EP2282983A2

EP2282983A2 - PROCESS FOR PRODUCING COMPOUNDS OF THE CXHYO2 TYPE BY REDUCTION OF CARBON DIOXIDE (CO2) AND/OR CARBON MONOXIDE (CO)& xA;

Info

Publication number: EP2282983A2
Application number: EP09761903A
Authority: EP
Inventors: Béatrice Sala; Olivier Lacroix
Original assignee: Areva SA
Current assignee: Areva SA
Priority date: 2008-05-15
Filing date: 2009-05-15
Publication date: 2011-02-16
Also published as: BRPI0912654A2; CN102056866A; FR2931168A1; RU2010151465A; JP2011521104A; RU2493293C2; US20110132770A1; FR2931168B1; WO2009150352A3; WO2009150352A2

Abstract

The present invention relates to a process for electrolysing steam introduced under pressure into an anode 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 CO2 and/or CO under pressure into the cathode compartment (33) of the electrolyser (30); - reduction of the CO2 and/or CO injected into the cathode compartment (33) by said reactive hydrogen atoms generated, in such a way that the CO2 and/or the CO form compounds of the CxHyOz type where x>1, y is between 0 and 2x+2 and z is between 0 and 2x.

Description

Process for producing C _x HyO ₂ compounds by reduction of carbon dioxide (CO ₂ ) and / or carbon monoxide (CO)

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.

Conductive ceramic membranes are now the subject of much research to increase their performance; in particular, these membranes find particularly interesting applications in the fields:

- the electrolysis of water at high temperature for the production of hydrogen, - in the treatment of carbonaceous gases (CO ₂ , CO) by electrochemical hydrogenation to obtain compounds of the CχH _y Oz type (x> 1 including between 0 and 2x + 2 and z between 0 and 2x). 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.

In this context, it is possible, for example, to synthesize hydrogen from the steam reforming of hydrocarbons. One of the major problems of this synthetic route is that it generates, as by-products, significant amounts of greenhouse gases of CO ₂ type. In fact, 8 to 10 tonnes of CO ₂ are released to produce 1 tonne of hydrogen. There are two challenges for future years: to find a new usable energy carrier that is safe for our environment, such as hydrogen, and to reduce the amount of carbon dioxide.

Techno-economic estimates of industrial processes now take this latter data into account. However, it is mainly sequestration, especially underground sequestration in crevices that do not necessarily correspond to old oil deposits, which in the long run may not be safe.

It seems advisable to recycle this carbon dioxide in the form of compounds that can be used in the field of chemistry or in the field of energy production. The energy required for this transformation could be electricity, for example of nuclear origin, and in particular that of reactors such as high-temperature nuclear reactors of the type

HTR (High Temperature Reactor) or 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.

At present, two methods of producing electrolysis of water vapor are known:

According to a first method illustrated in FIG. 1, an electrolyte capable of conducting O ^{2 -} ions and operating at temperatures generally between 750 ° C. and 1000 ° C. is used.

More precisely, 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 Krόger-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:

Ol → -O ', 2 + V _n + 2e

Thus, 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.

According to a second method illustrated in FIG. 2, 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.

More precisely, this 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.

The application of a potential difference between the anode 12 and the cathode 13 causes an oxidation of the water vapor H ₂ O on the side of the anode 12. The water vapor introduced into the anode 12 is thus oxidized to form oxygen O ₂ and H ⁺ ions (or OH ₀ in Krόger-Vink notation), this reaction releasing electrons e ^" according to the equation:

H ₂ O + 20 _o → 2OH ₀ + -O ₂ + 2e

The H ⁺ ions (or OH ₀ in the Krόger-Vink notation) migrate through the electrolyte 11, to form hydrogen H ₂ on the surface of the method 13 according to the equation:

Thus, this process provides at the outlet of the electrolyzer 10 pure hydrogen - cathode compartment - and oxygen mixed with water vapor - anodic compartment.

More specifically, the formation of 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 Krόger-Vink notation). These species being highly reactive, they usually recombine to form hydrogen H ₂ according to the equation:

2 "Electrode ^→ " 2

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. To this end, 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. in this membrane under water vapor, an oxidation of water introduced in the form of vapor is carried out at the anode so as to generate protonated species in the membrane which migrate within this same membrane and reduce to 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: 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. As explained above, 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 Kroger- Vink).

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).

These highly reactive hydrogen atoms Hξ _lectmde are formed on the cathode surface according to the reaction:

e + OH _o → O * + H _E ^x _electrode

In fact, in the presence of CO ₂ and / or CO on the cathode side, the highly reactive hydrogen _electrode reacts with the carbon compounds on the electrode to give reduced compounds of the dioxide and / or carbon monoxide. of the type C _x H _y O _z with x>1; including between O and 2x + 2 and z between O and 2x).

By way of example, 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 process according to the invention may also have one or more of the following characteristics, considered individually or in any technically possible combination: 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

H2 allowing the incorporation of protonated species into the membrane under vapor pressure;

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,

an anode,

a cathode, 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:

means for the insertion under pressure of steam into said electrolyte via said anode; means for introducing CO ₂ and / or CO under pressure into the cathode compartment of the electrolyser, and

- Means for reducing CO ₂ and / or CO introduced into the cathode compartment according to a method according to one of the preceding embodiments. 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.

Other features and advantages of the invention will emerge clearly from the description which is given below, as an indication and in no way limiting, with reference to the appended figures, among which:

FIGS. 1 and 2, already described, are simplified schematic representations of electrolysers of water vapor, and

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 cathode 33,

an electrolyte 31,

- 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).

According to the invention, it 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.

At the anode 32, 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.

These 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 chemical equations of the different reactions can be written in particular:

(6n + 2) H _E ^x _electrode + nCO ₂ → C _n H _{2n + 2} + InH ₂ O 6nH ^x _electrode + nCO ₂ → C _n H _2n + InH ₂ O

^ H _E ^x _Uctrode + n CO ₂ → C _n H _{2n + 2} O + (In - I) H ₂ O (6n - 2) H _E ^x _lectnde + n CO ₂ → C _n H _2n O + (In - I) H ₂ O

Since the nature of the compound formed depends on the operating conditions, the overall formation reaction of C _x H _y O _z can therefore be written as follows:

(Ax - 2z + y) H _E ^x _electrode + xC0 ₂ → C _x H _y O _z + (2x - Z) H ₂ O

The nature of the compounds C _x H _y O _z synthesized at the cathode depends on numerous process parameters such as, for example, pressure gas, the operating temperature T1 and the potential / current torque applied to the cathode as described below:

As regards the pressure of the gases, 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.

It will be noted that the term "relative pressure" refers to the insertion pressure relative to the atmospheric pressure.

Note that it is possible to use either a gas stream containing only water vapor or a gas stream containing partially water vapor. Thus, depending on the case, the term "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.

Note that 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.

Regarding the T1 operating temperature of the device 30, 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.

In fact, a large variety of compounds can be obtained such as methane, methanol, formaldehyde, carboxylic acids (formic acid, ...) and other compounds with longer chains, this can go as far as formation synthetic gasoline. For example, one can have for reactions to the cathode the following reactions:

8H * _electrode + CO ₂ → CH _{4 +} IH ₂ O *> HL _trode + CO ₂ → CH ₂ + 2H ₂ O

*> HL _trode + CO ₂ → CH ₃ OH + H ₂ O

4H * _electrode + CO ₂ → CH ₂ O + H ₂ O

H _E ^x _electrode + CO ₂ → COOH

As regards the potential / current torque applied to the cathode, it should be noted that the nature of the carbon compounds formed also depends on this potential. In fact, the more the cathodic medium is reducing (low redox potential E), the more the carbon compounds generated are hydrogenated as shown diagrammatically in the diagram below (R being, for example, an alkyl group).

E 7I

R-CH ₃ <R-CH ₂ OH <R-COH <R-COOH 4

Hvdroeénation 71

For the advantageous realization of these reactions, it is necessary to have electrodes having a large number of triple points, namely points or contact surfaces between an ion conductor, an electronic conductor and a gas phase.

For example, electrodes envisaged are preferably cermets formed by a mixture of ionic conducting ceramic, and an electronically conductive metal.

However, the use of electrically conductive "all ceramic" electrodes can also be considered in place of a cermet. It should be noted that a given electrolyte may be a proton or ionic conductor O ^{2 "} depending on the temperature and pressure of the applied vapor.

But the use of proton conductive membranes, generating hydrogen (in the form of a hydrogen atom more or less adsorbed on the surface of the cathode) highly more reactive than hydrogen H ₂ (or dihydrogen), allow thus a better hydrogenation of CO ₂ and CO compared to a conventional hydrogenation process (in the presence of H ₂ ). In addition, the use of 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 surges at the electrodes

- contact resistances at the electrodes / electrolytes interfaces, - ohmic drop within the materials and in particular inside the electrolyte

the standard thermodynamic voltage of reaction with the electrodes. In this context, 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. Thus, 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,

- Electrolysis of water vapor and reduction of the gas (CO ₂ and / or CO) in the cathode compartment. Thanks to the gaseous stream containing water vapor, the protonation of the membrane is promoted by the steam under pressure and this pressure is advantageously used to obtain the desired conductivity at a given temperature. Such a method is described, for example, in the French patent application filed under number 07/55418 on June 1, 2007.

As indicated in this application, the Applicant has observed that increasing the partial and relative pressure of water vapor causes an increase in the ionic conductivity of the membrane.

This correlation between the increase of partial and relative pressure with the increase of conductivity makes it possible to work at lower temperature with suitable materials. In other words, the decrease in conductivity caused by operation at lower temperature is compensated by the increase in the partial and relative pressure of water vapor. According to the invention, it is produced at the cathode of hydrogen

"Highly reactive" capable of generating hydrogen (H ₂ ), in the absence of a reducible compound, or compounds of the CχH _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 Dχθ ₃ -χ _{/ 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. In general, 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-ιo (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.

More generally, 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 present invention is capable of many variants. In particular, 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%.

In fact, a good compromise must be found between the densification rate which must be as high as possible (in particular for the mechanical resistance of the electrolytes and the permeation of the gases) and the capacity of the material to allow the incorporation of protonated species. The increase in the partial pressure of water vapor which forces the incorporation of the protonated species into the membrane makes it possible to compensate for the increase in the densification rate. According to one variant, 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. Moreover, the lacunary oxide in oxygen atoms may have stoichiometric differences and / or is doped. Indeed, non-stoichiometry and / or doping allow the creation of gaps in oxygen atoms. Thus, in the case of proton conduction, the pressure exposure of a perovskite with stoichiometric and / or doped (and therefore deficient in oxygen) deviations to water vapor induces the incorporation of protonated species into the structure. The water molecules fill the oxygen vacancies and dissociate into 2 hydroxyl groups (or H ⁺ proton on an oxide site) according to the reaction:

O _Q + V ₀ + H ₂ O ≈ 2OH ₀ It should be noted that other materials than non-stoichiometric and / or doped perovskites can be used as a material promoting the incorporation of water and its dissociation in the form of protonated species and / or hydroxides.

For example, 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. In fact, all structures having a high affinity with water and / or protons can be envisaged.

Claims

1. A method of electrolysis of water vapor introduced under pressure into an anode compartment (32) of an electrolyzer (30) provided with a proton conducting membrane (31) made of a material allowing the incorporation of species protonated in this membrane under water vapor, an oxidation of water introduced in the form of vapor being carried out at the anode (32) so as to generate protonated species in the membrane which migrate within the same membrane and reduce on the surface of the cathode (33) 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 (33) of the electrolyser (30), the reduction of CO ₂ and / or CO introduced into the cathode compartment (33) from said generated hydrogen reactive atoms such that CO ₂ and / or CO form compounds of the type C _x HyOz _, with x>1; between 0 and 2x + 2 and z between 0 and 2x.

2. electrolysis process according to claim 1 characterized in that it comprises a step of controlling the nature of CxHyOz type compounds formed as a function of the potential torque / current applied to the cathode.

3. An electrolysis method according to claim 1 or 2 characterized in that it comprises a step of using a proton conductive membrane (31) impermeable to the diffusion of oxygen O ₂ and H ₂ and allowing the incorporation of protonated species in this membrane (31) under vapor pressure.

4. An electrolysis method according to claim 3 characterized in that it comprises a step of using a proton conductive membrane (31) of the type: lacunary perovskites, non-stoichiometric perovskites and / or doped with the 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 structure hydroxyapatite Meio (X0 ₄ ) ₆ (OH) 2, of silicate structure, alumina-silicates, phyllosilicates, zeolite, silicates grafted with oxyacids or silicates grafted with phosphates.

5. electrolysis process according to claim 4 characterized in that it comprises a step of use, as a proton conducting membrane (31), an electrolyte supported by the cathode (33) or by the anode (32). in order to reduce its thickness in order to increase its mechanical strength.

6. Electrolysis method according to one of the preceding claims characterized in that it comprises a step of using a partial pressure and relative 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 bar.

7. electrolysis process according to one of the preceding claims characterized in that the partial pressure and relative water vapor is preferably greater than or equal to 50 bar.

8. electrolysis process according to one of the preceding claims characterized in that 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, this last being greater than or equal to at least 100 bar.

9. Electrolysis process according to one of the preceding claims characterized in that 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.

10. An electrolysis method according to one of the preceding claims characterized in that the electrodes (32, 33) of porous structure, are either cermets, or "ceramic" electrodes with mixed electronic conduction and ionic.

1 1. electrolysis process according to claim 10 characterized in that the cermets are, for the cathode (33), cermets whose ceramic is compatible with the electrolyte forming the membrane (31) and in which the nature of the metal dispersed 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.

12. Electrolysis method according to claim 10 or 1 1 characterized in that the cermets are, for the anode (32), cermets whose ceramics are compatible with the electrolyte forming the membrane (31) and in which nature of the dispersed metal is preferably a metal alloy or a passivable metal.

13. Device (30) for electrolysis of water vapor introduced under pressure into an anode compartment of an electrolyzer provided with a proton conductive membrane, made of a material allowing the incorporation of protonated species into this membrane under water vapor after oxidation, comprising:

an electrolyte (31) in the form of an ionic conducting membrane made in said material allowing the incorporation of protonated species under the effect of the water pressure in said membrane,

an anode (32),

a cathode (33),

a generator (34) for generating current and for applying a potential difference between said anode (32) and said cathode (33), characterized in that it comprises:

means (35) for the insertion under pressure of steam into said electrolyte (31) via said anode (32),

means (36) for introducing CO ₂ and / or CO under pressure into the cathode compartment of the electrolyser,

- Means for reducing CO ₂ and / or CO introduced into the cathode compartment according to a method according to one of the preceding claims.

14. Device according to claim 13 characterized in that the material for the incorporation of protonated species is impermeable to O ₂ and H ₂ gas.

15. Device according to one of claims 13 or 14 characterized in that the material for the incorporation of protonated species has a densification rate greater than 88%, preferably at least 94%.

16. Device according to one of claims 13 to 15 characterized in that the material for the incorporation of protonated species is a gap oxide oxygen atoms such as a lacuna perovskite oxygen acting as proton conductor.

17. Device according to claim 16 characterized in that the lacunary oxide oxygen atoms has stoichiometric differences and / or is doped.