Process for producing compounds of the cxhyoz type by reduction of carbon dioxide (co2) and/or carbon monoxide (co)

Abstract

The present invention relates to a process for electrolysing steam introduced under pressure into an anode in compartment ( 32 ) of an electrolyser ( 30 ) provided with a proton-conducting membrane ( 31 ) made of a material that allows protonated species to be incorporated into this membrane under steam, water injected in steam form being oxidized at the anode ( 32 ) so as to generate protonated species in the membrane that migrate within this same membrane and are reduced at the surface of the cathode ( 33 ) in the form of reactive hydrogen atoms capable of reducing carbon dioxide and/or carbon monoxide, said process comprising the following steps: injection of CO 2 and/or CO under pressure into the cathode compartment ( 33 ) of the electrolyser ( 30 ); -reduction of the CO 2 and/or CO injected into the cathode compartment ( 33 ) by said reactive hydrogen atoms generated, in such a way that the CO 2 and/or the CO form compounds of the C x H y O z type where x>1, y is between 0 and 2x+2 and z is between 0 and 2x.

1 . A process for electrolyzing steam injected under pressure into an anode compartment of an electrolyzer provided with a proton-conducting membrane made of a material enabling protonated species to be incorporated into this membrane under steam, oxidation of the water injected in steam form taking place at the anode so as to generate protonated species in the membrane that migrate within this same membrane and are reduced at the surface of the cathode in the form of reactive hydrogen atoms capable of reducing carbon dioxide CO 2  and/or carbon monoxide CO, said process comprising the following steps:
 the introduction of CO 2  and/or CO under pressure into the cathode compartment of the electrolyzer,   the reduction of CO 2  and/or CO introduced into the cathode compartment from said reactive hydrogen atoms generated such that the CO 2  and/or CO form C x H y O x  type compounds, with x≧1; y is between 0 and 2x+2 and z is between 0 and 2x.   
     
     
         2 . The electrolysis process according to  claim 1 , wherein the process comprises a step of controlling the nature of the C x H y O z  type compounds formed according to the voltage-current pair applied to the cathode. 
     
     
         3 . The electrolysis process according to  claim 1  wherein the process comprises a step of the utilization of a proton-conducting membrane that is impermeable to the diffusion of oxygen O 2  and H 2  and enables the incorporation of protonated species into this membrane under steam pressure. 
     
     
         4 . The electrolysis process according to  claim 3 , wherein the process comprises a step of utilizing a proton-conducting membrane of the type: perovskite vacancies, non-stoichiometric perovskites and/or perovskites doped with general formula ABO 3 , of fluorite, pyrochlore A 2 B 2 X 7 , apatite Me 10 (XO 4 ) 6 Y 2 , oxyapatite Me 10 (XO 4 ) 6 O 2  structure, of hydroxylapatite Me 10 (XO 4 ) 6 (OH) 2  structure, of silicate structure, aluminosilicates, phyllosilicates, zeolite, silicates grafted with oxyacids or silicates grafted with phosphates. 
     
     
         5 . The electrolysis process according to  claim 4 , wherein the process comprises a step of utilizing, as a proton-conducting membrane, an electrolyte supported by the cathode or by the anode so as to reduce its thickness in order to increase its mechanical strength. 
     
     
         6 . The electrolysis process according to  claim 1 , wherein the process comprises a step of the utilization of a relative partial pressure of steam greater than or equal to 1 bar and less than or equal to a burst pressure of the assembly, the latter being greater than or equal to at least 100 bars. 
     
     
         7 . The electrolysis process according to  claim 1 , wherein the relative partial pressure of steam is advantageously greater than or equal to 50 bars. 
     
     
         8 . The electrolysis process according to  claim 1 , wherein the relative pressure of CO 2  and/or CO is greater than or equal to 1 bar and less than or equal to the burst pressure of the assembly, the latter being greater than or equal to at least 100 bars. 
     
     
         9 . The electrolysis process according to  claim 1 , wherein the electrolysis temperature is greater than or equal to 200° C. and less than or equal to 800° C., advantageously between 350° C. and 650° C. 
     
     
         10 . The electrolysis process according to  claim 1 , wherein the electrodes, of porous structure, are either ceramic-metal materials, or “ceramic” electrodes with mixed electronic and ionic conduction. 
     
     
         11 . The electrolysis process according to  claim 10 , wherein the ceramic-metal materials are, for the cathode, ceramic-metal materials in which the ceramic is compatible with the electrolyte forming the membrane and in which the nature of the metal dispersed is advantageously a metal and/or a metal alloy among which metals such as cobalt, copper, molybdenum, silver, iron, zinc, noble metals (gold, platinum, palladium) and/or transition elements may be cited. 
     
     
         12 . The electrolysis process according to  claim 10 , wherein the ceramic-metal materials are, for the anode, ceramic-metal materials in which the ceramics are compatible with the electrolyte forming the membrane and in which the nature of the metal dispersed is advantageously a metal alloy or a passivable metal. 
     
     
         13 . A steam electrolysis device for electrolyzing steam introduced under pressure into an anode compartment of an electrolyzer provided with a proton-conducting membrane, made of a material enabling the injection of protonated species into this membrane under steam after oxidation, comprising:
 an electrolyte in the form of an ion conducting membrane made in said material enabling the injection of protonated species under the effect of the water pressure in said membrane,   an anode,   a cathode,   a generator enabling current to be generated and to apply a potential difference between said anode and said cathode,   means for the insertion of steam under pressure in said electrolyte via said anode,   means to inject CO 2  and/or CO under pressure into the cathode compartment of the electrolyzer, and   means to reduce the CO 2  and/or the CO introduced into the cathode compartment according to a process in conformance with one of the previous embodiments.   
     
     
         14 . The device according to  claim 13 , wherein the material enabling the injection of protonated species is impermeable to O 2  and H 2  gases. 
     
     
         15 . The device according to  claim 13 , wherein the material enabling the injection of protonated species has a densification level of over 88%, preferably equal at least to 94%. 
     
     
         16 . The device according to  claim 13 , wherein the material enabling the injection of protonated species is an oxygen atom-defective oxide such as an oxygen-defective perovskite acting as a proton conductor. 
     
     
         17 . The device according to  claim 16 , wherein the oxygen atom-defective oxide presents stoichiometric intervals and/or is doped.