U.S. patent application number 10/424605 was filed with the patent office on 2003-10-02 for method for low temperature catalytic production of hydrogen.
This patent application is currently assigned to Brookhaven Science Associates LLC. Invention is credited to Mahajan, Devinder.
Application Number | 20030185749 10/424605 |
Document ID | / |
Family ID | 25223152 |
Filed Date | 2003-10-02 |
United States Patent
Application |
20030185749 |
Kind Code |
A1 |
Mahajan, Devinder |
October 2, 2003 |
Method for low temperature catalytic production of hydrogen
Abstract
The invention provides a process for the catalytic production of
a hydrogen feed by exposing a hydrogen feed to a catalyst which
promotes a base-catalyzed water-gas-shift reaction in a liquid
phase. The hydrogen feed can be provided by any process known in
the art of making hydrogen gas. It is preferably provided by a
process that can produce a hydrogen feed for use in proton exchange
membrane fuel cells. The step of exposing the hydrogen feed takes
place preferably from about 80.degree. C. to about 150.degree.
C.
Inventors: |
Mahajan, Devinder; (South
Setauket, NY) |
Correspondence
Address: |
BROOKHAVEN SCIENCE ASSOCIATES/
BROOKHAVEN NATIONAL LABORATORY
BLDG. 475D - P.O. BOX 5000
UPTON
NY
11973
US
|
Assignee: |
Brookhaven Science Associates
LLC
|
Family ID: |
25223152 |
Appl. No.: |
10/424605 |
Filed: |
April 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10424605 |
Apr 28, 2003 |
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09817468 |
Mar 26, 2001 |
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6596423 |
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Current U.S.
Class: |
423/648.1 ;
423/652 |
Current CPC
Class: |
C01B 2203/0205 20130101;
C01B 2203/1041 20130101; B01J 2531/821 20130101; C01B 2203/0283
20130101; B01J 2531/824 20130101; B01J 2531/845 20130101; B01J
2531/828 20130101; B01J 2531/847 20130101; C01B 3/48 20130101; Y02P
20/52 20151101; C01B 2203/066 20130101; C01B 2203/1205 20130101;
C01B 3/16 20130101; B01J 2531/827 20130101; B01J 31/183 20130101;
B01J 31/1815 20130101; B01J 31/1805 20130101; B01J 2531/16
20130101; B01J 2531/842 20130101; B01J 2531/822 20130101 |
Class at
Publication: |
423/648.1 ;
423/652 |
International
Class: |
C01B 003/02 |
Goverment Interests
[0001] This invention was made with Government support under
contract number DE-AC02-98CH10886, awarded by the U.S. Department
of Energy. The Government has certain rights in the invention.
Claims
1. A process for catalytic production of a hydrogen feed which
comprises: providing a hydrogen feed; and exposing said hydrogen
feed to a catalyst which promotes a water-gas-shift reaction in a
liquid phase.
2. The process of claim 1, wherein said hydrogen feed is provided
by steam reforming, oxidation of methanol, oxidation of methane,
oxidation of biomass, coal gasification or gasification of organic
wastes, plastics wastes farm wastes or wood chips
3. The process of claim 1 wherein said exposing step is conducted
in a temperature range from about 80.degree. C. to about
150.degree. C.
4. The process of claim 1, wherein formate is formed in a
base-catalyzed water-gas-shift reaction.
5. The process of claim 4, wherein said water-gas-shift reaction is
conducted in the presence of a base added in an effective amount to
promote formate formation.
6. The process of claim 5, wherein said exposing step is conducted
at a pH greater than 8.
7. The process of claim 5, wherein said base is selected from
hydroxides, alkoxides, carbonates, bicarbonates of lithium, sodium,
potassium or cesium, amines having C.sub.1 to C.sub.4 or mixtures
thereof.
8. The process of claim 1, wherein said catalyst is a homogenous
transition metal complex.
9. The process of claim 8, wherein said transition metal is
selected from the group consisting of Ru, Ni, Rh, Pt, Co, Cu, Pd,
Ir and Fe.
10. The process of claim 8, wherein said catalyst is a transition
metal coupled to at least one N-donor ligand.
11. The process of claim 10, wherein said N-donor ligand is
selected from 2,2'-dipyridyl, sodium salt of ethylenediamine
tetraacetic acid, ethylenediamine, 1,10-phenanthroline,
4,4'-dipyridyl, 1,4,8,11-tetraazacyclotetradecane,
N,N-Bis(2-hydroxybenzyl)ethylenediamin- e H.sub.4, or mixtures
thereof.
12. The process of claim 1, wherein said liquid phase is water,
methanol, glyme, polyglycol, other alcohols from C.sub.2 to
C.sub.10 or ethers from C.sub.2 to C.sub.10, and mixtures
thereof.
13. The process of claim 1, wherein said hydrogen feed has a CO
concentration in an amount from about 50 ppm to less than about 20
ppm.
14. A process for reducing CO content of a hydrogen feed for use in
a proton exchange membrane fuel cell, said process comprising
producing said hydrogen feed from formate in a liquid phase in the
presence of a formate decomposition catalyst.
15. The process of claim 14, wherein said process for producing
hydrogen feed from formate is conducted in a temperate range from
about 80.degree. C. to about 150.degree. C.
16. The process of claim 15, wherein said formate is selected from
formates of sodium, potassium, lithium and cesium.
17. The process of claim 14, wherein said liquid phase is selected
from water, methanol, glyme, polyglycol, other alcohols from
C.sub.2 to C.sub.10 or ethers from C.sub.2 to C.sub.10, and
mixtures thereof.
18. The process of claim 14, wherein said formate is generated from
CO and hydroxide in a basic solution wherein the process is a
water-gas-shift reaction.
19. The process of claim 18, wherein said water-gas-shift reaction
comprises the steps of: (a) producing formate from CO and water;
and (b) decomposing formate in the presence of water to form said
hydrogen feed and carbon dioxide.
20. The process of claim 14, wherein said formate decomposition
catalyst is a homogenous metal complex.
21. The process of claim 20, wherein said homogenous metal complex
is a transition metal complex having a metal selected from group
VIII A.
22. The process of claim 21, wherein said metal is selected from
the group consisting of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt and
Cu.
23. The process of claim 21, wherein said transition metal complex
is selected from the group consisting of RuCl.sub.3.xH.sub.2O,
Ru.sub.3(CO).sub.12, NiCl.sub.2.6H.sub.2O, RhCl.sub.3.3H.sub.2O,
CoCl.sub.2, K.sub.2PtCl.sub.4, FeCl.sub.2, Ru(CO).sub.5,
Ni(CO).sub.4, Rh.sub.6(CO).sub.16, Co.sub.2(CO).sub.8,
[Pt(CO)(Cl.sub.2)].sub.2 and mixtures thereof.
24. The process of claim 23, wherein said transition metal complex
is in the presence of 2,2'-dipyridyl.
25. The process of claim 14, wherein said hydrogen feed contains an
amount of CO from about 50 ppm to less than about 20 ppm.
26. A process for the production of a hydrogen rich gas from a gas
stream including CO, H.sub.2O, H.sub.2 and CH.sub.3OH which
comprises oxidizing CO to CO.sub.2 in the presence of a
liquid-phase homogenous catalytic system.
27. The process of claim 24, wherein said homogenous catalytic
system is a metal complex coupled to at least one N-donor
ligand.
28. A process for catalytic production of a hydrogen feed which
comprises: providing a hydrogen feed; and exposing said hydrogen
feed to a homogenous catalyst which promotes a water-gas-shift
reaction in a liquid phase at a temperature from about 80.degree.
C. to about 150.degree. C.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a process for the production of
hydrogen. More specifically, this invention relates to a catalytic
process for the production of hydrogen at low temperatures for use
in methanol or proton exchange membrane fuel cells.
[0004] 2. Description of the Related Art
[0005] Fuel cells combine hydrogen and oxygen without combustion to
form water and to produce direct current electric power. The
process can be described as electrolysis in reverse. Fuel cells
have been pursued as a source of power for transportation because
of their high energy efficiency, their potential for fuel
flexibility, and their extremely low emissions. Fuel cells have
potential for stationary and vehicular power applications; however,
the commercial viability of fuel cells for power generation in
stationary and transportation applications depends upon solving a
number of manufacturing, cost, and durability problems.
[0006] The most promising fuel cells for widespread transportation
use are Proton Exchange Membrane (PEM) fuel cells. PEM fuel cells
operate at low temperatures, produce fast transient response, and
have relatively high energy density compared to other fuel cell
technologies. Any fuel cell design must: (a) allow for supply of
the reactants (typically hydrogen and oxygen); (b) allow for mass
transport of product (water) and inert gases (nitrogen and carbon
dioxide from air), and (c) provide electrodes to support catalyst,
collect electrical charge, and dissipate heat.
[0007] Proton exchange membranes (PEM) fuel cells that typically
utilize Pt on carbon support (Pt/C) as anode electrocatalyst
operate at a lower temperature of 80.degree. C. hold commercial
promise. For methanol fuel cells, H.sub.2 feed can be produced via
one of the following reactions:
CH.sub.3OH+H.sub.2O.fwdarw.3H.sub.2+CO.sub.2 .DELTA.H=+49.4
kJ.mol.sup.-1 (1)
CH.sub.3OH+1/2O.sub.2.fwdarw.2H.sub.2+CO.sub.2 .DELTA.H=-192.2
kJ.mol.sup.-1 (2)
[0008] Steam reforming of methanol in Reaction 1 is carried out at
temperatures greater than 280.degree. C. over supported Cu/Zn
catalysts as described by Velu, Suzuki and Osaki in Chem.
Communications, No.23, 2341-2342 (1999). Partial oxidation of
methanol in Reaction 2 is also feasible and the reaction is
exothermic. See Cubeiro and Fierro in Journal of Catalysts 179,
150-162 (1998). However, a shortcoming of the above process is that
the hydrogen feed produced in this manner has a high content of
carbon monoxide (CO). It is known that Pt is readily poisoned by
CO. Therefore, a major challenge to the commercializing of the PEM
fuel cell technology is to produce H.sub.2 that is essentially free
of CO. Several catalysts of the type Pt--Ru/C or Pt--Mo/C, have
been formulated to increase CO tolerance of the Pt catalyst as
discussed in a review article by Mukerjee, et al., Electrochemical
and Solid-State Letters. 2(1) 12-15 (1999). But even at a CO
content of 100 ppm in the H.sub.2 feed, severe catalyst poisoning
is observed.
[0009] H.sub.2 produced via Reaction 1 or 2 contains more than 100
ppm CO. Currently, a catalytic water-gas-shift (WGS) step as
illustrated by Reaction 3 is added to remove CO to acceptable
levels (<20 ppm) prior to feeding H.sub.2 to the fuel cell.
CO.sub.(g)+H.sub.2O.sub.(g)H.sub.2(g)+CO.sub.2(g) .DELTA.H=-39.4
kJ.mol.sup.-1 (3)
[0010] Reaction 3 is typically catalyzed by promoted iron oxides at
temperatures greater than 300.degree. C. as discussed by C. L.
Thomas, in "Catalytic Processes and Proven Catalysts", Academic
Press, New York, 1970. As a result, such high temperature
pretreatment unnecessarily adds cost to the process. Moreover, in
the gas phase, Reaction 3 is in an equilibrium that invariably
leaves some CO in the product H.sub.2 stream.
[0011] Accordingly, there is still a need in the art of PEM fuel
cells to utilize hydrogen that is essentially free of carbon
monoxide. Additionally, there is also a need to provide the
hydrogen gas in a process that is conducted at low temperature by
using inexpensive and simple methods.
OBJECTS OF THE INVENTION
[0012] It is, therefore, an object of the present invention to
provide an improved process for the production of hydrogen gas.
[0013] It is a further object of the invention to provide a
catalytic process for the production of hydrogen gas which contains
reduced carbon monoxide content.
SUMMARY OF THE INVENTION
[0014] The present invention, which addresses the needs of the
prior art, provides a process for the catalytic production of a
hydrogen feed by exposing a hydrogen feed to a catalyst which
promotes a water-gas-shift reaction in a liquid phase. The hydrogen
feed can be provided by any process known in the art of making
hydrogen gas. It is preferably provided by steam reforming or
oxidation of methanol or by any other process that can produce a
hydrogen feed for use in proton exchange membrane fuel cells. The
step of exposing the hydrogen feed takes place preferably from
about 80.degree. C. to about 150.degree. C. Formate is formed when
the water-gas-shift reaction is base catalyzed.
[0015] The catalyst used in the process of the present invention
can be selected from homogenous transition metal complexes. The
transition metal of the complex is preferably a metal selected from
Group V III A of the periodic table, including, for example, Fe,
Co, Ni, Ru, Rh, Pd, Os, Ir, Pt and Cu. The transition metal can be
coupled to at least one N donor ligand such as
2,2'-dipyridyl(BIPY), sodium salt of ethylenediamine tetraacetic
acid, ethylenediamine, 1,10-phenanthroline, 4,4'-dipyridyl,
1,4,8,11-tetraazacyclotetradecane(CYCLAM),
N,N-Bis(2-hydroxybenzl)ethylen- ediamine H.sub.4(SALEN), or
mixtures thereof. The catalytic process of the invention is carried
out preferably in a highly basic liquid phase such as provided by
water, methanol, glyme, polyglycol, other alcohols from C.sub.2 to
C.sub.10 or ethers from C.sub.2 to C.sub.10 and mixtures thereof.
The liquid phase is made basic by adding bases in an amount
sufficient to promote formate formation The pH of the liquid phase
is preferably greater than 8.
[0016] As a result of the process of the present invention, a new
integrated system that operates at low temperatures is provided.
The system consists of two steps: 1) catalyzed methanol
decomposition at a temperature of less than 150.degree. C. to
produce 1 mol CO and 2 mol H.sub.2 followed by, 2) fast and
complete CO conversion to CO.sub.2 with concomitant production of 1
mol of H.sub.2 via the present invention. The present integrated
system thus produces 3 mol H.sub.2/mol methanol at low temperature
of less than 150.degree. C. compared to schemes for methanol fuel
cell systems that are under development.
[0017] Other improvements which the present invention provides over
the prior art will be identified as a result of the following
description which set forth the preferred embodiments of the
present invention. The description is not in any way intended to
limit the scope of the present invention, but rather only to
provide the working example of the present preferred embodiments.
The scope of the present invention will be pointed out in the
appended claims.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention is a process for the catalytic
production of hydrogen feed at low temperatures for use in proton
exchange membrane fuel cells. More specifically, the gaseous feed
formed by the process of the present invention is hydrogen rich and
contains very low levels of carbon monoxide.
[0019] In the process of the present invention a hydrogen feed can
be formed by any process known in the art. A hydrogen feed is
preferably formed by steam reforming or oxidation of methanol,
methane or biomass. Hydrogen feed can also be obtained from
gasification of coal and other carbonaceous materials including,
without limitations, wastes of organic materials, plastics, farm,
wood chips and other industrial wastes. Once formed, the hydrogen
feed is exposed to a catalytic liquid phase homogeneous systems to
achieve a water-gas-shift reaction for CO removal to levels less
than 50 ppm. In the reaction know as water-gas-shift, water is
reacted with carbon monoxide to yield hydrogen and carbon dioxide.
This reaction is shown below:
CO.sub.(g)+H.sub.2O.sub.(1)H.sub.2(g)+CO.sub.2(g) .DELTA.H=+2.8
kJ.mol.sup.-1 (3A)
[0020] This reaction operates at a low temperature of less than
150.degree. C. CO is dissolved in the liquid phase and reacts with
water on a homogenous catalytic system to produce H.sub.2 and
CO.sub.2.
[0021] For application to PEM fuel cells, two requirements must be
met. These are: 1) the reaction preferably operates at a lower
temperature of from about 80.degree. C. to about 150.degree. C.:
and 2) CO removal to less than 50 ppm is achieved with fast
reaction rates. In studies reported in literature, the mechanism of
homogeneously catalyzed WGS reaction has been established. For
example, in base-catalyzed WGS reactions, formate ion is invoked as
an intermediate as shown in Reactions 4 and 5 below:
CO+.sup.-OH.fwdarw.HCO.sub.2.sup.- (4)
HCO.sub.2.sup.-+H.sub.2O.fwdarw.H.sub.2+CO.sub.2+.sup.-OH (5)
[0022] The sum of Reactions 4 and 5 is the WGS reaction (3) above.
Thus, catalyzed formate decomposition is also a measure of WGS
activity of a catalyst.
[0023] The advantage of the present invention is provided by the
thermodynamic advantage of Reaction (3A) as opposed to Reaction (3)
above. In the prior art the WGS reactions are in the gas phase. As
a result of a negative enthalpy, Reaction (3) tends to go backwards
to produce large amounts of CO. In the present invention, the
mechanism illustrated in Reaction (3A) indicates that the reaction
goes only in forward direction because in the liquid phase the
homogenous catalyst reacts with CO and then picks up water to form
CO.sub.2. That is why by using a catalytic liquid phase homogenous
system almost 100% of CO is converted to CO.sub.2
[0024] Commercially available from Aldrich Corp. and several other
vendors, several metals (heterogeneous) and metal complexes
(homogeneous) have been employed as catalysts useful in the present
invention. Under basic conditions, at pH greater than 8, formate
formation is facilitated as shown in Equation 6 below:
AM-OH+CO.fwdarw.AM-HCO.sub.2 (6)
(AM=Li, Na, K, Cs)
[0025] Thus, Equation 7 is a part of the WGS catalytic cycle:
AM-HCO.sub.2+H.sub.2O.fwdarw.AM-OH+H.sub.2+CO.sub.2 (7)
[0026] Useful sources of formate include formate salts of lithium,
sodium, potassium and cesium, all readily available commercially or
these materials can be conveniently synthesized in batches in the
laboratory according to procedures well known in the art. Useful
bases for inclusion in the liquid phase include, without
limitation, hydroxides, alkoxides, bicarbonates of lithium, sodium,
potassium and cesium. Alkyl amines wherein the alkyl group is from
C.sub.1-C.sub.4 are also useful bases for the purposes of the
present invention. A preferred base is potassium hydroxide.
[0027] In the present invention, commercially available transition
metal complexes, based on Ru, Ni, Rh, Pt, Co, Fe, Pd, Os, Ir, Cu
metals in methanol/H.sub.2O solvent mixture are employed. Useful
transition metal complexes for this invention are easily
commercially available and include without limitation
RuCl.sub.3.xH.sub.2O, Ru.sub.3(CO).sub.12, NiCl.sub.2.6H.sub.2O,
RhCl.sub.3.3H.sub.2O, CoCl.sub.2, K.sub.2PtCl.sub.4, FeCl.sub.2,
Ru(CO).sub.5, Ni(CO).sub.4, Rh.sub.6(CO).sub.16,
Co.sub.2(CO).sub.8, [Pt(CO)(Cl.sub.2)].sub.2 and mixtures thereof.
For RuCl.sub.3.xH.sub.2O, x is an integer between 0 to 3.
[0028] A preferred catalyst is formed by dissolving
RuCl.sub.3xH.sub.2O with a water-soluble ligand such as
2,2'-dipyridyl(BIPY) as manufactured by Aldrich, a commercial
vendor. An organic solvent may be added such as methanol, ethanol
and the like. Listed in Table 1 below are experiments that show the
activity pattern of various catalysts useful in formate
decomposition.
[0029] The experiments summarized in Table 1 were obtained by
catalyzing 50 mmol of KHCO.sub.2 in 130 ml of a solvent mixture of
5% H.sub.2O/10% methanol/85% triglyme, all placed in a 0.5L AE
Zipperclave batch reactor at a temperature of 120.degree. C. and a
pressure of 1.4 MPa.
1TABLE Decomposition of Inorganic Formates Catalyzed by Metal
Complexes Final Gas Analysis H.sub.2 CO Time % KHCO.sub.2 Run No.
Catalyst (mmol) mmol minutes Decomposition 1 -- 1 -- 140 2 2
RuCl.sub.3 .multidot. x H.sub.2O/- 35 -- 80 70 (3) 3
NiCL.sub.2..sub.6H.sub.2O/BIPY 5 -- 120 10 (3) (3) 4 RuCl.sub.3
.multidot. x H.sub.2O/BIPY 47 -- <5 94 (3) (3) 5
RhCl.sub.3.3H.sub.2O/BIPY 50 -- <30 80 (3) (3) 6 CoCl.sub.2/BIPY
2 -- 55 4 (3) (3) 7 K.sub.3PtCl.sub.4/BIPY 43 -- <10 86 (3) (3)
8 FeCl.sub.2/BIPY 3 -- 30 6 (3) (3) 9 RuCl.sub.3 .multidot. x
H.sub.2O/BIPY 50 -- <2 100* (3) (3) *(T = 140.degree. C.)
[0030] From Table 1 above, it is apparent that the preferred
catalyst system contained Ru and N-donor ligands. N-donor ligands
useful in the catalyst system of the present invention include but
not limited to are 2,2'-dipyridyl(BIPY), sodium salt of
ethylenediamine tetraacetic acid, ethylenediamine,
1,10-phenanthroline, 4,4'-dipyridyl,
1,4,8,11-tetraazacyclotetradecane(CYCLAM),
N,N-Bis(2-hydroxybenzyl)ethyle- nediamine H.sub.4(SALEN).
[0031] The solvent system typically employed for the homogenous
catalysts useful in the present on is an organic and/or aqueous
solvent such as methanol, ethanol, other higher alcohols, glymes,
polyglycol, water and mixtures thereof. H.sub.2 is produced with
extremely fast reaction rates. Turnover numbers as high as 8 mol
H.sub.2/mol Ru/min have been obtained. When the catalyst system
also contains N-donor ligands turnover numbers are enhanced and can
vary from about 0.1 to about 12 mol H.sub.2/mol metal/min. Applying
the process of the present invention to a gaseous stream of CO,
H.sub.2O and H.sub.2 and CH.sub.3OH results in removal of CO to
very low levels. For example, levels of carbon monoxide well below
50 ppm, and preferably less than 20 ppm can be achieved.
[0032] In the examples that follow, essentially complete formate
decomposition as well as CO to CO.sub.2 oxidation with H.sub.2O is
demonstrated. Such a system allows removal of CO to well below the
50 ppm level from a gas stream containing CO, H.sub.2O, H.sub.2,
CH.sub.3OH.
EXAMPLES
[0033] The examples below further illustrate the various features
of the invention and are not intended in any way to limit the scope
of the invention which is defined in the appended claims. All
materials used in the examples of the present invention are readily
commercially available. Gas analysis data were collected on Gow-Mac
550 gas chromatographs, operating in the thermal conductivity
detector (TCD) mode, as follows: H.sub.2 was analyzed on a 5 .ANG.
molecular sieve column manufactured by Linde Corp. (6
feet.times.1/8 inch) with N.sub.2 as the carrier gas, CO was also
analyzed on a 5 .ANG. molecular sieve column manufactured by Linde
Corp. (8 feet.times.1/8 inch) with He as the carrier gas and
CO.sub.2 was analyzed on Carboxen-1000 column (5 feet.times.1/8
inch) gas with He as the carrier gas.
Example 1
[0034] This example illustrates the catalytic activity of ruthenium
trichloride for potassium formate (KHCO.sub.2) decomposition. A
deep red solution resulted on adding 3 mmol RuCl.sub.3.xH.sub.2O to
130 ml of 85% triglyme/10% MeOH/5% H.sub.2O solvent mixture. The
red solution and 50 mmol of KHCO.sub.2 were loaded into an AE
Zipperclave batch unit consisting of a 0.5 L pressure vessel, as
manufactured by Autoclave Engineers (AE). The vessel was
pressurized with 1.4 MPa N.sub.2 and heated to 120.degree. C. The
pressure increased with time at a constant temperature of
120.degree. C. Heating was continued for 80 minutes until a
constant temperature was attained indicating that gas evolution of
mainly CO.sub.2 and H.sub.2 from formate decomposition had ceased.
On cooling the vessel, a net pressure increase of 0.22 MPa was
noted.
[0035] The final gas analysis at room temperature was as follows:
H.sub.2=10.8%, CO.sub.2=4.1%, CO less than 50 ppm. N.sub.2 was
calculated by difference with an accurate overall mass balance. The
CO value of less than 50 ppm represents the detection limit of the
gas chromatograph operating in that TCD mode. Equivalent amounts of
50 mmol each of H.sub.2 and CO.sub.2 were expected from the
complete decomposition of 50 mmol KHCO.sub.2. The measured H.sub.2
concentration of 35 mmol was equivalent to 70% KHCO.sub.2
decomposition. The interaction of produced CO.sub.2 with dissolved
base such as KOH in the solution resulted in the CO.sub.2 value
that was at 11 mmol lower than expected. These data established
that the decomposition reaction was catalytic with respect to Ru
because turnover numbers as high as 12 mol H.sub.2/mol Ru/min were
obtained.
Example 2--Comparative
[0036] Example 1 was repeated without adding the catalyst
RuCl.sub.3.xH.sub.2O. After 140 minutes at 120.degree. C. the gas
phase was analyzed as follows: H.sub.2=0.8%, CO.sub.2=1.1%,
CO=0.3%. 1 mmol of H.sub.2 produced was equivalent to 2% KHCO.sub.2
decomposition. This run established that the Ru catalyst was
necessary to achieve KHCO.sub.2 decomposition.
Example 3
[0037] Example 1 was repeated using as the catalyst 1 mmol
RuCl.sub.3.xH.sub.2O in the absence of H.sub.2O and the solvent
mixture was adjusted to 90% triglyme/10% MeOH. The initial 1.40 MPa
N.sub.2 pressure stabilized in 70 minutes at 2.46 MPa. The final
analysis yielded H.sub.2=6.0%, CO.sub.2=1.4%, CO<50 ppm. From
the measured concentration of H.sub.2, the KHCO.sub.2 decomposition
was calculated to be about 30%. The data showed that the absence of
H.sub.2O retarded the decomposition reaction.
Example 4
[0038] In this example, the effect of the nature of the alkali
metal associated with the formate was evaluated. The experimental
conditions were the same as in Example 1 except that KHCO.sub.2 was
replaced with an equivalent amount of NaHCO.sub.2 and only 1 mmol
RuCl.sub.3.xH.sub.2O was used. After 188 minutes at 120.degree. C.,
the final gas analysis was as follows: H.sub.2=9.5%, CO.sub.2=4.5%
CO=0.1%. NaHCO.sub.2 decomposition was calculated to be about
46%.
Example 5
[0039] In this example, the conditions were kept constant as in
Example 1 except that RuCl.sub.3.x H.sub.2O was replaced with 1
mmol Ru.sub.3(CO).sub.12 which provides 3 mmol Ru equivalent. The
final gas phase contained 9 mmol H.sub.2, 3 mmol CO.sub.2, 1 mmol
CO. The produced H.sub.2 corresponded to about 18% KHCO.sub.2
decomposition.
Example 6
[0040] In this example, the effect of an added ligand was
evaluated. Example 1 was repeated in the presence of
2,2'-dipyridyl. The initial 1.4 MPa pressure stabilized at 2.54 MPa
in less than 5 minutes at 120.degree. C. The gas analysis was as
follows: H.sub.2=15.4%, CO.sub.2=1.7%, CO less than 50 ppm. The
measured H.sub.2 concentration of 47 mmol corresponded to 94%
KHCO.sub.2 decomposition. These data showed that the reaction was
catalyzed by both Ru as well as the ligand. Sixteen turnover
numbers each were obtained.
Example 7
[0041] Example 6 was repeated except that, in the solvent mixture,
triglyme was replaced with polyglycol (Peg-400). The initial
pressure of 1.4 MPa at room temperature increased to 2.39 MPa at
120.degree. C. The pressure was further increased to 2.53 MPa in 20
minutes and then remained constant. The final gas analysis was as
follows: H.sub.2=14.5%, CO.sub.2=2.9%, CO less than 50 ppm. The
measured H.sub.2 concentration of 43 mmol indicated that about 86%
KHCO.sub.2 decomposed.
[0042] In the above examples, formate was decomposed to hydrogen,
carbon dioxide and less than 50 ppm of carbon monoxide in the
presence of ruthenium metal complexes. Especially (rood results
were obtained when the metal complexes were in the presence of
2.2'-bipyridyl. Examples 8-20 demonstrate that the decomposition of
KHCO.sub.2 can be catalyzed by transition metal complexes other
than Ru.
Example 8
[0043] Under the conditions of Example 1, RuCl.sub.3.xH.sub.2O was
replaced with NiCl.sub.2.6H.sub.2O. The lime green solution of the
Ni complex was mixed with KHCO.sub.2 and the solution was heated to
120.degree. C. under 1.4 MPa N.sub.2. At 120 minutes at 120.degree.
C., the pressure was constant at 2.25 MPa indicating that any
H.sub.2 production from KHCO.sub.2 decomposition had ceased. Gas
analysis indicated that the gas-phase H.sub.2 value was constant.
The final room temperature gas analysis was as follows:
H.sub.2=1.8%, CO.sub.2=1.6%, CO<0.01%. These results indicated
that only 8% formate decomposed was achieved.
Example 9
[0044] Example 8 was repeated with NiCl.sub.2.6H.sub.2O in the
presence of 3 mmol of 2,2'-dipyridyl. After 105 minutes at
120.degree. C., the final value corresponded to 10% decomposition
of formate. The results of this experiment indicate that the added
ligand only marginally accelerated the decomposition reaction.
Example 10
[0045] Example 9 was repeated except that NiCl.sub.2.6H.sub.2O was
replaced with FeCl.sub.2. The solution was heated to 120.degree. C.
under 1.4 MPa N.sub.2. After 120 minutes at 120.degree. C., the
pressure was constant at 2.15 MPa. Gas analysis indicated that the
gas-phase H.sub.2 value was constant. The final room temperature
gas analysis was as follows: H.sub.2=0.9%, CO.sub.2=0.6%,
CO<0.01%. The measured H.sub.2 yield indicated that only 6%
formate decomposed.
Example 11
[0046] Example 9 was repeated except that NiCl.sub.2.6H.sub.2O was
replaced with 3 mmol Fe(CO).sub.5. After 30 minutes at 120.degree.
C., the pressure was constant at 2.33 MPa. The final gas analysis
was as follows: H.sub.2=3.3%, CO.sub.2=1.5%, CO=4.7%. The H.sub.2
yield of 10 mmol corresponed to 20% KHCO.sub.2 decomposition
equivalent. The reaction also produced 16.5 mmol CO.
Example 12
[0047] Example 8 was repeated with 5 minol Fe(CO).sub.5 as the
catalyst. After heating at 120.degree. C. for 129 minutes, the
final pressure was constant at 2.37 MPa. The final gas analysis was
as follows: H.sub.2=2.2%, CO.sub.2=2.1%, CO=2.1%. The produced
H.sub.2 concentration of 6 mmol corresponed to 12% KHCO.sub.2
decomposition equivalent. In this run, 5 mmol CO was also produced
as a gaseous product.
Example 13
[0048] In Example 8, NiCl.sub.2.6H.sub.2O was replaced with 3 mmol
RhCl.sub.3.3H.sub.2O and 3 mmol of 2,2'-dipyridyl ligand was added.
After 30 minutes at 120.degree. C., the pressure stabilized at 2.43
MPa. The final gas analysis was: H.sub.2=13.5%, CO.sub.2=3.5%,
CO<50 ppm. These results showed that 40 mmol H.sub.2 was
produced. The H.sub.2 value corresponded to 80% KHCO.sub.2
decomposition equivalent.
Example 14
[0049] Example 8 was repeated with 0.5 mmol Rh.sub.6(CO).sub.16
which corresponded to 3 mmol Rh equivalent. After heating at
120.degree. C. for 60 minutes, the final pressure was constant at
2.54 MPa. The final gas analysis was as follows: H.sub.2=15.1%,
CO.sub.2=2.6%, CO =0.17%). The produced H.sub.2 value of 41 mmol
corresponded to about 82% KHCO.sub.2 decomposition.
Example 15
[0050] Example 14 was repeated with Rh.sub.6(CO).sub.16 in the
presence of added 3 mimol of 2,2'-dipyridyl ligand. The final
pressure was constant at 2.40 MPa after 110 minutes at 120.degree.
C. The final gas analysis was as follows: H.sub.2=12.7%,
CO.sub.2=2.8%, CO<50 ppm. The produced H.sub.2 value of 33 mmol
corresponded to about 66% KHCO.sub.2 decomposition.
Example 16
[0051] Example 8 was repeated with 3 mmol of K.sub.2PtCl.sub.6 as
the catalyst. The pressure stabilized at 2.52 MPa. after 25 minutes
at 120.degree. C. The final gas analysis was as follows:
H.sub.2=16.0%, CO.sub.2=3.2%, CO<50 ppm. The formate
decomposition was calculated to be about 87% from produced H.sub.2
concentration of 43.5 mmol.
Example 17
[0052] Example 16 was repeated with 3 mmol of 2,2'-dipyridyl ligand
added to K.sub.2PtCl.sub.6. The final constant pressure was
recorded at 2.61 MPa after 10 minutes at 120.degree. C. The gas
analysis was as follows: H.sub.2=16.0%, CO.sub.2=4.8%, CO<50
ppm. The formate decomposition was calculated to be 86% from the
produced H.sub.2 value of 43 mmol.
Example 18
[0053] Example 17 was repeated, however, K.sub.2PtCl.sub.6 was
replaced with 3 mmol of K.sub.2PtCl.sub.4. The final pressure
stabilized at 2.57 MPa after 20 minutes at 120.degree. C. The gas
analysis was as follows: H.sub.2=16.9%, CO.sub.2=3.1%, CO<50
ppm. H.sub.2 was calculated to be 48 mmol that corresponed to about
96% formate decomposition.
Example 19
[0054] Example 8 was repeated after replacing NiCl.sub.2.6H.sub.2O
with 3 mmol CoCl.sub.2 in the presence of 3 mmol of 2,2'-dipyridyl
ligand. The final pressure was 2.08 MPa in 55 minutes at
120.degree. C. The gas analysis was as follows: H.sub.2=0.7%,
CO.sub.2=0.6%. The H.sub.2 value of 2 mmol corresponded to 4%
KHCO.sub.2 decomposition.
Example 20
[0055] Example 8 was repeated after replacing NiCl.sub.2.6H.sub.2O
with 1.5 mmol Co.sub.2(CO).sub.8 which represents 3 mmol Co
equivalent and 3 mmol of added 2,2'-dipyridyl ligand. The final
pressure was 2.32 MPa in 150 minutes at 120.degree. C. From the gas
analysis, based on 8 mmol H.sub.2, KHCO.sub.2 decomposition was
calculated to be about 16%.
[0056] Examples 21-25 illustrate the applicability of
metal-catalyzed liquid-phase homogeneous systems to oxidize
efficiently CO to CO.sub.2 in a gas stream containing a mixture of
CO, H.sub.2O. CH.sub.3OH and CO.sub.2.
Example 21
[0057] 3 mmol of RuCl.sub.3.xH.sub.2O, 3 mmol of 2,2'-dipyridyl,
and 0.3 mmol of KOH were dissolved in 130 mL 50% MeOH/50% H.sub.2O
solvent mixture. The resulting deep red solution was loaded and
sealed in a 0.5 L pressure vessel in the AE Zipperclave batch unit.
The vessel was purged twice with 50 psi CO, charged with 0.767 MPa
CO and the gas phase of the vessel was analyzed to be 99.8% CO,
with no H.sub.2 detected. After heating the vessel, the pressure
increased to 1.807 at 130.degree. C. and remained constant. A gas
sample taken at time, t=0, at 130.degree. C. analyzed as follows:
H.sub.2=97.8%, CO<0.005%. The gas-phase composition remained
constant after the solution was cooled to room temperature. From
equivalent added CO, a total of 120 mmol H.sub.2 was produced.
These data showed that the reaction was catalytic both in
RuCl.sub.3.xH.sub.2O as well as in 2,2'-dipyridyl. Forty turnover
numbers were obtained each for Ru and the ligand.
Example 22
[0058] The final solution in Example 21 was heated to 140.degree.
C. and then further charged with CO to 3.22 MPa. The gas analysis
data as a function of time at 140.degree. C. is given below:
2 Gas Analysis Time, min P.sub.T, MPa % CO % H.sub.2 % CO.sub.2 0
3.17 * * * 5 3.22 13.0 77.5 * 16 2.80 3.4 87.0 * 23 3.09 1.12 81.9
* 35 3.23 0.22 83.1 * 45 3.33 0.083 84.0 * 90 3.38 0.014 84.3 8.4
*Not measured.
[0059] The above data shows that a quick drop in the CO
concentration from 13.0% to 3.4% was observed after the first 16
minutes. Thereafter, the CO dropped from 3.4% to 0.014% in 90
mimnutes . The ratio of H.sub.2 produced to KOH was 0.71. These
data illustrate that the reaction was dependent on the KOH
concentration.
Example 23
[0060] The example further confirms that the CO removal from the
initial gas stream is dependent on KOH concentration. A dark brown
solution resulted on adding 3 mmol of RuCl.sub.3.xH.sub.2O 6 mmol
of 2,2'-dipyridyl in 85% triglyme/10% MeOH/5% H.sub.2O solvent
mixture. 50 mmol of KHO was then added to the dark brown solution.
The base dissolved but the solution became biphasic. The biphasic
solution was initially heated to 115.degree. C. and then to
140.degree. C. under 1.10 MPa syngas (H.sub.2/CO=66%/34%). The gas
analysis data is as follows:
3 Gas Analysis Time, min T, .degree. C. P.sub.T, MPa % CO % H.sub.2
% CO.sub.2 1 115 1.20 36.3 28.0 * 5 140 1.50 34.0 53.3 0.5 85 140
1.63 28.3 60.0 3.0 *Not measured.
[0061] The above data shows that of the initial amount of 64 mmol
CO (in syngas), 45 mmol remained unconverted after 85 minutes at
140.degree. C. In this reaction, 20 mmol CO and 44 mmol H.sub.2
were consumed to generate products, likely methanol, in addition to
CO.sub.2 and H.sub.2.
Example 24
[0062] Example 21 was repeated with 3 mmol of RuCl.sub.3.xH.sub.2O,
3 mmol of 2,2'-dipyridyl and 100 mmol KOH dissolved in 20% MeOH/20%
H.sub.2O/60% Peg-400 solvent mixture. The dark brown solution was
heated to 140.degree. C. under 1.10 MPa syngas
(H.sub.2/CO=66%/34%). After 3 minutes the gas analysis was as
follows: H.sub.2=94.7%, CO=0.14%. The analysis after 27 minutes at
140.degree. C. was H.sub.2=95.4%, CO<50 ppm. This data showed
that the catalyst was: 1) effective in polyethylene glycol solvent,
and 2) active in a solvent mixture containing high H.sub.2O
concentration.
Example 25
[0063] Example 21 was repeated after replacing KOH with 100 mmol of
KHCO.sub.2. Thus, KHCO.sub.2 served as a source of CO. The dark
brown solution was heated to 140.degree. C. under 0.67 MPa H.sub.2.
The pressure increased to 2.46 MPa at 140.degree. C. and continued
to increase to 3.06 MPa. After 11 minutes, less than 50 ppm CO was
detected. The corresponding H.sub.2 and CO.sub.2 values were 93.8%
and 4.5% respectively.
Example 26
[0064] Example 21 was repeated with reduced loading of KOH (100
mmol instead of 300 mmol) and the vessel was charged with 1.20 MPa
syngas (H.sub.2/CO=66%/34%) instead of 0.767 CO. On heating the
solution to 140.degree. C., the pressure increased to 2.0 MPa. The
gas analysis after 60 minutes was as follows: H.sub.2=96.1%,
CO.sub.2=0.2%, CO<50 ppm. Note that with an equivalent amount of
(100 mmol) KHCO.sub.2 in Example 25, the corresponding reaction
time was 11 minutes. These data showed that the reaction was faster
with preformed KHCO.sub.2. Also, a comparison of the reaction time
data in Example 21 in which 300 mmol KOH was used and a reaction
time of 21 minutes showed that the reaction was also dependent on
base concentration.
[0065] Thus, while we described what are the preferred embodiments
of the present invention, further changes and modifications can be
made by those skilled in the art without departing from the true
spirit of the invention, and it is intended to include all such
changes and modifications as come within the scope of the claims
set forth below.
* * * * *