Catalytic bed containing particulate photocatalytic catalyst

Abstract

This invention relates to a catalytic bed comprising a specific photocatalytic catalyst. The bed comprises structural particles b made of inorganic material, said structural particles being combined with at least one semiconductor material a having photocatalytic properties, said combination being achieved by: - ​​mixing the structural particles b made of inorganic material with the semiconductor material a in particulate form, - and / or by chemically or physicochemically depositing the semiconductor material a onto the structural particles b made of inorganic material, said structural particles b being substantially spherical and having an average diameter between 22 nm and 8.0 μm.

Description

Technical Field

[0001] This invention relates to the field of photocatalysis, and aims to treat liquid or gas phases by contacting a photocatalytic material, which is then irradiated by a light source emitting light within an appropriate wavelength range. More specifically, this invention relates to a novel photocatalytic material, its preparation method, and its applications. Existing technology

[0002] Photocatalysis is based on the principle of activating a semiconductor, which acts as a photocatalyst, using energy provided by radiation. Semiconductors are characterized by their band gap, the energy difference between their conduction band and valence band, which is unique to them. Photocatalysis can be defined as the absorption of photons with energy greater than the width of the band gap between the valence and conduction bands, which, in the case of a semiconductor, induces the formation of electron-hole pairs. Electrons are thus excited to the conduction band and holes are formed in the valence band. These electron-hole pairs enable the formation of free radicals, which will react with compounds present in the medium to initiate oxidation / reduction reactions or recombine according to various mechanisms. Any photon with energy greater than its band gap can be absorbed by a semiconductor. Photons with energy lower than its band gap cannot be absorbed by a semiconductor.

[0003] The applications are wide-ranging: photocatalysis can therefore be used to purify gaseous media, particularly by oxidizing and converting VOC (Volatile Organic Compounds) type compounds, or to treat liquid media, such as those containing toluene, benzene, ethanol, or acetone. Photocatalysis can also be used to convert gaseous CO2 into renewable compounds, particularly those with one or more carbon atoms, such as CO, methane, methanol, carboxylic acids, ketones, or other alcohols: CO2 will thus be actively converted rather than captured and stored, reducing its concentration in the atmosphere. It can also photolyze water in liquid or gaseous media to produce renewable hydrogen (H2), particularly as a low-carbon energy source.

[0004] As known from patent WO2018 / 197432, a photocatalytic material in the form of a porous monolithic material comprises 20% to 70% TiO2 by weight relative to the total weight of the monolithic material and 30% to 80% by weight of a refractory oxide selected from silica, alumina, or silica-alumina by weight relative to the total weight of the monolithic material, and has a packing density of less than 0.19 g / ml, possessing a specific porosity, particularly in terms of macroporosity and mesoporosity. Therefore, this relates to a material that, in combination with a semiconductor (titanium oxide) as the source of its photocatalytic properties, one or both of the refractory oxides, and further possesses a specific porosity, resulting in a photocatalytic performance quality superior to that obtained using materials composed entirely of titanium oxide.

[0005] Therefore, the subject of this invention is to develop an improved photocatalytic material, particularly in terms of further improved photocatalytic performance quality, as well as additional improvements in implementation and / or production. Invention Overview

[0007] This invention first relates to a catalytic bed comprising a particulate photocatalytic catalyst, the bed comprising structural particles b made of inorganic material, the structural particles b being bonded to at least one semiconductor material a having photocatalytic properties, the bonding being achieved by the following method:

[0008] - By mixing structural particles b made of inorganic materials with semiconductor material a in particulate form,

[0009] - and / or by chemically or physicochemically depositing semiconductor material a onto structural particles b made of inorganic material,

[0010] The structural particle b is substantially spherical and has an average diameter between 22 nm and 8.0 μm, and preferably between 30 nm and 7.5 μm.

[0011] The target inorganic material of this invention is an electrically insulating type, and therefore is essentially inert in terms of photocatalysis: it is a material with a band gap greater than 6 eV.

[0012] Preferably, the catalytic bed is intended to be a fixed bed (particularly the opposite of a fluidized bed).

[0013] Therefore, this invention chooses to disperse the semiconductor material within an inorganic material, and calibrates the particle size of the inorganic material as a function of the target wavelength range for irradiating the semiconductor material. This irradiation allows for the generation of electron-hole pairs, thereby producing the desired photocatalytic reaction. This is because, typically in the field of photocatalysis, radiation sources are selected in the UV-A, UV-B, and / or visible light ranges, which define the wavelength range capable of activating conventional semiconductor materials (e.g., titanium oxide).

[0014] In fact, the present invention utilizes scattering known as Mie scattering (by optimizing the scattering of radiation, preferably in the direction of incident radiation) by selecting spherical particles (referred to herein as structural particles) made of inorganic materials with a specific average diameter. Mie scattering is directly related to the wavelength of the incident radiation and indicates the preferred scattering of the radiation along the incident axis of the spherical particles, the radius of which is 0.1 to 10 times the wavelength in question. Therefore, the structural particles of the present invention, with correspondingly adjusted diameters, will enhance the effectiveness of radiation from UV-A rays to the visible light range: they will scatter the radiation primarily in the direction of incident radiation from the surface of the catalyst bed. This greatly increases the likelihood of the semiconductor material being irradiated, thereby improving its photocatalytic activity. This is because the penetration depth of the incident radiation within the catalyst bed will be greater, allowing the radiation to reach regions of the semiconductor material that would otherwise be difficult to reach.

[0015] It has been found that the photocatalytic performance of this material can be improved by up to 2 times, and in fact even by 3 or 4 times, and even by 10 times or more in the most advantageous configuration, compared to materials composed in the same manner (but using particles beyond this diameter range and / or non-spherical). This provides great flexibility in the implementation of the present invention. Therefore, the performance quality of the material can be increased as much as possible using the same number of semiconductors, or increased to a lesser extent, or at least kept the same, while reducing the number of semiconductors in the material, depending on whether the performance quality or cost of the catalyst is advantageous.

[0016] This invention provides two alternative or additive variations for constituting the material, both of which have the following advantages:

[0017] The variant with two types of particles (structural particles and semiconductor particles) is advantageous because it is simple to produce, since it does not seek to integrate the two types of materials and because preparation is based solely on mixing the two powders, without chemical reactions, thermal treatments, etc. This variant also allows for very easy adaptation to any shape and size of the catalytic bed. It enables the bed to be formed in situ directly in the reactor in which it must be placed, without prior pretreatment, by easily adjusting (depending on the specific circumstances) the ratio, particularly between the two types of particles, in addition to providing suitable means to ensure the most uniform mixing possible between the two types of particles. The mixture can also be pre-prepared so that only one product is deposited to form the bed.

[0018] Another variation, which involves chemically / physicochemically depositing semiconductors onto structured particles, also exhibits advantages: it ensures a controlled distribution of the semiconductors relative to the particles, and the integration between the two materials facilitates their interaction, particularly in the case of radiation scattered by the particles. Therefore, it provides a "ready-to-use" product for forming catalytic beds in reactors. It should be noted that the structured particles can be completely or only partially covered by semiconductors. It should also be noted that, according to this variation, a certain proportion of the structured particles can be specified to remain free of semiconductor material deposits.

[0019] Advantageously, the structural particles are (basically) spherical and solid: their solidity gives them better mechanical properties, better mechanical strength, wear resistance, abrasion resistance, etc.

[0020] Preferably, all particles within the bed are arranged in a non-organized manner. This is because it has surprisingly proven beneficial in terms of the photocatalytic performance quality of the material. The term "non-organized" is understood to mean that the particles of the material are not arranged in an ordered manner, and there is no layer of particles arranged in three dimensions. The material according to the invention thus exhibits interparticle spaces with non-uniform size and location, randomly positioned within the material. Furthermore, these spaces differ depending on whether a variant involving a mixture of particles (with different sizes and shapes) or a variant involving only one type of particle (structural particles at least partially covered with semiconductors).

[0021] Preferably, when the bed comprises semiconductor material a in particulate form, the particles have an average size of at most 100 nm, particularly at most 50 nm, and at least 5 nm, preferably between 10 and 30 nm. It should be noted that in this case, these particles are not spherical, or do not necessarily have to be spherical, and their average size is not limited by the wavelength of the irradiating radiation.

[0022] Preferably, the catalytic bed according to the invention exhibits a porosity of at least 40%, preferably at most 80%, particularly between 40% and 70%, which is equal to the ratio of the void volume in the photocatalytic bed to the total volume of the bed composed of voids and particles. This porosity indirectly indicates the disordered arrangement of the aforementioned materials. This is because the porosity is minimal when it involves perfectly organized spheres, and the porosity according to the invention is greater than this minimum ratio.

[0023] Preferably, the catalyst bed according to the invention has a “dilution ratio” of up to 80%, particularly between 5% and 70%, and more preferably between 10% and 50%, which is equal to the ratio between the volume occupied by the structural particles b made of inorganic material and the volume occupied by the semiconductor materials a, a′ and the sum of the structural particles b made of inorganic material. This dilution rate of up to 80% is chosen particularly in cases where the semiconductor material a is chemically or physicochemically deposited on the structural particles b made of inorganic material, but naturally applicable to both variations of the invention.

[0024] The term "dilution ratio" is used to reflect the proportion of active material (semiconductor) relative to structural particles that have little or no prior activity. A higher dilution ratio indicates a greater amount of structural particles. As will be seen from the examples listed later, this dilution ratio can be increased without decreasing, and even simultaneously improve the overall photocatalytic performance of the material. It is more sensible to infer the dilution ratio by volume than by mass, because the density of materials, especially semiconductors, can vary considerably from one semiconductor to another.

[0025] In one embodiment of the invention, the catalyst bed may comprise (at least) two different semiconductor materials, a first material a and a′. It can be prepared by the following method:

[0026] - By mixing structural particles b made of inorganic materials with particles of a first material a and a second material a′.

[0027] - and / or by chemically or physicochemically depositing semiconductor materials a, a′ on carrier particles b, or by depositing both first semiconductor material a and second semiconductor material a′ on structural particles b, or by depositing first semiconductor material a on a first portion of structural particles b and depositing second semiconductor material a′ on a second portion of structural particles b.

[0028] Therefore, there are three powders of three different materials a, a′ and b to be mixed, namely two powders b+a and b+a′ (structural particles covered with the first semiconductor or the second semiconductor), or a single powder b+a+a′ (structural particles covered with the first and second semiconductors).

[0029] Naturally, based on the same principle, more than two different semiconductor materials can be used. Furthermore, the option of a bed is retained: in variations where semiconductors are deposited on its surface, the bed also contains structural particles in specific portions not covered by the semiconductor material.

[0030] Advantageously, the structural particles b made of inorganic materials can be made of metal oxides, particularly oxides of metals of Group IIIa and IVa of the periodic table, and the oxides are preferably selected from aluminum oxide, silicon oxide, and mixed oxides of aluminum and silicon.

[0031] Advantageously, at least one of the semiconductor materials a, a′, or thereto can be selected from inorganic semiconductors. Inorganic semiconductors can be selected from one or more Group IVa elements, such as silicon, germanium, silicon carbide, or silicon-germanium. They can also be composed of Group IIIa and Va elements, such as GaP, GaN, InP, and InGaAs; or of Group IIb and VIa elements, such as CdS, ZnO, and ZnS; or of Group Ib and VIIa elements, such as CuCl and AgBr; or of Group IVa and VIa elements, such as PbS, PbO, SnS, and PbSnTe; or of Group Va and VIa elements, such as Bi₂Te₃ and Bi₂O₃; or of Group IIb and Va elements, such as Cd₃P₂, Zn₃P₂, and Zn₃As₂; or of Group Ib and VIa elements, such as CuO, Cu₂O, and Ag. 2S, or composed of Group VIIIb and VIa elements, such as CoO, PdO, Fe2O3 and NiO, or composed of Group VIb and VIa elements, such as MoS2 and WO3, or composed of Group Vb and VIa elements, such as V2O5 and Nbr2O5, or composed of Group IVb and VIa elements, such as TiO2 and HfS2, or composed of Group IIIa and VIa elements, such as In2O3 and In2S3, or composed of Group VIa elements and lanthanides, such as Ce2O3, Pr2O3, Sm2S3, Tb2S3 and La2S3, or composed of Group VIa elements and actinides, such as UO2 and UO3.

[0032] Preferably, they comprise at least one of the following metal oxides: titanium oxide, tungsten oxide, cerium oxide, bismuth oxide, zinc oxide, copper oxide, vanadium oxide, iron oxide, cadmium oxide, preferably selected from TiO2, Bi2O3, CdO, Ce2O3, CeO2, CeAlO3, CuO, Fe2O3, FeTiO3, ZnFe2O3, V2O5, ZnO, WO3, and ZnFe2O4, alone or as a mixture.

[0033] The semiconductor materials a, a′, or at least one of them may be doped with one or more ions selected from metal ions, particularly V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, Ti, or selected from non-metal ions, particularly C, N, S, F, P, or a mixture of metal and non-metal ions.

[0034] The semiconductor materials a, a′, and at least one thereof may further comprise one or more metallic elements selected from Groups IVb, Vb, VIb, VIIb, VIIIb, Ib, IIb, IIIa, IVa, and Va of the periodic table, and preferably in direct contact with the semiconductor material. It is preferably a metal selected from platinum, palladium, gold, nickel, cobalt, ruthenium, silver, copper, rhenium, or rhodium.

[0035] It should be noted that throughout this article, the chemical groups are given according to the CAS IUPAC classification (CRC Handbook of Chemistry and Physics, CRC Press, 81st edition, 2000-2001) rather than according to the new classification. For example, according to the CAS classification, Group VIII corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification.

[0036] The catalytic bed according to the invention can have a thickness of up to 1 cm, particularly up to 5 mm, and particularly at least 10 μm. Preferably, its thickness is at least 100 or 200 micrometers. This thickness depends in particular on the depth to which radiation penetrates from the radiation source into the bed.

[0037] Another subject of the invention is a method for obtaining a catalytic bed as defined above, wherein structural particles b of an inorganic material are mixed with particles a of a semiconductor material on the other hand to produce a uniform distribution of both types of particles within the bed. Spiral mixer / mill type equipment exists on both laboratory and industrial scales to ensure uniform mixing.

[0038] Another subject of the invention is a method for obtaining a catalytic bed as defined above, wherein at least one of the semiconductor materials a, a′, or thereto is deposited on structural particles b of an inorganic material: by impregnating the structural particles with a solution of a precursor of at least one semiconductor material, or by ion exchange, or by an electrochemical route, particularly using a molten salt type, followed by drying and optionally calcination. Chemical vapor deposition (CVD), spray drying, or atomic layer deposition (ALD), or any other technique known to those skilled in the art of such deposition, may also be selected.

[0039] Another subject of the invention is any reactor for the photocatalytic treatment of gaseous and / or liquid feedstocks, comprising at least one photocatalytic bed as defined above and mounted in a fixed manner within the reactor. This is because the benefits of Mie scattering on structured particles can be best utilized when the bed is fixed (as opposed to a moving bed reactor).

[0040] Another subject of the present invention is a method for photocatalytic treatment of raw materials in gaseous or liquid form, such that:

[0041] -At least one photocatalytic bed as defined above is arranged in a fixed manner in the reactor.

[0042] - To bring the feedstock into contact with the catalyst bed in the reactor.

[0043] - And during the contact operation, the photocatalytic bed is irradiated by at least one radiation source that emits in the UVA-A range and / or UV-B range and / or visible light range, particularly in the wavelength range between 220-800 nm, preferably in the range between 300-750 nm.

[0044] Another subject of the present invention is a method in which photocatalytic treatment is:

[0045] - To photo-oxidize components present in raw materials in liquid or gaseous form, specifically for the purpose of decontamination / purification of raw materials.

[0046] -Or enable the photocatalytic reduction of CO2 from liquid or gaseous feedstocks.

[0047] - Alternatively, it can photolyze the water in liquid or gaseous feedstock to produce H2. Attached Figure Description

[0048] Figure 1 This represents the graphical re-emission modes of the incident beam on the particle, based on Rayleigh-type scattering and Mie-type scattering.

[0049] Figure 2 The image shows a transmission electron microscope (TEM) image of semiconductor particles made of titanium oxide used in accordance with an embodiment of the photocatalytic material according to the present invention.

[0050] Figure 3 The image shows a scanning electron microscope (SEM) image of structural particles made of silicon dioxide used in an embodiment of the photocatalytic material according to the present invention.

[0051] Figure 4 A simplified diagram showing an apparatus designed to measure the performance quality of the photocatalytic material according to the present invention.

[0052] Figure 5 A graph representing the photocatalytic performance quality of two examples of materials according to the present invention, wherein the horizontal axis represents the volume fraction of the titanium oxide semiconductor in the material of the present invention, comprising semiconductors made of titanium oxide and structural particles made of silicon oxide, and the vertical axis represents the total electron consumption per square meter over 20 hours, in μmol / m². 2 express.

[0053] Implementation Plan Description

[0054] The present invention relates to a composition of a photocatalytic bed having mineral-structured particles, in this case solid particles, which are calibrated according to the wavelength of radiation emitted by a light source to activate a semiconductor material such that the radiation is scattered over a wide range, preferably by means of Mie scattering in the direction of incident radiation hitting the surface of these spheres.

[0055] therefore, Figure 1 The above-described Mie scattering phenomenon is simply illustrated graphically: on the left, a light source S emitting radiation with a given wavelength λ is symbolically represented. A spherical particle P1, whose diameter is not calibrated according to the invention and is less than 0.1λ, will re-emit the incident radiation fairly uniformly in all directions; this is Rayleigh scattering. On the other hand, particle P2, whose diameter is calibrated between 0.1λ and 10λ, will re-emit the radiation in a favorable manner along the direction of the incident radiation; this is Mie scattering. This is the scattering used in the present invention, which allows the calibrated particle to "guide" more radiation into the depths of the catalyst bed, thereby promoting radiation propagation and thus better utilizing the semiconductor material.

[0056] The semiconductor materials bound to these particles subsequently experienced a remarkable enhancement in their photocatalytic activity. This activity can be applied to all known areas of photocatalytic activity in liquid and / or gaseous fluids. It can be the reduction of CO2, the photocatalytic production of H2 via the photoconversion of water (also known as "water splitting"), or the photocatalytic purification of air (conversion of VOCs) or water.

[0057] The present invention will be described below in non-limiting embodiments using different photocatalytic materials and different structural particles:

[0058] Photocatalytic materials

[0059] -The photocatalyst material a1 is titanium dioxide: it is from Aldrich under the trade name... TiO2 obtained from P25 has a purity of 99.5%. The titanium oxide is in particulate form. Its particle size, measured by transmission electron microscopy (TEM), is 21 nm. Its specific surface area, measured by the BET method, is 52 m². 2 / g. BET is an abbreviation: it is the Brunauer-Emmett-Teller method as defined by S. Brunauer, PHEmmett and E. Teller in J. Am. Chem. Soc., 1938, 60(2), pp. 309-319.

[0060] In crystallography, this titanium dioxide is a mixture of rutile and anatase.

[0061] Figure 2This is a schematic diagram of these titanium dioxide particles obtained by TEM: they appear to have irregular shapes and tend to aggregate.

[0062] - Photocatalyst material a2 is titanium dioxide, with platinum metal particles prepared by photodeposition in the following manner:

[0063] 0.0712 g of H₂PtCl₆·6H₂O (37.5 wt% metal) was introduced into 500 ml of distilled water. 50 ml of this solution was then transferred to a jacketed glass reactor. 3 ml of methanol was then added with stirring, followed by 250 mg of a1-type TiO₂ (…). P25, Aldrich TM (with a purity > 99.5%), to form a suspension.

[0064] The mixture was then stirred and placed under UV radiation for two hours. The lamp used to provide the UV radiation was 125WHPK. TM A mercury vapor lamp was used. The mixture was then centrifuged at 3000 rpm for 10 minutes to recover the solids. Two washing operations with water were then performed, followed by centrifugation after each wash. Finally, the recovered powder was placed in an oven at 70°C for 24 hours.

[0065] The photocatalyst material a2 was then obtained. The Pt content was measured to be 0.99% by weight by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0066] - The photocatalyst material a3 is a commercial semiconductor based on WO3 (available from Sigma-Aldrich, with a particle size of less than 100 nm). Its specific surface area, measured by the BET method, is equal to 20 m². 2 / g. The particle size of the photocatalytic material, measured by X-ray diffraction (Debye-Scherrer method), is 50±5 nm.

[0067] - Photocatalyst a4 is a mixed oxide of titanium and copper, containing platinum Cu2O / Pt / TiO2 particles. It is prepared by the following method:

[0068] Cu(NO3)2 solution is prepared by passing 0.125g Cu(NO3)2·3H2O (Sigma-Aldrich). TM Cu was prepared by dissolving 98% of the solution in 50 ml of a 50 / 50 isopropanol / H2O mixture. 2+ The concentration was 10.4 mmol / L.

[0069] The following substances were introduced into the reactor: 0.20 g of photocatalyst a2, 25 ml of distilled water, and finally 25 ml of isopropanol. The system was purged in the dark under an argon flow (100 ml / min) for 2 hours. The reactor temperature was maintained at 25 °C throughout the synthesis process.

[0070] The argon flow rate was then reduced to 30 ml / min and irradiation of the reaction mixture began. A 125W HPK lamp was used to provide UV radiation. TM A mercury vapor lamp was used. Then, 50 ml of copper nitrate solution was added to the mixture. The mixture was stirred and placed under irradiation for 10 hours. Subsequently, the mixture was centrifuged at 3000 rpm for 10 minutes to recover the solid. This was followed by two washings with water, centrifuged after each washing. Finally, the recovered powder was placed in an oven at 70°C for 24 hours.

[0071] The photocatalyst material a4, Cu2O / Pt / TiO2, was obtained. The Cu content was 2.2% by weight as measured by ICP-AES. The copper oxide phase was 67% Cu2O and 33% CuO as measured by XPS (X-Ray Photoelectron Spectrometry).

[0072] Structural particles

[0073] - In some of the following embodiments, the structural particles b1 selected are spherical particles made of silicon oxide based on commercial SiO2, available from Alfa Aesar (CAS: 7631-86-9): these are beads with a purity greater than 99.9% and an average diameter of 0.4 μm as determined by laser particle size analysis.

[0074] Figure 3 These are SEM images of the beads, which actually show that they are very uniform in size and shape.

[0075] - In other embodiments, the structural particles b2 selected are made of silicon oxide based on commercial SiO2, which can be obtained from Sigma-Aldrich with commercial reference number Davisil Grade 710, 10-14 μm: these are beads with a purity greater than 99% and an average size of 12.7 μm (volume distribution) as measured by laser particle size analysis.

[0076] Semiconductor particles a1-a4 and structural particles b1 (SiO2 powder) or b2 (SiO2 powder with a particle size larger than b1) are mechanically mixed at a dilution ratio of 0-75% by volume to obtain a uniform distribution of the two types of particles in the material. As a reminder, within the meaning of this invention, "dilution ratio" is equal to the ratio of the volume occupied by the structural particles made of inorganic material to the total volume occupied by the semiconductor material and the structural particles.

[0077] Subsequently, as Figure 4 As shown, each sample 3 of each photocatalytic material in each embodiment was subjected to a photocatalytic reduction test of CO2 in the gas phase in the following manner: a reactor 1, which operates continuously, is used, having a horizontally arranged fixed bed 2 in its cavity, the bed comprising sintered material 4, on which the sample 3 is placed. The reactor 1 has an optical window 5 made of quartz in its upper wall, with the sample 3 facing the window. An ultraviolet-visible light radiation source 6 is arranged above the reactor and facing the window 5.

[0078] In operation, reactor 1 is fed with a gaseous CO2 stream 7 through the top inlet, which is pre-bubbled into a container / saturator filled with water 8. Stream 7 passes through sample 3 and is then discharged as stream 9 through the outlet at the bottom, which is analyzed online by a micro gas chromatograph-type gas analyzer 10.

[0079] The UV-visible light source 6 is a xenon lamp, available from Asahi under the trade name MAX 303.

[0080] Samples 3, totaling between 45 and 70 mg, were tested. Their weight varied depending on the dilution ratio they selected. The thickness of the catalytic bed 2, and therefore the thickness of sample 3, remained constant and equal to 0.3 mm.

[0081] The operating conditions are as follows:

[0082] -Ambient temperature

[0083] -Atmospheric pressure

[0084] - The flow rate of CO2 through water saturator 8 is 18 ml / h.

[0085] - Testing duration for each sample: 20 hours

[0086] - Irradiation power of xenon lamp 6: kept constant at 80W / m 2 Measurements were performed in the wavelength range of 315-400nm.

[0087] The target conversion of CO2 corresponds to the following reaction:

[0088] CO2·+·H2O·+·hv··→·O2+·H2,·CO,·CH4,·C2H6

[0089] The photocatalytic performance of the samples was measured using microchromatography in apparatus 10. The preparation of H2, CH4, and CO from the reduction of CO2 and H2O was monitored by analysis every 6 minutes. The reduction products of CO2, such as CO, methane, or ethane, were identified. Average photocatalytic activity was expressed as μmol of photogenerated electrons consumed per square meter of irradiated catalyst surface area during the test. Example

[0090] All implementation examples and results are shown in Table 1 below:

[0091] Table 1

[0092]

[0093] The table shows that the photocatalytic activity of the "hybrid" material, which combines semiconductor material with structural particles according to the present invention, is significantly greater than that of the material composed solely of the semiconductor material responsible for the photocatalytic activity of the material.

[0094] Comparing the results of Example 1 (Comparative) and Example 2, it can be seen that using 25% less semiconductor material (Example 2), the photocatalytic activity jumps by 4.5 times. Starting with another semiconductor (materials a2, a3, a4), the photocatalytic activity is even higher for materials made of 100% semiconductors, and the present invention still successfully increases it by at least 4 times by combining it with structural particles: Example 9 thus achieves an impressive level of photocatalytic activity.

[0095] Figure 5 The results of Examples 2 and 3 are presented in graphical form. The volume fraction of particles made from TiO2 is represented on the horizontal axis, and the total electron consumption per square meter over 20 hours is represented on the vertical axis. As can be seen from the graph, Example 3, with its oversized structural particles b2 (diamonds in the graph), yielded significantly worse results than Example 2, which used structural particles b1 (circles in the graph), whose size was calibrated to favor Mie scattering.

[0096] This calibration of structured particles is easy to select and obtain, and is significantly simpler than having to refine other parameters (which are more complex to control the macroporosity or microporosity of the material type).

[0097] It can be seen that the invention is very flexible in its implementation: depending on the required performance level and the project with selected equipment and reactors, the composition of the materials according to the invention can be adjusted by changing the choice of materials, the dilution ratio, and the method of mixing between the two materials (mechanical mixing, chemical or physicochemical integration, etc.).

Claims

1. A catalytic bed comprising a particulate photocatalytic catalyst, characterized in that, The bed comprises structural particles b made of inorganic material, which are combined with at least one semiconductor material a having photocatalytic properties, the combination being achieved by the following method: - By mixing structural particles b made of inorganic materials with semiconductor material a in particulate form, - and / or by chemically or physicochemically depositing semiconductor material a onto the surface of structural particles b made of inorganic material, Structural particle b is spherical and solid, with an average diameter between 22 nm and 8.0 μm. The catalyst bed has a dilution ratio of up to 80%, which is equal to the ratio of the volume occupied by the structural particles b made of inorganic material to the total volume occupied by the semiconductor material a and the structural particles b made of inorganic material; and The catalyst bed has a porosity of at least 40% and at most 80%, which is equal to the ratio of the void volume in the catalyst bed to the total volume of the catalyst bed consisting of voids and particles.

2. The catalytic bed as described in claim 1, characterized in that, The structural particle b has an average diameter between 30 nm and 7.5 μm.

3. The catalytic bed as described in claim 1, characterized in that, All particles within the bed are arranged in an unorganized manner.

4. The catalytic bed according to any one of claims 1-3, characterized in that, When the bed contains semiconductor material a in the form of particles, the particles a have an average size of at least 5 nm and at most 100 nm.

5. The catalytic bed according to any one of claims 1-3, characterized in that, When the bed contains semiconductor material a in the form of particles, the particles a have an average size of at least 5 nm and at most 50 nm.

6. The catalytic bed according to any one of claims 1-3, characterized in that, When the bed contains semiconductor material a in particulate form, the particulate a has an average size between 10-30 nm.

7. The catalytic bed according to any one of claims 1-3, characterized in that, It has a porosity between 40% and 70%.

8. The catalytic bed according to any one of claims 1-3, characterized in that, It has a dilution ratio between 5% and 70% when semiconductor material a is chemically or physicochemically deposited on structural particles b made of inorganic material.

9. The catalytic bed as described in claim 8, characterized in that, It has a dilution ratio between 10% and 50% when semiconductor material a is chemically or physicochemically deposited on structural particles b made of inorganic material.

10. The catalytic bed according to any one of claims 1-3, characterized in that, It comprises at least two different semiconductor materials, a first material a and a', and it is prepared by the following method: - By mixing structural particles b made of inorganic materials with semiconductor materials in the form of particles of a first material a and particles of a second material a', - and / or by chemically or physicochemically depositing semiconductor materials a and / or a' onto carrier particles b.

11. The catalytic bed according to any one of claims 1-3, characterized in that, It comprises at least two different semiconductor materials, a first material a and a', and it is prepared by the following method: - By mixing structural particles b made of inorganic materials with semiconductor materials in the form of particles of a first material a and particles of a second material a', - and / or by depositing both the first semiconductor material a and the second semiconductor material a' onto the structural particle b.

12. The catalytic bed according to any one of claims 1-3, characterized in that, It comprises at least two different semiconductor materials, a first material a and a', and it is prepared by the following method: - By mixing structural particles b made of inorganic materials with semiconductor materials in the form of particles of a first material a and particles of a second material a', - and / or by depositing a first semiconductor material a on a first portion of the structural particle b and depositing a second semiconductor material a' on a second portion of the structural particle b.

13. The catalytic bed according to any one of claims 1-3, characterized in that, The structural particles b, made of inorganic materials, are made of metal oxides.

14. The catalytic bed according to any one of claims 1-3, characterized in that, The structural particles b, made of inorganic materials, are made of oxides of metals from Group IIIA and IVA of the periodic table.

15. The catalytic bed according to any one of claims 1-3, characterized in that, The structural particles b, made of inorganic materials, are made of oxides selected from alumina, silicon oxide, and mixed oxides of aluminum and silicon.

16. The catalytic bed as described in claim 10, characterized in that, At least one of the semiconductor materials a and a' includes at least one of the following metal oxides: titanium oxide, tungsten oxide, cerium oxide, bismuth oxide, zinc oxide, copper oxide, vanadium oxide, iron oxide, and cadmium oxide.

17. The catalytic bed as described in claim 10, characterized in that, At least one of the semiconductor materials a and a' includes at least one metal oxide selected from the following: TiO2, Bi2O3, CdO, Ce2O3, CeO2, CeAlO3, CuO, Fe2O3, FeTiO3, ZnFe2O3, V2O5, ZnO, WO3, and ZnFe2O4.

18. The catalytic bed as described in claim 10, characterized in that, At least one of the semiconductor materials a and a' is doped with one or more ions selected from metal ions, or non-metal ions, or a mixture of metal ions and non-metal ions.

19. The catalytic bed as described in claim 18, characterized in that, The metal ions are V, Ni, Cr, Mo, Fe, Sn, Mn, Co, Re, Nb, Sb, La, Ce, Ta, and Ti ions.

20. The catalytic bed as described in claim 18, characterized in that, The non-metallic ions are C, N, S, F, and P ions.

21. The catalytic bed as described in claim 10, characterized in that, At least one of the semiconductor materials a and a' further comprises one or more metallic elements selected from Groups IVB, VB, VIB, VIIB, VIIIB, IB, IIB, IIIA, IVA and VA of the periodic table, and is in direct contact with the semiconductor material.

22. The catalytic bed as described in claim 21, characterized in that, The element is selected from platinum, palladium, gold, nickel, cobalt, ruthenium, silver, copper, rhenium, or rhodium.

23. A method for obtaining a catalytic bed as described in any one of claims 1 to 22, characterized in that, Structural particles b of inorganic material and particles a of semiconductor material are mixed to produce a uniform distribution of the two types of particles within the bed.

24. A method for obtaining a catalytic bed as described in any one of claims 1 to 22, characterized in that, The semiconductor material a is deposited on the structural particles b of the inorganic material by impregnation of the structural particles with a solution of at least one semiconductor material precursor, or by ion exchange, or by an electrochemical route of the molten salt type, followed by drying and optionally calcination, or by chemical vapor deposition or by atomic layer deposition.

25. A reactor (1) for photocatalytic treatment of gaseous or liquid feedstock, comprising at least one catalyst bed (2) as claimed in any one of claims 1 to 22, the catalyst bed being fixedly mounted in the reactor.

26. A method for photocatalytic treatment of a feedstock (7) in gaseous and / or liquid form, characterized in that: - At least one catalyst bed (2) as described in any one of claims 1 to 22 is arranged in a fixed manner in the reactor (1), -The raw material (7) is brought into contact with the catalyst bed (2) in the reactor. - and the catalyst bed (2) is irradiated during contact operation with at least one radiation source (6) emitting in the wavelength range between 220-800 nm.

27. The method according to claim 26, characterized in that, The catalyst bed (2) is irradiated during contact operation with at least one radiation source (6) that emits in the UVA and / or UVB and / or visible light ranges.

28. The method according to claim 26, characterized in that, The catalyst bed (2) is irradiated during contact operation with at least one radiation source (6) emitting in the wavelength range of 300-750 nm.

29. The method as described in claim 26, characterized in that, Photocatalytic treatment is: - To purify the components present in liquid or gaseous raw materials by photo-oxidation. -Or enable the photocatalytic reduction of CO2 from liquid or gaseous feedstocks. - Alternatively, it can photolyze the water in liquid or gaseous feedstock to produce H2.

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