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WO2024260714A1 - Method for photocatalysis by light/dark cycles - Google Patents

Method for photocatalysis by light/dark cycles Download PDF

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Publication number
WO2024260714A1
WO2024260714A1 PCT/EP2024/065225 EP2024065225W WO2024260714A1 WO 2024260714 A1 WO2024260714 A1 WO 2024260714A1 EP 2024065225 W EP2024065225 W EP 2024065225W WO 2024260714 A1 WO2024260714 A1 WO 2024260714A1
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WO
WIPO (PCT)
Prior art keywords
minutes
duration
chosen
molecule
photocatalyst
Prior art date
Application number
PCT/EP2024/065225
Other languages
French (fr)
Inventor
Celine Pagis
Mickael RIVALLAN
Joudy DANKAR
Audrey Bonduelle
Mohamad EL-ROZ
Philippe Bazin
Original Assignee
IFP Energies Nouvelles
Centre National De La Recherche Scientifique
Ecole Nationale Superieure D'ingenieurs De Caen
Universite De Caen Normandie
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Publication of WO2024260714A1 publication Critical patent/WO2024260714A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/063—Titanium; Oxides or hydroxides thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
    • B01J35/39—Photocatalytic properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B01J35/45—Nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/615—100-500 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C1/00—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon
    • C07C1/02—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2521/00—Catalysts comprising the elements, oxides or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium or hafnium
    • C07C2521/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2523/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00
    • C07C2523/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals
    • C07C2523/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group C07C2521/00 of noble metals of the platinum group metals
    • C07C2523/42—Platinum

Definitions

  • dihydrogen H2 for example by photoconversion of water into liquid phase and/or gas phase
  • VOCs volatile organic compounds
  • the process of using solar energy to convert carbon dioxide is of major interest because it allows solar energy to be stored in the form of solar fuel and/or other recoverable platform molecules.
  • all the carbon atoms present in these solar fuels come from gaseous CO2, the process is considered carbon neutral.
  • the present invention relates to a photocatalysis process carried out in the gas phase and/or in the liquid phase comprising the following steps: a) bringing a feedstock comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or as a mixture, into contact with a photocatalyst, and forming a reaction medium; b) irradiating the reaction medium with at least one irradiation source producing at least one wavelength between 280 and 2500 nm, for n cycles of a duration t1 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 10 and 30 minutes, n being greater than or equal to 2, the n cycles being spaced apart by a duration t2 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 15 and 45 minutes, during which the reaction medium is not irradiated.
  • the expression "between ... and " and “between .... and " are equivalent and mean that the limit values of the interval are included in the range of values described. If this is not the case and the limit values are not included in the range described, such precision will be provided by the present invention.
  • the different parameter ranges for a given step such as pressure ranges and/or temperature ranges can be used alone or in combination.
  • a preferred pressure value range can be combined with a more preferred temperature value range.
  • photodegradable organic compound means a molecule comprising at least one carbon-hydrogen (C-H) bond and which is capable of being degraded by the action of photons. Degradation means a reduction in its molecular weight.
  • sacrificial compound corresponds to an oxidizable compound, in gaseous or liquid form.
  • the groups of chemical elements correspond to those of the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief D.R. Lide, 81st edition, 2000-2001).
  • group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.
  • the total pore volume and pore distribution are determined by nitrogen porosimetry as described in the book “Adsorption by powders and porous solids. Principles, methodology and applications” written by F. Rouquérol, J. Rouquérol and K. Sing, Academic Press, 1999.
  • Specific surface area means the BET specific surface area (SBET in m2/g) determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 1938, 60, 309.
  • the maximum wavelength absorbable by a semiconductor is calculated using the following equation: With Amax the maximum wavelength absorbable by a semiconductor (in m), h the Planck constant (4.13433559.10-15 eV.s), c the speed of light in vacuum (299 792 458 ms-1) and Eg the forbidden band width or "bandgap" according to the Anglo-Saxon terminology of the semiconductor (in eV).
  • reaction medium means the mixture formed by the charge, the possible sacrificial compound and the photocatalyst.
  • VOCs Volatile organic compounds
  • VOCs European Council Directive 1999/13/EC means any compound containing at least the element carbon and one or more of the following elements: hydrogen, halogen, oxygen, sulfur, phosphorus, silicon or nitrogen, with the exception of carbon dioxide, and having a vapor pressure of 0.01 kPa or more at a temperature of 273.15 K.
  • the present invention comprises a step a) of bringing into contact a charge comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or in a mixture, with a photocatalyst, and forming a reaction medium.
  • the process is carried out in gaseous, liquid or biphasic, gaseous and liquid phase, meaning respectively that the feedstock treated according to the process is in gaseous, liquid or biphasic, gaseous and liquid form.
  • the molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound is also in gaseous form.
  • a diluting fluid such as N2 or Ar, may be present in the reaction medium when the process is carried out in the gas phase.
  • the presence of a diluting fluid is not required for carrying out the invention, however it may be useful to add one to the feedstock to ensure the dispersion of the feedstock and/or the photocatalyst in said medium, the control of the adsorption of the reactants/products on the surface of the photocatalyst, the control of the absorption of photons by the photocatalyst, the dilution of the products to limit their recombination and other parasitic reactions of the same order.
  • a diluting fluid also allows the control of the temperature of the reaction medium, thus being able to compensate for the possible exo/endothermicity of the photocatalyzed reaction.
  • the nature of the diluting fluid is chosen in such a way that its influence is neutral on the reaction medium or that its possible reaction does not harm the achievement of the desired application.
  • a charge in liquid form this may be in ionic, organic or aqueous form.
  • the charge in liquid form is preferably aqueous.
  • a basic or acidic agent may be added to the feedstock.
  • the basic agent may be chosen from alkali or alkaline earth hydroxides, organic bases, for example amines or ammonia.
  • the acidic agent may be chosen from inorganic acids, for example nitric, sulfuric, phosphoric, hydrochloric, hydrobromic acid or organic acids such as carboxylic or sulfonic acids.
  • the liquid charge when it is aqueous, it may contain in any quantity any solvated ion, such as for example K + , Li + , Na + , Ca 2+ , Mg2 + , SO4 2 CI; F; NCh 2 '.
  • any solvated ion such as for example K + , Li + , Na + , Ca 2+ , Mg2 + , SO4 2 CI; F; NCh 2 '.
  • the molecule is chosen from H2O, NH3, and a photodegradable organic compound chosen from CH4 and an alcohol, alone or in a mixture.
  • the molecule is chosen from H2O, NH3, and a photodegradable organic compound being an alcohol, alone or in a mixture.
  • the molecule is CO2 in gaseous form.
  • the molecule When the desired application is the photoconversion of CO2 in liquid phase, the molecule is CO2 solubilized in the form of aqueous CO2, hydrogen carbonate or carbonate.
  • the feedstock and the photocatalyst are also brought into contact with at least one gaseous sacrificial compound which is an oxidizable compound chosen from H2O, NH3, H2, CH4 and an alcohol, alone or in a mixture.
  • at least one gaseous sacrificial compound is chosen from H2O, H2 and an alcohol, alone or in a mixture.
  • the feedstock and the photocatalyst are also brought into contact with at least one sacrificial compound which is a liquid or solid oxidizable compound soluble in the liquid feedstock chosen from H2O, NH3, an alcohol, an aldehyde, a carboxylic acid and an amine, alone or in combination.
  • the sacrificial compound is H2O or an alcohol.
  • the pH is generally between 2 and 12, preferably between 3 and 10.
  • the sacrificial compound is advantageously present to enable reduction reactions (e.g. CO2 reduction or H2O reduction)
  • the molecule is a photodegradable organic compound being a volatile organic compound (VOC).
  • VOC volatile organic compound
  • the at least one volatile organic compound is chosen from halogenated hydrocarbons, aromatic hydrocarbons, alkanes, alkenes, alkynes, aldehydes, ketones, alone or as a mixture.
  • the molecule is a photodegradable organic compound solubilized in aqueous form.
  • the at least one solubilized photodegradable organic compound is chosen from halogenated hydrocarbons, aromatic hydrocarbons, alkanes, alkenes, alkynes, aldehydes, ketones, alone or as a mixture.
  • the photocatalyst is advantageously composed of one or more inorganic, organic or organic-inorganic semiconductors, and/or one or more transition metal complexes.
  • the maximum wavelength of the photons absorbable by said photocatalysts is between 280 nm and 2500 nm (i.e. a forbidden band width generally between 0.50 and 4.43 eV).
  • the semiconductor is chosen from inorganic semiconductors.
  • the inorganic semiconductors may be chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium. They may also be composed of elements of groups 111 A and VA, such as GaP, GaN, InP and InGaAs, or elements of groups IIB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VIIA, such as CuCI and AgBr, or elements of groups IVA and VIA, such as PbS, PbO, SnS and PbSnTe, or elements of groups VA and VIA, such as Bi2Te3 and Bi2O3, or elements of groups IIB and VA, such as CdsP2, ZnsP2 and ZnsAs2, or elements of groups IB and VIA, such as CuO, CU2O and Ag2S, or elements of groups VII IB and VIA, such as CoO, PdO, Fe2
  • the semiconductor is selected from TiO2, SiC, Bi2S3, Bi2O3, CdO, CdS, Ce2O3, CeO2, CeAIOs, CoO, CU2O, Fe2O3, FeTiOs, In 2 O 3 , In(OH) 3 , NiO, PbO, ZnO, Ag 2 S, CdS, Ce 2 S 3 , Cu 2 S, Cu nS 2 , In 2 S 3 , MOS 2 , ZnFe 2 O 3 , ZnS, ZnO, WO 3 , ZnFe 2 O 4 and ZrS 2 , alone or in mixture.
  • the semiconductor is chosen from organic semiconductors.
  • Said organic semiconductors can be chosen from tetracene, anthracene, polythiophene, polystyrene sulfonate, phosphyrenes, fullerenes and carbon nitrides.
  • the semiconductor is chosen from organic-inorganic semiconductors.
  • organic-inorganic semiconductors we can cite MOF (for Metal Organic Frameworks) type crystallized solids.
  • MOFs are made up of inorganic subunits (transition metals, lanthanides, etc.) and connected to each other by organic ligands (carboxylates, phosphonates, imidazolates, etc.), thus defining crystallized hybrid networks, sometimes porous.
  • the transition metal complexes are in the form of a metal center of varying oxidation state and organic ligands having the following formula M(L)n, with M the metallic element and the n organic ligands L.
  • the metallic element M is included in the transition metals of the periodic table of elements, preferably the metallic element M is Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Ir.
  • the transition metal complex is bimetallic (or binuclear) then the formula becomes M1M2(L)n.
  • the L ligands can be monodentate ( H2O , OHNH3 , CH3OH , Cl; NCS; CN; CO, ...), bidentate (oxalate, 1,2-diaminoethane, ...), polydentate (EDTA, %) and macrocyclic (crown ether, ...) ligands.
  • n>1 the L ligands can be the same or different.
  • the photocatalyst is composed of one or more inorganic semiconductors.
  • the semiconductors constituting said photocatalyst may optionally be doped with one or more ions chosen from metal ions, such as for example ions of V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti, non-metallic ions, such as for example C, N, S, F, P, or by a mixture of metal and non-metallic ions.
  • metal ions such as for example ions of V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti
  • non-metallic ions such as for example C, N, S, F, P, or by a mixture of metal and non-metallic ions.
  • the semiconductors constituting said photocatalyst may contain particles comprising one or more elements in the metallic state selected from an element of groups IVB, VB, VIB, VI IB, VI II B, IB, II B, I HA, IVA and VA of the periodic table of elements.
  • Said particles comprising one or more elements in the metallic state are in direct contact with said semiconductor.
  • Said particles may be composed of a single element in the metallic state or of several elements in the metallic state which may be formed an alloy.
  • the term "element in the metallic state" (not to be confused with "metallic element") means an element belonging to the family of metals, said element being in the zero oxidation state (and therefore in the form of metal).
  • the element(s) in the metallic state are chosen from a metallic element from groups VIIB, VIIIB, IB and IIB of the periodic table of elements, and particularly preferably from platinum, palladium, gold, nickel, cobalt, ruthenium, silver, copper, rhenium or rhodium.
  • Said particles comprising one or more element(s) in the metallic state are preferably in the form of particles with sizes between 0.5 nm and 1000 nm, preferably between 0.5 nm and 100 nm and even more preferably between 1 and 20 nm.
  • the semiconductors constituting said photocatalyst can be sensitized on the surface with any organic molecules capable of absorbing photons.
  • the method of preparing the photocatalyst may be any preparation method known to those skilled in the art and suitable for the desired photocatalyst.
  • the photocatalyst used in the process according to the invention can be in different forms (nanometric powder, nanoobjects with or without cavities, etc.) or shaped (films, monolith, micrometric or millimetric sized beads, etc.).
  • the photocatalyst is advantageously in the form of nanometric powder.
  • the contacting of the charge comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or in a mixture, can be done by any means known to those skilled in the art.
  • the contacting of said charge can advantageously be carried out in a fixed crossed bed, in a fixed licking bed or in suspension (also called “slurry” according to the Anglo-Saxon terminology).
  • the photocatalyst can also be deposited directly on optical fibers.
  • the photocatalyst When the contact is in a fixed crossed bed, the photocatalyst is preferentially deposited in a layer on a porous support, for example of the ceramic or metallic sintered type, and the charge is sent through the photocatalytic bed.
  • the photocatalyst When the contact is in a fixed licking bed, the photocatalyst is preferentially deposited in a layer on a non-porous support of the ceramic or metallic type, and the charge is sent to the photocatalytic bed.
  • the photocatalyst is preferably in the form of particles suspended in a liquid or liquid-gas charge comprising the molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone. or in mixture.
  • a liquid or liquid-gas charge comprising the molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone. or in mixture.
  • the implementation can be done in a closed reactor or continuously.
  • the method according to the invention comprises a step b) of irradiating the reaction medium with at least one irradiation source producing at least one wavelength between 280 and 2500 nm, preferably between 280 and 1100 nm, preferably between 315 nm and 800 nm, for n cycles of a duration t1 between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 10 and 30 minutes, n being greater than or equal to 2, the n cycles being spaced apart by a duration t2 between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 15 and 45 minutes, during which the reaction medium is not irradiated.
  • the durations t1 and t2 can be equal or different.
  • the duration t2 is greater than or equal to the duration t1, preferably the duration t2 is greater than the duration t1.
  • the quantity of photocatalysis products obtained is increased, the applicant has demonstrated that the use of a dark time of duration t2 greater than or equal to the duration t1 during which the reaction medium is irradiated allows more efficient recharging of the surface of the photocatalyst.
  • n is greater than or equal to 3.
  • n is greater than or equal to 4.
  • n is greater than or equal to 5.
  • n is greater than or equal to 6.
  • a photocatalyst is advantageously composed of one or more semiconductors, and/or one or more transition metal complexes, which can be activated by the absorption of at least one photon.
  • absorbable photons are those whose energy is greater than the forbidden band width.
  • photocatalysts can be activated by at least one photon of a wavelength corresponding to the energy associated with the forbidden band widths of the semiconductors constituting the photocatalyst or of a lower wavelength.
  • any irradiation source emitting at least one wavelength suitable for activating said photocatalyst present in the reaction medium, i.e. absorbable by said photocatalyst can be used according to the invention.
  • the irradiation source can be both natural by solar irradiation, and artificial such as laser, Hg, incandescent lamp, tube fluorescent, plasma or light-emitting diode (LED).
  • the irradiation source is natural by solar irradiation.
  • the irradiation source produces radiation of which at least a portion of the wavelengths is less than the maximum absorbable wavelength ( ⁇ max) by the semiconductors constituting the photocatalyst.
  • ⁇ max maximum absorbable wavelength
  • the irradiation source is solar irradiation, it generally emits in the ultraviolet, visible and infrared spectrum, i.e. it emits a wavelength range from 280 nm to 2500 nm (according to ASTM G173-03).
  • the irradiation source provides a flux of photons that irradiates the reaction medium containing the photocatalyst.
  • the interface between the reaction medium and the light source varies depending on the applications and the nature of the light source.
  • the irradiation source When the irradiation source is natural, for example by solar irradiation, the irradiation source is located outside the reactor and the interface between the two can be an optical window made of pyrex, quartz, organic glass or any other interface allowing the photons absorbable by the photocatalyst according to the invention to diffuse from the external environment within the reactor.
  • the performance of the photocatalysis reaction is conditioned by the supply of photons adapted to the photocatalyst for the reaction envisaged and is therefore not limited to specific pressure or temperature ranges outside of those allowing the stability of the product to be ensured.
  • the temperature range used for the photocatalysis reaction according to the invention is generally between -10 and +200°C, preferably between 0 and 150°C, and very preferably between 0 and 50°C.
  • the pressure range used for the photocatalysis reaction according to the invention is generally between 0.01 and 70 MPa (0.1 to 700 bar), preferably between 0.1 and 5 MPa (1 to 50 bar) and very preferably between 0.1 and 2 MPa (1 to 20 bar).
  • Figure 1 shows the cumulative amount of methane in arbitrary units produced as a function of time in minutes for a continuous CO2 photoconversion process over 3 hours of testing.
  • Example 1 Catalyst based on TiO2 and impregnated with 1% weight of Pt
  • the photocatalyst is a commercial TiO2-based semiconductor (CristalACTiVTM PC-500, Tronox, anatase, purity >99 wt%).
  • the particle size of the photocatalyst measured by X-ray diffraction (XRD) is 6 nm and the specific surface area measured by BET method is equal to 393 m2 /g.
  • the reduced platinum particles were deposited by photodeposition, average particle size: 3 nm.
  • the sample is subjected to a gas-phase photocatalytic reduction test of CO2 in a continuous flow-through reactor equipped with a quartz optical window with a surface area of 5.3.10' 4 m 2 and a sintered porous filter placed in front of the optical window on which the photocatalytic solid is deposited.
  • the tests are carried out at room temperature of 23°C under atmospheric pressure of 1 atm.
  • a CO2 flow rate of 5 cc/min passes through a water saturator (allowing the carrier gas to be loaded at a level of 20,000 ppm H2O) before being distributed into the reactor.
  • Example 2 Catalyst based on TiO2 only
  • the photocatalyst is a commercial TiO2-based semiconductor (CristalACTiVTM PC-500, Tronox, anatase, purity >99 wt%).
  • the particle size of the photocatalyst measured by X-ray diffraction (XRD) is 6 nm and the specific surface area measured by BET method is 393 m2 /g.
  • the sample is subjected to a gas-phase photocatalytic reduction test of CO2 in a continuous flow-through reactor equipped with a quartz optical window with a surface area of 5.3.10 -4 m 2 and a sintered porous filter placed in front of the optical window on which the photocatalytic solid is deposited.
  • the tests are carried out at room temperature of 23°C under atmospheric pressure of 1 atm.
  • a CO2 flow rate of 5 cc/min passes through a water saturator (allowing the carrier gas to be loaded at a level of 20,000 ppm H2O) before being distributed into the reactor.

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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Abstract

The present invention relates to a photocatalysis method carried out in the gas phase and/or in the liquid phase, comprising the following steps: a) bringing a feedstock comprising a molecule selected from CO2, H2O, NH3 and a photodegradable organic compound, alone or as a mixture, into contact with a photocatalyst, and forming a reaction medium; b) irradiating the reaction medium with at least one irradiation source producing at least one wavelength of between 280 and 2500 nm, for n cycles of a duration t1 of between 1 and 60 minutes, n being greater than or equal to 2, the n cycles being spaced apart from one another by a duration t2 of between 1 and 60 minutes during which the reaction medium is not irradiated.

Description

PROCEDE DE PHOTOCATALYSE PAR CYCLES LUMIERE/OBSCURITE PHOTOCATALYSIS PROCESS BY LIGHT/DARK CYCLES

DOMAINE TECHNIQUE TECHNICAL AREA

Le domaine technique est celui de la photocatalyse et son application pour : The technical field is that of photocatalysis and its application for:

- La photoconversion du CO2 en phase liquide et/ou en phase gaz ; - Photoconversion of CO2 into liquid phase and/or gas phase;

- La production de dihydrogène H2 par exemple par photoconversion de l’eau en phase liquide et/ou en phase gaz ; - The production of dihydrogen H2 for example by photoconversion of water into liquid phase and/or gas phase;

- La Photooxydation des polluants d'un milieu gazeux tels que les composés organiques volatils (COV) et/ou les polluants d'un milieu liquide. - Photooxidation of pollutants of a gaseous medium such as volatile organic compounds (VOCs) and/or pollutants of a liquid medium.

TECHNIQUE ANTERIEURE PRIOR TECHNIQUE

Le procédé d’utilisation de l’énergie solaire pour convertir le dioxyde de carbone est d’intérêt majeur car il permet de stocker l’énergie solaire sous forme de carburant solaire et/ou autre molécule plateforme valorisable. De plus, puisque tous les atomes de carbone présents dans ces carburants solaires proviennent du CO2 gazeux, le procédé est qualifié de neutre en termes d’empreinte carbone. The process of using solar energy to convert carbon dioxide is of major interest because it allows solar energy to be stored in the form of solar fuel and/or other recoverable platform molecules. In addition, since all the carbon atoms present in these solar fuels come from gaseous CO2, the process is considered carbon neutral.

Corma et al. WO2012168355A1 « Photoconversion directe de dioxyde de carbone en produits liquides » ont notamment décrit un procédé photocatalytique pour la réduction de dioxyde de carbone et d'eau. Le procédé comprend les réactifs : dioxyde de carbone (CO2) et eau (H2O) en présence d’un photocatalyseur qui est exposé à un rayonnement électromagnétique ayant une longueur d'onde dans la plage de 200 à 700 nm. Corma et al. WO2012168355A1 “Direct photoconversion of carbon dioxide to liquid products” have described in particular a photocatalytic process for the reduction of carbon dioxide and water. The process comprises the reactants: carbon dioxide (CO2) and water (H2O) in the presence of a photocatalyst which is exposed to electromagnetic radiation having a wavelength in the range of 200 to 700 nm.

L’utilisation d’une source lumineuse pour convertir le CO2 a été reportée pour la première fois en 1978 dans les travaux de Inoue et al. (Nature 1979, 277, 637-638). Depuis, différents matériaux photocatalytiques (Li et al. Chem. Rev. 2019, 119, 3962) ont été utilisés dans des conditions opératoires variables en termes de concentration en CO2, H2O, ratio CO2/H2O, présence d’C>2, température, pression. Cependant il en résulte dans la majorité des études que l’efficacité du procédé reste faible à ce jour pour différentes raisons évoquées dans la littérature (Protti et al. Phys. Chem. Chem. Phys., 2014, 16, 19790) : The use of a light source to convert CO2 was first reported in 1978 in the work of Inoue et al. (Nature 1979, 277, 637-638). Since then, different photocatalytic materials (Li et al. Chem. Rev. 2019, 119, 3962) have been used under variable operating conditions in terms of CO2 concentration, H2O, CO2/H2O ratio, presence of C>2, temperature, pressure. However, the result in the majority of studies is that the efficiency of the process remains low to date for various reasons mentioned in the literature (Protti et al. Phys. Chem. Chem. Phys., 2014, 16, 19790):

- Faible absorption de la lumière (spectre solaire) par le semiconducteur (tels que TiC>2, ZnO, WO3, BiVO4...) ; - Low absorption of light (solar spectrum) by the semiconductor (such as TiC>2, ZnO, WO 3 , BiVO 4 ...);

- Faible séparation de charge; - Low charge separation;

- Faible solubilité du CO2 dans l’eau (conditions phase liquide) ; - Low solubility of CO2 in water (liquid phase conditions);

- Présence de réactions inverses au cours de la réduction du CO2 ; - Compétition entre la réduction du CO2 vers carburant solaire et de H2O vers H2. - Presence of reverse reactions during CO2 reduction ; - Competition between CO2 reduction to solar fuel and H2O to H2.

Les conditions d’utilisation des photocatalyseurs nécessitent d’être optimisées. The conditions of use of photocatalysts need to be optimized.

Le document Thompson et al. (ACS Sustainable Chem. Eng. 2020, 8, 12, 4677) divulgue une perte d’activité lorsque le photocatalyseur travaille en flux continu probablement lié à une désactivation suite à la formation d’intermédiaires réactionnels. The Thompson et al. paper (ACS Sustainable Chem. Eng. 2020, 8, 12, 4677) discloses a loss of activity when the photocatalyst works in continuous flow probably linked to a deactivation following the formation of reaction intermediates.

Le document US5439652A « Use of controlled periodic illumination for an improved method of photocatalysis and an improved reactor design » par Sczechowski et al. met également en évidence qu’il était possible d’améliorer l’efficacité d’un procédé photocatalytique de conversion de formiates en CO2 et H2O en irradiant de façon périodique un photoréacteur de type slurry. Les cycles décrits sont très courts de l’ordre de quelques secondes. US5439652A “Use of controlled periodic illumination for an improved method of photocatalysis and an improved reactor design” by Sczechowski et al. also highlights that it was possible to improve the efficiency of a photocatalytic process for converting formates into CO2 and H2O by periodically irradiating a slurry-type photoreactor. The cycles described are very short, of the order of a few seconds.

Il est potentiellement possible d’améliorer les performances des procédés de photocatalyse en modifiant notamment différents paramètres de ces procédés. La demanderesse a démontré de façon surprenante, que l’alternance de cycles lumière/obscurité de durées respectives comprises entre 1 et 60 minutes dans un procédé de photocatalyse permet d’augmenter significativement la production de produits de photocatalyse par unité de temps d’irradiation et de masse de catalyseur par rapport à un procédé de photocatalyse par irradiation continue. It is potentially possible to improve the performance of photocatalysis processes by modifying in particular various parameters of these processes. The applicant has demonstrated, surprisingly, that the alternation of light/dark cycles of respective durations between 1 and 60 minutes in a photocatalysis process makes it possible to significantly increase the production of photocatalysis products per unit of irradiation time and catalyst mass compared to a photocatalysis process by continuous irradiation.

RESUME DE L’INVENTION SUMMARY OF THE INVENTION

La présente invention concerne un procédé de photocatalyse réalisé en phase gazeuse et/ou en phase liquide comprenant les étapes suivantes : a) mise en contact d’une charge comprenant une molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable, seuls ou en mélange, avec un photocatalyseur, et formation d’un milieu réactionnel ; b) irradiation du milieu réactionnel par au moins une source d'irradiation produisant au moins une longueur d'onde comprise entre 280 et 2500 nm, pendant n cycles d’une durée t1 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 10 et 30 minutes, n étant supérieur ou égal à 2, les n cycles étant espacés entre eux d’une durée t2 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 15 et 45 minutes pendant laquelle le milieu réactionnel n’est pas irradié. The present invention relates to a photocatalysis process carried out in the gas phase and/or in the liquid phase comprising the following steps: a) bringing a feedstock comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or as a mixture, into contact with a photocatalyst, and forming a reaction medium; b) irradiating the reaction medium with at least one irradiation source producing at least one wavelength between 280 and 2500 nm, for n cycles of a duration t1 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 10 and 30 minutes, n being greater than or equal to 2, the n cycles being spaced apart by a duration t2 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 15 and 45 minutes, during which the reaction medium is not irradiated.

DESCRIPTION DETAILLEE DE L’INVENTION DETAILED DESCRIPTION OF THE INVENTION

Selon la présente invention, l’expression « compris entre ... et ... » et « entre .... et ... » sont équivalentes et signifient que les valeurs limites de l’intervalle sont incluses dans la gamme de valeurs décrite. Si tel n’est pas le cas et que les valeurs limites ne sont pas incluses dans la gamme décrite, une telle précision sera apportée par la présente invention. Dans le sens de la présente invention, les différentes plages de paramètres pour une étape donnée telles que les plages de pression et/ou les plages de température peuvent être utilisées seules ou en combinaison. Par exemple, dans le sens de la présente invention, une plage de valeurs préférées de pression peut être combinée avec une plage de valeurs de température plus préférée. According to the present invention, the expression "between ... and ..." and "between .... and ..." are equivalent and mean that the limit values of the interval are included in the range of values described. If this is not the case and the limit values are not included in the range described, such precision will be provided by the present invention. In the sense of the present invention, the different parameter ranges for a given step such as pressure ranges and/or temperature ranges can be used alone or in combination. For example, in the sense of the present invention, a preferred pressure value range can be combined with a more preferred temperature value range.

Dans la suite, des modes de réalisation particuliers de l’invention peuvent être décrits. Ils pourront être mis en œuvre séparément ou combinés entre eux, sans limitation de combinaisons lorsque c’est techniquement réalisable. In the following, particular embodiments of the invention may be described. They may be implemented separately or combined with each other, without limitation of combinations when this is technically feasible.

Les termes suivants sont définis dans le cadre de la présente invention pour une meilleure compréhension : The following terms are defined within the scope of the present invention for better understanding:

On entend par « composé organique photodégradable », une molécule comprenant au moins une liaison carbone-hydrogène (C-H) et qui est apte à être dégradée sous l’action de photons. Par dégradation, on entend une diminution de son poids moléculaire. The term "photodegradable organic compound" means a molecule comprising at least one carbon-hydrogen (C-H) bond and which is capable of being degraded by the action of photons. Degradation means a reduction in its molecular weight.

Le terme « composé sacrificiel » correspond à un composé oxydable, sous forme gazeuse ou liquide. The term "sacrificial compound" corresponds to an oxidizable compound, in gaseous or liquid form.

Les groupes d'éléments chimiques correspondent à ceux de la classification CAS (CRC Handbook of Chemistry and Physics, éditeur CRC press, rédacteur en chef D.R. Lide, 81ème édition, 2000-2001). Par exemple, le groupe VIII selon la classification CAS correspond aux métaux des colonnes 8, 9 et 10 selon la nouvelle classification IUPAC. The groups of chemical elements correspond to those of the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief D.R. Lide, 81st edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.

Les propriétés texturales et structurales du support et du catalyseur décrits ci-après, sont déterminées par les méthodes de caractérisation connues de l'homme du métier. The textural and structural properties of the support and the catalyst described below are determined by the characterization methods known to those skilled in the art.

Le volume poreux total et la distribution poreuse sont déterminés par porosimétrie à l’azote tel que décrit dans l'ouvrage « Adsorption by powders and porous solids. Principles, methodology and applications » écrit par F. Rouquérol, J. Rouquérol et K. Sing, Academic Press, 1999.The total pore volume and pore distribution are determined by nitrogen porosimetry as described in the book “Adsorption by powders and porous solids. Principles, methodology and applications” written by F. Rouquérol, J. Rouquérol and K. Sing, Academic Press, 1999.

On entend par « surface spécifique », la surface spécifique BET (SBET en m2/g) déterminée par adsorption d’azote conformément à la norme ASTM D 3663-78 établie à partir de la méthode BRUNAUER-EMMETT-TELLER décrite dans le périodique "The Journal of American Society", 1938, 60, 309. "Specific surface area" means the BET specific surface area (SBET in m2/g) determined by nitrogen adsorption in accordance with ASTM D 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 1938, 60, 309.

On calcule la longueur d'onde maximale absorbable par un semiconducteur à l'aide de l'équation suivante :

Figure imgf000005_0001
Avec Àmax la longueur l'onde maximale absorbable par un semiconducteur (en m), h la constante de Planck (4,13433559.10-15 eV.s), c la vitesse de la lumière dans le vide (299 792 458 m.s-1) et Eg la largeur de bande interdite ou "bandgap" selon la terminologie anglo- saxonne du semiconducteur (en eV). The maximum wavelength absorbable by a semiconductor is calculated using the following equation:
Figure imgf000005_0001
With Amax the maximum wavelength absorbable by a semiconductor (in m), h the Planck constant (4.13433559.10-15 eV.s), c the speed of light in vacuum (299 792 458 ms-1) and Eg the forbidden band width or "bandgap" according to the Anglo-Saxon terminology of the semiconductor (in eV).

On entend par « milieu réactionnel », le mélange formé par la charge, l’éventuel composé sacrificiel et le photocatalyseur. The term “reaction medium” means the mixture formed by the charge, the possible sacrificial compound and the photocatalyst.

On entend par « composés organiques volatiles (COV) », selon la directive 1999/13/CE du conseil européen, tout composé contenant au moins l’élément carbone et un ou plusieurs éléments suivants : hydrogène, halogène, oxygène, soufre, phosphore, silicium ou azote, à l’exception du dioxyde de carbone, et ayant une pression de vapeur de 0,01 kPa ou plus à une température de 273,15 K. "Volatile organic compounds (VOCs)" according to European Council Directive 1999/13/EC means any compound containing at least the element carbon and one or more of the following elements: hydrogen, halogen, oxygen, sulfur, phosphorus, silicon or nitrogen, with the exception of carbon dioxide, and having a vapor pressure of 0.01 kPa or more at a temperature of 273.15 K.

Etape a) de mise en contact Step a) of contacting

La présente invention comprend une étape a) de mise en contact d’une charge comprenant une molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable, seuls ou en mélange, avec un photocatalyseur, et formation d’un milieu réactionnel. The present invention comprises a step a) of bringing into contact a charge comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or in a mixture, with a photocatalyst, and forming a reaction medium.

La charge The charge

Le procédé est réalisé en phase gazeuse, liquide ou biphasique, gazeuse et liquide, signifiant respectivement que la charge traitée selon le procédé se présente sous forme gazeuse, liquide ou biphasique, gazeuse et liquide. The process is carried out in gaseous, liquid or biphasic, gaseous and liquid phase, meaning respectively that the feedstock treated according to the process is in gaseous, liquid or biphasic, gaseous and liquid form.

Lorsque le procédé est réalisé en phase gazeuse, avec une charge se présentant sous forme gazeuse, la molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable est aussi sous-forme gazeuse. When the process is carried out in the gas phase, with a feedstock in gaseous form, the molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound is also in gaseous form.

Un fluide diluant tel que N2 ou Ar, peut être présent dans le milieu réactionnel lorsque le procédé est réalisé en phase gazeuse. La présence d'un fluide diluant n'est pas requis pour la réalisation de l'invention, cependant il peut être utile d'en adjoindre à la charge pour assurer la dispersion de la charge et/ou du photocatalyseur dans ledit milieu, le contrôle de l'adsorption des réactifs/produits à la surface du photocatalyseur, le contrôle de l’absorption des photons par le photocatalyseur, la dilution des produits pour limiter leur recombinaison et autres réactions parasites du même ordre. La présence d’un fluide diluant permet aussi le contrôle de la température du milieu réactionnel pouvant ainsi compenser l'éventuelle exo/endo- thermicité de la réaction photocatalysée. La nature du fluide diluant est choisie de telle façon que son influence soit neutre sur le milieu réactionnel ou que son éventuelle réaction ne nuise pas à la réalisation de l’application désirée. Lorsque le procédé est réalisé en phase liquide, avec une charge se présentant sous forme liquide, celle-ci peut être sous forme ionique, organique ou aqueuse. La charge sous forme liquide est préférentiellement aqueuse. A diluting fluid such as N2 or Ar, may be present in the reaction medium when the process is carried out in the gas phase. The presence of a diluting fluid is not required for carrying out the invention, however it may be useful to add one to the feedstock to ensure the dispersion of the feedstock and/or the photocatalyst in said medium, the control of the adsorption of the reactants/products on the surface of the photocatalyst, the control of the absorption of photons by the photocatalyst, the dilution of the products to limit their recombination and other parasitic reactions of the same order. The presence of a diluting fluid also allows the control of the temperature of the reaction medium, thus being able to compensate for the possible exo/endothermicity of the photocatalyzed reaction. The nature of the diluting fluid is chosen in such a way that its influence is neutral on the reaction medium or that its possible reaction does not harm the achievement of the desired application. When the process is carried out in the liquid phase, with a charge in liquid form, this may be in ionic, organic or aqueous form. The charge in liquid form is preferably aqueous.

Éventuellement, et afin de moduler le pH de la charge liquide aqueuse, un agent basique ou acide peut être ajouté à la charge. L’agent basique peut être choisi parmi les hydroxydes d’alcalins ou d’alcalinoterreux, les bases organiques par exemple les amines ou l’ammoniaque. L’agent acide peut être choisi parmi les acides inorganiques, par exemple l’acide nitrique, sulfurique, phosphorique, chlorhydrique, bromhydrique ou les acides organiques tels que des acides carboxyliques ou sulfoniques. Optionally, and in order to modulate the pH of the aqueous liquid feedstock, a basic or acidic agent may be added to the feedstock. The basic agent may be chosen from alkali or alkaline earth hydroxides, organic bases, for example amines or ammonia. The acidic agent may be chosen from inorganic acids, for example nitric, sulfuric, phosphoric, hydrochloric, hydrobromic acid or organic acids such as carboxylic or sulfonic acids.

Éventuellement, lorsque la charge liquide est aqueuse, celle-ci peut contenir en toute quantité tout ion solvaté, tels que par exemple K+, Li+, Na+, Ca2+, Mg2+, SO42 CI; F; NCh2'. Optionally, when the liquid charge is aqueous, it may contain in any quantity any solvated ion, such as for example K + , Li + , Na + , Ca 2+ , Mg2 + , SO4 2 CI; F; NCh 2 '.

Lorsque l’application recherchée est la production de H2 en phase gazeuse, la molécule est choisie parmi H2O, NH3, et un composé organique photodégradable choisi parmi CH4 et un alcool, seuls ou en mélange. When the desired application is the production of H2 in the gas phase, the molecule is chosen from H2O, NH3, and a photodegradable organic compound chosen from CH4 and an alcohol, alone or in a mixture.

Lorsque l’application recherchée est la production de H2 en phase liquide, la molécule est choisie parmi H2O, NH3, et un composé organique photodégradable étant un alcool, seuls ou en mélange. When the desired application is the production of H2 in liquid phase, the molecule is chosen from H2O, NH3, and a photodegradable organic compound being an alcohol, alone or in a mixture.

Lorsque l’application recherchée est la photoconversion du CO2 en phase gazeuse, la molécule est le CO2 sous forme gazeux. When the desired application is the photoconversion of CO2 into the gas phase, the molecule is CO2 in gaseous form.

Lorsque l’application recherchée est la photoconversion du CO2 en phase liquide, la molécule est le CO2 solubilisé sous forme de CO2 aqueux, d’hydrogénocarbonate ou de carbonate.When the desired application is the photoconversion of CO2 in liquid phase, the molecule is CO2 solubilized in the form of aqueous CO2, hydrogen carbonate or carbonate.

Avantageusement, lorsque l’application recherchée est la production de H2 ou la photoconversion du CO2, et que le procédé est réalisé en phase gazeuse, la charge et le photocatalyseur sont également mis en contact avec au moins un composé sacrificiel gazeux qui est un composé oxydable choisi parmi H2O, NH3, H2, CH4 et un alcool, seuls ou en mélange. De manière préférée, le au moins un composé sacrificiel gazeux est choisi parmi H2O, H2 et un alcool, seuls ou en mélange. Advantageously, when the desired application is the production of H2 or the photoconversion of CO2, and the process is carried out in the gas phase, the feedstock and the photocatalyst are also brought into contact with at least one gaseous sacrificial compound which is an oxidizable compound chosen from H2O, NH3, H2, CH4 and an alcohol, alone or in a mixture. Preferably, the at least one gaseous sacrificial compound is chosen from H2O, H2 and an alcohol, alone or in a mixture.

Avantageusement, lorsque l’application recherchée est la production de H2 ou la photoconversion du CO2, et que le procédé est réalisé en phase liquide, la charge et le photocatalyseur sont également mis en contact avec au moins un composé sacrificiel qui est un composé oxydable liquide ou solide soluble dans la charge liquide choisi parmi H2O, NH3, un alcool, un aldéhyde, un acide carboxylique et une amine, seuls ou en combinaison. De manière préférée, le composé sacrificiel est H2O ou un alcool. Le pH est généralement compris entre 2 et 12, de préférence entre 3 et 10. De manière générale, le composé sacrificiel est avantageusement présent pour permettre les réactions de réduction (par exemple la réduction du CO2 ou la réduction de H2O)Advantageously, when the desired application is the production of H2 or the photoconversion of CO2, and the process is carried out in the liquid phase, the feedstock and the photocatalyst are also brought into contact with at least one sacrificial compound which is a liquid or solid oxidizable compound soluble in the liquid feedstock chosen from H2O, NH3, an alcohol, an aldehyde, a carboxylic acid and an amine, alone or in combination. Preferably, the sacrificial compound is H2O or an alcohol. The pH is generally between 2 and 12, preferably between 3 and 10. Generally, the sacrificial compound is advantageously present to enable reduction reactions (e.g. CO2 reduction or H2O reduction)

Lorsque l’application recherchée est la photooxydation des polluants d'un milieu gazeux, la molécule est un composé organique photodégradable étant un composé organique volatile (COV). When the desired application is the photooxidation of pollutants in a gaseous medium, the molecule is a photodegradable organic compound being a volatile organic compound (VOC).

Avantageusement, le au moins un composé organique volatile est choisi parmi les hydrocarbures halogénés, les hydrocarbures aromatiques, les alcanes, les alcènes, les alcynes, les aldéhydes, les cétones, seuls ou en mélange. Advantageously, the at least one volatile organic compound is chosen from halogenated hydrocarbons, aromatic hydrocarbons, alkanes, alkenes, alkynes, aldehydes, ketones, alone or as a mixture.

Lorsque l’application recherchée est la photooxydation des polluants d'un milieu liquide, la molécule est un composé organique photodégradable solubilisé sous forme aqueux. When the desired application is the photooxidation of pollutants in a liquid medium, the molecule is a photodegradable organic compound solubilized in aqueous form.

Avantageusement, le au moins un composé organique photodégradable solubilisé est choisi parmi les hydrocarbures halogénés, les hydrocarbures aromatiques, les alcanes, les alcènes, les alcynes, les aldéhydes, les cétones, seuls ou en mélange. Advantageously, the at least one solubilized photodegradable organic compound is chosen from halogenated hydrocarbons, aromatic hydrocarbons, alkanes, alkenes, alkynes, aldehydes, ketones, alone or as a mixture.

Le photocatalyseur The photocatalyst

Le photocatalyseur est avantageusement composé d’un ou de plusieurs semi-conducteurs inorganiques, organiques ou organique-inorganique, et/ou d’un ou de plusieurs complexes de métaux de transition. La longueur d’onde maximale des photons absorbables par lesdits photocatalyseurs est comprise entre 280 nm et 2500 nm (soit une largeur de bande interdite généralement comprise entre 0,50 et 4,43 eV). The photocatalyst is advantageously composed of one or more inorganic, organic or organic-inorganic semiconductors, and/or one or more transition metal complexes. The maximum wavelength of the photons absorbable by said photocatalysts is between 280 nm and 2500 nm (i.e. a forbidden band width generally between 0.50 and 4.43 eV).

Selon une première variante, le semi-conducteur est choisi parmi les semi-conducteurs inorganiques. Les semi-conducteurs inorganiques peuvent être choisis parmi un ou plusieurs éléments du groupe IVA, tels que le silicium, le germanium, le carbure de silicium ou le silicium- germanium. Ils peuvent être également composés d’éléments des groupes 111 A et VA, tels que GaP, GaN, InP et InGaAs, ou d’éléments des groupes IIB et VIA, tels que CdS, ZnO et ZnS, ou d'éléments des groupes IB et VIIA, tels que CuCI et AgBr, ou d'éléments des groupes IVA et VIA, tels que PbS, PbO, SnS et PbSnTe, ou d’éléments des groupes VA et VIA, tels que Bi2Te3 et Bi2O3, ou d’éléments des groupes IIB et VA, tels que CdsP2, ZnsP2 et ZnsAs2, ou d’éléments des groupes IB et VIA, tels que CuO, CU2O et Ag2S, ou d’éléments des groupes VII IB et VIA, tels que CoO, PdO, Fe2O3 et NiO, ou d’éléments des groupes VI B et VIA, tels que M0S2 et WO3, ou d’éléments des groupes VB et VIA, tels que V2O5 et Nb20s, ou d’éléments des groupes IVB et VIA, tels que TiÛ2 et HfS2, ou d’éléments des groupes II IA et VIA, tels que ln2O3 et 10283, ou d’éléments des groupes VIA et des lanthanides, tels que Ce2O3, Pr2Û3, 801283, Tb2Ss et La2Ss, ou d’éléments des groupes VIA et des actinides, tels que UO2 et UO3. De manière préférée, le semi-conducteur est choisi parmi le TiÛ2, le SiC, le Bi2S3, le Bi2O3, le CdO, le CdS, le Ce2O3, le CeO2, le CeAIOs, le CoO, le CU2O, le Fe2O3, le FeTiOs, l’ln2O3, l’ln(OH)3, le NiO, le PbO, le ZnO, l’Ag2S, le CdS, le Ce2S3, le Cu2S, le CulnS2, l’ln2S3, le MOS2, le ZnFe2O3, le ZnS, le ZnO, le WO3, le ZnFe2Û4 et le ZrS2, seuls ou en mélange.According to a first variant, the semiconductor is chosen from inorganic semiconductors. The inorganic semiconductors may be chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium. They may also be composed of elements of groups 111 A and VA, such as GaP, GaN, InP and InGaAs, or elements of groups IIB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VIIA, such as CuCI and AgBr, or elements of groups IVA and VIA, such as PbS, PbO, SnS and PbSnTe, or elements of groups VA and VIA, such as Bi2Te3 and Bi2O3, or elements of groups IIB and VA, such as CdsP2, ZnsP2 and ZnsAs2, or elements of groups IB and VIA, such as CuO, CU2O and Ag2S, or elements of groups VII IB and VIA, such as CoO, PdO, Fe2O3 and NiO, or elements of groups VI B and VIA, such as M0S2 and WO3, or elements from groups VB and VIA, such as V2O5 and Nb20s, or elements from groups IVB and VIA, such as TiO2 and HfS2, or elements from groups II IA and VIA, such as ln 2 O3 and 10283, or elements from groups VIA and lanthanides, such as Ce2O3, Pr2O3, 801283, Tb2Ss and La2Ss, or elements from groups VIA and actinides, such as UO2 and UO3. Preferably, the semiconductor is selected from TiO2, SiC, Bi2S3, Bi2O3, CdO, CdS, Ce2O3, CeO2, CeAIOs, CoO, CU2O, Fe2O3, FeTiOs, In 2 O 3 , In(OH) 3 , NiO, PbO, ZnO, Ag 2 S, CdS, Ce 2 S 3 , Cu 2 S, Cu nS 2 , In 2 S 3 , MOS 2 , ZnFe 2 O 3 , ZnS, ZnO, WO 3 , ZnFe 2 O 4 and ZrS 2 , alone or in mixture.

Selon une autre variante, le semi-conducteur est choisi parmi les semi-conducteurs organiques. Lesdits semi-conducteurs organiques peuvent être choisis parmi le tétracène, l’anthracène, le polythiophène, le polystyrène sulfonate, les phosphyrènes, les fullerènes et les nitrures de carbone. According to another variant, the semiconductor is chosen from organic semiconductors. Said organic semiconductors can be chosen from tetracene, anthracene, polythiophene, polystyrene sulfonate, phosphyrenes, fullerenes and carbon nitrides.

Selon une autre variante, le semi-conducteur est choisi parmi les semi-conducteurs organiques-inorganiques. Parmi les semi-conducteurs organiques-inorganiques, on peut citer les solides cristallisés de type MOF (pour Metal Organic Frameworks selon la terminologie anglo-saxonne). Les MOFs sont constitués de sous-unités inorganiques (métaux de transition, lanthanides...) et connectées entre elles par des ligands organiques (carboxylates, phosphonates, imidazolates...), définissant ainsi des réseaux hybrides cristallisés, parfois poreux. According to another variant, the semiconductor is chosen from organic-inorganic semiconductors. Among organic-inorganic semiconductors, we can cite MOF (for Metal Organic Frameworks) type crystallized solids. MOFs are made up of inorganic subunits (transition metals, lanthanides, etc.) and connected to each other by organic ligands (carboxylates, phosphonates, imidazolates, etc.), thus defining crystallized hybrid networks, sometimes porous.

Selon une autre variante, les complexes de métaux de transition se présentent sous la forme d’un centre métallique de degré d’oxydation varié et de ligands organiques ayant la formule suivante M(L)n, avec M l’élément métallique et les n ligands organiques L. L’élément métallique M est compris dans les métaux de transition du tableau périodique des éléments, de manière préférée l’élément métallique M est le Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Ir. Lorsque le complexe de métaux de transition bimétallique (ou binucléaire), alors la formule devient M1M2(L)n. Les ligands L peuvent être des ligands monodentés (H2O, OH NH3, CH3OH, Cl; NCS; CN; CO, ...), bidentés (oxalate, 1 ,2-diaminoéthane, ...), polydentés (EDTA, ...) et macrocycliques (éther couronne, ...). Lorsque n>1 , alors les ligands L peuvent être identiques ou différents. According to another variant, the transition metal complexes are in the form of a metal center of varying oxidation state and organic ligands having the following formula M(L)n, with M the metallic element and the n organic ligands L. The metallic element M is included in the transition metals of the periodic table of elements, preferably the metallic element M is Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Ir. When the transition metal complex is bimetallic (or binuclear), then the formula becomes M1M2(L)n. The L ligands can be monodentate ( H2O , OHNH3 , CH3OH , Cl; NCS; CN; CO, ...), bidentate (oxalate, 1,2-diaminoethane, ...), polydentate (EDTA, ...) and macrocyclic (crown ether, ...) ligands. When n>1, then the L ligands can be the same or different.

De manière préférée, le photocatalyseur est composé d’un ou de plusieurs semi-conducteurs inorganiques. Preferably, the photocatalyst is composed of one or more inorganic semiconductors.

Les semi-conducteurs constitutifs dudit photocatalyseur peuvent éventuellement être dopés avec un ou plusieurs ions choisis parmi des ions métalliques, tels que par exemple des ions de V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti, des ions non-métalliques, tels que par exemple C, N, S, F, P, ou par un mélange d’ions métalliques et non-métalliques.The semiconductors constituting said photocatalyst may optionally be doped with one or more ions chosen from metal ions, such as for example ions of V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti, non-metallic ions, such as for example C, N, S, F, P, or by a mixture of metal and non-metallic ions.

Les semi-conducteurs constitutifs dudit photocatalyseur peuvent contenir des particules comportant un ou plusieurs élément(s) à l’état métallique choisis parmi un élément des groupes IVB, VB, VIB, VI I B, VI II B, IB, Il B, I HA, IVA et VA de la classification périodique des éléments. Lesdites particules comportant un ou plusieurs élément(s) à l’état métallique sont en contact direct avec ledit semi-conducteur. Lesdites particules peuvent être composées d’un seul élément à l’état métallique ou de plusieurs éléments à l’état métallique pouvant formés un alliage. On entend par « élément à l’état métallique » (à ne pas confondre avec « élément métallique ») un élément appartenant à la famille des métaux, ledit élément étant au degré d’oxydation zéro (et donc sous forme de métal). De préférence, le ou les éléments à l’état métallique sont choisis parmi un élément métallique des groupes VIIB, VIIIB, IB et IIB de la classification périodique des éléments, et de manière particulièrement préférée, parmi le platine, le palladium, l’or, le nickel, le cobalt, le ruthénium, l’argent, le cuivre, le rhénium ou le rhodium. Lesdites particules comportant un ou plusieurs élément(s) à l’état métallique se présentent préférentiellement sous la forme de particules de tailles comprises entre 0,5 nm et 1000 nm, de manière préférée entre 0,5 nm et 100 nm et encore plus préférentiellement entre 1 et 20 nm. The semiconductors constituting said photocatalyst may contain particles comprising one or more elements in the metallic state selected from an element of groups IVB, VB, VIB, VI IB, VI II B, IB, II B, I HA, IVA and VA of the periodic table of elements. Said particles comprising one or more elements in the metallic state are in direct contact with said semiconductor. Said particles may be composed of a single element in the metallic state or of several elements in the metallic state which may be formed an alloy. The term "element in the metallic state" (not to be confused with "metallic element") means an element belonging to the family of metals, said element being in the zero oxidation state (and therefore in the form of metal). Preferably, the element(s) in the metallic state are chosen from a metallic element from groups VIIB, VIIIB, IB and IIB of the periodic table of elements, and particularly preferably from platinum, palladium, gold, nickel, cobalt, ruthenium, silver, copper, rhenium or rhodium. Said particles comprising one or more element(s) in the metallic state are preferably in the form of particles with sizes between 0.5 nm and 1000 nm, preferably between 0.5 nm and 100 nm and even more preferably between 1 and 20 nm.

Les semi-conducteurs constitutifs dudit photocatalyseur peuvent être sensibilisés en surface avec toutes molécules organiques susceptibles d’absorber des photons. The semiconductors constituting said photocatalyst can be sensitized on the surface with any organic molecules capable of absorbing photons.

Le procédé de préparation du photocatalyseur peut être n’importe quel procédé de préparation connu de l’homme du métier et adapté au photocatalyseur souhaité. The method of preparing the photocatalyst may be any preparation method known to those skilled in the art and suitable for the desired photocatalyst.

Le photocatalyseur utilisé dans le procédé selon l’invention peut se présenter sous différentes formes (poudre nanométrique, nanoobjets comportant ou non des cavités, ...) ou mises en forme (films, monolithe, billes de taille micrométrique ou millimétrique, ...). Le photocatalyseur se présente avantageusement sous forme de poudre nanométrique. The photocatalyst used in the process according to the invention can be in different forms (nanometric powder, nanoobjects with or without cavities, etc.) or shaped (films, monolith, micrometric or millimetric sized beads, etc.). The photocatalyst is advantageously in the form of nanometric powder.

La mise en contact The contact

La mise en contact de la charge comprenant une molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable, seuls ou en mélange, peut se faire par tout moyen connu de l'homme du métier. The contacting of the charge comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or in a mixture, can be done by any means known to those skilled in the art.

La mise en contact de ladite charge peut avantageusement être réalisée en lit fixe traversé, en lit fixe léchant ou en suspension (aussi appelé "slurry" selon la terminologie anglo-saxonne). Le photocatalyseur peut également être déposé directement sur des fibres optiques. The contacting of said charge can advantageously be carried out in a fixed crossed bed, in a fixed licking bed or in suspension (also called "slurry" according to the Anglo-Saxon terminology). The photocatalyst can also be deposited directly on optical fibers.

Lorsque la mise en contact est en lit fixe traversé, le photocatalyseur est préférentiellement déposé en couche sur un support poreux, par exemple de type fritté céramique ou métallique, et la charge est envoyée à travers le lit photocatalytique. When the contact is in a fixed crossed bed, the photocatalyst is preferentially deposited in a layer on a porous support, for example of the ceramic or metallic sintered type, and the charge is sent through the photocatalytic bed.

Lorsque la mise en contact est en lit fixe léchant, le photocatalyseur est préférentiellement déposé en couche sur un support non poreux de type céramique ou métallique, et la charge est envoyée sur le lit photocatalytique. When the contact is in a fixed licking bed, the photocatalyst is preferentially deposited in a layer on a non-porous support of the ceramic or metallic type, and the charge is sent to the photocatalytic bed.

Lorsque que la mise en contact est en suspension, le photocatalyseur est préférentiellement sous forme de particules en suspension dans une charge liquide ou liquide-gaz comprenant la molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable, seuls ou en mélange. En suspension, la mise en œuvre peut se faire dans un réacteur fermé ou en continu. When the contact is in suspension, the photocatalyst is preferably in the form of particles suspended in a liquid or liquid-gas charge comprising the molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone. or in mixture. In suspension, the implementation can be done in a closed reactor or continuously.

Etape b) d’irradiation du milieu réactionnel Step b) irradiation of the reaction medium

Le procédé selon l’invention comprend une étape b) d’irradiation du milieu réactionnel par au moins une source d'irradiation produisant au moins une longueur d'onde comprise entre 280 et 2500 nm, de préférence entre 280 et 1100 nm, de manière préférée entre 315 nm et 800 nm, pendant n cycles d’une durée t1 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 10 et 30 minutes, n étant supérieur ou égal à 2, les n cycles étant espacés entre eux d’une durée t2 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 15 et 45 minutes pendant laquelle le milieu réactionnel n’est pas irradié. The method according to the invention comprises a step b) of irradiating the reaction medium with at least one irradiation source producing at least one wavelength between 280 and 2500 nm, preferably between 280 and 1100 nm, preferably between 315 nm and 800 nm, for n cycles of a duration t1 between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 10 and 30 minutes, n being greater than or equal to 2, the n cycles being spaced apart by a duration t2 between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 15 and 45 minutes, during which the reaction medium is not irradiated.

Les durées t1 et t2 peuvent être égales ou différentes. The durations t1 and t2 can be equal or different.

Avantageusement, la durée t2 est supérieure ou égale à la durée t1 , de préférence la durée t2 est supérieure à la durée t1. Dans ce mode de réalisation, la quantité de produits de photocatalyse obtenus est augmentée, la demanderesse a démontré que l’utilisation d'un temps d'obscurité de durée t2 supérieure ou égale à la durée t1 pendant laquelle le milieu réactionnel est irradié permet un rechargement plus efficace de la surface du photocatalyseur.Advantageously, the duration t2 is greater than or equal to the duration t1, preferably the duration t2 is greater than the duration t1. In this embodiment, the quantity of photocatalysis products obtained is increased, the applicant has demonstrated that the use of a dark time of duration t2 greater than or equal to the duration t1 during which the reaction medium is irradiated allows more efficient recharging of the surface of the photocatalyst.

Dans un mode de réalisation n est supérieur ou égal à 3. In one embodiment n is greater than or equal to 3.

Dans un mode de réalisation n est supérieur ou égal à 4. In one embodiment n is greater than or equal to 4.

Dans un mode de réalisation n est supérieur ou égal à 5. In one embodiment n is greater than or equal to 5.

Dans un mode de réalisation n est supérieur ou égal à 6. In one embodiment n is greater than or equal to 6.

Un photocatalyseur est avantageusement composé d’un ou plusieurs semi-conducteurs, et/ou un ou plusieurs complexes de métaux de transition, pouvant être activé par l'absorption d'au moins un photon. A photocatalyst is advantageously composed of one or more semiconductors, and/or one or more transition metal complexes, which can be activated by the absorption of at least one photon.

Dans le cas des semi-conducteurs, les photons absorbables sont ceux dont l'énergie est supérieure à la largeur de bande interdite. Autrement dit, les photocatalyseurs sont activables par au moins un photon d'une longueur d'onde correspondant à l'énergie associée aux largeurs de bandes interdites des semi-conducteurs constituant le photocatalyseur ou d'une longueur d'onde inférieure. In the case of semiconductors, absorbable photons are those whose energy is greater than the forbidden band width. In other words, photocatalysts can be activated by at least one photon of a wavelength corresponding to the energy associated with the forbidden band widths of the semiconductors constituting the photocatalyst or of a lower wavelength.

Toute source d'irradiation émettant au moins une longueur d'onde adaptée à l'activation dudit photocatalyseur présent dans le milieu réactionnel, c'est-à-dire absorbable par ledit photocatalyseur peut être utilisée selon l'invention. La source d’irradiation peut être aussi bien naturelle par irradiation solaire, qu’artificielle de type laser, Hg, lampe à incandescence, tube fluorescent, plasma ou diode électroluminescente (DEL, ou LED en anglais pour Light-Emitting Diode). De manière préférée, la source d'irradiation est naturelle par irradiation solaire. Any irradiation source emitting at least one wavelength suitable for activating said photocatalyst present in the reaction medium, i.e. absorbable by said photocatalyst, can be used according to the invention. The irradiation source can be both natural by solar irradiation, and artificial such as laser, Hg, incandescent lamp, tube fluorescent, plasma or light-emitting diode (LED). Preferably, the irradiation source is natural by solar irradiation.

La source d'irradiation produit un rayonnement dont au moins une partie des longueurs d'onde est inférieure à la longueur d'onde maximale absorbable (Àmax) par les semi-conducteurs constitutifs du photocatalyseur. Lorsque la source d’irradiation est l’irradiation solaire, elle émet généralement dans le spectre ultra-violet, visible et infra-rouge, c'est-à-dire elle émet une gamme de longueur d'onde de 280 nm à 2500 nm (selon la norme ASTM G173-03). The irradiation source produces radiation of which at least a portion of the wavelengths is less than the maximum absorbable wavelength (λmax) by the semiconductors constituting the photocatalyst. When the irradiation source is solar irradiation, it generally emits in the ultraviolet, visible and infrared spectrum, i.e. it emits a wavelength range from 280 nm to 2500 nm (according to ASTM G173-03).

La source d'irradiation fournit un flux de photons qui irradie le milieu réactionnel contenant le photocatalyseur. L'interface entre le milieu réactionnel et la source lumineuse varie en fonction des applications et de la nature de la source lumineuse. The irradiation source provides a flux of photons that irradiates the reaction medium containing the photocatalyst. The interface between the reaction medium and the light source varies depending on the applications and the nature of the light source.

Lorsque la source d’irradiation est naturelle, par exemple par irradiation solaire, la source d'irradiation est localisée à l'extérieur du réacteur et l’interface entre les deux peut être une fenêtre optique en pyrex, en quartz, en verre organique ou toute autre interface permettant aux photons absorbables par le photocatalyseur selon l’invention, de diffuser du milieu extérieur au sein du réacteur. When the irradiation source is natural, for example by solar irradiation, the irradiation source is located outside the reactor and the interface between the two can be an optical window made of pyrex, quartz, organic glass or any other interface allowing the photons absorbable by the photocatalyst according to the invention to diffuse from the external environment within the reactor.

La réalisation de la réaction de photocatalyse est conditionnée par la fourniture de photons adaptés au photocatalyseur pour la réaction envisagée et de ce fait n’est pas limitée à des gammes de pression ou de température spécifiques en dehors de celles permettant d’assurer la stabilité du produit. The performance of the photocatalysis reaction is conditioned by the supply of photons adapted to the photocatalyst for the reaction envisaged and is therefore not limited to specific pressure or temperature ranges outside of those allowing the stability of the product to be ensured.

Avantageusement, la gamme de température employée pour la réaction de photocatalyse selon l’invention est généralement comprise entre -10 et + 200 °C, de manière préférée entre 0 et 150 °C, et de manière très préférée entre 0 et 50 °C. Advantageously, the temperature range used for the photocatalysis reaction according to the invention is generally between -10 and +200°C, preferably between 0 and 150°C, and very preferably between 0 and 50°C.

Avantageusement, la gamme de pression employée pour la réaction de photocatalyse selon l’invention est généralement comprise entre 0,01 et 70 MPa (0,1 à 700 bar), de manière préférée entre 0,1 et 5 MPa (1 à 50 bar) et de manière très préférée entre 0,1 et 2 MPa (1 à 20 bar). Advantageously, the pressure range used for the photocatalysis reaction according to the invention is generally between 0.01 and 70 MPa (0.1 to 700 bar), preferably between 0.1 and 5 MPa (1 to 50 bar) and very preferably between 0.1 and 2 MPa (1 to 20 bar).

Les exemples suivants illustrent l'invention sans en limiter la portée. The following examples illustrate the invention without limiting its scope.

DESCRIPTION DES FIGURES DESCRIPTION OF FIGURES

La Figure 1 représente la quantité cumulée de méthane en unité arbitraire produite en fonction du temps en minutes pour un procédé de photoconversion du CO2 en continu sur 3 heures de test. L’encart en bas à droite représente la quantité de méthane en unité arbitraire produite en fonction du temps en minutes (analysée par spectroscopie de masse, m/z = 15). Figure 1 shows the cumulative amount of methane in arbitrary units produced as a function of time in minutes for a continuous CO2 photoconversion process over 3 hours of testing. The bottom right inset shows the amount of methane in arbitrary units produced as a function of time in minutes (analyzed by mass spectroscopy, m/z = 15).

La Figure 2 représente la quantité cumulée de méthane en unité arbitraire produite en fonction du temps en minutes sur 6 heures de test dont 3 heures d’irradiation cumulée par cycles lumière I obscurité pour un procédé de photoconversion du CO2 selon un mode de réalisation de l’invention, t1 = 30 min, t2 = 30 min, n = 6. L’encart en bas à droite représente la quantité de méthane en unité arbitraire produite en fonction du temps en minutes (analysée par spectroscopie de masse, m/z = 15). On observe qu’à temps d’irradiation similaire, le procédé de photoconversion du CO2 selon un mode de réalisation de l’invention permet une production de méthane accrue comparé à un procédé classique d’irradiation continue. Figure 2 shows the cumulative amount of methane in arbitrary units produced as a function of time in minutes over 6 hours of testing including 3 hours of cumulative irradiation by cycles light I darkness for a CO2 photoconversion process according to an embodiment of the invention, t1 = 30 min, t2 = 30 min, n = 6. The bottom right insert represents the amount of methane in arbitrary units produced as a function of time in minutes (analyzed by mass spectroscopy, m/z = 15). It is observed that at a similar irradiation time, the CO2 photoconversion process according to an embodiment of the invention allows an increased methane production compared to a conventional continuous irradiation process.

EXEMPLES EXAMPLES

Exemple 1 : Catalyseur à base de TiÛ2 et imprégné de 1% poids de Pt Example 1: Catalyst based on TiO2 and impregnated with 1% weight of Pt

Le photocatalyseur est un semi-conducteur à base de TiÛ2 commercial (CristalACTiV™ PC- 500, Tronox, anatase, pureté > 99 wt%). La granulométrie du photocatalyseur mesurée par diffraction aux rayons X (DRX) est de 6 nm et la surface spécifique mesurée par méthode BET est égale à 393 m2/g. Les particules de Platine réduit ont été déposées par photodéposition, taille moyenne des particules : 3 nm. The photocatalyst is a commercial TiO2-based semiconductor (CristalACTiV™ PC-500, Tronox, anatase, purity >99 wt%). The particle size of the photocatalyst measured by X-ray diffraction (XRD) is 6 nm and the specific surface area measured by BET method is equal to 393 m2 /g. The reduced platinum particles were deposited by photodeposition, average particle size: 3 nm.

L’échantillon est soumis à un test de réduction photocatalytique du CO2 en phase gazeuse dans un réacteur continu à lit traversé muni d’une fenêtre optique en quartz d’une surface de 5,3.10'4 m2 et d’un filtre poreux de type fritté placé en face de la fenêtre optique sur lequel est déposé le solide photocatalytique. The sample is subjected to a gas-phase photocatalytic reduction test of CO2 in a continuous flow-through reactor equipped with a quartz optical window with a surface area of 5.3.10' 4 m 2 and a sintered porous filter placed in front of the optical window on which the photocatalytic solid is deposited.

Les tests sont réalisés à température ambiante de 23 °C sous pression atmosphérique de 1 atm. Un débit de CO2 de 5 cc/min traverse un saturateur d’eau (permettant de charger le gaz vecteur à hauteur de 20 000 ppm H2O) avant d’être distribué dans le réacteur. The tests are carried out at room temperature of 23°C under atmospheric pressure of 1 atm. A CO2 flow rate of 5 cc/min passes through a water saturator (allowing the carrier gas to be loaded at a level of 20,000 ppm H2O) before being distributed into the reactor.

Après 3h d’irradiation continue ou par n=6 cycles d’une durée t1= 30 min avec une période d’obscurité (absence d’irradiation) d’une durée t2 = 30 minutes également entre chaque cycle, l’analyse des produits de sortie montre qu’il est produit beaucoup plus de méthane dans le cas du schéma cyclique selon un mode de réalisation de l’invention comparé à l’irradiation continue. After 3 hours of continuous irradiation or by n=6 cycles of a duration t1= 30 min with a period of darkness (absence of irradiation) of a duration t2 = 30 minutes also between each cycle, the analysis of the output products shows that much more methane is produced in the case of the cyclic scheme according to an embodiment of the invention compared to continuous irradiation.

Les résultats sont présentés dans le tableau suivant : The results are presented in the following table:

Figure imgf000014_0001
Figure imgf000014_0001

On observe un gain de 1 ,8 pour la production de méthane (photoconversion du CO2) et de 1 ,2 pour la production de dihydrogène (photoconversion de H2O). We observe a gain of 1.8 for the production of methane (photoconversion of CO2) and of 1.2 for the production of dihydrogen (photoconversion of H2O).

Exemple 2 : Catalyseur à base de TiÛ2 seulement Example 2: Catalyst based on TiO2 only

Le photocatalyseur est un semi-conducteur à base de TiÛ2 commercial (CristalACTiV™ PC- 500, Tronox, anatase, pureté > 99 wt%). La granulométrie du photocatalyseur mesurée par diffraction aux rayons X (DRX) est de 6 nm et la surface spécifique mesurée par méthode BET est égale à 393 m2/g. The photocatalyst is a commercial TiO2-based semiconductor (CristalACTiV™ PC-500, Tronox, anatase, purity >99 wt%). The particle size of the photocatalyst measured by X-ray diffraction (XRD) is 6 nm and the specific surface area measured by BET method is 393 m2 /g.

L’échantillon est soumis à un test de réduction photocatalytique du CO2 en phase gazeuse dans un réacteur continu à lit traversé muni d’une fenêtre optique en quartz d’une surface de 5,3.10-4 m2 et d’un filtre poreux de type fritté placé en face de la fenêtre optique sur lequel est déposé le solide photocatalytique. The sample is subjected to a gas-phase photocatalytic reduction test of CO2 in a continuous flow-through reactor equipped with a quartz optical window with a surface area of 5.3.10 -4 m 2 and a sintered porous filter placed in front of the optical window on which the photocatalytic solid is deposited.

Les tests sont réalisés à température ambiante de 23 °C sous pression atmosphérique de 1 atm. Un débit de CO2 de 5 cc/min traverse un saturateur d’eau (permettant de charger le gaz vecteur à hauteur de 20 000 ppm H2O) avant d’être distribué dans le réacteur. The tests are carried out at room temperature of 23°C under atmospheric pressure of 1 atm. A CO2 flow rate of 5 cc/min passes through a water saturator (allowing the carrier gas to be loaded at a level of 20,000 ppm H2O) before being distributed into the reactor.

Après 1 h d’irradiation continue ou par n=2 cycles d’une durée t1= 30 min avec une période d’obscurité (absence d’irradiation) d’une durée t2 = 30 minutes également entre les deux cycles, l’analyse des produits de sortie montre que l’on produit beaucoup plus de méthane dans le cas du schéma cyclique pour un procédé de photoconversion du CO2 selon un mode de réalisation de l’invention comparé à une irradiation continue. After 1 h of continuous irradiation or by n=2 cycles of a duration t1= 30 min with a period of darkness (absence of irradiation) of a duration t2 = 30 minutes also between the two cycles, the analysis of the output products shows that much more methane is produced in the case of the cyclic scheme for a CO2 photoconversion process according to an embodiment of the invention compared to continuous irradiation.

Les résultats sont présentés dans le tableau suivant :

Figure imgf000015_0001
The results are presented in the following table:
Figure imgf000015_0001

On observe également un gain de 1 ,2 pour la production de dihydrogène (photoconversion de H2O). A gain of 1.2 is also observed for the production of dihydrogen (photoconversion of H2O ).

Claims

REVENDICATIONS 1 Procédé de photocatalyse réalisé en phase gazeuse et/ou en phase liquide comprenant les étapes suivantes : a) mise en contact d’une charge comprenant une molécule choisie parmi CO2, H2O, NH3 et un composé organique photodégradable, seuls ou en mélange, avec un photocatalyseur, et formation d’un milieu réactionnel ; b) irradiation du milieu réactionnel par au moins une source d'irradiation produisant au moins une longueur d'onde comprise entre 280 et 2500 nm, pendant n cycles d’une durée t1 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 10 et 30 minutes, n étant supérieur ou égal à 2, les n cycles étant espacés entre eux d’une durée t2 comprise entre 1 et 60 minutes, de préférence comprise entre 5 et 45 minutes, de façon préférée comprise entre 15 et 45 minutes pendant laquelle le milieu réactionnel n’est pas irradié. 1 Photocatalysis process carried out in the gas phase and/or in the liquid phase comprising the following steps: a) bringing a feedstock comprising a molecule chosen from CO2, H2O, NH3 and a photodegradable organic compound, alone or in a mixture, into contact with a photocatalyst, and forming a reaction medium; b) irradiating the reaction medium with at least one irradiation source producing at least one wavelength between 280 and 2500 nm, for n cycles of a duration t1 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 10 and 30 minutes, n being greater than or equal to 2, the n cycles being spaced apart by a duration t2 of between 1 and 60 minutes, preferably between 5 and 45 minutes, preferably between 15 and 45 minutes, during which the reaction medium is not irradiated. 2 Procédé selon la revendication 1 dans lequel, la durée t2 est supérieure ou égale à la durée t1 , de préférence la durée t2 est supérieure à la durée t1. 2 Method according to claim 1 in which the duration t2 is greater than or equal to the duration t1, preferably the duration t2 is greater than the duration t1. 3 Procédé selon l’une quelconque des revendications précédentes dans lequel, ladite au moins une longueur d'onde est comprise entre 280 et 1100 nm, de manière préférée entre 315 nm et 800 nm. 3 Method according to any one of the preceding claims, in which said at least one wavelength is between 280 and 1100 nm, preferably between 315 nm and 800 nm. 4 Procédé selon l’une quelconque des revendications précédentes dans lequel, le photocatalyseur est composé d’un ou de plusieurs semi-conducteurs inorganiques, organiques ou organique-inorganique, et/ou d’un ou de plusieurs complexes de métaux de transition. 4. A method according to any one of the preceding claims, in which the photocatalyst is composed of one or more inorganic, organic or organic-inorganic semiconductors, and/or one or more transition metal complexes. 5 Procédé selon la revendication 4 dans lequel, le semi-conducteur est choisi parmi le TiC>2, le SiC, le Bi2Sa, le Bi20s, le CdO, le CdS, le Ce2C>3, le CeC>2, le CeAICh, le CoO, le CU2O, le Fe2C>3, le FeTiOs, l’I^Ch, I’ I n(OH)s, le NiO, le PbO, le ZnO, l’Ag2S, le CdS, le Ce2S3, le CU2S, le CulnS2, l’ln2S3, le M0S2, le ZnFe2C>3, le ZnS, le ZnO, le WO3, le ZnFe2Û4 et le ZrS2, seuls ou en mélange. 5 Method according to claim 4 in which the semiconductor is chosen from TiC>2, SiC, Bi2Sa, Bi20s, CdO, CdS, Ce2C>3, CeC>2, CeAICh, CoO, CU2O, Fe2C>3, FeTiOs, I^Ch, I' I n(OH)s, NiO, PbO, ZnO, Ag2S, CdS, Ce2S3, CU2S, CulnS2, ln 2 S 3 , M0S2, ZnFe2C>3, ZnS, ZnO, WO3, ZnFe2O4 and ZrS2, alone or as a mixture. 6 Procédé selon la revendication 4 dans lequel, le semi-conducteur est un semi-conducteur organique choisi parmi le tétracène, l’anthracène, le polythiophène, le polystyrène sulfonate, les phosphyrènes, les fullerènes et les nitrures de carbone. 6. The method of claim 4, wherein the semiconductor is an organic semiconductor selected from tetracene, anthracene, polythiophene, polystyrene sulfonate, phosphyrenes, fullerenes and carbon nitrides. 7 Procédé selon la revendication 4 dans lequel, le semi-conducteur est un semi-conducteur organique-inorganique tel qu’un solide cristallisé de type MOF. 7 Method according to claim 4 in which the semiconductor is an organic-inorganic semiconductor such as a crystalline solid of the MOF type. 8 Procédé selon l’une quelconque des revendications précédentes dans lequel, la mise en contact de la charge est réalisée en lit fixe traversé, en lit fixe léchant ou en suspension. 9 Procédé selon l’une quelconque des revendications précédentes dans lequel, la source d'irradiation est naturelle par irradiation solaire. 8 Method according to any one of the preceding claims, in which the contacting of the load is carried out in a fixed traversed bed, in a fixed licking bed or in suspension. 9 Method according to any one of the preceding claims in which the source of irradiation is natural by solar irradiation. 10 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est choisie parmi H2O, NH3, et un composé organique photodégradable choisi parmi CH4 et un alcool, seuls ou en mélange. 10 Method according to any one of claims 1 to 9 in which the molecule is chosen from H2O, NH3, and a photodegradable organic compound chosen from CH4 and an alcohol, alone or in a mixture. 11 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est choisie parmi H2O, NH3, et un composé organique photodégradable étant un alcool, seuls ou en mélange. 11 Method according to any one of claims 1 to 9 in which the molecule is chosen from H2O, NH3, and a photodegradable organic compound being an alcohol, alone or in a mixture. 12 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est le CO2 sous forme gazeux. 12 Method according to any one of claims 1 to 9 in which the molecule is CO2 in gaseous form. 13 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est le CO2 solubilisé sous forme de CO2 aqueux, d’hydrogénocarbonate ou de carbonate. 13 Method according to any one of claims 1 to 9 in which the molecule is CO2 solubilized in the form of aqueous CO2, hydrogen carbonate or carbonate. 14 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est un composé organique photodégradable étant un composé organique volatile. 15 Procédé selon l’une quelconque des revendications 1 à 9 dans lequel, la molécule est un composé organique photodégradable solubilisé sous forme aqueux choisi parmi les hydrocarbures halogénés, les hydrocarbures aromatiques, les alcanes, les alcènes, les alcynes, les aldéhydes, les cétones, seuls ou en mélange. 14 Method according to any one of claims 1 to 9 in which the molecule is a photodegradable organic compound being a volatile organic compound. 15 Method according to any one of claims 1 to 9 in which the molecule is a photodegradable organic compound solubilized in aqueous form chosen from halogenated hydrocarbons, aromatic hydrocarbons, alkanes, alkenes, alkynes, aldehydes, ketones, alone or in a mixture.
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