Chemistry: electrical and wave energy – Processes and products
Patent
1983-10-03
1987-02-17
Andrews, R. L.
Chemistry: electrical and wave energy
Processes and products
429 13, C25G19100
Patent
active
046438068
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrochemical reactions for energy and chemical productions and especially to improved yields that can be obtained when conducting the reactions using a cross-flow monolith reactor.
One of the emerging uses of solid-state electrocatalytic systems is in fuel cells to convert a significant portion of the Gibbs free energy change of exothermic reactions into electricity rather than heat. The thermodynamic efficiency of such power generating schemes compares favorably with thermal power generation which is limited by Carnot-type constraints.
Solid-electrolyte fuel cells, operating on H.sub.2 or CO as the fuel, have been constructed and tested for years. For example, see Archer, Alles, English, Elican, Sverdrup, and Zahradnik in "Fuel Cell Systems", Adv. Chem. Series, R. F. Gould ed., pg. 32 (1965) and Etsell and Flengas in J. Electrochem. Soc., vol. 118 (12), pg. 1980 (1971). Similar devices have been used for steam electrolysis as disclosed by Weissbart, Smart, and Wydeven, in Aerosp. Med., vol. 40, pg. 136 (1969), for NO decomposition as disclosed by Gur and Huggins, in J. Electrochem. Soc., vol. 126 pg. 1067 (1979), and for methane synthesis from CO and H.sub.2 as disclosed by Gur and Huggins in Solid State Ionics, vol. 5, pg. 567 (1981).
Zirconia cells with Pt catalyst-electrodes can also be used to convert ammonia to nitric oxide with simultaneous electrical energy generation as disclosed by Vayenas and Farr in Science, vol. 208, pg. 593 (1980) and by Sigal and Vayenas in Solid State Ionics, vol. 5, pg. 567 (1981). A number of other industrially important oxidations were proposed to be carried out in solid-state electrocatalytic reactors, such as the conversion of sulfur to SO.sub.2 or SO.sub.3 as described by Yang, Debenedetti, Britt, Vayenas, and Evans in Proc. Intern. Symp. on Process Systems Engineering, Tokyo, (1982), or such as ethylene epoxidation as described by Stoukides and Vayenas in "Catalysis under Transient Conditions", ACS Symp. Series, No. 178, Bell and Hegedus, eds., pg. 181 (1982).
The practical usefulness of these electrochemical converters is limited by their very low power densities, arising from their low ion-transfer surface area per unit reactor volume. Thus, although the use of thin solid electrolyte walls can lead to current densities on the order of 0.5 A/cm.sup.2 of electrolyte surface, previous high-temperature fuel cells exhibited volume power densities only up to 300-400 W/l as described by Archer et al in "Fuel Cell Systems", Adv. Chem. Series, Gould ed. pg. 32 (1965) and by Federmann et al in DOE/ET/11305-T8 (1981). The commercial viabililty of electrocatalytic energy conversion systems could be enhanced if there is a significant increase of their volume power density. Similar considerations apply for obtaining high chemical conversions per unit volume. One needs to have high surface to volume geometries for the production of chemicals.
It is an object of this invention to obtain novel oxidation and unsaturation producing reactions.
It is a further object of this invention to obtain high yield electrocatalytic energy conversions and chemical productions.
It is a further object of this invention to utilize high surface to volume geometries in electrochemical reactors for the production of chemicals.
It is a further object of this invention to utilize a solid-state cross-flow monolith reactor to conduct electrochemical reactions.
These and further objects will become apparent as the description of the invention proceeds.
The electrochemical reactions of this invention may be considered as two parts. First there are the new oxidation and unsaturation producing reactions which can be performed using any type solid-state electrocatalytic reactor. Secondly, there are the generally known reactions which now can be carried out with much higher efficiencies by use of the special monolith cross-flow fuel cell reactor. This novel fuel cell reactor configuration is described in U.S. patent application Ser. No. 345,146, filed Feb. 2, 1982, now U.S. Pat. No.
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Archer, D. H., Alles, J. J., English, W. A., Elikan, L., Sverdrup, E. F., and Zahradnik, R. L., in "Fuel Cell Systems", Adv. Chem. Series, R. F. Gould, ed. 1965, 47, 332.
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Debenedetti, P. G. and Vayenas, C. G., "Steady-State Analysis of High Temperature Fuel Cells", Chemical Engineering Science, vol. 38, No. 11, pp. 1817-1829, 1983.
Hegedus Louis
Michaels James N.
Vayenas Costas G.
Andrews R. L.
Cabic Edward J.
Massachusetts Institute of Technology
W. R. Grace & Co.
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