposed into H.sub.2 with
H.sub.2O;
[0011] Storage in form of complex metal hydrides, for example,
LiAIH.sub.4, NaBH.sub.4, etc., which are decomposed into H.sub.2
with H.sub.2O.
[0012] Most of the aforementioned methods are technically or
energetically very complex, and allow only the storage of very low
quantities of H.sub.2, or are not controllable from the point of
view of safety for broader applications.
[0013] From DE 601 08 744 T2 is known a process for producing
hydrogen for a fuel cell. The process steps comprise the conversion
of a metal hydride, which is different from NaAlH.sub.4, with at
least one alcohol, wherein hydrogen is formed, and the hydrogen is
fed into a hydrogen chamber of a fuel cell. Hydrides of the metals
Li, Na, K, Mg, Ca, Zr and Ti are mentioned as particularly suitable
hydrides. Compounds having the formula M2.sub.vM3.sub.wH.sub.y are
presented as particularly suitable complex hydrides, wherein M2 is
a metal selected from among the group consisting of Li, Na, K, Mg,
Ca, Fe and Zr; M3 is selected from among the group consisting of
Al, B, Be and Ti.
[0014] One of the disadvantages of H.sub.2 storage with the aid of
metal hydrides is that metal hydrides or complex metal hydrides are
solids as a rule. These solids are difficult to store, deliver and
meter. They are frequently insoluble. Fueling with these substances
represents already a not inconsiderable problem, in particular in
motor vehicles. The delivery of metal hydride from the storage tank
to a hydrogen generator that may be necessary in the motor vehicle
is also difficult. A further disadvantage is that the degradation
products or hydrolysis products of metal hydrides are generally
highly corrosive brines, in particular LiOH, NaOH, KOH,
Ca(OH).sub.2, etc. These degradation products are highly corrosive
and harmful to the environment. These substances are also
questionable with regard to their environmental safety because
unintentional release and therefore the formation of degradation
products can always be expected when these substances are utilized
in large scale.
SUMMARY
[0015] The teachings of the present disclosure make available a
hydrogen storage material with improved manageability with regard
to storage, delivery and dosage, and also better environmental
safety, as well as to disclose a suitable process for making
available hydrogen for fuel cells.
[0016] This is achieved according to the present disclosure by
means of a process for supplying a fuel cell with hydrogen
comprising the steps of:
[0017] Temporarily storing silanes or silane solutions in liquid
form;
[0018] Transferring the silanes or silane solutions into a reaction
chamber;
[0019] Converting the silanes or silane solutions in the reaction
chamber with an aqueous solution in order to release H.sub.2;
[0020] Separating the solid and/or liquid reaction products from
the reaction chamber;
[0021] Transferring the formed H.sub.2 into the fuel cell having
the features of claim 1, as well as by means of a process for
supplying a fuel cell with hydrogen comprising the steps of:
[0022] Temporarily storing polysilanes in solid form or from
polysilane solutions;
[0023] Transferring the polysilanes or polysilane solutions into a
reaction chamber;
[0024] Converting the polysilanes in the reaction chamber with an
aqueous solution or water vapor in order to release H.sub.2;
[0025] Separating the solid and/or liquid reaction products from
the reaction chamber; and
[0026] Transferring the formed H.sub.2 into the fuel cell having
the features of claim 2.
[0027] Another form of the present disclosure is achieved by a
hydrogen generator for fuel cells having the features of claim 18
as well as by utilizing silanes having the features of claims 21
and 22.
[0028] According to the present disclosure, silanes or polysilanes
are utilized as storage medium for hydrogen (hydrogen storage
material) or as hydrogen carriers. The silanes can be available in
liquid or dissolved form, the polysilanes in solid or dissolved
form. The silanes are binary compounds having the general formula
Si.sub.nH.sub.2n+2. They are the Si analogs of alkanes.
[0029] The difference between silanes and polysilanes resides in
their molecular weight or the magnitude of n, wherein those that
are still liquid under normal conditions are frequently called
silanes, and those that are solid are called polysilanes. The
silanes with n up to about 20 are called silanes according to the
invention, and the name polysilane is selected beyond that. Silanes
and/or polysilanes should be understood as (poly)silanes.
[0030] It is particularly advantageous for the present disclosure
if the (poly)silanes in liquid form are available in mobilized or
mobilizable form. The mobilization is achieved if necessary by
dissolving in a solvent. This has the advantage that an easy
manageability of the hydrogen storage material is possible.
[0031] The solvent has the further advantage that it can reduce the
reactivity of the silanes, and that undesirable decomposition
reactions during storage are thus prevented.
[0032] However, it is also possible to use the polysilanes as
solids, even though this also requires other delivery means than
with the liquid variants.
[0033] The silanes can here be available in pure form. Mixtures of
silanes with few mass fractions of different additives are also
understood within the meaning of the invention by these. The
silanes can in turn be mixtures of the different representatives of
the substance class of the silanes.
[0034] Stabilizers, antioxidants or catalysts are taken especially
into consideration as additives.
[0035] The silanes can also be available in solution, wherein the
mentioned additives can likewise be admixed. The utilization of
solvents has the advantage that the selection of suitable silanes
is expanded, the mixability with additives is improved, and the
storage can be improved. Solutions of polysilanes with silanes are
also suitable hydrogen storage materials.
[0036] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DETAILED DESCRIPTION
[0037] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0038] In one form of the present disclosure, the silanes or silane
solutions are temporarily stored in liquid form. Holding tanks in
motor vehicles or liquid tanks in particular should be understood
as temporary storage tanks. The temporary storage tank can be
operated without pressure or under mild overpressure. A mild
overpressure can be appropriate when volatile silanes are utilized.
Pressure vessels represent preferred embodiments in particular in
stationary systems or fueling systems. The overpressure is
preferably limited to between 0.1 and 1 bar. However, the temporary
storage tank is particularly preferably not under pressure, in
particular for mobile applications, such as in motor vehicles.
[0039] The polysilanes can likewise be temporarily stored in
solution.
[0040] In a further embodiment, the polysilanes are stored
temporarily in solid form and are only to be mobilized in liquid
form with a solvent for transfer into the reaction chamber.
[0041] In a next step, it is provided that the (poly)silanes or
their solutions are to be transferred from the temporary storage
tank into a reaction chamber. In contrast with the solid hydrogen
storage tanks, a separation between storage and hydrogen production
can be carried out easily here. This is of particular interest with
regard to the separation of the reaction products arising during
hydrogen production.
[0042] The reaction chamber can be configured, for example, as a
continuous reactor, in particular as a continuous flow reactor. The
silane or silane solution can be added into a reaction chamber
filled with aqueous solution, but can also be placed in the
reaction chamber and water or aqueous solution can be added.
[0043] The hydrolysis or conversion of the (poly)silanes takes
placed with an aqueous solution in the reaction chamber. The
silanes or polysilanes are hydrolyzed herein while forming silicic
acids and releasing H.sub.2. The silicic acids can occur in
different forms depending on the hydrolysis degree and pH value. It
is possible in this way, for example, to obtain colloidal dissolved
silicic acids or silica sols or also to form solid SiO.sub.2 with
corresponding intermediate forms.
[0044] Alkaline pH values are preferably adjusted, in particular by
means of NaOH, which make possible the formation of silica sols or
dissolved silicic acids.
[0045] The temporary storage tank and reaction chamber can also be
constructively consolidated in the event of solid polysilanes. This
means that the aqueous solution is guided across or through the
polysilane and hydrogen and the reaction products are formed. The
reaction products are suitably separated thereafter from the
polysilanes that are insoluble in water as colloidal dissolved
silicic acids or silica sols in liquid form and are washed out of
the reaction chamber/temporary storage tank.
[0046] The separation of the solid and/or liquid reaction products
from the reaction chamber is carried out in the next step.
[0047] In a process of the present disclosure, it is desirable that
the formed hydrolysis products be easy to separate from the system.
The process has a particularly simple configuration in particular
with regard to the solid hydrogen storage materials. If the formed
silicic acid precipitates as colloidal solution, then it can be
discharged from the reaction chamber, for example, with excess
reaction water. This takes place particularly easily in a
continuous flow reactor. The solid silicic acid can also be flushed
out of the reaction chamber by means of water. It may also be
practical to mechanically remove the solid reaction products.
[0048] The separation of the silicic acid from the solid
polysilanes is carried out in one form by flushing with alkaline
aqueous solution.
[0049] The hydrogen formed is transferred into the fuel cell or
into the fuel cell unit, in one form, at temperatures above about
80.degree. C.
[0050] The silanes or (poly)silanes are typically transferred in
liquid form into the reaction chamber.
[0051] In a further variant, it is provided that the silanes or
part of the silanes are caused to evaporate directly ahead of or in
the reaction chamber. A vaporizer can be provided if necessary
between the reaction chamber and the temporary storage tank.
Evaporation is particular appropriate when volatile silanes are
utilized. The reaction energy released during the hydrolysis of the
silanes can be advantageously utilized to evaporate the
silanes.
[0052] The silanes are preferably selected from among linear or
branched silanes having the general formula Si.sub.nH.sub.2n+2,
wherein n=1, 2, 3, 4, 5, 6, 7 or 8.
[0053] Si.sub.3H.sub.8 and n--S.sub.4H.sub.10 or i--S.sub.4H.sub.10
are liquid at room temperature and are used particularly well
therefore in pure form, especially with admixtures of stabilizers.
The addition of stabilizers against oxidation and hydrolysis during
storage is appropriate in this connection.
[0054] Silanes that are liquid at room temperature are preferably
utilized as hydrogen storage material to supply a fuel cell with
hydrogen.
[0055] Si.sub.3H.sub.8 is particularly preferred as hydrogen
storage material for supplying a fuel cell with hydrogen.
[0056] Preferred mixtures of pure silanes comprise Si.sub.3H.sub.8
and n--S.sub.4H.sub.10 or i--Si.sub.4H.sub.10 in proportions of 1:1
to 1:20.
[0057] Si.sub.2H.sub.6 has a boiling point of -14.degree. C. and
must be kept under mild overpressure when used in pure form. It is
however also suitable as minor constituent in a silane mixture or
silane solution with heavy homologous silanes. It acts herein as a
diluter or liquefier.
[0058] Further preferred mixtures of pure silanes consist of
Si.sub.2H.sub.6, Si.sub.3H.sub.8 and n--S.sub.4H.sub.10 or
i--S.sub.4H.sub.10 in proportions of 0.5:1:1 to 0.5:1:50.
[0059] The higher homologues of the silanes with n>4 are
increasingly chemically instable in pure form. They are therefore
preferably used in solution and with additions of stabilizers. It
may also be practical to utilize higher silanes with n>4 as
minor constituents of low silanes in pure form or particularly
preferably in their solution.
[0060] Among polysilanes, those are preferred with polymerization
degrees n>100. n is particularly preferably on the average
higher than about 500.
[0061] If a silane solution or polysilane solution is utilized,
then it is preferably essentially composed of (poly)silanes and a
carrier liquid of aprotic organic solvents. The organic solvents
comprise mineral oils and/or alkanes with about 6 to about 14
carbon atoms. Cyclic ethers can also be suitable.
[0062] The aqueous solutions used for the conversion of
(poly)silanes comprise pure water or water with additives. A class
of additives is represented by low alcohols. The alcohols are also
suitable for splitting the Si--H bond and releasing hydrogen. The
reactivity of the alcohols and the released reaction heat is lower
when compared to that of water. The reaction in the reaction
chamber can be better controlled if required via mixtures of
H.sub.2O and alcohols. Low alcohols, C1 to C3 alcohols, in
particular methanol and ethanol are preferred.
[0063] Mineral acids or alkalis should be mentioned as further
additives in the aqueous solution, which are used to adjust the pH
value in the reactor to acid or alkaline. They have a catalytic
effect on the hydrolysis of (poly)silanes. Alkaline conditions are
preferably adjusted, for example, by utilizing sodium hydroxide.
The reactivity of the silanes is increased in this way and the
solubility of the silicic acid that forms during the hydrolysis is
improved and also the formation of a liquid silica sol is
promoted.
[0064] It can also be appropriate, however, to adjust to acid
conditions in order to precipitate solid silicic acid or solid
SiO.sub.2 from the aqueous medium. This solid can then be extracted
from the system by means of filter units.
[0065] Other catalysts can also be arranged in the reaction
chamber. Metal catalysts, for example, steel wool, are preferred
herein.
[0066] Another aspect of the present disclosure concerns a hydrogen
generator for fuel cells, which comprises:
[0067] a temporary storage tank for liquid silanes, silane
solutions or polysilane solutions;
[0068] a temporary storage tank for aqueous solution;
[0069] a reaction chamber into which lead at least two liquid
supply lines from the two temporary storage tanks;
[0070] a separator for separating the H.sub.2 gas from the solid
and/or liquid reaction products.
[0071] The reaction chamber preferably contains a mixing device for
liquid silane or silane solution together with the aqueous
solution.
[0072] Another form of the reaction chamber is a continuous flow
reactor in which the silanes or silane solution are introduced into
the aqueous solution and mixed through.
[0073] A form of the hydrogen generator provides that the water
formed during the fuel call reaction is fed back into the temporary
storage tank, or also directly into the reaction chamber. In this
way, it becomes possible to reduce the amount of temporarily stored
water, since the waste water produced during the operation of the
fuel cell is utilized for hydrolysis of the (poly)silanes. Another
advantage of the utilization of waste water is that the water
produced during the fuel cell reaction frequently precipitates as
vapor or hot water, and the hydrolysis reaction can be carried out
at a high temperature level in the reaction chamber without having
to undertake a heating of the hydrolysis water.
[0074] The temporary storage tank and/or the reaction chamber are
here connected via supply lines to the exhaust system of the fuel
cell.
[0075] It should be noted that the disclosure is not limited to the
embodiments described and illustrated as examples. A large variety
of modifications have been described and more are part of the
knowledge of the person skilled in the art. These and further
modifications as well as any replacement by technical equivalents
may be added to the description and figures, without leaving the
scope of the protection of the disclosure and of the present
patent.
* * * * *