WO2021121980A1 - Process for the photocatalytic reduction of carbon dioxide in the presence of a photocatalyst prepared by impregnation in a molten medium - Google Patents
Process for the photocatalytic reduction of carbon dioxide in the presence of a photocatalyst prepared by impregnation in a molten medium Download PDFInfo
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- WO2021121980A1 WO2021121980A1 PCT/EP2020/084175 EP2020084175W WO2021121980A1 WO 2021121980 A1 WO2021121980 A1 WO 2021121980A1 EP 2020084175 W EP2020084175 W EP 2020084175W WO 2021121980 A1 WO2021121980 A1 WO 2021121980A1
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- Prior art keywords
- photocatalyst
- support
- elements
- groups
- acid
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 125
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 103
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 64
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 60
- 238000000034 method Methods 0.000 title claims abstract description 56
- 230000001699 photocatalysis Effects 0.000 title claims abstract description 54
- 230000008569 process Effects 0.000 title claims abstract description 31
- 230000009467 reduction Effects 0.000 title claims abstract description 31
- 238000005470 impregnation Methods 0.000 title abstract description 31
- 150000001875 compounds Chemical class 0.000 claims abstract description 34
- 239000012071 phase Substances 0.000 claims abstract description 26
- 239000002105 nanoparticle Substances 0.000 claims abstract description 24
- PTISTKLWEJDJID-UHFFFAOYSA-N sulfanylidenemolybdenum Chemical compound [Mo]=S PTISTKLWEJDJID-UHFFFAOYSA-N 0.000 claims abstract description 20
- XCUPBHGRVHYPQC-UHFFFAOYSA-N sulfanylidenetungsten Chemical compound [W]=S XCUPBHGRVHYPQC-UHFFFAOYSA-N 0.000 claims abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 8
- 239000007791 liquid phase Substances 0.000 claims abstract description 7
- 239000002253 acid Substances 0.000 claims description 49
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 36
- 229910052750 molybdenum Inorganic materials 0.000 claims description 34
- 229910052751 metal Inorganic materials 0.000 claims description 33
- 239000002184 metal Substances 0.000 claims description 33
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 31
- 239000011733 molybdenum Substances 0.000 claims description 31
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 28
- 238000002844 melting Methods 0.000 claims description 26
- 230000008018 melting Effects 0.000 claims description 26
- 239000007787 solid Substances 0.000 claims description 26
- 239000004065 semiconductor Substances 0.000 claims description 23
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 22
- 229910052721 tungsten Inorganic materials 0.000 claims description 20
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 19
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 18
- 238000005987 sulfurization reaction Methods 0.000 claims description 18
- 239000010937 tungsten Substances 0.000 claims description 17
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 16
- 239000002243 precursor Substances 0.000 claims description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 13
- 239000008247 solid mixture Substances 0.000 claims description 10
- -1 Ce 2 Û 3 Chemical class 0.000 claims description 9
- 239000012530 fluid Substances 0.000 claims description 8
- 239000000377 silicon dioxide Substances 0.000 claims description 8
- 229910021529 ammonia Inorganic materials 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 6
- 239000003085 diluting agent Substances 0.000 claims description 6
- 150000001412 amines Chemical class 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 4
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 4
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 claims description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- 229910000577 Silicon-germanium Inorganic materials 0.000 claims description 3
- LEVVHYCKPQWKOP-UHFFFAOYSA-N [Si].[Ge] Chemical compound [Si].[Ge] LEVVHYCKPQWKOP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052768 actinide Inorganic materials 0.000 claims description 3
- 150000001255 actinides Chemical class 0.000 claims description 3
- 229910052732 germanium Inorganic materials 0.000 claims description 3
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 3
- 229910052747 lanthanoid Inorganic materials 0.000 claims description 3
- 150000002602 lanthanoids Chemical class 0.000 claims description 3
- 229910052760 oxygen Inorganic materials 0.000 claims description 3
- DHRLEVQXOMLTIM-UHFFFAOYSA-N phosphoric acid;trioxomolybdenum Chemical compound O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.O=[Mo](=O)=O.OP(O)(O)=O DHRLEVQXOMLTIM-UHFFFAOYSA-N 0.000 claims description 3
- IYDGMDWEHDFVQI-UHFFFAOYSA-N phosphoric acid;trioxotungsten Chemical compound O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.O=[W](=O)=O.OP(O)(O)=O IYDGMDWEHDFVQI-UHFFFAOYSA-N 0.000 claims description 3
- CGFYHILWFSGVJS-UHFFFAOYSA-N silicic acid;trioxotungsten Chemical compound O[Si](O)(O)O.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1.O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 CGFYHILWFSGVJS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052709 silver Inorganic materials 0.000 claims description 3
- ADZWSOLPGZMUMY-UHFFFAOYSA-M silver bromide Chemical compound [Ag]Br ADZWSOLPGZMUMY-UHFFFAOYSA-M 0.000 claims description 3
- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 claims description 2
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 claims 1
- 230000001678 irradiating effect Effects 0.000 abstract description 2
- 238000005486 sulfidation Methods 0.000 abstract 1
- 238000006722 reduction reaction Methods 0.000 description 29
- 239000007789 gas Substances 0.000 description 15
- 238000002360 preparation method Methods 0.000 description 14
- 239000000243 solution Substances 0.000 description 13
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- 239000003054 catalyst Substances 0.000 description 8
- 239000012429 reaction media Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000000725 suspension Substances 0.000 description 7
- 125000004429 atom Chemical group 0.000 description 6
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 238000004847 absorption spectroscopy Methods 0.000 description 5
- 150000001298 alcohols Chemical class 0.000 description 5
- 150000001299 aldehydes Chemical class 0.000 description 5
- 238000004458 analytical method Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 229910002091 carbon monoxide Inorganic materials 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 102100030393 G-patch domain and KOW motifs-containing protein Human genes 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 229910052982 molybdenum disulfide Inorganic materials 0.000 description 4
- 230000003287 optical effect Effects 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- ITRNXVSDJBHYNJ-UHFFFAOYSA-N tungsten disulfide Chemical compound S=[W]=S ITRNXVSDJBHYNJ-UHFFFAOYSA-N 0.000 description 4
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 3
- 150000001735 carboxylic acids Chemical class 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 235000019253 formic acid Nutrition 0.000 description 3
- 150000002576 ketones Chemical class 0.000 description 3
- 230000035800 maturation Effects 0.000 description 3
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 3
- 238000007146 photocatalysis Methods 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- 238000001429 visible spectrum Methods 0.000 description 3
- XDTMQSROBMDMFD-UHFFFAOYSA-N Cyclohexane Chemical compound C1CCCCC1 XDTMQSROBMDMFD-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000007865 diluting Methods 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 238000002211 ultraviolet spectrum Methods 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- RZVAJINKPMORJF-UHFFFAOYSA-N Acetaminophen Chemical compound CC(=O)NC1=CC=C(O)C=C1 RZVAJINKPMORJF-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- GQNYZFMTYSVKQV-UHFFFAOYSA-N [Mo+5].CC[O-].CC[O-].CC[O-].CC[O-].CC[O-] Chemical group [Mo+5].CC[O-].CC[O-].CC[O-].CC[O-].CC[O-] GQNYZFMTYSVKQV-UHFFFAOYSA-N 0.000 description 1
- SHMVRUMGFMGYGG-UHFFFAOYSA-N [Mo].S=O Chemical class [Mo].S=O SHMVRUMGFMGYGG-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000003426 co-catalyst Substances 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 238000004320 controlled atmosphere Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000000265 homogenisation Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 239000003317 industrial substance Substances 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000000626 liquid-phase infiltration Methods 0.000 description 1
- 230000010198 maturation time Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 150000007530 organic bases Chemical class 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 239000012041 precatalyst Substances 0.000 description 1
- 239000005297 pyrex Substances 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 239000011833 salt mixture Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000009919 sequestration Effects 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- IJZPACDOFYWLKH-UHFFFAOYSA-N sulfinyltungsten Chemical class O=S=[W] IJZPACDOFYWLKH-UHFFFAOYSA-N 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000009489 vacuum treatment Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
Classifications
-
- 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
- B01J21/12—Silica and alumina
-
- 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
- B01J21/08—Silica
-
- 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
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/28—Molybdenum
-
- B01J35/23—
-
- B01J35/39—
-
- 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
- B01J37/0207—Pretreatment of the support
-
- 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
- B01J37/08—Heat treatment
- B01J37/082—Decomposition and pyrolysis
- B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
-
- 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
- B01J37/20—Sulfiding
-
- 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
- C07C1/12—Preparation of hydrocarbons from one or more compounds, none of them being a hydrocarbon from oxides of a carbon from carbon dioxide with hydrogen
-
- 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
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/24—Chromium, molybdenum or tungsten
- B01J23/30—Tungsten
Definitions
- the field of the invention is that of the photocatalytic reduction of carbon dioxide (CO2) under irradiation by the use of a photocatalyst prepared by impregnation in a molten medium.
- CO2 carbon dioxide
- Fossil fuels such as coal, oil and natural gas
- combustion produces carbon dioxide emissions which are considered to be the main cause of global warming.
- CCS capture and sequestration "passive”
- other strategies should be considered, including strategies "active” conversion of CO2 into products with economic value, such as fuels and industrial chemicals.
- active strategies are based on the reduction of carbon dioxide into valuable products.
- the reduction of carbon dioxide can be carried out by biological, thermal, electrochemical or even photocatalytic means. Among these options, photocatalytic CO2 reduction is gaining increased attention as it can potentially consume alternative forms of energy, for example by harnessing solar energy, which is abundant, cheap, and environmentally clean and safe.
- the photocatalytic reduction of carbon dioxide makes it possible to obtain carbon molecules in C1 or more, such as carbon monoxide (CO), methane, methanol, ethanol, formaldehyde, formic acid or even d ' other molecules such as acids carboxylics, aldehydes, ketones or various alcohols.
- CO carbon monoxide
- methane methane
- methanol ethanol
- formaldehyde formaldehyde
- formic acid or even d ' other molecules such as acids carboxylics, aldehydes, ketones or various alcohols.
- CO carbon monoxide
- CO can also be energetically upgraded as a mixture with hydrogen for the formation of fuels by Fischer-Tropsch synthesis.
- the molecules of carboxylic acids, aldehydes, ketones or various alcohols they can find applications in chemical or petrochemical processes. All these molecules are therefore of great interest from an industrial point of view.
- Photocatalysis is based on the principle of activating a semiconductor or a set of semiconductors such as a photocatalyst, using the energy provided by the irradiation.
- Photocatalysis can be defined as the absorption of a photon, the energy of which is greater than the forbidden bandwidth or "bandgap" according to English terminology between the valence band and the conduction band, which induces the formation of an electron-hole pair in the case of a semiconductor.
- a semiconductor is characterized by its forbidden band or “bandgap”, i.e. the energy difference between its conduction band and its valence band, is specific to it. Any photon with energy greater than its forbidden band can be absorbed by the semiconductor. Any photon with energy below its bandgap cannot be absorbed by the semiconductor.
- the band gap of semiconductors in the form of particles varies depending on the size of these particles.
- the semiconductor bandgap increases for nanoparticle sizes that decrease down to the nanometer scale. This known physical phenomenon is called the quantum size effect.
- sulfurized molybdenum nanoparticles exhibiting a bandgap greater than that of mass sulfurized molybdenum are known from the prior art.
- Document FR3073429 describes a process for the photocatalytic reduction of carbon dioxide using a photocatalyst based on molybdenum sulphide or supported tungsten sulphide.
- the photocatalyst is prepared by impregnation using an impregnation solution containing an organic solvent and a mononuclear precursor to molybdenum or tungsten base, followed by a maturation step, a drying step and a sulfurization step.
- the mononuclear precursors used in this document have the disadvantage of having to be handled under a controlled atmosphere (in the absence of water) and the impregnation support must therefore undergo prior to the impregnation of the vacuum treatments in order to evacuate the water.
- impregnation in a molten medium consists in mixing a support with a solid metal salt having a relatively low melting point, in particular lower than its decomposition temperature, then heating the mixture to a temperature higher than the melting temperature of said metal salt in order to melt the salt in the support.
- this technique has the disadvantage of requiring a metal salt having a relatively low melting point, in particular lower than its decomposition temperature. There does not appear to be any Group VIB salts that meet these low melting point criteria. This is because salts based on a Group VIB metal tend to decompose before reaching their melting point.
- one of the objectives of the present invention is to provide a process for the photocatalytic reduction of carbon dioxide using a photocatalyst based on nanoparticles of molybdenum sulphide or of tungsten sulphide prepared by impregnation in a molten medium.
- the object of the invention is to provide a new, sustainable and more efficient way of producing carbon molecules that can be upgraded by photocatalytic conversion of carbon dioxide using a photocatalyst based on molybdenum sulphide or sulphide nanoparticles. of tungsten prepared by impregnation in a molten medium.
- the photocatalytic CO2 reduction process according to the invention achieves improved performance.
- the invention describes a process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and / or in the gas phase, said process comprising the following steps: a) a charge containing carbon dioxide is brought into contact and at least a sacrificial compound with a photocatalyst, b) the photocatalyst is irradiated with at least one irradiation source producing at least one wavelength absorbable by said photocatalyst so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said source of irradiation, so as to produce an effluent containing at least in part carbon molecules in C1 or more, other than CO2, said photocatalyst comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having an upper band gap at 2.3 eV, said photocatalyst being prepared by a process comprising the following steps: i) water
- Molybdenum sulfide or tungsten sulfide nanoparticles with a bandgap greater than 2.3 eV advantageously absorb part of the visible spectrum of natural (solar) or artificial irradiation while allowing the reduction of carbon dioxide by levels suitable bands, which does not allow the sulphide phases of molybdenum or tungsten in the form of nanoparticles of larger size having a forbidden band of less than 2.3 eV.
- photocatalyst for the photocatalytic reduction of CO2 thus makes it possible to enhance the visible part of the spectrum since it can absorb all photons with a wavelength of less than 620 nm (against 400 nm for a conventional photocatalyst of the Ti0 2 type ).
- these supported nanoparticles have the advantage of better stability against colloidal suspensions.
- hydrated metallic acid comprising at least molybdenum or tungsten and having a melting point of between 20 and 100 ° C makes it possible to introduce molybdenum or tungsten into a support by impregnation in a molten medium to obtain a photocatalytic precursor making it possible to obtain, after sulphurization (step iv), a photocatalyst having nanoparticles of molybdenum sulphide or of tungsten sulphide having a forbidden band greater than 2.3 eV dispersed in the support.
- the hydrated metallic acid which is in the form of powder, is mixed with the support (step ii), then this solid mixture is heated in order to melt the metallic acid in the support, thus making it possible to obtain the catalyst (step iii).
- the acid has the peculiarity of only melting in the presence of sufficient partial pressure of water. In other words, it is necessary to keep the molecules of water of crystallization to ensure its fusion.
- the support is first moistened by impregnating with water (step i).
- the preparation process according to the invention thus has the advantages of an impregnation in a molten medium, in particular the absence of any preparation of solution or the use of solvent.
- the preparation process according to the invention makes it possible to obtain a photocatalyst highly charged with molybdenum or tungsten having in particular metal contents of molybdenum or of tungsten which are not attainable by impregnation with the aid of a solution. impregnation.
- the photocatalyst obtained according to the preparation process according to the invention makes it possible to observe a photocatalytic activity at least at the same level as a photocatalyst prepared by impregnation using an impregnation solution with, however, a simplified preparation and the ability to load more molybdenum or tungsten.
- the hydrated metal acid is selected from hydrated phosphomolybdic acid, hydrated silicomolybdic acid, hydrated molybdosilicic acid, hydrated phosphotungstic acid and hydrated silicotungstic acid.
- the quantity of water introduced into the support is between 10 and 70% of its water uptake volume.
- the support is a support based on alumina or silica or silica-alumina.
- the support is a support based on a solid semiconductor.
- the support is a solid semiconductor chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium, of elements of groups NIA and VA, such as as GaP, GaN, InP and InGaAs, or elements of groups MB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VI IA, 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 BhTe 3 and B1 2 O 3 , or elements of groups MB and VA, such as Cd 3 P 2 , Zh 3 R ⁇ and Zn 3 As 2 , or elements of groups IB and VIA, such as CuO, CU 2 O and Ag 2 S, or elements of groups VIIIB and VIA, such as CoO, PdO, Fe 0 and NiO, or elements of groups VIB and VIA
- the content of molybdenum sulphide or of tungsten sulphide in the photocatalyst is between 4 and 50% by weight relative to the total weight of the photocatalyst.
- the surface density which corresponds to the quantity of atoms of molybdenum Mo or of tungsten atoms W, deposited per surface unit of support is between 0.5 and 12 atoms of Mo or of W per square nanometers. support.
- the sacrificial compound is a gaseous compound chosen from water, ammonia, dihydrogen, methane or an alcohol.
- a diluting fluid is present in steps a) and / or b).
- the sacrificial compound is a liquid or solid oxidizable compound soluble in the liquid charge, chosen from water, ammonia, an alcohol, an aldehyde or an amine.
- the irradiation source is a natural or artificial irradiation source.
- the irradiation source emits at least in a range of wavelengths between 280 nm and 2500 nm.
- sacrificial compound corresponds to an oxidizable compound, in gaseous or liquid form.
- carbon molecules in C1 or more molecules resulting from the reduction of CO2 containing one or more carbon atoms, with the exception of CO2.
- Such molecules are for example CO, methane, methanol, ethanol, formaldehyde, formic acid, methane or even other molecules such as carboxylic acids, aldehydes, ketones, various alcohols or hydrocarbons containing more than 2 carbon atoms.
- the groups of chemical elements correspond to those of the CAS classification (CRC Handbook of Chemistry and Physics, editor 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 the 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, internationale Press, 1999.
- the term “specific surface” is understood to mean the BET specific surface (SBET in m 2 / g) determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established using the BRUNAUER-EMMETT-TELLER method described in the periodical "The Journal of American Society", 1938, 60, 309.
- the maximum absorbable wavelength 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 792458 ms-1) and Eg the forbidden bandwidth or "bandgap" of the semiconductor (in eV).
- the value of the band gap of semiconductor materials is measured by diffuse reflection absorption spectroscopy as described by the Tauc method (J. Tauc, R. Grigorovici, and A. Vancu, Phys. Status Solidi, 1966, 15, p 627; J. Tauc, "Optical Properties of Solids", F. Abeles ed., North-Holland, 1972; EA Davis and NF Mott, Philos. Mag., 1970, 22 p 903).
- reaction medium is understood to mean the mixture formed by the charge containing the carbon dioxide, the sacrificial compound and the photocatalyst.
- the invention relates to a process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and / or in the gas phase, said process comprising the following steps: a) a charge containing carbon dioxide and at least one compound is brought into contact. sacrificial with a photocatalyst, b) the photocatalyst is irradiated with at least one irradiation source producing at least one wavelength absorbable by said photocatalyst so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said source of irradiation, so as to produce an effluent containing at least in part carbon molecules in C1 or more, other than CO2, said photocatalyst comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having an upper band gap at 2.3 eV, said photocatalyst being prepared by impregnation in a molten medium.
- a charge containing carbon dioxide (CO2) and at least one sacrificial compound is brought into contact with a photocatalyst.
- the process is carried out in gaseous, liguid or two-phase, gaseous and liguid phase, meaning respectively that the feed treated according to the process is in gaseous, liquid or two-phase, gaseous and liquid form.
- the process is carried out in the gas phase.
- the CO2 present in the feed is also in gaseous form
- the sacrificial compound (s) used for step a ) are also in gaseous form.
- Gaseous sacrificial compounds are oxidizable compounds such as water (H 2 O), ammonia (NH3), dihydrogen (H2), methane (CH4) or even alcohols.
- the gaseous sacrificial compounds are water or hydrogen.
- a diluent fluid such as N 2 or Ar, can 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 it to the charge to ensure the dispersion of the charge and / or of the photocatalyst in the reaction medium, the control of the adsorption of reagents / products at the surface of the photocatalyst, control of the absorption of photons by the photocatalyst, dilution of the products to limit their recombination and other side reactions of the same order.
- a diluent fluid also makes it possible to control the temperature of the reaction medium, thus being able to compensate for the possible exo / endothermicity of the photocatalysed reaction.
- the nature of the diluent fluid is chosen such that its influence is neutral on the reaction medium or that its possible reaction does not harm the achievement of the desired reduction of carbon dioxide.
- a feed in liquid form When the process is carried out in the liquid phase, with a feed in liquid form, it can be in ionic, organic or aqueous form.
- the feed in liquid form is preferably aqueous.
- the CO2 When the liquid feed is an aqueous solution, the CO2 is then solubilized in the form of aqueous CO2, hydrogen carbonate or carbonate.
- the sacrificial compounds used in this case are liquid or solid oxidizable compounds soluble in the liquid charge, such as water (H 0), ammonia (NH), alcohols, aldehydes, amines.
- the sacrificial compound is water.
- the pH is generally between 2 and 12, preferably between 3 and 10.
- a basic or acidic agent can be added to the feed.
- the basic agent can be chosen from alkali or alkaline earth hydroxides, organic bases, for example amines or ammonia.
- the acidic agent can be selected from inorganic acids, for example nitric, sulfuric, phosphoric, hydrochloric, hydrobromic or organic acids, such as carboxylic or sulfonic acids.
- the liquid filler when it is aqueous, it can contain in any quantity any solvated ion, such as for example K + , Li + , Na + , Ca 2+ , Mg 2+ , SO4 2 -, Ch, F- , NO3 2 -.
- any solvated ion such as for example K + , Li + , Na + , Ca 2+ , Mg 2+ , SO4 2 -, Ch, F- , NO3 2 -.
- the charge containing carbon dioxide and the photocatalyst can be brought into contact by any means known to those skilled in the art.
- the contact between the charge and the photocatalyst can be carried out in a crossed fixed bed, in a licking fixed bed or in suspension (also called "slurry" according to the English terminology).
- the photocatalyst can also be deposited directly on optical fibers.
- the photocatalyst is preferably deposited in a layer on a porous support, for example of the ceramic or metallic sintered type, and the charge containing the carbon dioxide to be converted in gaseous and / or liquid form, is sent through the photocatalytic bed.
- the photocatalyst When the contacting is in a fixed licking bed, the photocatalyst is preferably deposited on a non-porous support of ceramic or metallic type, and the charge containing the carbon dioxide to be converted in gaseous and / or liquid form is sent to the photocatalytic bed.
- the photocatalyst is preferably in the form of particles in suspension in a liquid or liquid-gas charge containing carbon dioxide.
- the implementation can be carried out in a closed reactor or continuously.
- the photocatalyst is irradiated by at least one irradiation source producing at least photons with a wavelength less than 540 nm or an energy greater than 2.3 eV ( either the minimum band gap of the photocatalyst), so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said irradiation source, so as to produce an effluent containing at least part of carbon molecules in C1 or more, different from CO2.
- any irradiation source emitting at least one wavelength suitable for the activation of said photocatalyst, that is to say absorbable by the photocatalyst, can be used according to the invention.
- the irradiation source can be natural by solar irradiation as well as by artificial irradiation of laser, Hg, incandescent lamp, fluorescent tube, plasma or light-emitting diode (LED, or LED in English for Light-Emitting Diode).
- the source of irradiation is natural by solar irradiation.
- the source of irradiation is solar irradiation, it Usually emits in the ultra-violet, visible and infrared spectrum, i.e. it emits a wavelength range of approximately 280 nm to 2500 nm (according to ASTM G173-03).
- the source emits at at least one wavelength range greater than 280 nm, very preferably between 315 nm and 800 nm, which includes the UV spectrum and / or the visible spectrum.
- the irradiation source provides a flow of photons which 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 source of irradiation is natural, for example by solar irradiation
- the source of irradiation 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 medium within the reactor.
- the realization of the photocatalytic reduction of carbon dioxide is conditioned by the supply of photons adapted to the photocatalytic system for the envisaged reaction and therefore is not limited to specific pressure or temperature ranges outside those allowing ensure the stability of the product (s).
- the temperature range employed for the photocatalytic reduction of the charge containing carbon dioxide is generally -10 ° C to + 200 ° C, preferably 0 to 150 ° C, and very preferably 0 and 50 ° vs.
- the pressure range employed for the photocatalytic reduction of the carbon dioxide-containing feedstock is generally 0.01 MPa to 70 MPa (0.1 to 700 bar), more preferably 0.1 MPa to 5 MPa (1 to 50 bar).
- a diluent fluid as described in step a) may be present in the reaction medium when the process is carried out in the gas phase, during irradiation.
- the effluent obtained after the photocatalytic reduction reaction of carbon dioxide contains on the one hand at least one or more C1 molecule different from the carbon dioxide resulting from the reaction and on the other hand from the unreacted feed, as well as the possible diluent fluid, but also products of parallel reactions such as dihydrogen resulting from the photocatalytic reduction of H2O when this compound is used as a sacrificial compound.
- the photocatalytic process according to the invention uses a photocatalyst prepared by impregnation in a molten medium comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having a forbidden band greater than 2.3 eV.
- the process for preparing said photocatalyst comprises the following steps: i) water is brought into contact with said support so as to obtain a wet support, ii) said wet support is brought into contact with at least one metallic acid hydrate comprising at least molybdenum or tungsten and whose melting point of said hydrated metallic acid is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said support being between 0.1 and 2.5, iii) the solid mixture obtained at the end of step ii) is heated with stirring to a temperature between the melting point of said hydrated metal acid and 100 ° C. to form a photocatalytic precursor, iv) a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out.
- the different preparation steps are detailed below.
- water is brought into contact with said support so as to obtain a wet support.
- This step of humidifying the support is necessary in order to be able to melt the hydrated metal acid in step iii).
- the acid has the particularity of melting only in the presence of a sufficient partial pressure of water.
- the contacting step a) can be carried out by dry impregnation.
- the water can for example be poured dropwise onto the support contained in a rotating bezel.
- the quantity of water introduced into the support is between 10 and 70%, and preferably between 30 and 50% of its water uptake volume.
- the wet support is allowed to mature. Maturation allows the water to disperse homogeneously within the medium.
- Any maturation step is advantageously carried out at atmospheric pressure, in an atmosphere saturated with water and at a temperature between 17 ° C and 50 ° C, and preferably at room temperature.
- a maturation time of between ten minutes and forty-eight hours, preferably between thirty minutes and fifteen hours and particularly preferably between thirty minutes and six hours, is sufficient.
- said wetted support is brought into contact with at least one hydrated metal acid comprising at least molybdenum or tungsten, the melting point of said hydrated metal acid of which is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said hydrated metal acid and said support being between 0.1 and 2.5.
- the hydrated metal acid should have a relatively low melting point, especially below its decomposition temperature.
- the melting point of hydrated metal acid is between 20 and 100 ° C, and preferably between 50 and 90 ° C.
- the hydrated metal acid includes at least molybdenum or tungsten.
- the hydrated metal acid can additionally include phosphorus and silicon.
- the metal acid can be an acid of a heteropolyanion of the Keggin type.
- the mass ratio between said hydrated metal acid and said support is between 0.1 and 2.5, preferably between 0.3 and 2.0.
- the hydrated metallic acid is in solid form, that is to say that the contacting between said support and said hydrated metallic acid is carried out at a temperature below the melting temperature of said hydrated metallic acid.
- Step ii) is preferably carried out at room temperature.
- the contacting of said support and the hydrated metal acid can be done by any method known to those skilled in the art.
- the bringing into contact of said support and of said hydrated metal acid is carried out with contact means chosen from convective mixers, drum mixers or static mixers.
- Step ii) is preferably carried out for a period of between 5 minutes to 12 hours depending on the type of mixer used, preferably between 10 minutes and 4 hours, and even more preferably between 15 minutes and 3 hours.
- step ii) consists of bringing said wet support into contact with at least one hydrated metal acid comprising at least molybdenum or tungsten, the melting point of said hydrated metal acid of which is between 20 and 100 ° C. , to form a solid mixture, the mass ratio between said hydrated metallic acid and said support being between 0.1 and 2.5.
- step iii) of the process for preparing said photocatalyst the solid mixture obtained at the end of step ii) is heated with stirring to a temperature between melting point of said hydrated metal acid and 100 ° C to form a photocatalytic precursor.
- Step iii) is advantageously carried out at atmospheric pressure.
- Step iii) is generally carried out between 5 minutes and 12 hours, preferably between 5 minutes and 4 hours.
- the stirring (mechanical homogenization) of the mixture can be carried out by any method known to those skilled in the art.
- convective mixers, drum mixers or static mixers can be used.
- step iii) is carried out by means of a drum mixer whose speed of rotation is between 4 and 70 revolutions / minute, preferably between 10 and 60 revolutions / minute.
- a photocatalytic precursor which comprises at least one support and molybdenum or tungsten.
- step iv) of the preparation process according to the invention a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out.
- Step iv) of sulfurization can be carried out advantageously using an H2S / H2 or H2S / N2 gas mixture containing at least 5% by volume of H2S in the mixture at a temperature equal to or greater than ambient temperature, under a total pressure equal to or greater than 1 bar (0.1 MPa) for at least 2 hours.
- the sulfurization temperature is less than 350 ° C.
- the sulfurization temperature is between 100 and 600 ° C.
- the sulfurization step iv) is intended to obtain the photocatalyst based on molybdenum or tungsten sulfide.
- the process for preparing the photocatalyst makes it possible to obtain nanoparticles of molybdenum sulphide or of tungsten sulphide having a forbidden band greater than 2.3 eV, this forbidden band value corresponds to particle sizes less than 3.5 nm. It is important to emphasize that the photocatalyst prepared by impregnation in a molten medium has a different morphology than a photocatalyst prepared by impregnation using an impregnation solution (such as for example described in document FR3073429). This difference in morphology is also present after sulfurization.
- the photocatalyst can also comprise nanoparticles of molybdenum oxysulphides or tungsten oxysulphides. These nanoparticles are defined by their crude formula MoO y S z such that 0 ⁇ y + z ⁇ 5 with y and z being strictly positive integers.
- the degree of sulfurization of the metals constituting the catalytic materials is at least equal to 10%, preferably at least equal to 30%.
- the sulfur content in the sulfurized material is measured by XPS.
- the content of molybdenum sulphide or of tungsten sulphide in the photocatalyst is between 4 and 50% by weight relative to the total weight of the photocatalyst, and preferably between 5 and 45% by weight.
- the surface density which corresponds to the quantity of molybdenum Mo atoms or tungsten W atoms deposited per surface unit of support is advantageously between 0.5 and 12 atoms of Mo or W per square nanometers of support, and preferably between 1 and 10 atoms of Mo or W per square nanometers of support.
- the photocatalyst according to the invention comprises a support based on alumina or silica or silica-alumina.
- the support has no photocatalytic function but makes it possible to stabilize the nanoparticles of molybdenum sulphide or tungsten sulphide.
- the support of said catalyst when the support of said catalyst is based on alumina, it contains more than 50% alumina and, in general, it contains only alumina or silica-alumina as defined below.
- the support of said catalyst is a silica-alumina containing at least 50% by weight of alumina.
- the silica content in the support is at most 50% by weight, most often less than or equal to 45% by weight, preferably less than or equal to 40%.
- the support of said catalyst is based on silica, it contains more than 50% by weight of silica and, in general, it contains only silica.
- the support consists of alumina, silica or silica-alumina.
- the support is based on alumina, and particularly preferably the support is made of alumina.
- the alumina can be a transition alumina, for example an alpha phase alumina, a delta phase alumina, a gamma phase alumina or a mixture of alumina of these different phases.
- the support has a specific surface area (measured according to the ASTM D 3663-78 standard established from the Brunauer, Emmett, Teller method, ie the BET method, as defined in S. Brunauer, PH Emmett, E. Teller , J. Am. Chem. Soc., 1938, 60 (2), pp 309-319.) Between 10 and 1000 m 2 / g, preferably between 50 and 600 m 2 / g.
- the photocatalyst according to the invention comprises a support based on a solid semiconductor.
- the support has a photocatalytic function.
- semiconductors generally have a forbidden bandwidth of between 1, 24 and 4 eV.
- the wavelengths of the photons absorbable by said photocatalysts are thus between 310 nm and 1000 nm.
- the combination of molybdenum sulfide or tungsten sulfide nanoparticles having photocatalytic activity with a support based on a solid semiconductor also having photocatalytic activity makes it possible to benefit from the heterojunctions thus created.
- This particular interaction between 2 semiconductors makes it possible to separate the charge carriers (+ and -) more efficiently and to avoid their recombination. Heterojunctions thus make it possible to use the photons irradiating the solid more efficiently and thus to be able to increase the photocatalytic activity.
- the solid semiconductor can be chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium.
- groups II IA and VA such as GaP, GaN, InP and InGaAs, or elements of groups MB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VI IA, 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 BhTes and B1 2 O 3 , or elements of groups MB and VA, such as Cd 3 P 2 , Zn 3 P 2 and Zn 3 As 2 , or elements of groups IB and VIA, such as CuO, CU 2 O and Ag 2 S, or d 'elements of groups VIIIB and VIA, such as CoO, PdO, Fe 2 Ü 3 and NiO, or elements of groups VIB and VIA, such as MoS 2 and WO 3 , or elements of groups VB and VIA, such that V 2 O
- the solid semiconductor is chosen from T1O 2 , SiC, B1 2 S 3 , Bi 2 0 3 , CdO, CdS, Ce 2 0, Ce0 2 , CeAI0, CoO, Cu 2 0, Fe 0, FeTi0, Ph 2 0 3 , ln (OH) 3 , NiO, PbO, ZnO, Ag 2 S, CdS, Ce 2 S 3 , Cu 2 S, CulnS 2 , ln 2 S 3 , M0S 2 , ZnFe 2 0 3 , ZnS, ZnO, WO 3 , ZnFe 2 0 4 , ZrS 2 , TaO x N y and C 3 N 4 , alone or as a mixture.
- the photocatalyst used in the process according to the invention can be in different forms (nanometric powder, nanoobjects with or without cavities, ...) or shaped (films, monolith, beads of micrometric or millimeter size, ... ).
- the photocatalyst is advantageously in the form of a nanometric powder.
- the use of the photocatalyst in a process for photocatalytic reduction of C0 2 makes it possible to absorb the visible part of the solar spectrum, and thus to exploit a large proportion of the incident solar energy.
- the photocatalyst obtained according to the preparation process according to the invention makes it possible to observe a photocatalytic activity at least at the same level as a photocatalyst prepared by impregnation using an impregnation solution with, however, a simplified preparation and the possibility load more molybdenum or tungsten.
- Example 1 Photocatalyst A (not in accordance with the invention) MoO x S Y / Al203
- a support of alumina y (Y-Al2O3) is loaded into a quartz reactor and calcined for 6 hours at 300 ° C with a temperature rise ramp of 5 ° C / min, then placed under vacuum (10 5 mbar) at the same temperature for 16h. Then, the dehydroxylated support is removed from the vacuum line and is cooled to 140 ° C and then stored in a glove box.
- the specific surface of the alumina support is 284 m 2 / g.
- the precursor of molybdenum is molybdenum pentaethoxide Mo (OC2Hs) 5 (Gelest TM, 90%). Dry, degassed cyclohexane is used as the solvent. 1.96 mL of impregnation solution, prepared from 0.67 g of precursor and cyclohexane, are impregnated on 2.58 g of dry support on a synthesis ramp using schlenks. The impregnation of the support with the impregnation solution is carried out using a needle from one schlenk to another.
- the amount of molybdenum is adjusted so as to obtain approximately 1.7 Mo / nm 2, ie a mass content of Mo of 8%.
- the extrudates are dried under vacuum (10 -5 mbar) for 2 hours at room temperature.
- the solid is subjected to 2 drying cycles under vacuum at room temperature, first by the Schlenk line ( ⁇ 8.10 2 mbar) for 1 h and then by the high vacuum line at 10 5 mbar. for 1 hour.
- the solid undergoes a sulfurization step carried out at 100 ° C. with a flow rate of H2S / H2 gas (15/85 vol) of 2 L / h / g.
- XPS analysis shows that 60% of molybdenum is surrounded by sulfur.
- the band gap of photocatalyst A is measured by diffuse reflection absorption spectrometry at 3.18 eV.
- Photocatalyst B is prepared identically to photocatalyst A, only the sulfurization step differs with a treatment temperature of 200 ° C.
- the reflux is set up and the reactor is heated to 85 ° C. with stirring for 3 h.
- the catalyst is then left to mature for 18 hours.
- the precatalyst C is thus obtained.
- the solid undergoes a sulfurization step carried out at 200 ° C. with a flow rate of HS / H 2 gas (15/85 vol) of 2 L / h / g.
- XPS analysis shows that 40% of molybdenum is surrounded by sulfur.
- the band gap of the photocatalyst C is measured by diffuse reflection absorption spectrometry at 3.04 eV.
- Photocatalyst D is prepared identically to photocatalyst C, only the sulfurization step differs with a treatment temperature of 400 ° C.
- XPS analysis gives 85% molybdenum sulfurization.
- the band gap of photocatalyst D is measured by diffuse reflection absorption spectrometry at 2.54 eV.
- Example 5 Implementation of photocatalysts in photocatalytic reduction of CO2 in the gas phase
- Photocatalysts A, B, C and D are subjected to a photocatalytic reduction test of CO2 in the gas phase in a continuous steel cross-bed reactor fitted with a quartz optical window and a frit opposite the optical window. on which is deposited the photocatalytic solid.
- a sufficient quantity of powder is deposited on the frit so as to cover the entire irradiated surface of the reactor (approximately 100 mg).
- the irradiated geometric surface for all the photocatalysts is 5.3.10 04 m 2 .
- Tests are carried out at room temperature under atmospheric pressure.
- a CO2 flow rate of 0.3 ml / min passes through a water saturator before being distributed into the reactor.
- the production of CH 4 resulting from the reduction of carbon dioxide is monitored by analysis of the effluent every 10 minutes by gas phase microchromatography.
- the UV-Visible irradiation source is provided by an Xe-Hg lamp (Asahi TM, MAX302 TM).
- the irradiation power is always maintained at 80 W / m 2 for a wavelength range between 315 and 400 nm.
- the duration of the test is 20 hours.
- the photocatalytic activities are expressed in micromoles (pmol) of methane produced per hour and per m 2 irradiated. These are average activities over the entire duration of the tests.
- the results are reported in Table 1 (below) which shows the performance of the photocatalysts relative to their average activity for the production of methane from a mixture of CO2 and H2O in the gas phase.
- the activity values show that the use of the solids according to the invention C and D allow the photocatalytic reduction of carbon dioxide to CH4.
- the solids C and D prepared much more simply than the catalysts A and B, exhibit very slightly better performances than those of the solids A and B respectively.
Abstract
The invention relates to a process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and/or in the gas phase under irradiation using a photocatalyst comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having a band gap greater than 2.3 eV, said photocatalyst being prepared by impregnation in a molten medium followed by a sulfidation. Said process is carried out by bringing a charge containing CO2 and at least one sacrificial compound into contact with said photocatalyst, then by irradiating the photocatalyst so as to reduce the CO2 and oxidize the sacrificial compound so as to produce an effluent containing at least part of the C1 or more C1 carbon molecules different from the CO2.
Description
PROCEDE DE REDUCTION PHOTOCATALYTIQUE DU DIOXYDE DE CARBONE EN PRESENCE D’UN PHOTOCATALYSEUR PREPARE PAR IMPREGNATION PROCESS FOR PHOTOCATALYTICAL REDUCTION OF CARBON DIOXIDE IN THE PRESENCE OF A PHOTOCATALYZER PREPARED BY IMPREGNATION
EN MILIEU FONDU IN MELTED ENVIRONMENT
Domaine technique Le domaine de l'invention est celui de la réduction photocatalytique du dioxyde de carbone (CO2) sous irradiation par l'emploi d'un photocatalyseur préparé par imprégnation en milieu fondu. Technical field The field of the invention is that of the photocatalytic reduction of carbon dioxide (CO2) under irradiation by the use of a photocatalyst prepared by impregnation in a molten medium.
Art antérieur Prior art
Les combustibles fossiles, comme le charbon, le pétrole et le gaz naturel, sont les principales sources d'énergie conventionnelles dans le monde en raison de leur disponibilité, de leur stabilité et de leur densité d'énergie élevée. Cependant la combustion produit des émissions de dioxyde de carbone qui sont considérées comme la principale cause du réchauffement climatique. Ainsi, il existe un besoin croissant pour atténuer les émissions de CO2, soit en le captant, soit en le transformant. Bien que la capture et séquestration « passives » du carbone (CSC) soient généralement considérées comme un procédé efficace pour réduire les émissions de C02, d’autres stratégies doivent être envisagées, notamment des stratégies « actives » de conversion du CO2 en produits ayant une valeur économique, tels que les carburants et produits chimiques industriels. De telles stratégies « actives » se basent sur la réduction du dioxyde de carbone en produits valorisables. La réduction du dioxyde de carbone peut être réalisée par voie biologique, thermique, électrochimique ou encore photocatalytique. Parmi ces options, la réduction photocatalytique du CO2 gagne une attention accrue car elle peut potentiellement consommer des formes alternatives d'énergie, par exemple en exploitant l'énergie solaire, qui est abondante, bon marché, et écologiquement propre et sûre. Fossil fuels, such as coal, oil and natural gas, are the main conventional energy sources in the world due to their availability, stability and high energy density. However, combustion produces carbon dioxide emissions which are considered to be the main cause of global warming. Thus, there is a growing need to mitigate CO2 emissions, either by capturing it or by transforming it. Although the capture and sequestration "passive" (CCS) are generally regarded as an effective method for reducing C0 2 emissions, other strategies should be considered, including strategies "active" conversion of CO2 into products with economic value, such as fuels and industrial chemicals. Such “active” strategies are based on the reduction of carbon dioxide into valuable products. The reduction of carbon dioxide can be carried out by biological, thermal, electrochemical or even photocatalytic means. Among these options, photocatalytic CO2 reduction is gaining increased attention as it can potentially consume alternative forms of energy, for example by harnessing solar energy, which is abundant, cheap, and environmentally clean and safe.
La réduction photocatalytique du dioxyde de carbone permet d’obtenir des molécules carbonées en C1 ou plus, telles que le monoxyde de carbone (CO), le méthane, le méthanol, l’éthanol, le formaldéhyde, l’acide formique ou encore d’autre molécules telles que les acides
carboxyliques, les aldéhydes, les cétones ou différents alcools. Ces molécules peuvent trouver une utilité énergétique directement, telles que le méthanol, l’éthanol, l’acide formique ou encore le méthane et tous les hydrocarbures en C1+. Le monoxyde de carbone (CO) peut également être valorisé énergétiquement en mélange avec du dihydrogène pour la formation de carburants par synthèse Fischer-Tropsch. Les molécules d’acides carboxyliques, d’aldéhydes, de cétones ou de différents alcools quant à elles peuvent trouver des applications dans les procédés de chimie ou de pétrochimie. Toutes ces molécules présentent donc un grand intérêt d'un point de vue industriel. The photocatalytic reduction of carbon dioxide makes it possible to obtain carbon molecules in C1 or more, such as carbon monoxide (CO), methane, methanol, ethanol, formaldehyde, formic acid or even d ' other molecules such as acids carboxylics, aldehydes, ketones or various alcohols. These molecules can find energy use directly, such as methanol, ethanol, formic acid or even methane and all C1 + hydrocarbons. Carbon monoxide (CO) can also be energetically upgraded as a mixture with hydrogen for the formation of fuels by Fischer-Tropsch synthesis. As for the molecules of carboxylic acids, aldehydes, ketones or various alcohols, they can find applications in chemical or petrochemical processes. All these molecules are therefore of great interest from an industrial point of view.
La photocatalyse repose sur le principe d'activation d'un semi-conducteur ou d’un ensemble de semi-conducteurs tel qu’un photocatalyseur, à l'aide de l'énergie apportée par l'irradiation. La photocatalyse peut être définie comme l'absorption d'un photon, dont l'énergie est supérieure à la largeur de bande interdite ou "bandgap" selon la terminologie anglo-saxonne entre la bande de valence et la bande de conduction, qui induit la formation d'une paire électron-trou dans le cas d’un semi-conducteur. On a donc l'excitation d'un électron au niveau de la bande de conduction et la formation d'un trou sur la bande de valence. Cette paire électron-trou va permettre la formation de radicaux libres qui vont soit réagir avec des composés présents dans le milieu, afin d’initier des réactions d’oxydo-réduction, ou alors se recombiner suivant divers mécanismes. Un semi-conducteur est caractérisé par sa bande interdite ou « bandgap », i.e. la différence d'énergie entre sa bande de conduction et sa bande de valence, lui est propre. Tout photon d’énergie supérieure à sa bande interdite peut être absorbé par le semi-conducteur. Tout photon d’énergie inférieure à sa bande interdite ne peut pas être absorbé par le semi-conducteur. Photocatalysis is based on the principle of activating a semiconductor or a set of semiconductors such as a photocatalyst, using the energy provided by the irradiation. Photocatalysis can be defined as the absorption of a photon, the energy of which is greater than the forbidden bandwidth or "bandgap" according to English terminology between the valence band and the conduction band, which induces the formation of an electron-hole pair in the case of a semiconductor. We therefore have the excitation of an electron at the level of the conduction band and the formation of a hole on the valence band. This electron-hole pair will allow the formation of free radicals which will either react with compounds present in the medium, in order to initiate redox reactions, or else recombine according to various mechanisms. A semiconductor is characterized by its forbidden band or “bandgap”, i.e. the energy difference between its conduction band and its valence band, is specific to it. Any photon with energy greater than its forbidden band can be absorbed by the semiconductor. Any photon with energy below its bandgap cannot be absorbed by the semiconductor.
D’autre part, il est connu de l’homme du métier que la bande interdite des semi-conducteurs sous forme de particules varie en fonction de la taille de ces particules. La bande interdite de semi-conducteur augmente pour des tailles de nanoparticules qui diminuent jusqu’à l’échelle du nanomètre. Ce phénomène physique connu est appelé effet quantique de taille. On the other hand, it is known to those skilled in the art that the band gap of semiconductors in the form of particles varies depending on the size of these particles. The semiconductor bandgap increases for nanoparticle sizes that decrease down to the nanometer scale. This known physical phenomenon is called the quantum size effect.
Des procédés de réduction photocatalytique du dioxyde de carbone en présence d’un photocatalyseur contenant une phase sulfurée de molybdène sont connus dans l’état de l’art.
Tu et al. (Nanoscale, 9(26), p. 9065-9070, 2017) proposent un composé hybride M0S2-T1O2 pour la réduction photocatalytique du CO2 en méthanol. Cependant, la phase sulfurée de molybdène joue le rôle de co-catalyseur et ne participe pas à l’absorption des photons permettant la réduction du CO2 en raison de la faible bande interdite de ce matériau. Seul T1O2 joue ce rôle de semi-conducteur et implique ainsi une absorption de photons uniquement dans la gamme des ultraviolets. La synthèse implique la dispersion de T1O2 dans une solution contenant du Na2Mo0 -2H20 et du C2H5NS, suivie d’un chauffage pour faire précipiter le M0S2. Processes for the photocatalytic reduction of carbon dioxide in the presence of a photocatalyst containing a molybdenum sulphide phase are known in the state of the art. Tu et al. (Nanoscale, 9 (26), p. 9065-9070, 2017) propose a hybrid compound M0S2-T1O2 for the photocatalytic reduction of CO2 to methanol. However, the molybdenum sulphide phase acts as a cocatalyst and does not participate in the absorption of photons allowing the reduction of CO2 due to the low band gap of this material. Only T1O2 plays this semiconductor role and thus involves absorption of photons only in the ultraviolet range. The synthesis involves the dispersion of T1O2 in a solution containing Na2Mo0 -2H20 and C2H5NS, followed by heating to precipitate the MOS2.
Zang et al. (Journal of Energy Chemistry, 25(3), p. 500-506, 2016) proposent quant à eux un solide hybride à base de MoS3-Ti02. Ici également, la phase sulfurée de molybdène joue le rôle de co-catalyseur et n’est pas capable d’absorber des photons efficaces pour la réduction du CO2 en raison de la faible bande interdite de ce matériau, c’est encore le T1O2 qui joue ce rôle avec encore la contrainte de n’absorber que les photons dans la gamme de l’ultraviolet. La synthèse implique la dispersion de T1O2 dans une solution contenant du NH4M0S4, suivi d’un chauffage pour faire précipiter le M0S2. Zang et al. (Journal of Energy Chemistry, 25 (3), p. 500-506, 2016), for their part, propose a hybrid solid based on MoS 3 -Ti0 2 . Here also, the sulphide phase of molybdenum plays the role of co-catalyst and is not able to absorb effective photons for the reduction of CO2 due to the low band gap of this material, it is again T1O2 which plays this role with the further constraint of only absorbing photons in the ultraviolet range. Synthesis involves the dispersion of T1O2 in a solution containing NH4M0S4, followed by heating to precipitate the MOS2.
D’autre part, des nanoparticules de molybdène sulfuré présentant une bande interdite supérieure à celle d’un molybdène sulfuré massique sont connues de l’art antérieur. On the other hand, sulfurized molybdenum nanoparticles exhibiting a bandgap greater than that of mass sulfurized molybdenum are known from the prior art.
En effet, Wilcoxon et al. (The Journal of Physical Chemistry B, 103, p.11-17, 1999) propose la synthèse de suspensions colloïdales de nanoparticules de M0S2 ayant une bande interdite de 2,25 eV pour des tailles moyennes de nanoparticules de 4 nm, alors que les nanoparticules de M0S2 pour les tailles supérieures à 10 nm possèdent une bande interdite bien inférieure à 2,25 eV. Ces nanoparticules de molybdène sulfurées ont été mises en œuvre en oxydation photoassistée de composés organiques. Néanmoins, les suspensions colloïdales souffrent de problèmes de stabilité et de coût de production élevé. La synthèse implique l’utilisation d’une solution contenant un sel d’halogénure de molybdène (IV). Indeed, Wilcoxon et al. (The Journal of Physical Chemistry B, 103, p.11-17, 1999) proposes the synthesis of colloidal suspensions of MOS2 nanoparticles having a band gap of 2.25 eV for average nanoparticle sizes of 4 nm, whereas the MOS2 nanoparticles for sizes greater than 10 nm have a bandgap much less than 2.25 eV. These sulphurized molybdenum nanoparticles have been used in photoassisted oxidation of organic compounds. However, colloidal suspensions suffer from problems of stability and high production cost. Synthesis involves the use of a solution containing a molybdenum (IV) halide salt.
Le document FR3073429 décrit un procédé de réduction photocatalytique du dioxyde de carbone mettant un œuvre un photocatalyseur à base de sulfure de molybdène ou de sulfure de tungstène supporté. Le photocatalyseur est préparé par imprégnation à l’aide d’une solution d’imprégnation contenant un solvant organique et un précurseur mononucléaire à
base de molybdène ou de tungstène, suivi d’une étape de maturation, d’une étape de séchage et d’une étape de sulfuration. Les précurseurs mononucléaires utilisés dans ce document présentent le désavantage de devoir être manipulés sous atmosphère contrôlée (en l’absence d’eau) et le support d’imprégnation doit donc subir préalablement à l’imprégnation des traitements sous vide pour évacuer l’eau. Document FR3073429 describes a process for the photocatalytic reduction of carbon dioxide using a photocatalyst based on molybdenum sulphide or supported tungsten sulphide. The photocatalyst is prepared by impregnation using an impregnation solution containing an organic solvent and a mononuclear precursor to molybdenum or tungsten base, followed by a maturation step, a drying step and a sulfurization step. The mononuclear precursors used in this document have the disadvantage of having to be handled under a controlled atmosphere (in the absence of water) and the impregnation support must therefore undergo prior to the impregnation of the vacuum treatments in order to evacuate the water.
Les mises en œuvre connues de l’art antérieur révèle que le sulfure de molybdène ou de sulfure de tungstène est dans tous les cas préparé par une solution contenant un précurseur de molybdène dissous. The known implementations of the prior art reveal that the molybdenum sulphide or tungsten sulphide is in all cases prepared by a solution containing a dissolved molybdenum precursor.
Il apparaît intéressant de trouver d’autres moyens de préparation d’un photocatalyseur à base d’un sulfure de molybdène ou d’un sulfure de tungstène pour la réduction photocatalytique du dioxyde de carbone, permettant d'obtenir de nouveaux photocatalyseurs à performances améliorées. It appears interesting to find other means of preparing a photocatalyst based on molybdenum sulphide or tungsten sulphide for the photocatalytic reduction of carbon dioxide, making it possible to obtain new photocatalysts with improved performance.
Il apparaît particulièrement intéressant de proposer un procédé de préparation d’un photocatalyseur à base d’un sulfure de molybdène ou de sulfure de tungstène ayant une très forte teneur en métal. It appears particularly advantageous to provide a process for preparing a photocatalyst based on a molybdenum sulphide or tungsten sulphide having a very high metal content.
Une toute autre voie de préparation est l’imprégnation en milieu fondu. Cette technique, particulièrement bien décrite dans la publication « Melt Infiltration : an Emerging Technique for the Préparation of Novel Functional Nanostructured Materials », P.E. de Jongh, T.M. Eggenhuisen, Adv. Mater. 2013, 25, 6672-6690 se base sur un procédé en une seule étape basé sur l’infiltration sans pression et par capillarité d’un liquide en fusion dans un corps poreux. A completely different method of preparation is impregnation in a molten medium. This technique, particularly well described in the publication “Melt Infiltration: an Emerging Technique for the Preparation of Novel Functional Nanostructured Materials”, P.E. de Jongh, T.M. Eggenhuisen, Adv. Mater. 2013, 25, 6672-6690 is based on a one-step process based on the pressure-free and capillary infiltration of a molten liquid into a porous body.
Appliqué au domaine de la photocatalyse, l’imprégnation en milieu fondu consiste à mélanger un support avec un sel métallique solide ayant une température de fusion relativement basse, notamment inférieure à sa température de décomposition, puis de chauffer le mélange à une température supérieure à la température de fusion dudit sel métallique afin de faire fondre le sel dans le support. Applied to the field of photocatalysis, impregnation in a molten medium consists in mixing a support with a solid metal salt having a relatively low melting point, in particular lower than its decomposition temperature, then heating the mixture to a temperature higher than the melting temperature of said metal salt in order to melt the salt in the support.
Cette technique se distingue ainsi par rapport à l’imprégnation classique par plusieurs avantages, notamment par une préparation simplifiée. En effet, elle ne nécessite pas de préparation de solution ou de solvant car les précurseurs métalliques sont utilisés sous
forme de solides. De même, le photocatalyseur obtenu après le chauffage du mélange solide support/sel n’a pas besoin d’étapes supplémentaires de séchage. De plus, un avantage majeur de l’imprégnation en milieu fondu est le fait de pouvoir obtenir en une seule étape un photocatalyseur à très forte teneur en métal. This technique is thus distinguished from conventional impregnation by several advantages, in particular by a simplified preparation. Indeed, it does not require preparation of solution or solvent because the metal precursors are used under form of solids. Likewise, the photocatalyst obtained after heating the solid support / salt mixture does not need additional drying steps. In addition, a major advantage of impregnation in a molten medium is the fact that it is possible to obtain in a single step a photocatalyst with a very high metal content.
Cependant, cette technique a le désavantage de nécessiter un sel métallique ayant une température de fusion relativement basse, notamment inférieure à sa température de décomposition. Il ne semble pas avoir de sels du groupe VIB qui répondent à ces critères de faible point de fusion. En effet, les sels à base d’un métal du groupe VIB ont plutôt tendance à se décomposer avant d’atteindre leur point de fusion. However, this technique has the disadvantage of requiring a metal salt having a relatively low melting point, in particular lower than its decomposition temperature. There does not appear to be any Group VIB salts that meet these low melting point criteria. This is because salts based on a Group VIB metal tend to decompose before reaching their melting point.
Dans ce contexte, un des objectifs de la présente invention est de proposer un procédé de réduction photocatalytique du dioxyde de carbone utilisant un photocatalyseur à base de nanoparticules de sulfure de molybdène ou de sulfure de tungstène préparé par imprégnation en milieu fondu. In this context, one of the objectives of the present invention is to provide a process for the photocatalytic reduction of carbon dioxide using a photocatalyst based on nanoparticles of molybdenum sulphide or of tungsten sulphide prepared by impregnation in a molten medium.
Objet de l’invention Object of the invention
L’objet de l’invention est de proposer une voie nouvelle, durable et plus performante de production de molécules carbonées valorisables par conversion photocatalytique du dioxyde de carbone à l’aide d’un photocatalyseur à base de nanoparticules de sulfure de molybdène ou de sulfure de tungstène préparé par imprégnation en milieu fondu. Le procédé de réduction photocatalytique de CO2 selon l’invention permet d’atteindre des performances améliorées. The object of the invention is to provide a new, sustainable and more efficient way of producing carbon molecules that can be upgraded by photocatalytic conversion of carbon dioxide using a photocatalyst based on molybdenum sulphide or sulphide nanoparticles. of tungsten prepared by impregnation in a molten medium. The photocatalytic CO2 reduction process according to the invention achieves improved performance.
Plus particulièrement, l'invention décrit un procédé de réduction photocatalytique du dioxyde de carbone effectué en phase liquide et/ou en phase gazeuse, ledit procédé comprenant les étapes suivantes : a) on met en contact une charge contenant le dioxyde de carbone et au moins un composé sacrificiel avec un photocatalyseur, b) on irradie le photocatalyseur par au moins une source d'irradiation produisant au moins une longueur d'onde absorbable par ledit photocatalyseur de manière à réduire le dioxyde de carbone et oxyder le composé sacrificiel en présence dudit photocatalyseur activé par ladite
source d'irradiation, de manière à produire un effluent contenant au moins en partie des molécules carbonées en C1 ou plus, différentes du CO2, ledit photocatalyseur comprenant un support et des nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV, ledit photocatalyseur étant préparé par un procédé comprenant les étapes suivantes : i) on met en contact de l’eau avec ledit support de manière à obtenir un support mouillé, ii) on met en contact ledit support mouillé avec au moins un acide métallique hydraté comprenant au moins du molybdène ou du tungstène et dont la température de fusion dudit acide métallique hydraté est comprise entre 20 et 100°C, pour former un mélange solide, le rapport massique entre ledit acide métallique et ledit support étant compris entre 0,1 et 2,5, iii) on chauffe sous agitation le mélange solide obtenu à l’issue de l’étape ii) à une température comprise entre la température de fusion dudit acide métallique hydraté et 100°C pour former un précurseur photocatalytique, iv) on effectue une étape de sulfuration du précurseur photocatalytique obtenu à l’étape iii).More particularly, the invention describes a process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and / or in the gas phase, said process comprising the following steps: a) a charge containing carbon dioxide is brought into contact and at least a sacrificial compound with a photocatalyst, b) the photocatalyst is irradiated with at least one irradiation source producing at least one wavelength absorbable by said photocatalyst so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said source of irradiation, so as to produce an effluent containing at least in part carbon molecules in C1 or more, other than CO2, said photocatalyst comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having an upper band gap at 2.3 eV, said photocatalyst being prepared by a process comprising the following steps: i) water is brought into contact with said support so as to obtain a wet support, ii) said wet support is brought into contact with at at least one hydrated metallic acid comprising at least molybdenum or tungsten and whose melting point of said hydrated metallic acid is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said support being included between 0.1 and 2.5, iii) the solid mixture obtained at the end of step ii) is heated with stirring to a temperature between the melting point of said acid m hydrated metal and 100 ° C to form a photocatalytic precursor, iv) a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out.
Les nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV absorbent avantageusement une partie du spectre visible de l’irradiation naturelle (solaire) ou artificielle tout en permettant la réduction du dioxyde de carbone par des niveaux de bandes adaptés, ce que ne permet pas les phases sulfures de molybdène ou de tungstène sous forme de nanoparticules de plus grande taille présentant une bande interdite inférieure à 2,3 eV. La mise en oeuvre dudit photocatalyseur pour la réduction photocatalytique du CO2 permet ainsi de valoriser la partie visible du spectre puisqu’il peut absorber tous les photons de longueur d’onde inférieure à 620 nm (contre 400 nm pour un photocatalyseur classique de type Ti02). Molybdenum sulfide or tungsten sulfide nanoparticles with a bandgap greater than 2.3 eV advantageously absorb part of the visible spectrum of natural (solar) or artificial irradiation while allowing the reduction of carbon dioxide by levels suitable bands, which does not allow the sulphide phases of molybdenum or tungsten in the form of nanoparticles of larger size having a forbidden band of less than 2.3 eV. The use of said photocatalyst for the photocatalytic reduction of CO2 thus makes it possible to enhance the visible part of the spectrum since it can absorb all photons with a wavelength of less than 620 nm (against 400 nm for a conventional photocatalyst of the Ti0 2 type ).
De plus, ces nanoparticules supportées présentent l’avantage d’une meilleure stabilité vis-à- vis des suspensions colloïdales. In addition, these supported nanoparticles have the advantage of better stability against colloidal suspensions.
La demanderesse a en effet constaté que l’utilisation d’acide métallique hydraté comprenant au moins du molybdène ou du tungstène et ayant une température de fusion comprise entre 20 et 100°C permet d’introduire du molybdène ou du tungstène dans un support par
imprégnation en milieu fondu pour obtenir un précurseur photocatalytique permettant d’obtenir, après sulfuration (étape iv), un photocatalyseur ayant des nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV dispersés dans le support. The Applicant has in fact observed that the use of hydrated metallic acid comprising at least molybdenum or tungsten and having a melting point of between 20 and 100 ° C makes it possible to introduce molybdenum or tungsten into a support by impregnation in a molten medium to obtain a photocatalytic precursor making it possible to obtain, after sulphurization (step iv), a photocatalyst having nanoparticles of molybdenum sulphide or of tungsten sulphide having a forbidden band greater than 2.3 eV dispersed in the support.
L’acide métallique hydraté, qui se présente sous forme de poudre, est mélangé avec le support (étape ii), puis ce mélange solide est chauffé afin de faire fondre l’acide métallique dans le support permettant ainsi d’obtenir le catalyseur (étape iii). Cependant, l’acide présente la particularité de ne fondre qu’en présence d’une pression partielle d’eau suffisante. En d’autres termes, il est nécessaire de garder les molécules d’eau de cristallisation pour assurer sa fusion. Afin de garantir une pression partielle d’eau suffisante, le support est au préalable humidifié par une imprégnation d’eau (étape i). The hydrated metallic acid, which is in the form of powder, is mixed with the support (step ii), then this solid mixture is heated in order to melt the metallic acid in the support, thus making it possible to obtain the catalyst (step iii). However, the acid has the peculiarity of only melting in the presence of sufficient partial pressure of water. In other words, it is necessary to keep the molecules of water of crystallization to ensure its fusion. In order to guarantee sufficient partial water pressure, the support is first moistened by impregnating with water (step i).
Le procédé de préparation selon l’invention présente ainsi les avantages d’une imprégnation en milieu fondu, notamment l’absence de toute préparation de solution ou l’utilisation de solvant. The preparation process according to the invention thus has the advantages of an impregnation in a molten medium, in particular the absence of any preparation of solution or the use of solvent.
De plus, le procédé de préparation selon l’invention permet d’obtenir un photocatalyseur fortement chargé en molybdène ou en tungstène ayant notamment des teneurs en métal de molybdène ou de tungstène qui ne sont pas atteignables par imprégnation à l’aide d’une solution d’imprégnation. In addition, the preparation process according to the invention makes it possible to obtain a photocatalyst highly charged with molybdenum or tungsten having in particular metal contents of molybdenum or of tungsten which are not attainable by impregnation with the aid of a solution. impregnation.
Ainsi, le photocatalyseur obtenu selon le procédé de préparation selon l’invention permet d’observer une activité photocatalytique au moins au même niveau qu’un photocatalyseur préparé par imprégnation à l’aide d’une solution d’imprégnation avec cependant une préparation simplifiée et la possibilité de charger plus de molybdène ou de tungstène. Thus, the photocatalyst obtained according to the preparation process according to the invention makes it possible to observe a photocatalytic activity at least at the same level as a photocatalyst prepared by impregnation using an impregnation solution with, however, a simplified preparation and the ability to load more molybdenum or tungsten.
Selon une variante, l’acide métallique hydraté est choisi parmi l’acide phosphomolybdique hydraté, l’acide silicomolybdique hydraté, l’acide molybdosilicique hydraté, l’acide phosphotungstique hydraté et l’acide silicotungstique hydraté. Alternatively, the hydrated metal acid is selected from hydrated phosphomolybdic acid, hydrated silicomolybdic acid, hydrated molybdosilicic acid, hydrated phosphotungstic acid and hydrated silicotungstic acid.
Selon une variante, à l’étape i) la quantité d’eau introduite dans le support est entre 10 et 70 % de son volume de reprise en eau.
Selon une variante, le support est un support à base d'alumine ou de silice ou de silice- alumine. According to one variant, in step i) the quantity of water introduced into the support is between 10 and 70% of its water uptake volume. According to one variant, the support is a support based on alumina or silica or silica-alumina.
Selon une variante, le support est un support à base d’un semi-conducteur solide. According to one variant, the support is a support based on a solid semiconductor.
Selon cette variante, le support est un semi-conducteur solide choisi parmi un ou plusieurs éléments du groupe IVA, tels que le silicium, le germanium, le carbure de silicium ou le silicium-germanium, d'éléments des groupes NIA et VA, tels que GaP, GaN, InP et InGaAs, ou d'éléments des groupes MB et VIA, tels que CdS, ZnO et ZnS, ou d'éléments des groupes IB et VI IA, 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 BhTe3 et B12O3, ou d'éléments des groupes MB et VA, tels que Cd3P2, Zh3Rå et Zn3As2, ou d'éléments des groupes IB et VIA, tels que CuO, CU2O et Ag2S, ou d'éléments des groupes VIIIB et VIA, tels que CoO, PdO, Fe 0 et NiO, ou d'éléments des groupes VIB et VIA, tels que MoS2 et W03, ou d'éléments des groupes VB et VIA, tels que V2O5 et Nb20 et TaOxNy, ou d'éléments des groupes IVB et VIA, tels que HO2 et HfS2, ou d'éléments des groupes NIA et VIA, tels que ln2Ü3 et ln2S3, ou d'éléments des groupes VIA et des lanthanides, tels que Ce2C>3, Pr203, S1TI2S3, Tb2S et La2S3, ou d'éléments des groupes VIA et des actinides, tels que UO2 et U03, ou encore le nitrure de carbone C3N4. According to this variant, the support is a solid semiconductor chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium, of elements of groups NIA and VA, such as as GaP, GaN, InP and InGaAs, or elements of groups MB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VI IA, 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 BhTe 3 and B1 2 O 3 , or elements of groups MB and VA, such as Cd 3 P 2 , Zh 3 R å and Zn 3 As 2 , or elements of groups IB and VIA, such as CuO, CU 2 O and Ag 2 S, or elements of groups VIIIB and VIA, such as CoO, PdO, Fe 0 and NiO, or elements of groups VIB and VIA, such as MoS 2 and W0 3 , or elements of groups VB and VIA, such as V 2 O 5 and Nb 2 0 and TaO x N y , or d '' elements of groups IVB and VIA, such as HO 2 and HfS 2 , or elements of groups NIA and VIA, such s that ln 2 Ü 3 and ln 2 S 3 , or elements of VIA groups and lanthanides, such as Ce 2 C> 3 , Pr 2 0 3 , S1TI2S3, Tb 2 S and La2S 3 , or elements of VIA groups and actinides, such as UO2 and U0 3 , or else carbon nitride C 3 N 4 .
Selon une variante, la teneur en sulfure de molybdène ou en sulfure de tungstène du photocatalyseur est comprise entre 4 et 50% poids par rapport au poids total du photocatalyseur. According to one variant, the content of molybdenum sulphide or of tungsten sulphide in the photocatalyst is between 4 and 50% by weight relative to the total weight of the photocatalyst.
Selon une variante, la densité surfacique qui correspond à la quantité d'atomes de molybdène Mo ou d’atomes de tungstène W, déposés par unité surfacique de support, est comprise entre 0,5 et 12 atomes de Mo ou de W par nanomètres carré de support. According to one variant, the surface density which corresponds to the quantity of atoms of molybdenum Mo or of tungsten atoms W, deposited per surface unit of support, is between 0.5 and 12 atoms of Mo or of W per square nanometers. support.
Selon une variante, lorsque le procédé photocatalytique est effectué en phase gazeuse, le composé sacrificiel est un composé gazeux choisi parmi l’eau, l’ammoniaque, le dihydrogène, le méthane ou un alcool. According to one variant, when the photocatalytic process is carried out in the gas phase, the sacrificial compound is a gaseous compound chosen from water, ammonia, dihydrogen, methane or an alcohol.
Selon cette variante, un fluide diluant est présent dans les étapes a) et/ou b).
Selon une autre variante, lorsque le procédé photocatalytique est effectué en phase liquide, le composé sacrificiel est un composé oxydable liquide ou solide soluble dans la charge liquide, choisi parmi l’eau, l’ammoniaque, un alcool, un aldéhyde ou une amine. According to this variant, a diluting fluid is present in steps a) and / or b). According to another variant, when the photocatalytic process is carried out in the liquid phase, the sacrificial compound is a liquid or solid oxidizable compound soluble in the liquid charge, chosen from water, ammonia, an alcohol, an aldehyde or an amine.
Selon une variante, la source d’irradiation est une source d’irradiation naturelle ou artificielle.Alternatively, the irradiation source is a natural or artificial irradiation source.
Selon une variante la source d’irradiation émet à au moins dans une gamme de longueurs d'ondes comprise entre 280 nm et 2500 nm. According to one variant, the irradiation source emits at least in a range of wavelengths between 280 nm and 2500 nm.
Définitions et abréviations Definitions and abbreviations
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 a better understanding:
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.
On entend par « molécules carbonées en C1 ou plus », des molécules issues de la réduction du CO2 contenant un ou plus d’atomes de carbone, à l’exception du CO2. De telles molécules sont par exemple le CO, le méthane, le méthanol, l’éthanol, le formaldéhyde, l’acide formique, le méthane ou encore d’autre molécules telles que les acides carboxyliques, les aldéhydes, les cétones, différents alcools ou des hydrocarbures contenant plus de 2 atomes de carbone. By "carbon molecules in C1 or more" is meant molecules resulting from the reduction of CO2 containing one or more carbon atoms, with the exception of CO2. Such molecules are for example CO, methane, methanol, ethanol, formaldehyde, formic acid, methane or even other molecules such as carboxylic acids, aldehydes, ketones, various alcohols or hydrocarbons containing more than 2 carbon atoms.
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, editor 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 of 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, Academie 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. The total pore volume and the 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, Academie Press, 1999. The term “specific surface” is understood to mean the BET specific surface (SBET in m 2 / g) determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established using 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 :
avec Amax 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 792458 m.s-1) et Eg la largeur de bande interdite ou "bandgap" du semiconducteur (en eV).The maximum absorbable wavelength 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 792458 ms-1) and Eg the forbidden bandwidth or "bandgap" of the semiconductor (in eV).
On mesure la valeur de la bande interdite de matériaux semi-conducteurs par spectroscopie d’absorption en réflexion diffuse tel que décrit par la méthode de Tauc (J. Tauc, R. Grigorovici, and A. Vancu, Phys. Status Solidi, 1966, 15, p 627 ; J. Tauc,”Optical Properties of Solids”, F. Abeles ed., North-Holland, 1972 ; E.A. Davis and N. F. Mott, Philos. Mag., 1970, 22 p 903). The value of the band gap of semiconductor materials is measured by diffuse reflection absorption spectroscopy as described by the Tauc method (J. Tauc, R. Grigorovici, and A. Vancu, Phys. Status Solidi, 1966, 15, p 627; J. Tauc, "Optical Properties of Solids", F. Abeles ed., North-Holland, 1972; EA Davis and NF Mott, Philos. Mag., 1970, 22 p 903).
On entend par « milieu réactionnel », le mélange formé par la charge contenant le dioxyde de carbone, le composé sacrificiel et le photocatalyseur. The term “reaction medium” is understood to mean the mixture formed by the charge containing the carbon dioxide, the sacrificial compound and the photocatalyst.
Description détaillée de l'invention Detailed description of the invention
L'invention porte sur un procédé de réduction photocatalytique du dioxyde de carbone effectué en phase liquide et/ou en phase gazeuse, ledit procédé comprenant les étapes suivantes : a) on met en contact une charge contenant le dioxyde de carbone et au moins un composé sacrificiel avec un photocatalyseur, b) on irradie le photocatalyseur par au moins une source d'irradiation produisant au moins une longueur d'onde absorbable par ledit photocatalyseur de manière à réduire le dioxyde de carbone et oxyder le composé sacrificiel en présence dudit photocatalyseur activé par ladite
source d'irradiation, de manière à produire un effluent contenant au moins en partie des molécules carbonées en C1 ou plus, différentes du CO2, ledit photocatalyseur comprenant un support et des nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV, ledit photocatalyseur étant préparé par une imprégnation en milieu fondu. The invention relates to a process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and / or in the gas phase, said process comprising the following steps: a) a charge containing carbon dioxide and at least one compound is brought into contact. sacrificial with a photocatalyst, b) the photocatalyst is irradiated with at least one irradiation source producing at least one wavelength absorbable by said photocatalyst so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said source of irradiation, so as to produce an effluent containing at least in part carbon molecules in C1 or more, other than CO2, said photocatalyst comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having an upper band gap at 2.3 eV, said photocatalyst being prepared by impregnation in a molten medium.
Les différentes étapes du procédé sont détaillées par la suite. The different steps of the process are detailed below.
Etape a) de mise en contact d’une charge, d’au moins un composé sacrificiel et d’un photocatalyseur Step a) contacting a filler, at least one sacrificial compound and a photocatalyst
Selon l’étape a) du procédé selon l’invention, on met en contact une charge contenant le dioxyde de carbone (CO2) et au moins un composé sacrificiel avec un photocatalyseur.According to step a) of the process according to the invention, a charge containing carbon dioxide (CO2) and at least one sacrificial compound is brought into contact with a photocatalyst.
La charge et le composé sacrificiel The charge and the sacrificial compound
Le procédé est effectué en phase gazeuse, liguide ou biphasigue, gazeuse et liguide, signifiant respectivement que la charge traitée selon le procédé se présente sous forme gazeuse, liquide ou biphasique, gazeuse et liquide. De préférence, le procédé est effectué en phase gazeuse. The process is carried out in gaseous, liguid or two-phase, gaseous and liguid phase, meaning respectively that the feed treated according to the process is in gaseous, liquid or two-phase, gaseous and liquid form. Preferably, the process is carried out in the gas phase.
- Lorsque le procédé est effectué en phase gazeuse, avec une charge se présentant sous forme gazeuse, le CO2 présent dans la charge est aussi sous forme gazeuse, et le(s) composé(s) sacrificiel(s) utilisés pour l’étape a) sont également sous forme gazeuse. - When the process is carried out in the gas phase, with a feed in gaseous form, the CO2 present in the feed is also in gaseous form, and the sacrificial compound (s) used for step a ) are also in gaseous form.
Les composés sacrificiels gazeux sont des composés oxydables tels que l’eau (H20), l’ammoniaque (NH3), le dihydrogène (H2), le méthane (CH4) ou encore les alcools. Gaseous sacrificial compounds are oxidizable compounds such as water (H 2 O), ammonia (NH3), dihydrogen (H2), methane (CH4) or even alcohols.
De manière préférée, les composés sacrificiels gazeux sont l’eau ou le dihydrogène. Un fluide diluant tel que N2 ou Ar, peut être présent dans le milieu réactionnel lorsque le procédé est effectué en phase gazeuse. La présence d'un fluide diluant n'est pas requise 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 le milieu réactionnel, 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 la réduction souhaitée du dioxyde de carbone. Preferably, the gaseous sacrificial compounds are water or hydrogen. A diluent fluid, such as N 2 or Ar, can 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 it to the charge to ensure the dispersion of the charge and / or of the photocatalyst in the reaction medium, the control of the adsorption of reagents / products at the surface of the photocatalyst, control of the absorption of photons by the photocatalyst, dilution of the products to limit their recombination and other side reactions of the same order. The presence of a diluent fluid also makes it possible to control the temperature of the reaction medium, thus being able to compensate for the possible exo / endothermicity of the photocatalysed reaction. The nature of the diluent fluid is chosen such that its influence is neutral on the reaction medium or that its possible reaction does not harm the achievement of the desired reduction of carbon dioxide.
- Lorsque le procédé est effectué en phase liquide, avec une charge se présentant sous forme liquide, celle-ci peut être sous forme ionique, organique ou aqueux. La charge sous forme liquide est préférentiellement aqueuse. - When the process is carried out in the liquid phase, with a feed in liquid form, it can be in ionic, organic or aqueous form. The feed in liquid form is preferably aqueous.
Lorsque la charge liquide est une solution aqueuse, le CO2 est alors solubilisé sous forme de CO2 aqueux, d’hydrogénocarbonate ou de carbonate. Les composés sacrificiels utilisés dans ce cas, sont des composés oxydables liquides ou solides solubles dans la charge liquide, tels que l’eau (H 0), l’ammoniaque (NH ), les alcools, les aldéhydes, les amines. De manière préférée, le composé sacrificiel est l’eau. Le pH est généralement compris entre 2 et 12, de préférence entre 3 et 10. When the liquid feed is an aqueous solution, the CO2 is then solubilized in the form of aqueous CO2, hydrogen carbonate or carbonate. The sacrificial compounds used in this case are liquid or solid oxidizable compounds soluble in the liquid charge, such as water (H 0), ammonia (NH), alcohols, aldehydes, amines. Preferably, the sacrificial compound is water. The pH is generally between 2 and 12, preferably between 3 and 10.
Eventuellement, 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 feed, a basic or acidic agent can be added to the feed. The basic agent can be chosen from alkali or alkaline earth hydroxides, organic bases, for example amines or ammonia. The acidic agent can be selected from inorganic acids, for example nitric, sulfuric, phosphoric, hydrochloric, hydrobromic or organic acids, such as carboxylic or sulfonic acids.
Eventuellement, 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-, Ch, F-, NO32-.Optionally, when the liquid filler is aqueous, it can contain in any quantity any solvated ion, such as for example K + , Li + , Na + , Ca 2+ , Mg 2+ , SO4 2 -, Ch, F- , NO3 2 -.
La mise en contact Contacting
La mise en contact de la charge contenant le dioxyde de carbone et du photocatalyseur peut se faire par tout moyen connu de l'homme du métier. La mise en contact de la charge et du photocatalyseur peut se faire 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.
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 contenant le dioxyde de carbone à convertir sous forme gazeuse et/ou liquide, est envoyée à travers le lit photocatalytique. The charge containing carbon dioxide and the photocatalyst can be brought into contact by any means known to those skilled in the art. The contact between the charge and the photocatalyst can be carried out in a crossed fixed bed, in a licking fixed bed or in suspension (also called "slurry" according to the English terminology). The photocatalyst can also be deposited directly on optical fibers. When the contact is in a fixed bed crossed, the photocatalyst is preferably deposited in a layer on a porous support, for example of the ceramic or metallic sintered type, and the charge containing the carbon dioxide to be converted in gaseous and / or liquid form, is sent through the photocatalytic bed.
Lorsque la mise en en contact est en lit fixe léchant, le photocatalyseur est préférentiellement déposé sur un support non poreux de type céramique ou métallique, et la charge contenant le dioxyde de carbone à convertir sous forme gazeuse et/ou liquide, est envoyée sur le lit photocatalytique. When the contacting is in a fixed licking bed, the photocatalyst is preferably deposited on a non-porous support of ceramic or metallic type, and the charge containing the carbon dioxide to be converted in gaseous and / or liquid form is sent to the photocatalytic bed.
Lorsque la mise en contact est en suspension, le photocatalyseur est préférentiellement sous forme de particules en suspension dans une charge liquide ou liquide-gaz contenant le dioxyde de carbone. En suspension, la mise en oeuvre peut se faire dans un réacteur fermé ou en continu. When the contacting is in suspension, the photocatalyst is preferably in the form of particles in suspension in a liquid or liquid-gas charge containing carbon dioxide. In suspension, the implementation can be carried out in a closed reactor or continuously.
Etape b) d’irradiation du photocatalyseur Step b) irradiation of the photocatalyst
Selon l’étape b) du procédé selon l’invention, on irradie le photocatalyseur par au moins une source d'irradiation produisant au moins des photons de longueur d'onde inférieure à 540 nm ou d’énergie supérieure à 2,3 eV (soit la bande interdite minimum du photocatalyseur), de manière à réduire le dioxyde de carbone et oxyder le composé sacrificiel en présence dudit photocatalyseur activé par ladite source d'irradiation, de manière à produire un effluent contenant au moins en partie des molécules carbonées en C1 ou plus, différentes du CO2.According to step b) of the method according to the invention, the photocatalyst is irradiated by at least one irradiation source producing at least photons with a wavelength less than 540 nm or an energy greater than 2.3 eV ( either the minimum band gap of the photocatalyst), so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said irradiation source, so as to produce an effluent containing at least part of carbon molecules in C1 or more, different from CO2.
Toute source d'irradiation émettant au moins une longueur d'onde adaptée à l'activation dudit photocatalyseur c'est-à-dire absorbable par le 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 the activation of said photocatalyst, that is to say absorbable by the photocatalyst, can be used according to the invention. The irradiation source can be natural by solar irradiation as well as by artificial irradiation of laser, Hg, incandescent lamp, fluorescent tube, plasma or light-emitting diode (LED, or LED in English for Light-Emitting Diode). Preferably, the source of irradiation 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 (Âmax=540 nm) par les nanoparticules de sulfure de molybdène ou de sulfure de tungstène constitutives du photocatalyseur selon l’invention. 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 environ (selon la norme ASTM G173- 03). De préférence, la source émet à au moins une gamme de longueur d'onde supérieure à 280 nm, de manière très préférée comprise entre 315 nm et 800 nm, ce qui inclut le spectre UV et/ou le spectre visible. The irradiation source produces radiation, at least part of the wavelengths of which is less than the maximum absorbable wavelength (Â m ax = 540 nm) by the molybdenum sulphide or tungsten sulphide nanoparticles constituting the photocatalyst according to the invention. When the source of irradiation is solar irradiation, it Usually emits in the ultra-violet, visible and infrared spectrum, i.e. it emits a wavelength range of approximately 280 nm to 2500 nm (according to ASTM G173-03). Preferably, the source emits at at least one wavelength range greater than 280 nm, very preferably between 315 nm and 800 nm, which includes the UV spectrum and / or the visible spectrum.
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 flow of photons which 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 source of irradiation is natural, for example by solar irradiation, the source of irradiation 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 medium within the reactor.
La réalisation de la réduction photocatalytique du dioxyde de carbone est conditionnée par la fourniture de photons adaptés au système photocatalytique 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 ou des produit(s). La gamme de température employée pour la réduction photocatalytique de la charge contenant le dioxyde de carbone est généralement de -10°C à + 200°C, de manière préférée de 0 à 150°C, et de manière très préférée de 0 et 50°C. La gamme de pression employée pour la réduction photocatalytique de la charge contenant le dioxyde de carbone est généralement de 0,01 MPa à 70 MPa (0,1 à 700 bar), de manière préférée de 0,1 MPa à 5 MPa (1 à 50 bar). The realization of the photocatalytic reduction of carbon dioxide is conditioned by the supply of photons adapted to the photocatalytic system for the envisaged reaction and therefore is not limited to specific pressure or temperature ranges outside those allowing ensure the stability of the product (s). The temperature range employed for the photocatalytic reduction of the charge containing carbon dioxide is generally -10 ° C to + 200 ° C, preferably 0 to 150 ° C, and very preferably 0 and 50 ° vs. The pressure range employed for the photocatalytic reduction of the carbon dioxide-containing feedstock is generally 0.01 MPa to 70 MPa (0.1 to 700 bar), more preferably 0.1 MPa to 5 MPa (1 to 50 bar).
Un fluide diluant tel que décrit dans l’étape a), peut être présent dans le milieu réactionnel lorsque le procédé est effectué en phase gazeuse, durant l’irradiation. A diluent fluid as described in step a) may be present in the reaction medium when the process is carried out in the gas phase, during irradiation.
L'effluent obtenu après la réaction de réduction photocatalytique du dioxyde de carbone contient d'une part au moins une molécule en C1 ou plus, différente du dioxyde de carbone issue de la réaction et d'autre part de la charge non réagie, ainsi que l'éventuel fluide diluant, mais aussi des produits de réactions parallèles tels que le dihydrogène résultant de la
réduction photocatalytique d’H20 lorsque ce composé est utilisé en tant que composé sacrificiel. The effluent obtained after the photocatalytic reduction reaction of carbon dioxide contains on the one hand at least one or more C1 molecule different from the carbon dioxide resulting from the reaction and on the other hand from the unreacted feed, as well as the possible diluent fluid, but also products of parallel reactions such as dihydrogen resulting from the photocatalytic reduction of H2O when this compound is used as a sacrificial compound.
Le photocatalyseur The photocatalyst
Le procédé photocatalytique selon l’invention met en œuvre un photocatalyseur préparé par imprégnation en milieu fondu comprenant un support et des nanoparticules de sulfure de molybdène ou sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV.The photocatalytic process according to the invention uses a photocatalyst prepared by impregnation in a molten medium comprising a support and nanoparticles of molybdenum sulphide or tungsten sulphide having a forbidden band greater than 2.3 eV.
Plus particulièrement, le procédé de préparation dudit photocatalyseur comprend les étapes suivantes : i) on met en contact de l’eau avec ledit support de manière à obtenir un support mouillé, ii) on met en contact ledit support mouillé avec au moins un acide métallique hydraté comprenant au moins du molybdène ou du tungstène et dont la température de fusion dudit acide métallique hydraté est comprise entre 20 et 100°C, pour former un mélange solide, le rapport massique entre ledit acide métallique et ledit support étant compris entre 0,1 et 2,5, iii) on chauffe sous agitation le mélange solide obtenu à l’issue de l’étape ii) à une température comprise entre la température de fusion dudit acide métallique hydraté et 100°C pour former un précurseur photocatalytique, iv) on effectue une étape de sulfuration du précurseur photocatalytique obtenu à l’étape iii). Les différentes étapes de préparation sont détaillées par la suite. More particularly, the process for preparing said photocatalyst comprises the following steps: i) water is brought into contact with said support so as to obtain a wet support, ii) said wet support is brought into contact with at least one metallic acid hydrate comprising at least molybdenum or tungsten and whose melting point of said hydrated metallic acid is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said support being between 0.1 and 2.5, iii) the solid mixture obtained at the end of step ii) is heated with stirring to a temperature between the melting point of said hydrated metal acid and 100 ° C. to form a photocatalytic precursor, iv) a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out. The different preparation steps are detailed below.
Etape i) : Mise en contact de l’eau avec le support Selon l’étape i) du procédé de préparation dudit photocatalyseur, on met en contact de l’eau avec ledit support de manière à obtenir un support mouillé. Step i): Bringing Water into Contact with the Support According to step i) of the process for preparing said photocatalyst, water is brought into contact with said support so as to obtain a wet support.
Cette étape d’humidification du support est nécessaire afin de pouvoir faire fondre l’acide métallique hydraté dans l’étape iii). En effet, l’acide présente la particularité de ne fondre qu’en présence d’une pression partielle d’eau suffisante. En d’autres termes, il est nécessaire de garder les molécules d’eau de cristallisation de l’acide métallique hydraté pour assurer sa fusion.
L’étape a) de mise en contact peut être réalisée par imprégnation à sec. L’eau peut par exemple être versée en goutte à goutte sur le support contenu dans un drageoir en rotation. This step of humidifying the support is necessary in order to be able to melt the hydrated metal acid in step iii). Indeed, the acid has the particularity of melting only in the presence of a sufficient partial pressure of water. In other words, it is necessary to keep the water molecules of crystallization of the metallic acid hydrated to ensure its fusion. The contacting step a) can be carried out by dry impregnation. The water can for example be poured dropwise onto the support contained in a rotating bezel.
Selon une variante, la quantité d’eau introduit dans le support est entre 10 et 70 %, et de préférence entre 30 et 50% de son volume de reprise en eau. According to one variant, the quantity of water introduced into the support is between 10 and 70%, and preferably between 30 and 50% of its water uptake volume.
Avantageusement, après la mise en contact de l’eau avec le support, on laisse maturer le support mouillé. La maturation permet à l’eau de se disperser de manière homogène au sein du support. Advantageously, after the water has come into contact with the support, the wet support is allowed to mature. Maturation allows the water to disperse homogeneously within the medium.
Toute étape de maturation est avantageusement réalisée à pression atmosphérique, dans une atmosphère saturée en eau et à une température comprise entre 17°C et 50°C, et de préférence à température ambiante. Généralement une durée de maturation comprise entre dix minutes et quarante-huit heures, de préférence comprise entre trente minutes et quinze heures et de manière particulièrement préférée entre trente minutes et six heures, est suffisante. Any maturation step is advantageously carried out at atmospheric pressure, in an atmosphere saturated with water and at a temperature between 17 ° C and 50 ° C, and preferably at room temperature. Generally a maturation time of between ten minutes and forty-eight hours, preferably between thirty minutes and fifteen hours and particularly preferably between thirty minutes and six hours, is sufficient.
Etape ii) : Mise en contact de l’acide métallique avec le support mouillé Step ii): Bringing the metallic acid into contact with the wet support
Selon l’étape ii) du procédé de préparation dudit photocatalyseur, on met en contact ledit support mouillé avec au moins un acide métallique hydraté comprenant au moins du molybdène ou du tungstène dont la température de fusion dudit acide métallique hydraté est comprise entre 20 et 100°C, pour former un mélange solide, le rapport massique entre ledit acide métallique hydraté et ledit support étant compris entre 0,1 et 2,5. According to step ii) of the process for preparing said photocatalyst, said wetted support is brought into contact with at least one hydrated metal acid comprising at least molybdenum or tungsten, the melting point of said hydrated metal acid of which is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said hydrated metal acid and said support being between 0.1 and 2.5.
L’acide métallique hydraté doit avoir une température de fusion relativement basse, notamment inférieure à sa température de décomposition. La température de fusion est de l’acide métallique hydraté est comprise entre 20 et 100°C, et de préférence entre 50 et 90°C. The hydrated metal acid should have a relatively low melting point, especially below its decomposition temperature. The melting point of hydrated metal acid is between 20 and 100 ° C, and preferably between 50 and 90 ° C.
L’acide métallique hydraté comprend au moins du molybdène ou du tungstène. The hydrated metal acid includes at least molybdenum or tungsten.
L’acide métallique hydraté peut en plus comprendre du phosphore et du silicium. The hydrated metal acid can additionally include phosphorus and silicon.
L’acide métallique peut être un acide d’un hétéropolyanions de type Keggin.
L’acide métallique hydraté est de préférence choisi parmi l’acide phosphomolybdique hydraté (H3PM012O40, 28H2O, point de fusion T= 85°C), l’acide silicomolybdique hydraté (H4SNVI012O40, XH2O, point de fusion T= 47-55°C), l’acide molybdosilicique hydraté (H6Moi204iSi, XH2O, point de fusion T= 45-70°C), l’acide phosphotungstique hydraté (H3PW12O40, 28H2O, point de fusion T= 89°C), l’acide silicotungstique hydraté (H4SiWi204o, XH2O, point de fusion T= 53°C). The metal acid can be an acid of a heteropolyanion of the Keggin type. The hydrated metal acid is preferably chosen from hydrated phosphomolybdic acid (H3PM012O40, 28H2O, melting point T = 85 ° C), hydrated silicomolybdic acid (H4SNVI012O40, XH2O, melting point T = 47-55 ° C) ), hydrated molybdosilicic acid (H 6 Moi 2 0 4i Si, XH2O, melting point T = 45-70 ° C), hydrated phosphotungstic acid (H3PW12O40, 28H2O, melting point T = 89 ° C), hydrated silicotungstic acid (H 4 SiWi20 4 o, XH2O, melting point T = 53 ° C).
Le rapport massique entre ledit acide métallique hydraté et ledit support est compris entre 0,1 et 2,5, de préférence compris entre 0,3 et 2,0. The mass ratio between said hydrated metal acid and said support is between 0.1 and 2.5, preferably between 0.3 and 2.0.
Dans cette étape, l’acide métallique hydraté est sous forme solide, c’est-à-dire que la mise en contact entre ledit support et ledit acide métallique hydraté est réalisée à une température inférieure à la température de fusion dudit acide métallique hydraté. L’étape ii) est de préférence réalisée à température ambiante. In this step, the hydrated metallic acid is in solid form, that is to say that the contacting between said support and said hydrated metallic acid is carried out at a temperature below the melting temperature of said hydrated metallic acid. Step ii) is preferably carried out at room temperature.
Selon l’étape ii), la mise en contact dudit support et de l’acide métallique hydraté peut se faire par toute méthode connue de l’Homme du métier. De manière préférée, la mise en contact dudit support et dudit acide métallique hydraté est réalisée avec des moyens de contact choisis parmi les mélangeurs convectifs, les mélangeurs à tambour ou les mélangeurs statiques. According to step ii), the contacting of said support and the hydrated metal acid can be done by any method known to those skilled in the art. Preferably, the bringing into contact of said support and of said hydrated metal acid is carried out with contact means chosen from convective mixers, drum mixers or static mixers.
L’étape ii) est de préférence réalisée pendant une durée comprise entre 5 minutes à 12 heures selon le type de mélangeur utilisé, de préférence entre 10 minutes et 4 heures, et encore plus préférentiellement entre 15 minutes et 3 heures. Step ii) is preferably carried out for a period of between 5 minutes to 12 hours depending on the type of mixer used, preferably between 10 minutes and 4 hours, and even more preferably between 15 minutes and 3 hours.
Selon une variante, l’étape ii) consiste en la mise en contact dudit support mouillé avec au moins un acide métallique hydraté comprenant au moins du molybdène ou du tungstène dont la température de fusion dudit acide métallique hydraté est comprise entre 20 et 100°C, pour former un mélange solide, le rapport massique entre ledit acide métallique hydraté et ledit support étant compris entre 0,1 et 2,5. According to one variant, step ii) consists of bringing said wet support into contact with at least one hydrated metal acid comprising at least molybdenum or tungsten, the melting point of said hydrated metal acid of which is between 20 and 100 ° C. , to form a solid mixture, the mass ratio between said hydrated metallic acid and said support being between 0.1 and 2.5.
Etape iii) : Chauffage sous agitation Step iii): Heating with stirring
Selon l’étape iii) du procédé de préparation dudit photocatalyseur, on chauffe sous agitation le mélange solide obtenu à l’issue de l’étape ii) à une température comprise entre la
température de fusion dudit acide métallique hydraté et 100°C pour former un précurseur photocatalytique. According to step iii) of the process for preparing said photocatalyst, the solid mixture obtained at the end of step ii) is heated with stirring to a temperature between melting point of said hydrated metal acid and 100 ° C to form a photocatalytic precursor.
L’étape iii) est avantageusement effectuée à pression atmosphérique. L’étape iii) est généralement effectuée entre 5 minutes et 12 heures, de manière préférée entre 5 minutes et 4 heures. Step iii) is advantageously carried out at atmospheric pressure. Step iii) is generally carried out between 5 minutes and 12 hours, preferably between 5 minutes and 4 hours.
Selon l’étape iii), l’agitation (homogénéisation mécanique) du mélange peut se faire par toute méthode connue de l’Homme du métier. De manière préférée, on pourra employer des mélangeurs convectifs, des mélangeurs à tambour ou des mélangeurs statiques. According to step iii), the stirring (mechanical homogenization) of the mixture can be carried out by any method known to those skilled in the art. Preferably, convective mixers, drum mixers or static mixers can be used.
Encore plus préférentiellement, l’étape iii) est réalisée au moyen d’un mélangeur à tambour dont la vitesse de rotation est comprise entre 4 et 70 tours/minute, de préférence entre 10 et 60 tours/minute. Even more preferably, step iii) is carried out by means of a drum mixer whose speed of rotation is between 4 and 70 revolutions / minute, preferably between 10 and 60 revolutions / minute.
Après l’étape iii) on obtient un précurseur photocatalytique qui comprend au moins un support et du molybdène ou du tungstène. After step iii) a photocatalytic precursor is obtained which comprises at least one support and molybdenum or tungsten.
Etape iv) : Sulfuration Step iv): Sulfurization
Selon l’étape iv) du procédé de préparation selon l’invention, on effectue une étape de sulfuration du précurseur photocatalytique obtenu à l’étape iii). According to step iv) of the preparation process according to the invention, a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out.
L'étape iv) de sulfuration peut être réalisée avantageusement à l'aide d'un mélange gazeux H2S/H2 ou H2S/N2 contenant au moins 5% volumique d'H2S dans le mélange à une température égale ou supérieure à la température ambiante, sous une pression totale égale ou supérieure à 1 bar (0,1 MPa) pendant au moins 2h. De manière préférée, la température de sulfuration est inférieure à 350°C. De manière très préférée, la température de sulfuration est comprise entre 100 et 600°C. L’étape iv) de sulfuration est destinée à obtenir le photocatalyseur à base de sulfure de molybdène ou de tungstène. Step iv) of sulfurization can be carried out advantageously using an H2S / H2 or H2S / N2 gas mixture containing at least 5% by volume of H2S in the mixture at a temperature equal to or greater than ambient temperature, under a total pressure equal to or greater than 1 bar (0.1 MPa) for at least 2 hours. Preferably, the sulfurization temperature is less than 350 ° C. Very preferably, the sulfurization temperature is between 100 and 600 ° C. The sulfurization step iv) is intended to obtain the photocatalyst based on molybdenum or tungsten sulfide.
Le procédé de préparation du photocatalyseur permet d’obtenir des nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV, cette valeur de bande interdite correspond à des tailles de particules inférieures à 3,5 nm.
Il est important de souligner que le photocatalyseur préparé par imprégnation en milieu fondu a une morphologie différente qu’un photocatalyseur préparé par imprégnation à l’aide d’une solution d’imprégnation (tel que par exemple décrit dans le document FR3073429). Cette différence de morphologie est également aussi présente après sulfuration. The process for preparing the photocatalyst makes it possible to obtain nanoparticles of molybdenum sulphide or of tungsten sulphide having a forbidden band greater than 2.3 eV, this forbidden band value corresponds to particle sizes less than 3.5 nm. It is important to emphasize that the photocatalyst prepared by impregnation in a molten medium has a different morphology than a photocatalyst prepared by impregnation using an impregnation solution (such as for example described in document FR3073429). This difference in morphology is also present after sulfurization.
Les nanoparticules de sulfure de molybdène ou de sulfure tungstène se définissent par leur formule brute : MoSx ou WSxtel que x = 2 ou 3. Molybdenum sulfide or tungsten sulfide nanoparticles are defined by their gross formula: MoS x or WS x such that x = 2 or 3.
Le photocatalyseur peut également comprendre des nanoparticules d’oxysulfures de molybdène ou d’oxysulfures de tungstène. Ces nanoparticules se définissent par leur formule brute MoOySz tel que 0 < y+z <5 avec y et z des entiers strictement positifs. The photocatalyst can also comprise nanoparticles of molybdenum oxysulphides or tungsten oxysulphides. These nanoparticles are defined by their crude formula MoO y S z such that 0 <y + z <5 with y and z being strictly positive integers.
Le taux de sulfuration des métaux constituants les matériaux catalytiques est au moins égal à 10%, de préférence au moins égal à 30%. La teneur en soufre dans le matériau sulfuré est mesurée par XPS. The degree of sulfurization of the metals constituting the catalytic materials is at least equal to 10%, preferably at least equal to 30%. The sulfur content in the sulfurized material is measured by XPS.
La teneur en sulfure de molybdène ou en sulfure de tungstène du photocatalyseur est comprise entre 4 et 50% poids par rapport au poids total du photocatalyseur, et de manière préférée entre 5 et 45% poids. The content of molybdenum sulphide or of tungsten sulphide in the photocatalyst is between 4 and 50% by weight relative to the total weight of the photocatalyst, and preferably between 5 and 45% by weight.
La densité surfacique qui correspond à la quantité d'atomes de molybdène Mo ou d’atomes de tungstène W, déposés par unité surfacique de support est avantageusement comprise entre 0,5 et 12 atomes de Mo ou de W par nanomètres carré de support, et de manière préférée entre 1 et 10 atomes de Mo ou de W par nanomètres carré de support. The surface density which corresponds to the quantity of molybdenum Mo atoms or tungsten W atoms deposited per surface unit of support is advantageously between 0.5 and 12 atoms of Mo or W per square nanometers of support, and preferably between 1 and 10 atoms of Mo or W per square nanometers of support.
Selon une variante, le photocatalyseur selon l’invention comprend un support à base d'alumine ou de silice ou de silice-alumine. Selon cette variante, le support n’a pas de fonction photocatalytique mais permet de stabiliser les nanoparticules de sulfure de molybdène ou sulfure de tungstène. Alternatively, the photocatalyst according to the invention comprises a support based on alumina or silica or silica-alumina. According to this variant, the support has no photocatalytic function but makes it possible to stabilize the nanoparticles of molybdenum sulphide or tungsten sulphide.
Lorsque le support dudit catalyseur est à base d'alumine, il contient plus de 50 % d'alumine et, de façon générale, il contient uniquement de l'alumine ou de la silice-alumine telle que définie ci-dessous.
Dans un autre cas préféré, le support dudit catalyseur est une silice-alumine contenant au moins 50 % poids d'alumine. La teneur en silice dans le support est d'au plus 50% poids, le plus souvent inférieure ou égale à 45% poids, de préférence inférieure ou égale à 40%. When the support of said catalyst is based on alumina, it contains more than 50% alumina and, in general, it contains only alumina or silica-alumina as defined below. In another preferred case, the support of said catalyst is a silica-alumina containing at least 50% by weight of alumina. The silica content in the support is at most 50% by weight, most often less than or equal to 45% by weight, preferably less than or equal to 40%.
Lorsque le support dudit catalyseur est à base de silice, il contient plus de 50 % poids de silice et, de façon générale, il contient uniquement de la silice. When the support of said catalyst is based on silica, it contains more than 50% by weight of silica and, in general, it contains only silica.
Selon une variante particulièrement préférée, le support est constitué d’alumine, de silice ou de silice-alumine. According to a particularly preferred variant, the support consists of alumina, silica or silica-alumina.
De préférence, le support est à base d’alumine, et de manière particulièrement préférée le support est constitué d’alumine. Preferably, the support is based on alumina, and particularly preferably the support is made of alumina.
L’alumine peut être une alumine de transition, par exemple une alumine phase alpha, une alumine phase delta, une alumine phase gamma ou un mélange d'alumine de ces différentes phases. The alumina can be a transition alumina, for example an alpha phase alumina, a delta phase alumina, a gamma phase alumina or a mixture of alumina of these different phases.
Selon une variante, le support possède une surface spécifique (mesurée selon la norme ASTM D 3663-78 établie à partir de la méthode Brunauer, Emmett, Teller, i.e. méthode BET, telle que définie dans S. Brunauer, P. H. Emmett, E.Teller, J. Am. Chem. Soc., 1938, 60 (2), pp 309-319.) comprise entre 10 et 1000 m2/g, de manière préférée entre 50 et 600 m2/g. According to one variant, the support has a specific surface area (measured according to the ASTM D 3663-78 standard established from the Brunauer, Emmett, Teller method, ie the BET method, as defined in S. Brunauer, PH Emmett, E. Teller , J. Am. Chem. Soc., 1938, 60 (2), pp 309-319.) Between 10 and 1000 m 2 / g, preferably between 50 and 600 m 2 / g.
Selon une autre variante, le photocatalyseur selon l’invention comprend un support à base d'un semi-conducteur solide. Selon cette variante, le support a une fonction photocatalytique. En effet les semi-conducteurs ont généralement une largeur de bande interdite comprise entre 1 ,24 et 4 eV. Les longueurs d’onde des photons absorbables par lesdits photocatalyseurs sont ainsi comprises entre 310 nm et 1000 nm. According to another variant, the photocatalyst according to the invention comprises a support based on a solid semiconductor. According to this variant, the support has a photocatalytic function. In fact, semiconductors generally have a forbidden bandwidth of between 1, 24 and 4 eV. The wavelengths of the photons absorbable by said photocatalysts are thus between 310 nm and 1000 nm.
La combinaison des nanoparticules de sulfure de molybdène ou sulfure de tungstène ayant une activité photocatalytique avec un support à base d’un semi-conducteur solide ayant également une activité photocatalytique permet de bénéficier des hétérojonctions ainsi créées. Cette interaction particulière entre 2 semi-conducteurs permet de séparer les porteurs de charge(+ et -) plus efficacement et d’éviter leur recombinaison. Les hétérojonctions permettent ainsi d’utiliser les photons irradiant le solide de manière plus efficace et de pouvoir ainsi augmenter l’activité photocatalytique.
Le semi-conducteur solide peut être choisi parmi un ou plusieurs éléments du groupe IVA, tels que le silicium, le germanium, le carbure de silicium ou le silicium-germanium. Il peut être également composé d'éléments des groupes II IA et VA, tels que GaP, GaN, InP et InGaAs, ou d'éléments des groupes MB et VIA, tels que CdS, ZnO et ZnS, ou d'éléments des groupes IB et VI IA, 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 BhTes et B12O3, ou d'éléments des groupes MB et VA, tels que Cd3P2, Zn3P2 et Zn3As2, ou d'éléments des groupes IB et VIA, tels que CuO, CU2O et Ag2S, ou d'éléments des groupes VIIIB et VIA, tels que CoO, PdO, Fe2Ü3 et NiO, ou d'éléments des groupes VIB et VIA, tels que MoS2 et WO3, ou d'éléments des groupes VB et VIA, tels que V2O5 et Nb205 et TaOxNy, ou d'éléments des groupes IVB et VIA, tels que Ti02 et HfS2, ou d'éléments des groupes III A et VIA, tels que ln203 et ln2S3, ou d'éléments des groupes VIA et des lanthanides, tels que Ce2C>3, RG203, S1TI2S3, Tb2S3 et La2S3, ou d'éléments des groupes VIA et des actinides, tels que U02 et UO3. Il peut être aussi le C3N4. The combination of molybdenum sulfide or tungsten sulfide nanoparticles having photocatalytic activity with a support based on a solid semiconductor also having photocatalytic activity makes it possible to benefit from the heterojunctions thus created. This particular interaction between 2 semiconductors makes it possible to separate the charge carriers (+ and -) more efficiently and to avoid their recombination. Heterojunctions thus make it possible to use the photons irradiating the solid more efficiently and thus to be able to increase the photocatalytic activity. The solid semiconductor can be chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium. It can also be composed of elements of groups II IA and VA, such as GaP, GaN, InP and InGaAs, or elements of groups MB and VIA, such as CdS, ZnO and ZnS, or elements of groups IB and VI IA, 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 BhTes and B1 2 O 3 , or elements of groups MB and VA, such as Cd 3 P 2 , Zn 3 P 2 and Zn 3 As 2 , or elements of groups IB and VIA, such as CuO, CU 2 O and Ag 2 S, or d 'elements of groups VIIIB and VIA, such as CoO, PdO, Fe 2 Ü 3 and NiO, or elements of groups VIB and VIA, such as MoS 2 and WO 3 , or elements of groups VB and VIA, such that V 2 O 5 and Nb 2 0 5 and TaO x N y , or elements of groups IVB and VIA, such as Ti0 2 and HfS 2 , or elements of groups III A and VIA, such as ln 2 0 3 and ln 2 S 3 , or elements of VIA groups and lanthanides, such as Ce 2 C> 3 , RG 2 03, S1TI2S3, Tb 2 S3 and La 2 S3, or elements of groups pes VIA and actinides, such as U0 2 and UO3. It can also be C 3 N 4 .
De manière préférée, le semi-conducteur solide est choisi parmi le T1O2, le SiC, le B12S3, le Bi203, le CdO, le CdS, le Ce20 , le Ce02, le CeAI0 , le CoO, le Cu20, le Fe 0 , le FeTi0 , Ph203, l’ln(OH)3, le NiO, le PbO, le ZnO, l'Ag2S, le CdS, le Ce2S3, le Cu2S, le CulnS2, l'ln2S3, le M0S2, le ZnFe203, le ZnS, le ZnO, le WO3, le ZnFe204 , le ZrS2, le TaOxNy et le C3N4, seuls ou en mélange. Preferably, the solid semiconductor is chosen from T1O 2 , SiC, B1 2 S 3 , Bi 2 0 3 , CdO, CdS, Ce 2 0, Ce0 2 , CeAI0, CoO, Cu 2 0, Fe 0, FeTi0, Ph 2 0 3 , ln (OH) 3 , NiO, PbO, ZnO, Ag 2 S, CdS, Ce 2 S 3 , Cu 2 S, CulnS 2 , ln 2 S 3 , M0S 2 , ZnFe 2 0 3 , ZnS, ZnO, WO 3 , ZnFe 2 0 4 , ZrS 2 , TaO x N y and C 3 N 4 , alone or as a mixture.
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 formes (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, ...) or shaped (films, monolith, beads of micrometric or millimeter size, ... ). The photocatalyst is advantageously in the form of a nanometric powder.
L’emploi du photocatalyseur dans un procédé de réduction photocatalytique de C02 permet d’absorber la partie visible du spectre solaire, et ainsi de valoriser une proportion importante de l’énergie solaire incidente. Le photocatalyseur obtenu selon le procédé de préparation selon l’invention permet d’observer une activité photocatalytique au moins au même niveau qu’un photocatalyseur préparé par imprégnation à l’aide d’une solution d’imprégnation avec cependant une préparation simplifiée et la possibilité de charger plus de molybdène ou de tungstène.
EXEMPLES The use of the photocatalyst in a process for photocatalytic reduction of C0 2 makes it possible to absorb the visible part of the solar spectrum, and thus to exploit a large proportion of the incident solar energy. The photocatalyst obtained according to the preparation process according to the invention makes it possible to observe a photocatalytic activity at least at the same level as a photocatalyst prepared by impregnation using an impregnation solution with, however, a simplified preparation and the possibility load more molybdenum or tungsten. EXAMPLES
Exemple 1 : Photocatalyseur A (non-conforme à l’invention) MoOxSY/Al203 Example 1: Photocatalyst A (not in accordance with the invention) MoO x S Y / Al203
Un support d’alumine y (Y-AI2O3) est chargé dans un réacteur en quartz et calciné pendant 6h à 300°C avec une rampe de montée en température de 5°C/min, puis placé sous vide (105 mbar) à la même température pendant 16h. Ensuite, le support déshydroxylé est retiré de la ligne de vide et est refroidi à 140 °C puis stocké en boîte à gants. La surface spécifique du support d’alumine est de 284 m2/g. A support of alumina y (Y-Al2O3) is loaded into a quartz reactor and calcined for 6 hours at 300 ° C with a temperature rise ramp of 5 ° C / min, then placed under vacuum (10 5 mbar) at the same temperature for 16h. Then, the dehydroxylated support is removed from the vacuum line and is cooled to 140 ° C and then stored in a glove box. The specific surface of the alumina support is 284 m 2 / g.
Le précurseur du molybdène est le pentaéthoxyde de molybdène Mo(OC2Hs)5 (Gelest™, 90%). Du cyclohexane sec et dégazé est utilisé comme solvant. 1 ,96 mL de solution d'imprégnation, préparée à partir de 0,67 g de précurseur et de cyclohexane, sont imprégnés sur 2,58 g de support sec sur une rampe de synthèse utilisant des schlenks. L'imprégnation du support par la solution d’imprégnation se fait à l'aide d’une aiguille d’un schlenk à l’autre. The precursor of molybdenum is molybdenum pentaethoxide Mo (OC2Hs) 5 (Gelest ™, 90%). Dry, degassed cyclohexane is used as the solvent. 1.96 mL of impregnation solution, prepared from 0.67 g of precursor and cyclohexane, are impregnated on 2.58 g of dry support on a synthesis ramp using schlenks. The impregnation of the support with the impregnation solution is carried out using a needle from one schlenk to another.
La quantité de molybdène est ajustée de façon à obtenir environ 1,7 Mo/nm2 soit une teneur massique en Mo de 8 %. Après une maturation de 15 heures, les extrudés sont séchés sous vide (IO-5 mbar) durant 2 heures, à température ambiante. Après une maturation de 16 h, le solide est soumis à 2 cycles de séchage sous vide à température ambiante, d'abord par la ligne Schlenk (~ 8.102 mbar) pendant 1 h et ensuite par la ligne de vide poussé à 105 mbar pendant 1 h. Enfin le solide subit une étape de sulfuration effectuée à 100°C avec un débit de gaz H2S/H2 (15/85 vol) de 2 L/h/g. L'analyse XPS montre que 60% du molybdène est entouré de soufre. La bande interdite du photocatalyseur A est mesurée par spectrométrie d’absorption en réflexion diffuse à 3,18 eV. The amount of molybdenum is adjusted so as to obtain approximately 1.7 Mo / nm 2, ie a mass content of Mo of 8%. After maturing for 15 hours, the extrudates are dried under vacuum (10 -5 mbar) for 2 hours at room temperature. After maturing for 16 h, the solid is subjected to 2 drying cycles under vacuum at room temperature, first by the Schlenk line (~ 8.10 2 mbar) for 1 h and then by the high vacuum line at 10 5 mbar. for 1 hour. Finally, the solid undergoes a sulfurization step carried out at 100 ° C. with a flow rate of H2S / H2 gas (15/85 vol) of 2 L / h / g. XPS analysis shows that 60% of molybdenum is surrounded by sulfur. The band gap of photocatalyst A is measured by diffuse reflection absorption spectrometry at 3.18 eV.
Exemple 2 : Photocatalyseur B (non-conforme à l’invention) M0SX/AI2O3 Example 2: Photocatalyst B (not in accordance with the invention) M0S X / AI2O3
Le photocatalyseur B est préparé de manière identique au photocatalyseur A, seule l’étape de sulfuration diffère avec une température de traitement de 200°C. Photocatalyst B is prepared identically to photocatalyst A, only the sulfurization step differs with a treatment temperature of 200 ° C.
L'analyse XPS donne une sulfuration de molybdène de 87%. La bande interdite du photocatalyseur B est mesurée par spectrométrie d’absorption en réflexion diffuse à 2,49 eV.
Exemple 3: Photocatalyseur C conforme à l’invention MoOxSy/Al203 XPS analysis gives an 87% molybdenum sulfurization. The band gap of photocatalyst B is measured by diffuse reflection absorption spectrometry at 2.49 eV. Example 3: Photocatalyst C in accordance with the invention MoO x S y / Al 2 0 3
10 g du support d’alumine y (y-A Ch) concassé en 300-500 pm, utilisé pour la préparation du catalyseur A, ont été pré-imprégnés d’eau en ajoutant 5 cm3 d’eau, soit 42% du VRE. L’eau est versée en goutte à goutte sur le support contenu dans un drageoir en rotation. Afin de laisser le support s’imprégner correctement, il est placé en maturateur pendant 1h. Le support pré-imprégné d’eau est ensuite transféré dans le réacteur et du H3PM012O40, 28 H2O (PMA), dont le point de fusion est de 85°C, est ajouté. La quantité de molybdène est ajustée de façon à obtenir environ 1 ,7 Mo/nm2 soit une teneur massique en Mo de 8 %. Le reflux est mis en place et le réacteur est chauffé à 85°C avec agitation pendant 3h. Le catalyseur est ensuite laissé à maturer pendant 18h. On obtient ainsi le précatalyseur C. Enfin le solide subit une étape de sulfuration effectuée à 200 °C avec un débit de gaz H S/H2 (15/85 vol) de 2 L/h/g. L'analyse XPS montre que 40% du molybdène est entouré de soufre. La bande interdite du photocatalyseur C est mesurée par spectrométrie d’absorption en réflexion diffuse à 3,04 eV. 10 g of the alumina support γ (y-A Ch) crushed to 300-500 μm, used for the preparation of catalyst A, were pre-impregnated with water by adding 5 cm 3 of water, i.e. 42% of the VRE. The water is poured drop by drop onto the support contained in a rotating bezel. In order to let the support soak up properly, it is placed in a ripener for 1 hour. The water prepreg carrier is then transferred to the reactor and H3PM012O40, 28 H2O (PMA), the melting point of which is 85 ° C, is added. The amount of molybdenum is adjusted so as to obtain approximately 1.7 Mo / nm 2, ie a mass Mo content of 8%. The reflux is set up and the reactor is heated to 85 ° C. with stirring for 3 h. The catalyst is then left to mature for 18 hours. The precatalyst C is thus obtained. Finally, the solid undergoes a sulfurization step carried out at 200 ° C. with a flow rate of HS / H 2 gas (15/85 vol) of 2 L / h / g. XPS analysis shows that 40% of molybdenum is surrounded by sulfur. The band gap of the photocatalyst C is measured by diffuse reflection absorption spectrometry at 3.04 eV.
Exemple 4 : Photocatalyseur D (conforme à l’invention) M0SX/AI2O3 Example 4: Photocatalyst D (according to the invention) M0S X / AI 2 O 3
Le photocatalyseur D est préparé de manière identique au photocatalyseur C, seule l’étape de sulfuration diffère avec une température de traitement de 400 °C. Photocatalyst D is prepared identically to photocatalyst C, only the sulfurization step differs with a treatment temperature of 400 ° C.
L'analyse XPS donne une sulfuration du molybdène de 85%. La bande interdite du photocatalyseur D est mesurée par spectrométrie d’absorption en réflexion diffuse à 2,54 eV. XPS analysis gives 85% molybdenum sulfurization. The band gap of photocatalyst D is measured by diffuse reflection absorption spectrometry at 2.54 eV.
Exemple 5 : Mise en œuvre des photocatalyseurs en réduction photocatalytique du CO2 en phase gazeuse Example 5: Implementation of photocatalysts in photocatalytic reduction of CO2 in the gas phase
Les photocatalyseurs A, B, C et D sont soumis à un test de réduction photocatalytique du CO2 en phase gazeuse dans un réacteur continu à lit traversé en acier muni d’une fenêtre optique en quartz et d’un fritté en face de la fenêtre optique sur lequel est déposé le solide photocatalytique. Photocatalysts A, B, C and D are subjected to a photocatalytic reduction test of CO2 in the gas phase in a continuous steel cross-bed reactor fitted with a quartz optical window and a frit opposite the optical window. on which is deposited the photocatalytic solid.
Une quantité suffisante de poudre est déposée sur le fritté de manière à recouvrir l’ensemble de la surface irradiée du réacteur (environ 100 mg). La surface géométrique irradiée pour tous les photocatalyseurs est de 5,3.1004 m2. Les tests sont réalisés à température ambiante
sous pression atmosphérique. Un débit de CO2 de 0,3 ml/min traverse un saturateur d’eau avant d’être distribué dans le réacteur. On suit la production de CH4 issu de la réduction du dioxyde de carbone, par une analyse de l’effluent toutes les 10 minutes par micro chromatographie en phase gazeuse. La source d'irradiation UV-Visible est fournie par une lampe Xe-Hg (Asahi™, MAX302™). La puissance d’irradiation est toujours maintenue à 80 W/m2 pour une gamme de longueur d’onde comprise entre 315 et 400 nm. La durée du test est de 20 heures. A sufficient quantity of powder is deposited on the frit so as to cover the entire irradiated surface of the reactor (approximately 100 mg). The irradiated geometric surface for all the photocatalysts is 5.3.10 04 m 2 . Tests are carried out at room temperature under atmospheric pressure. A CO2 flow rate of 0.3 ml / min passes through a water saturator before being distributed into the reactor. The production of CH 4 resulting from the reduction of carbon dioxide is monitored by analysis of the effluent every 10 minutes by gas phase microchromatography. The UV-Visible irradiation source is provided by an Xe-Hg lamp (Asahi ™, MAX302 ™). The irradiation power is always maintained at 80 W / m 2 for a wavelength range between 315 and 400 nm. The duration of the test is 20 hours.
Les activités photocatalytiques sont exprimées en micromoles (pmol) de méthane produit par heure et par m2 irradié. Il s’agit d’activités moyennes sur l’ensemble de la durée des tests. Les résultats sont reportés dans le tableau 1 (ci-après) qui montre les performances des photocatalyseurs relatives à leur activité moyenne pour la production de méthane à partir d’un mélange CO2 et H2O en phase gazeuse
The photocatalytic activities are expressed in micromoles (pmol) of methane produced per hour and per m 2 irradiated. These are average activities over the entire duration of the tests. The results are reported in Table 1 (below) which shows the performance of the photocatalysts relative to their average activity for the production of methane from a mixture of CO2 and H2O in the gas phase.
Les valeurs d'activité montrent que la mise en œuvre des solides selon l'invention C et D permettent la réduction photocatalytique du dioxyde de carbone en CH4. Les solides C et D, préparés bien plus simplement que les catalyseurs A et B présentent des performances très légèrement supérieures à celles des solides A et B respectivement.
The activity values show that the use of the solids according to the invention C and D allow the photocatalytic reduction of carbon dioxide to CH4. The solids C and D, prepared much more simply than the catalysts A and B, exhibit very slightly better performances than those of the solids A and B respectively.
Claims
1. Procédé de réduction photocatalytique du dioxyde de carbone effectué en phase liquide et/ou en phase gazeuse, ledit procédé comprenant les étapes suivantes : a) on met en contact une charge contenant le dioxyde de carbone et au moins un composé sacrificiel avec un photocatalyseur, b) on irradie le photocatalyseur par au moins une source d'irradiation produisant au moins une longueur d'onde absorbable par ledit photocatalyseur de manière à réduire le dioxyde de carbone et oxyder le composé sacrificiel en présence dudit photocatalyseur activé par ladite source d'irradiation, de manière à produire un effluent contenant au moins en partie des molécules carbonées en C1 ou plus, différentes du CO2, ledit photocatalyseur comprenant un support et des nanoparticules de sulfure de molybdène ou de sulfure de tungstène présentant une bande interdite supérieure à 2,3 eV, ledit photocatalyseur étant préparé par un procédé comprenant les étapes suivantes : i) on met en contact de l’eau avec ledit support de manière à obtenir un support mouillé, ii) on met en contact ledit support mouillé avec au moins un acide métallique hydraté comprenant au moins du molybdène ou du tungstène et dont la température de fusion dudit acide métallique hydraté est comprise entre 20 et 100°C, pour former un mélange solide, le rapport massique entre ledit acide métallique et ledit support étant compris entre 0,1 et 2,5, iii) on chauffe sous agitation le mélange solide obtenu à l’issue de l’étape ii) à une température comprise entre la température de fusion dudit acide métallique hydraté et 100°C pour former un précurseur photocatalytique, iv) on effectue une étape de sulfuration du précurseur photocatalytique obtenu à l’étape iii). 1. Process for the photocatalytic reduction of carbon dioxide carried out in the liquid phase and / or in the gas phase, said process comprising the following steps: a) a charge containing carbon dioxide and at least one sacrificial compound is brought into contact with a photocatalyst , b) the photocatalyst is irradiated with at least one irradiation source producing at least one wavelength absorbable by said photocatalyst so as to reduce carbon dioxide and oxidize the sacrificial compound in the presence of said photocatalyst activated by said source of irradiation, so as to produce an effluent containing at least in part carbon molecules in C1 or more, different from CO2, said photocatalyst comprising a support and nanoparticles of molybdenum sulphide or of tungsten sulphide having a forbidden band greater than 2, 3 eV, said photocatalyst being prepared by a process comprising the following steps: i) water is brought into contact with said support so as to obtain a wet support, ii) contacting said wet support with at least one hydrated metal acid comprising at least molybdenum or tungsten and whose melting point of said hydrated metal acid is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said support being between 0.1 and 2.5, iii) the solid mixture obtained at the end of step ii) is heated with stirring at the end of step ii) at a temperature between the melting point of said hydrated metal acid and 100 ° C. to form a photocatalytic precursor, iv) a sulfurization step of the photocatalytic precursor obtained in step iii) is carried out.
2. Procédé selon la revendication précédente, dans lequel à l’étape ii) l’acide métallique hydraté est choisi parmi l’acide phosphomolybdique hydraté, l’acide silicomolybdique hydraté, l’acide molybdosilicique hydraté, l’acide phosphotungstique hydraté et l’acide silicotungstique hydraté.
2. Method according to the preceding claim, wherein in step ii) the hydrated metal acid is chosen from hydrated phosphomolybdic acid, hydrated silicomolybdic acid, hydrated molybdosilicic acid, hydrated phosphotungstic acid and hydrated silicotungstic acid.
3. Procédé selon l’une des revendications précédentes, dans lequel à l’étape i) la quantité d’eau introduite dans le support est entre 10 et 70 % de son volume de reprise en eau. 3. Method according to one of the preceding claims, wherein in step i) the amount of water introduced into the support is between 10 and 70% of its water uptake volume.
4. Procédé selon l’une des revendications précédentes, dans lequel le support est un support à base d'alumine ou de silice ou de silice-alumine. 4. Method according to one of the preceding claims, wherein the support is a support based on alumina or silica or silica-alumina.
5. Procédé selon l’une des revendications 1 à 3, dans lequel le support est un support à base d’un semi-conducteur solide. 5. Method according to one of claims 1 to 3, wherein the support is a support based on a solid semiconductor.
6. Procédé selon la revendication précédente, dans lequel le support est un semi- conducteur solide choisi parmi un ou plusieurs éléments du groupe IVA, tels que le silicium, le germanium, le carbure de silicium ou le silicium-germanium, d'éléments des groupes NIA et VA, tels que GaP, GaN, InP et InGaAs, ou d'éléments des groupes MB 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 BÎ2Îe3 et B12O3, ou d'éléments des groupes NB et VA, tels que Cd3P2, Zh3Rå et Zn3As2, ou d'éléments des groupes IB et VIA, tels que CuO, CU2O et Ag2S, ou d'éléments des groupes VIIIB et VIA, tels que CoO, PdO, Fe2Û3 et NiO, ou d'éléments des groupes VIB et VIA, tels que MoS2 et W03, ou d'éléments des groupes VB et VIA, tels que V2O5 et Nb205 et TaOxNy, ou d'éléments des groupes IVB et VIA, tels que T1O2 et HfS2, ou d'éléments des groupes NIA et VIA, tels que ln2Ü3 et ln2S3, ou d'éléments des groupes VIA et des lanthanides, tels que Ce2Û3, Pr2Û3, S1TI2S3, Tb2S3 et La2S3, ou d'éléments des groupes VIA et des actinides, tels que UO2 et UO3, ou encore le nitrure de carbone C3N4. 6. Method according to the preceding claim, wherein the support is a solid semiconductor chosen from one or more elements of group IVA, such as silicon, germanium, silicon carbide or silicon-germanium, elements of NIA and VA groups, such as GaP, GaN, InP and InGaAs, or elements of MB and VIA groups, such as CdS, ZnO and ZnS, or elements of IB and VIIA groups, 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 BÎ 2Î e 3 and B1 2 O 3 , or elements of groups NB and VA , such as Cd 3 P 2 , Zh 3 R å and Zn 3 As 2 , or elements of groups IB and VIA, such as CuO, CU 2 O and Ag 2 S, or elements of groups VIIIB and VIA, such as CoO, PdO, Fe 2 Û 3 and NiO, or elements of groups VIB and VIA, such as MoS 2 and W0 3 , or elements of groups VB and VIA, such as V 2 O 5 and Nb 2 0 5 and TaO x N y , or elements of groups IVB and VIA, such as T1O 2 and HfS 2 , or elements of groups NIA and VIA, such as ln 2 Ü 3 and ln 2 S 3 , or elements of groups VIA and lanthanides, such as Ce 2 Û 3 , Pr 2 Û 3 , S1TI 2 S 3 , Tb 2 S 3 and La 2 S 3 , or elements of VIA groups and actinides, such as UO 2 and UO 3 , or else carbon nitride C 3 N 4 .
7. Procédé selon l’une des revendications précédentes, dans lequel la teneur en sulfure de molybdène ou en sulfure de tungstène du photocatalyseur est comprise entre 4 et 50% poids par rapport au poids total du photocatalyseur. 7. Method according to one of the preceding claims, wherein the content of molybdenum sulphide or tungsten sulphide of the photocatalyst is between 4 and 50% by weight relative to the total weight of the photocatalyst.
8. Procédé selon l’une des revendications précédentes, dans lequel la densité surfacique qui correspond à la quantité d'atomes de molybdène Mo ou d’atomes de tungstène W, déposés par unité surfacique de support, est comprise entre 0,5 et 12 atomes de Mo ou de W par nanomètres carré de support.
8. Method according to one of the preceding claims, in which the surface density which corresponds to the quantity of atoms of molybdenum Mo or of tungsten atoms W, deposited per surface unit of support, is between 0.5 and 12. atoms of Mo or W per square nanometers of support.
9. Procédé selon l’une des revendications précédentes, dans lequel, lorsqu’il est effectué en phase gazeuse, le composé sacrificiel est un composé gazeux choisi parmi l’eau, l’ammoniaque, le dihydrogène, le méthane ou un alcool. 9. Method according to one of the preceding claims, wherein, when carried out in the gas phase, the sacrificial compound is a gaseous compound selected from water, ammonia, dihydrogen, methane or an alcohol.
10. Procédé selon l’une des revendications précédentes, dans lequel, lorsqu’il est effectué en phase gazeuse, un fluide diluant est présent dans les étapes a) et/ou b). 10. Method according to one of the preceding claims, wherein, when carried out in the gas phase, a diluent fluid is present in steps a) and / or b).
11. Procédé selon l’une des revendications 1 à 8, dans lequel, lorsqu’il est effectué en phase liquide, le composé sacrificiel est un composé oxydable liquide ou solide soluble dans la charge liquide, choisi parmi l’eau, l’ammoniaque, un alcool, un aldéhyde ou une amine. 11. Method according to one of claims 1 to 8, wherein, when it is carried out in the liquid phase, the sacrificial compound is a liquid or solid oxidizable compound soluble in the liquid charge, chosen from water, ammonia. , an alcohol, an aldehyde or an amine.
12. Procédé selon l’une des revendications précédentes, dans lequel la source d’irradiation est une source d’irradiation naturelle ou artificielle. 12. Method according to one of the preceding claims, wherein the irradiation source is a natural or artificial irradiation source.
13. Procédé selon l’une des revendications précédentes, dans lequel la source d’irradiation émet à au moins dans une gamme de longueurs d'ondes comprise entre 280 nm et 2500 nm.
13. Method according to one of the preceding claims, wherein the irradiation source emits at least in a wavelength range between 280 nm and 2500 nm.
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| CN114772644A (en) * | 2022-03-28 | 2022-07-22 | 西南科技大学 | Preparation and application of surface oxidized tungsten disulfide nanosheet for treating radioactive wastewater |
| CN114632536A (en) * | 2022-04-01 | 2022-06-17 | 吉林化工学院 | NiCo with photocatalytic properties2O4/NiO/g-C3N4Nanotube preparation method and application |
| CN114632536B (en) * | 2022-04-01 | 2023-10-20 | 吉林化工学院 | NiCo with photocatalytic properties 2 O 4 /NiO/g-C 3 N 4 Nanotube preparation method and application |
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| FR3104455A1 (en) | 2021-06-18 |
| FR3104455B1 (en) | 2021-12-03 |
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