Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction

Definitions

• the present invention relates to a process for producing compounds of the type C x H y O z , in particular with x>1; between 0 and 2x + 2 and z between 0 and 2x, by reduction of carbon dioxide (CO 2 ) and / or carbon monoxide (CO), in particular from highly reactive hydrogen species generated by a electrolysis of water.
• CO 2 carbon dioxide
• CO carbon monoxide
• Hydrogen (H 2 ) appears today as a very interesting energy vector, which will become increasingly important for processing petroleum products, among other things, and which could, in the long term, be a good substitute for oil. and fossil fuels, whose reserves will decline sharply in the coming decades. In this perspective, however, it is necessary to develop efficient processes for the production of hydrogen. Although many processes have been described for producing hydrogen from various sources, many of these processes are unsuitable for mass industrial hydrogen production.
• HTR High Temperature Reactor
• EPR pressurized water nuclear reactors of EPR (registered trademark) design.
• a promising route for the industrial production of hydrogen is the technique known as electrolysis of water vapor, for example at high temperature (EHT), at an average temperature, typically above 200 ° C., or at intermediate temperature. between 200 ° C and 1000 ° C.
• EHT high temperature
• an electrolyte capable of conducting O 2 - ions and operating at temperatures generally between 750 ° C. and 1000 ° C. is used.
• FIG. 1 schematically represents an electrolyser 1 comprising a ceramic membrane 2, conducting O 2 " ions, providing the electrolyte function separating an anode 3 and a cathode 4.
• the application of a difference of potential between the anode 3 and the cathode 4 causes a reduction of water vapor H 2 O on the side of the cathode 4.
• This reduction forms hydrogen H 2 and O 2 - ions (0% in the notation of Kr ⁇ ger-Vink) on the surface of the cathode 4 according to the reaction: 2nd '+ V ⁇ + H 2 O ⁇ O o + H 2
• the O 2 - ions more precisely the oxygen vacancies (Fj), migrate through the electrolyte 2 to form oxygen O 2 at the surface of the anode 3, electrons e being released following the reaction of oxidation:
• this first method makes it possible to generate at the outlet of the electrolyser 1 oxygen - anode compartment - and hydrogen mixed with water vapor - cathode compartment.
• an electrolyte capable of driving the protons and operating at temperatures lower than those required by the first method described above, generally between 200 ° C. and 800 ° C., is used.
• FIG. 2 schematically represents an electrolyzer 10 comprising a proton-conducting ceramic membrane 1 1 providing the electrolyte function separating an anode 12 and a cathode 13.
• this process provides at the outlet of the electrolyzer 10 pure hydrogen - cathode compartment - and oxygen mixed with water vapor - anodic compartment.
• H 2 passes through the formation of intermediate compounds which are hydrogen atoms adsorbed on the surface of the cathode with varying energies and degrees of interaction and / or radical hydrogen atoms. (or H * lectrode the Kr ⁇ ger-Vink notation). These species being highly reactive, they usually recombine to form hydrogen H 2 according to the equation:
• the present invention aims to reduce the amount of carbon dioxide existing, for example by recycling this carbon dioxide in the form of compounds used in the field of chemistry or in the field of energy production.
• the invention proposes a method of electrolysis of water vapor introduced under pressure into an anode compartment of an electrolyser provided with a proton conducting membrane made of a material allowing the incorporation of protonated species.
• reactive hydrogen atoms capable of reducing carbon dioxide CO 2 and / or carbon monoxide CO, said process comprising the following steps: introduction of CO 2 and / or CO under pressure in the cathode compartment of the electrolyser, the reduction of the CO 2 and / or of the CO introduced into the cathode compartment from said generated atoms of reactive hydrogen so that the CO 2 and / or the CO form compounds of the C x H y O z type , with x ⁇ i; between 0 and 2x + 2 and z between 0 and 2x.
• reactive hydrogen atoms are understood to mean hydrogen atoms adsorbed on the surface of the cathode with varying energies and degrees of interaction and / or radical hydrogen atoms H- (or H *) electrode in scoring
• the invention results from the observation that the second method described above generates highly reactive hydrogen at the cathode of the electrolyser (in particular hydrogen atoms adsorbed at the surface of the electrode and / or radical).
• the highly reactive hydrogen electrode reacts with the carbon compounds on the electrode to give reduced compounds of the dioxide and / or carbon monoxide.
• these compounds are paraffins C n H 2n + 2 , olefins C 2n H 2n , alcohols C n H 2n + 2 OH or C n H 2n-1 OH, aldehydes and ketones C n H 2n O, C n-1 H 2n + 1 COOH acids with n> 1.
• the invention thus makes it possible to electrolyze steam with joint electroreduction of carbon dioxide and / or carbon monoxide as described later.
• the method comprises a step of controlling the nature of the compounds of the C x H y O z type, formed as a function of the potential / current torque applied to the cathode;
• the method comprises a step of using a proton conducting membrane impervious to the diffusion of oxygen O 2 and
• the method comprises a step of using a proton conducting membrane of the type: lacunary perovskites, non-stoichiometric and / or doped perovskites of general formula ABO 3 , of fluorine structure, pyrochlore A 2 B 2 X 7 , apatite Me 10 ( XO 4 ) 6 Y 2 , oxyapatite Me 10 (XO 4 ) 6 O 2 , of hydroxyapatite structure Me 10 (XO 4 ) 6 (OH) 2 , of silicates, aluminosilicate (phyllosilicates or zeolites) structure, silicates grafted with oxyacids or silicates grafted with phosphates;
• the method comprises a step of using an electrolyte supported by the cathode or the anode so as to reduce its thickness in order to increase its mechanical strength; the method comprises a step of using a partial and relative pressure of water vapor greater than or equal to 1 bar and less than or equal to a breaking pressure of the assembly, the latter being greater than or equal to at least 100 bars;
• the partial and relative pressure of water vapor is advantageously greater than or equal to 50 bars; - the relative pressure of CO 2 and / or CO is greater than or equal to 1 bar and less than or equal to the breaking pressure of the assembly, the latter being greater than or equal to at least 100 bar;
• the electrolysis temperature is greater than or equal to 200 ° C and less than or equal to 800 ° C, preferably between 350 ° C and 650 ° C;
• the electrodes, of porous structure are either cermets or "ceramic" electrodes with mixed electronic and ionic conduction;
• the cermets are, for the cathodes, ceramics compatible with the electrolyte in which the nature of the dispersed metal is advantageously a metal and or an alloy of metals among which mention may be made of metals such as cobalt, copper, molybdenum, silver, iron, zinc, noble metals (gold, platinum, palladium) and / or elements of transitions;
• the cermets are, for the anodes, ceramics compatible with the electrolyte in which the nature of the dispersed metal is advantageously a metal alloy or a passivable metal.
• the invention also relates to a device for electrolysis of water vapor introduced under pressure into an anode compartment of an electrolyzer provided with a proton conducting membrane, made of a material allowing the incorporation of protonated species into this chamber.
• membrane under water vapor after oxidation comprising: an electrolyte in the form of an ionic conductive membrane made in said material allowing the incorporation of protonated species under the effect of the water pressure in said membrane,
• a generator making it possible to generate current and to apply a potential difference between said anode and said cathode, characterized in that it comprises:
• the device according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: the material allowing the incorporation of protonated species is impermeable to the O 2 and H 2 gases;
• the material for the incorporation of protonated species densification rate greater than 88%, preferably at least 94%. ;
• the material allowing the incorporation of protonated species is a lacunary oxide into oxygen atoms such as a lacunary perovskite into oxygen acting as a proton conductor; in this case, the lacunary oxide in oxygen atoms may have stoichiometric differences and / or be doped.
• FIGS. 1 and 2 already described, are simplified schematic representations of electrolysers of water vapor.
• FIG. 3 is a simplified schematic representation of a steam electrolyser effecting a joint electroreduction of CO 2 and / or CO.
• FIG. 3 is a schematic and simplified representation of an embodiment of an electrolysis device 30 for the production of hydrogen implementing the joint electroreduction method of CO2 and / or CO according to the invention.
• This electrolysis device 30 has a structure similar to that of the device 20 of FIG. 2. Thus, it comprises: an anode 32,
• a generator 34 providing a potential difference between the anode 32 and the cathode 33, - the means 35 for inserting under pressure water vapor pH 2 O into the membrane 31 via the cathode 33 (the partial pressure and relative water vapor is greater than or equal to 1 bar and lower or equal to a breaking pressure of the assembly, the latter being greater than or equal to at least 100 bars).
• the cathode compartment 33 further comprises means 36 for inserting under pressure gas (pCO 2 and / or CO) into the cathode compartment 33
• the steam is injected via the means 35 at the level of the anode 32 while the injection of the CO 2 gas and / or CO is via the means 36 at the level of the cathode 33.
• the water is oxidized by releasing electrons while H + ions (in OH 0 form) are generated according to a process similar to the method described with reference to FIG.
• H + ions migrate through the electrolyte 31, carbon compounds of the CO 2 and / or CO type reacting at the cathode 33 with these H + ions to form compounds of the C x H y O z type (with x> 1 including between 0 and 2x + 2 and z between 0 and 2x) and water at the cathode.
• the relative pressure of CO 2 and / or CO is greater than or equal to 1 bar and less than or equal to the rupture pressure of the assembly, the latter being greater than or equal to at least 100 bars.
• relative pressure refers to the insertion pressure relative to the atmospheric pressure.
• partial pressure denotes either the total pressure of the gas stream in the case where the latter consists solely of water vapor or the partial pressure of water vapor in the case where the gas stream includes other gases than water vapor.
• the total pressure imposed in one compartment - cathodic or anodic - can be compensated in the other compartment so as to have a pressure difference between the two compartments to prevent rupture of the membrane assembly, support electrode if it to a breaking strength too low.
• the latter depends on the type of material used for the membrane 31; in any case, this temperature is greater than 200 ° C and generally less than 800 ° C, or even lower than 600 ° C. This operating temperature corresponds to a conduction provided by H + protons.
• the operating temperature T1 of the device 30 also depends, in the range between 200 and 800 ° C, depending on the nature of the carbon compounds C x H y O z it is desired to generate.
• electrodes having a large number of triple points namely points or contact surfaces between an ion conductor, an electronic conductor and a gas phase.
• electrodes envisaged are preferably cermets formed by a mixture of ionic conducting ceramic, and an electronically conductive metal.
• electrically conductive "all ceramic” electrodes can also be considered in place of a cermet.
• a given electrolyte may be a proton or ionic conductor O 2 " depending on the temperature and pressure of the applied vapor.
• H + conductive ionic membranes operating at moderate temperature allows the synthesis of complex compound of the C x H y O z type (with x, y and z greater than 1) while the use of conductive membranes O 2 " , operating at a much higher temperature, preferentially generates CO, stable product at high temperature.
• the objective of the studies implemented is to obtain the maximum yield for the production of hydrogen and / or the hydrogenation of the product. CO 2 and / or CO. To do this, it is necessary that the majority of the current used intervenes in the faradic process, that is to say is used for the reduction of the water and consequently the production of hydrogen This means that the voltage used for the polarization must be at least affected by
• the present invention proposes the use of proton conductive electrolyte under vapor pressure for the electrolysis of water at high temperature for the production of hydrogen and for the electroreduction at the cathode of CO 2 and / or CO.
• the method comprises the following steps: - insertion of protonated species under the effect of the pressure of a gaseous stream containing water vapor, in said membrane,
• Highly reactive capable of generating hydrogen (H 2 ), in the absence of a reducible compound, or compounds of the C ⁇ H y Oz type, in the presence of CO 2 and / or CO with x ⁇ i; including between O and 2x + 2 and z including O and 2x.
• the proton conduction membrane is made of a material promoting the insertion of water such as a doped perovskite material of general formula AB 1-x D ⁇ 3 - ⁇ / 2 .
• the materials used for the anode and the cathode are preferably cermets (a mixture of metal with the perovskite material used for the electrolyte).
• the membrane is preferably impermeable to O 2 and H 2 gases.
• the membrane may be of the type: lacunary perovskites, non-stoichiometric and / or doped perovskites of general formula ABO 3 , of fluorine structures, pyrochlore A 2 B 2 X 7 , apatite Me- ⁇ o (XO 4 ) 6 Y 2 , oxyapatite Me 10 (XO 4 ) 6 O 2 and hydroxyapatite structures Me 10 (XO 4 ) 6 (OH) 2 , silicate structures, alumina-silicates (phyllosilicates or zeolite), silicates grafted with oxyacids, silicates grafted with phosphates.
• lacunary perovskites non-stoichiometric and / or doped perovskites of general formula ABO 3 , of fluorine structures, pyrochlore A 2 B 2 X 7 , apatite Me- ⁇ o (XO 4 ) 6 Y 2 , oxyapatit
• the electrolytes may advantageously be all of the compounds used as proton conductors at high temperature or intermediate temperature either by their tunnel structure or in sheets and / or by the presence of gaps capable of inserting protonated species whose Molecular size is low.
• the material allowing the incorporation of protonated species may be impermeable to O 2 and H 2 gases and / or may allow the incorporation of protonated species at a densification rate greater than 88%, preferably at least equal to 94%.
• the material allowing the incorporation of water is a lacunary oxide into oxygen atoms, such as a lacunary perovskite into oxygen acting as a proton conductor.
• the lacunary oxide in oxygen atoms may have stoichiometric differences and / or is doped.
• crystallographic structures such as fluorite structures, pyrochlore structures A 2 B 2 X 7 , apatite structures Me 10 (XO 4 ) 6 Y 2 , oxyapatite structures Me 10 (XO 4 ) 6 O 2 hydroxyapatite Meio (XO 4 ) 6 (OH) 2 structures , silicates, aluminosilicates, phyllosilicates, or phosphates.
• These structures may optionally be grafted with oxyacid groups.
• all structures having a high affinity with water and / or protons can be envisaged.

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• Chemical & Material Sciences (AREA)
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• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
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• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
• Inorganic Compounds Of Heavy Metals (AREA)
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• 2008
  • 2008-05-15 FR FR0853161A patent/FR2931168B1/fr not_active Expired - Fee Related
• 2009
  • 2009-05-15 BR BRPI0912654A patent/BRPI0912654A2/pt not_active Application Discontinuation
  • 2009-05-15 CN CN2009801219418A patent/CN102056866A/zh active Pending
  • 2009-05-15 US US12/992,740 patent/US20110132770A1/en not_active Abandoned
  • 2009-05-15 JP JP2011508988A patent/JP2011521104A/ja active Pending
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  • 2009-05-15 WO PCT/FR2009/050909 patent/WO2009150352A2/fr active Application Filing

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