Use of titanium dioxide particles supporting a metal or metal oxide for obtaining an alkene by photocatalytic action

Abstract

The present invention relates to the use of TiO2 particles supporting a metal and / or a metal oxide for obtaining alkenes by photocatalysis. The present invention also relates to a method for obtaining alkanes by photocatalysis of a carboxylic acid and / or an alcohol in the presence of a catalyst based on TiO2 particles supporting a metal and / or a metal oxide.

Description

Technical Field

[0001] The present invention relates to the use of TiO2 particles supporting a metal and / or a metal oxide for obtaining alkenes by photocatalysis. The present invention also encompasses a method for obtaining alkenes by photocatalysis of carboxylic acids and / or alcohols in the presence of a catalyst based on TiO2 particles supporting a metal and / or a metal oxide.

Background Art

[0002] Alkenes are generally produced during the refining of crude oil and are widely used in the chemical industry for many different applications as raw materials for the production of polymers such as plastics and lacquers, as well as for the synthesis of alcohols, surfactants and fuels.

[0003] Among alkenes, ethylene is the most widely produced and used organic molecule in the world. The global market that forms the basis of the petrochemical industry is worth over $130 billion annually, and the consumption exceeds 150 million tons per year. These high tonnages can be explained by the fact that ethylene is a basic monomer used in the production of over 75% of petrochemical products. Ethylene is mainly used for the synthesis of plastics such as polyethylene (PET), or for the synthesis of chemical surfactants such as ethylene oxide and ethylene glycol.

[0004] Currently, 99% of industrial ethylene production is based on the cracking of hydrocarbons such as naphtha (an intermediate between gasoline and kerosene produced by fractional distillation of petroleum) or ethane, usually heated to 750 - 950°C. The yield of ethylene varies, being about 35% for naphtha and 80% for ethane. However, this synthesis is not only very energy-intensive but also polluting and dependent on petroleum resources. With the depletion of fossil fuels and the pressing climate problem, it has become essential to develop a new low-energy, low-cost ethylene synthesis method based on renewable resources.

[0005] In view of these problems, many studies have been carried out to find alternatives to decompose petroleum derivatives to produce ethylene.

[0006] One of these alternative technologies is the catalytic dehydration of ethanol to ethylene. An example is bioethanol, a renewable resource produced at low cost without using toxic reagents. For ethanol dehydration, monofunctional oxides, typically acid catalysts such as γ-Al2O3 alumina, or "molecular sieves" such as zeolite structures like ZSM-5 (Zeolite Socony Mobil-5) are used. However, despite the use of acid catalysts, the ethanol dehydration reaction is still highly endothermic and shifts only to ethylene at high temperatures. Therefore, the operating temperature and pressure have a great impact on the yield of ethylene. As a result, with these technologies, generally, it is possible to obtain a high yield of ethylene, but the temperatures used (typically 300 - 550 °C) and pressures (generally 0.3 - 4 MPa) are still high, and thus, they are energy-intensive and costly. Also, generally, when the operating temperature is low, the formation of a non-negligible amount of by-products is observed, the ethanol conversion rate is limited, and the pressure is still high. Furthermore, the acid catalysts typically used to lower the operating temperature tend to deactivate by coking (formation by thermal decomposition of coke deposited on the surface of the system exposed to high temperatures, which leads to a decrease in its performance), so their service life is limited, and the regeneration reaction at high temperatures results in high costs and a significant loss of catalytic efficiency.

[0007] Subsequently, other technologies based on the photocatalytic production of ethylene using CuCl2 as a catalyst have been developed. These methods are interesting because they use light energy instead of thermal energy and high pressure. However, CuCl2-based catalysts become inactive very rapidly, typically in less than 1 hour, and thus must be regenerated regularly in air.

[0008] In addition to ethanol, carboxylic acids, especially propanoic acid (CH3CH2COOH), are of particular interest as renewable resources in biomass for producing liquid fuels and other molecules of interest to the energy field. Propanoic acid is a volatile fatty acid found as a contaminant in domestic wastewater. It can also be obtained from biomass by fermentation of glycerol and from fermentation of industrial water from extraction of, for example, rapeseed oil or potato-derived waste.

[0009] In this regard, a method for decarboxylating propanoic acid to alkanes by photocatalysis using platinum-impregnable TiO2 powder has been developed. Ethylene can also be formed using these methods, but is formed only in trace amounts as a result of secondary reactions. Furthermore, since the platinum used in certain methods is a precious metal, it is an expensive material to manufacture and is thus not suitable for development on an industrial scale.

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a method for obtaining alkenes, especially ethylene, by photocatalysis that avoids the above-mentioned drawbacks.

[0011] Accordingly, one object of the present invention is to provide a method for producing alkenes or alkenes, especially ethylene, that does not contain fossil resources and does not require significant heating (i.e., typically exceeding 200°C) or even input of thermal energy. None of the currently proposed solutions can achieve either good yield and / or selectivity in alkenes or alkenes, especially ethylene, under ambient temperature and pressure conditions and in a volume suitable for industrial scale, especially from alcohol or acid solutions that can be synthesized from biomass.

[0012] Another object of the present invention is to provide a method that is easy to implement, stable over time (e.g., at least 50 hours), and inexpensive. In fact, in some techniques of the prior art, the use of expensive photocatalysts based on precious metals has been proposed and / or they rapidly deactivate under irradiation and thus need to be regenerated, resulting in additional costs.

[0013] Another object of the present invention is to provide a method for obtaining alkenes, particularly ethylene, with excellent selectivity under simple UV / visible light irradiation, especially at ambient temperature and ambient pressure.

Means for Solving the Problems

[0014] Accordingly, according to a first aspect, the present invention provides a method for obtaining at least one alkene by photocatalysis from at least one carboxylic acid of formula (I) R a -COOH and / or at least one alcohol of formula (II) R b -OH, using particles consisting of or containing TiO2, having supported thereon at least on a part of the surface a metal M and / or an oxide of the metal M (M is selected from the group consisting of Cu, Zn, Fe, Mo, W, and Ni, particularly selected from the group consisting of Cu, Zn, Fe, and Ni), wherein R a and R b are independently selected from linear, branched, or cyclic alkyl groups, particularly selected from linear, branched, or cyclic C2-C 18 alkyl groups, more particularly selected from linear, branched, or cyclic C2-C6 alkyl groups, and the alkyl group may be substituted with at least one group X selected from arenes, particularly X is a phenyl group.

[0015] "Photocatalysis" particularly refers to a reaction catalyzed by the action of light on the surface of a catalyst called a photocatalyst.

[0016] According to certain embodiments, the maximum number-average dimension of the particles is from 1 to 100 nm, particularly from 5 to 70 nm. The maximum number-average dimension can be measured by any technique known to those skilled in the art, particularly by size measurement by counting on a transmission electron microscope (TEM) image using, for example, ImageJ software.

[0017] In certain embodiments, the particles consisting of or containing TiO2 are spherical, ellipsoidal, rod-shaped, wire-shaped, tubular and / or platelet-shaped. These include nanospheres, nanospheroids, nanorods, nanowires, nanotubes and / or nanoplatelets.

[0018] The particles consisting of or containing TiO2 may, particularly in one of the above forms, optionally be woven in a chain-like, particularly nanochain-like, form.

[0019] According to certain embodiments, TiO2 is in the form of anatase, rutile and / or brookite, particularly in the form of anatase, rutile, or a mixture of anatase and rutile, more particularly in the form of a mixture of anatase and rutile with an anatase / rutile ratio of 0.80 to 2.33, particularly 1.00 to 2.33, more particularly 1.00 to 2.00.

[0020] In certain embodiments, the particles consisting of or containing TiO2 have a specific surface area of from 10 to 500 m 2 / g, particularly from 30 to 150 m 2 / g. These ranges of specific surface area can correspond to the specific surface area of the particles consisting of or containing TiO2, excluding the surface area corresponding to the metal M and / or the oxide of the metal M. These ranges of specific surface area can correspond to the total specific surface area of the particles consisting of or containing TiO2 that carry the metal M and / or the oxide of the metal M.

[0021] According to certain embodiments, the content of metal M and / or the oxide of metal M with respect to TiO2 is 0.01 to 50% by mass, particularly 0.1 to 5% by mass, for example about 2% by mass, or more than 0.01% by mass and less than 2% by mass.

[0022] According to certain embodiments, the content of metal M and / or the oxide of metal M with respect to TiO2 is 0.01 to 1.0; 1.2; 1.4; 1.6; 1.8 or 1.9% by mass, particularly 0.1 to 1.0; 1.2; 1.4; 1.6; 1.8 or 1.9% by mass.

[0023] According to certain embodiments, particles composed of or containing TiO2 that support metal M and / or the oxide of metal M on at least a part of their surface also contain metal M and / or the oxide of metal M therein.

[0024] In certain further embodiments, most of the metal M and / or the oxide of metal M of particles composed of or containing TiO2 is present on the surface of the particles.

[0025] According to another specific embodiment, more than 50% by mass, particularly more than 60, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98 or 99% by mass, of the metal M and / or the oxide of metal M of particles composed of or containing TiO2 is present on the surface of the particles. This can be measured by comparing the measurements performed by any technique known to those skilled in the art, for example, inductively coupled plasma spectroscopy (ICP) that enables quantification of the total metal content of the material, with the measurements performed by X-ray photoelectron spectroscopy (XPS) that enables measurement of the amount of surface elements in the material.

[0026] According to certain embodiments, metal M and / or the oxide of metal M is present on the surface of at least particles composed of or containing TiO2 in the form of particles having a maximum number average particle size of 0.1 to 50 nm, particularly 0.5 to 10 nm, and more specifically 1 to 3 nm.

[0027] According to certain embodiments, the particles consisting of or containing TiO2 supporting metal M and / or an oxide of metal M on at least a part of the surface are obtained by laser pyrolysis or impregnation, and optionally subsequently annealed, particularly in air, particularly at a temperature of 300 to 500 °C, particularly 400 to 500 °C, for example about 450 °C, and / or particularly for 3 hours, particularly 3 to 6 hours.

[0028] In certain embodiments, the particles of the present invention do not contain gold.

[0029] According to certain embodiments, the present invention relates to a method for obtaining at least one alkene from at least one carboxylic acid, particularly propanoic acid, acetic acid, phenylpropanoic acid, particularly 2-phenylpropanoic acid, n-butyric acid, n-valeric acid or pivalic acid, more particularly from propanoic acid.

[0030] According to certain embodiments, the present invention relates to a method for obtaining at least one alkene from at least one alcohol, particularly ethanol or cyclohexanol, more specifically from ethanol.

[0031] In certain embodiments, at least one alkene is ethylene.

[0032] In certain embodiments, the present invention relates to a method for obtaining ethylene from propanoic acid.

[0033] According to another aspect, the present invention also provides a method for obtaining at least one alkene from at least one carboxylic acid of formula (I) R a -COOH and / or at least one alcohol of formula (II) R b -OH, wherein R a and R bis independently selected from linear, branched or cyclic alkyl groups which may be substituted with at least one group X selected from arenes, X being in particular a phenyl group, consisting of TiO2 supporting a metal M and / or an oxide of the metal M on at least a part of the surface, or consisting of particles containing the same, or containing the same, in the presence of a catalyst, comprising a photocatalysis step (i) by UV and / or visible light irradiation of at least one carboxylic acid and / or at least one alcohol, M being selected from the group comprising Cu, Zn, Fe, Mo, W and Ni, in particular from the group comprising Cu, Zn, Fe and Ni, relates to a method.

[0034] According to certain embodiments, the maximum number average dimension of the particles is from 1 to 100 nm, in particular from 5 to 70 nm. The maximum number average dimension can be measured by any technique known to those skilled in the art, in particular by size measurement by counting on a transmission electron microscope (TEM) image using, for example, ImageJ software.

[0035] In certain embodiments, the particles consisting of or containing TiO2 are spherical, ellipsoidal, rod-shaped, wire-shaped, tubular and / or platelet-shaped. These include nanospheres, nanospheroids, nanorods, nanowires, nanotubes and / or nanoplatelets.

[0036] The particles consisting of or containing TiO2 may, in particular in one of the above forms, optionally be woven in a chain-like manner, in particular in a nano-chain-like manner.

[0037] According to certain embodiments, TiO2 is in the form of anatase, rutile and / or brookite, in particular in the form of anatase, rutile, or a mixture of anatase and rutile, more particularly in the form of a mixture of anatase and rutile with an anatase / rutile ratio of 0.80 to 2.33, in particular 1.00 to 2.33, more particularly 1.00 to 2.00.

[0038] In certain embodiments, the particles consisting of or containing TiO2 are 10 - 500 m2 / g, particularly 30 to 150 m 2 / g. These ranges of specific surface area can correspond to the specific surface area of particles consisting of or containing TiO2, excluding the surface area corresponding to metal M and / or the oxide of metal M. These ranges of specific surface area can correspond to the total specific surface area of particles consisting of or containing TiO2 that supports metal M and / or the oxide of metal M.

[0039] According to a specific embodiment, the content of metal M and / or the oxide of metal M with respect to TiO2 is 0.01 to 50% by mass, particularly 0.1 to 5% by mass, for example about 2% by mass, or more than 0.01% by mass and less than 2% by mass.

[0040] According to a specific embodiment, the content of metal M and / or the oxide of metal M with respect to TiO2 is 0.01 to 1.0; 1.2; 1.4; 1.6; 1.8 or 1.9% by mass, particularly 0.1 to 1.0; 1.2; 1.4; 1.6; 1.8 or 1.9% by mass.

[0041] According to a specific embodiment, particles consisting of or containing TiO2 that support metal M and / or the oxide of metal M on at least a part of their surface also contain metal M and / or the oxide of metal M therein.

[0042] In a further specific embodiment, most of the metal M and / or the oxide of metal M of the particles consisting of or containing TiO2 is present on the surface of the particles.

[0043] According to another specific embodiment, a metal M and / or an oxide of the metal M of particles consisting of TiO2 or containing the same, which exceeds 50% by mass, particularly exceeds 60, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98 or 99% by mass, is present on the surface of the particles. This can be measured by comparing the measurements performed by any technique known to those skilled in the art, for example, inductively coupled plasma spectroscopy (ICP) that enables quantification of the total metal content of the material, with the measurements performed by X-ray photoelectron spectroscopy (XPS) that enables measurement of the amount of surface elements in the material.

[0044] According to a specific embodiment, the metal M and / or the oxide of the metal M is present in the form of particles having a maximum number average particle size of 0.1 to 50 nm, particularly 0.5 to 10 nm, more specifically 1 to 3 nm, on the surface of particles consisting of at least TiO2 or containing the same.

[0045] According to a specific embodiment, particles consisting of TiO2 or containing the same, which support a metal M and / or an oxide of the metal M on at least a part of the surface, are obtained by laser pyrolysis or impregnation, and optionally subsequently, particularly in air, and then optionally in dihydrogen, particularly at a temperature of 300 to 500 °C, particularly 400 to 500 °C, for example, at a temperature of about 450 °C, and / or particularly for 3 hours, particularly 3 to 6 hours by annealing.

[0046] Laser pyrolysis and impregnation are carried out using methods well-known to those skilled in the art, for example.

[0047] According to a more specific embodiment, laser pyrolysis is carried out by bringing an aerosol of a liquid composition comprising at least one TiO2 precursor, at least one precursor of a metal M and / or an oxide of the metal M, and an optional organic solvent into contact with a laser beam.

[0048] According to another more specific embodiment, the impregnation is carried out, for example, by bringing TiO2 obtained by laser pyrolysis into contact with a metal M and / or a precursor of an oxide of the metal M, and the impregnation is optionally followed by annealing, in particular in air and then optionally in dihydrogen, at a temperature of in particular 300 to 500 °C, in particular 400 to 500 °C, for example at a temperature of about 450 °C, and / or for in particular 3 hours, in particular 3 to 6 hours.

[0049] When TiO2, or a supported TiO2 having on at least a part of its surface a metal M and / or an oxide of the metal M, is obtained by laser pyrolysis, the annealing is carried out in air and then optionally in dihydrogen.

[0050] When TiO2 is commercially available and is configured to be impregnated as defined above, annealing in air is optional but preferred, and advantageously annealing in dihydrogen can be carried out thereafter.

[0051] “Dihydrogen annealing” refers in particular to annealing under pure dihydrogen or annealing diluted with an inert gas such as argon or dinitrogen. If necessary, annealing may limit the presence of oxides on the surface of the metal M.

[0052] According to a particular embodiment, the present invention relates to a method for obtaining at least one alkene from at least one carboxylic acid, in particular propanoic acid, acetic acid, phenylpropanoic acid, in particular 2-phenylpropanoic acid, n-butyric acid, n-valeric acid or pivalic acid, more particularly from propanoic acid.

[0053] According to a particular embodiment, the present invention relates to a method for obtaining at least one alkene from at least one alcohol, in particular ethanol or cyclohexanol, more specifically from ethanol.

[0054] In a particular embodiment, at least one alkene is ethylene.

[0055] In certain embodiments, the present invention relates to a method for obtaining ethylene from propanoic acid.

[0056] According to certain embodiments, step (i) is carried out in an atmosphere containing less than 1% by volume of oxygen, particularly less than 0.1% of oxygen, particularly less than 0.01% of oxygen, and more specifically less than 0.001% of oxygen.

[0057] According to certain embodiments, step (i) is carried out under an inert gas atmosphere, particularly under a nitrogen, helium and / or argon atmosphere, and more particularly under an argon atmosphere.

[0058] According to a more specific embodiment, the inert gas atmosphere is obtained by purging using a flow of inert gas, which flow is particularly from 1 to 500 mL / min, preferably from 50 to 70 mL / min.

[0059] According to certain embodiments, step (i) is carried out under a continuous flow of inert gas, particularly under a nitrogen, helium and / or argon atmosphere, and more particularly under an argon atmosphere, and the flow is more specifically from 1 to 500 mL / min, preferably from 50 to 70 mL / min. In this case, the mode can be described as dynamic.

[0060] According to another specific embodiment, step (i) is carried out in the absence of a continuous flow of inert gas. In this case, the mode can be described as static. In this case, step (i) is carried out under an inert gas atmosphere. In particular, the purge defined above is carried out before step (i). Then, this purge is stopped before step (i) is carried out.

[0061] According to certain embodiments, at least one carboxylic acid and / or at least one alcohol is present in a composition further comprising a solvent, and particularly when present in a solution in the solvent, the solvent is preferably water, and the concentration of particularly one or more alcohols and / or one or more carboxylic acids in the composition is 0.0001% by volume or more, particularly 0.01% by volume or more, and / or less than 100% by volume, for example about 1.00% by volume.

[0062] According to another particular embodiment, at least one carboxylic acid and / or at least one alcohol is absent in the presence of a solvent.

[0063] According to certain embodiments, the catalyst is present in a composition comprising at least one carboxylic acid and / or at least one alcohol and a solvent, or in at least one carboxylic acid and / or at least one alcohol in the absence of a solvent, at a concentration of 0.01 - 50 g / L, for example about 0.5 g / L.

[0064] According to certain embodiments, step (i) is carried out at a temperature of 10 - 200°C, particularly at a temperature of about 20 - about 40°C, or 40 - 200°C, particularly 40 - 150°C, or further 40 - 100°C.

[0065] According to certain embodiments, step (i) is carried out at a temperature of 60 - 200°C, particularly 60 - 150°C, particularly 60 - 100°C.

[0066] According to certain embodiments, the irradiation is UV - A, UV - B, UV - C, and / or visible light irradiation, particularly UV - A, particularly at a wavelength of 350 - 400 nm.

[0067] According to certain embodiments, the present invention relates to a method comprising, after step (i), a step (ii) of recovering one or more alkenes, and optionally followed by a step (iii) of isolating one or more alkenes after this step (ii).

[0068] Step (ii) can be carried out by any technique known to those skilled in the art, in particular by recovering the headspace of the photocatalytic device used.

[0069] Step (iii) can be carried out by any technique known to those skilled in the art, in particular by distillation, in particular by cryogenic distillation. This purification technique involves separating the gas mixture by changing the pressure and temperature of the gas storage medium based on the fact that each gas has its own boiling point. The gas mixture is first cooled to a low temperature (usually, T is less than 50 °C). After cooling, the gas is liquefied and sent to a distillation column. The liquid is gradually heated to enable the separation of the gases according to their boiling points.

[0070] Step (iii) can be carried out using an absorption-based technique. The separation is based on the principle that each gas has a specific affinity for an absorbent such as zeolite, alumina or activated carbon, or a solvent such as methanolamine (MEA). The pressure swing absorption (PSA) method is the best illustration of this technique. The separation occurs when the gas mixture comes into contact with the absorbent / solvent in a subsequently pressurized tank. The gas with the highest affinity for the absorbent is captured while other gas species pass through the system. The reservoir is regenerated by returning to atmospheric pressure and releasing the previously captured gas.

[0071] Step (iii) can also be carried out by membrane separation which enables the gas to penetrate more or less rapidly through the membrane based on the principle of the gas's affinity for the membrane. The membrane materials frequently encountered in the literature are diverse and include microporous organic polymers, zeolites and ceramic or metal-based materials. In the first tank, the gas mixture comes into contact with the membrane located at the interface of the second tank. The various gases diffuse into the second tank using a pressure gradient, facilitating mass transport across the membrane that separates the retained liquid from the permeate.

[0072] According to a particular embodiment, the molar selectivity for alkenes, in particular ethylene, is 40% or more, in particular more than 45%, and more particularly more than 50%.

[0073] According to a more specific embodiment, the molar selectivity of the alkene obtained from at least one carboxylic acid of formula (I) R a -COOH, particularly for ethylene, is 50% or more, particularly more than 60%, more specifically more than 70, 80 or 90%.

[0074] According to another more specific embodiment, the molar selectivity of the alkene obtained from at least one alcohol of formula (II) R b -OH, particularly for ethylene, is 40% or more, particularly more than 45%, more specifically more than 50%.

[0075] In certain embodiments, acetone and / or ethyl acetate are not formed at the end of the process.

[0076] According to certain embodiments, the molar selectivity of by-products selected from acetone and / or ethyl acetate is less than 1%, particularly less than 0.1%, more specifically less than 0.01%.

[0077] Definitions As used herein, the term "about" refers to a range of values within ±10% of a particular value. For example, the term "about 20" refers to a value of 20 ± 10%, i.e., values from 18 to 22.

[0078] For the purposes of this specification, percentages refer to mass percentages relative to the total mass of the formulation, unless otherwise specified.

[0079] As understood herein, a range of values in the form "x - y" or "from x to y" or "between x and y" includes the boundaries x and y and the integers between these boundaries. For example, "1 - 5" or "1~5" or "between 1 and 5" refers to the integers 1, 2, 3, 4 and 5. Preferred embodiments include each individual integer within the range of values, as well as any partial combinations of those integers. For example, preferred values of "1 - 5" can include the integers 1, 2, 3, 4, 5, 1 - 2, 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, 2 - 5, etc.

[0080] As used herein, the term "alkyl" refers to a straight-chain or branched-chain alkyl group having the number of carbon atoms indicated before the term, particularly 2 to 6 carbon atoms, such as ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isoamyl, neopentyl, 1-ethylpropyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, hexyl, etc. Thus, expressions such as "C1-C4 alkyl" refer to an alkyl group containing 1 to 4 carbon atoms. The same applies to the term "alkane".

[0081] Cycloalkyl is, in particular, alkyl containing a ring (as defined above). An example is cyclohexyl.

[0082] As used herein, the term "arene" refers to a substituted or unsubstituted monocyclic or bicyclic aromatic hydrocarbon ring system having 6 to 10 carbon atoms in the ring. Examples include benzene and naphthalene. Preferred arenes include unsubstituted or substituted benzene and naphthalene. The definition of "arene" includes fused ring systems, for example, ring systems in which an aromatic ring is fused to a cycloalkyl ring. Examples of such fused ring systems include, for example, indane, indene, and tetrahydronaphthalene.

Brief Description of the Drawings

[0083]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Example

[0084] Example 1: Example of a photocatalytic device for implementing the use or method according to the present invention The photocatalytic device (Figure 1) consists of a 250 mL Pyrex® airtight reactor equipped with 100 mL of aqueous solution, 150 mL of headspace, a glass mechanical stirrer, and a bubbler (made of glass) for supplying neutral gas. The neutral gas may be helium He, nitrogen N2, or preferably argon Ar.

[0085] 4.8 mW.cm -2 An 18 W Phillips PLL UVA lamp that supplies a power flux of was used as the light source, with the center at 370 nm. The emitted wavelength was 350 - 400 nm.

[0086] The concentration of one or more alcohols or one or more carboxylic acids in the solution is 0.01 - 100% by volume, preferably 1.00%. The alcohol compound and / or carboxylic acid may or may not be added as a mixture. The concentration of the metal (oxide) / TiO2 photocatalyst is 0.01 - 50 g / L, preferably 0.5 g / L.

[0087] After completely purging the ambient air in the reactor by bubbling in neutral gas, the aqueous suspension containing one or more alcohols and / or one or more carboxylic acids and the photocatalyst are irradiated with UVA. The photocatalytic reaction can be carried out preferably statically (without the flow of neutral gas) or under a continuous flow of neutral gas (dynamic mode). Typically, the flow rate of the neutral gas during purging and / or irradiation is 1 - 500 mL / min, preferably 50 - 70 mL / min.

[0088] The gas generated in the headspace of the reactor during photocatalysis is analyzed by gas chromatography using a hydrogen flame ionization detector (FID) and a helium plasma detector (PDHID). In the case of the reaction in dynamic mode, the gas is transported by the flow of the neutral gas, and in the case of the reaction in static mode, the gas is transported by pumping.

[0089] Example 2: Preparation of a catalyst enabling the use or implementation of the method according to the invention The metal and / or metal oxide can be brought into contact with the surface of the TiO2 particles by any technique known to those skilled in the art. For example, this can be laser pyrolysis or an impregnation technique.

[0090] Synthesis by laser pyrolysis: TiO2 (outside the present invention) and the metal (oxide) / TiO2 photocatalyst of the present invention can be synthesized by laser pyrolysis technology, an example of which is shown below using copper as the metal.

[0091] A liquid mixture containing titanium and copper precursors is inserted into an enclosure called a "pyrosol" equipped with a cooling device, a drive gas inlet, and a piezoelectric pellet. Typically, the titanium precursor is titanium isopropoxide (TTIP), and the copper precursor may be, for example, copper acetylacetonate Cu(acac)2. Optionally, the copper precursor may be pre-dissolved in one or more organic solvents such as a mixture of o-xylene / ethyl acetate in a volume ratio of 6.5:3.5.

[0092] The composition of the said mixture is shown in Table 1 below such that the target copper content is 2.00 wt% based on the mass of TiO2.

[0093]

Table 1

[0094] The liquid mixture of precursors is converted into an aerosol by operating the piezoelectric pellet. Optionally, the mixture may be heated throughout the synthesis over a range of 10 - 100 °C. Preferably, the mixture is heated to 30 °C.

[0095] Next, the resulting aerosol is transported via a carrier gas, which may be helium He, argon Ar, or nitrogen N2, into a closed reaction chamber with a neutral atmosphere. Similarly, the confinement gas within the reaction chamber may be helium He, argon Ar, or nitrogen N2. Preferably, the tuning gas and the confinement gas (chimney, reactor window) are argon Ar. The confinement flow rate is 0 to 5,000 cm 3 .min -1 , and for confinement at the chimney level, 0 cm 3 .min -1 , and for confinement at the viewing window level, 3,000 cm 3 .min -1 is desirable. The tuning gas flow rate is 50 to 10,000 cm 3 .min -1 , and preferably 2,000 cm 3 .min -1 .

[0096] Within the reaction chamber, a CO2 infrared laser beam having a wavelength of 10.6 μm and an output of up to 2,800 W is emitted orthogonally to the precursor mixture and transported in the form of fine droplets. Ideally, the laser output supplied to the reaction zone is 100 to 900 W, about 670 W, for the synthesis of TiO2 and Cu / TiO2. A gas that absorbs the laser radiation, preferably ethylene C2H4, may be added in a flow rate range of 0 to 5,000 cm 3 .min -1 . In this example, the flow rate of this gas is set at 800 cm 3 .min -1 . In this case, the laser output absorbed by the precursor aerosol reported in Table 1 is 276 W for TiO2 and 250 W for Cu / TiO2. The interaction between the laser beam, the precursor aerosol, and optionally ethylene gas enables the growth of nanoparticles collected on the surface of the filter barrier containing nanopores. It should be noted that the use of ethylene for synthesis is optional, and it is possible to synthesize TiO2 and Cu / TiO2 materials without it.

[0097] Next, the nano powder synthesized by the method is calcined in a tubular furnace through an air reactor to remove amorphous carbon from the precursor, and in some cases, from ethylene gas if ethylene is used. The heat treatment applied is, for example, a temperature of 450 °C for a period in the range of 3 - 6 hours, in this case, for example, 6 hours, under a 100 mL / min air flow until the amorphous carbon is substantially or completely removed. -1 The air flow is 100 mL / min, and the temperature is 450 °C for a period in the range of 3 - 6 hours.

[0098] Table 2 shows the main physicochemical properties of the TiO2 and Cu / TiO2 photocatalysts synthesized by laser pyrolysis.

[0099]

Table 2

[0100] It should be noted that the copper content in the Cu / TiO2 material synthesized by laser pyrolysis, measured by inductively coupled plasma spectroscopy (ICP), is 1.91 wt%, which is very similar to the ratio (2.00 wt%) introduced into the sol-gel.

[0101] Transmission electron microscope (TEM) images of the TiO2 and Cu / TiO2 nanoparticles obtained according to this method show that the nanoparticle sizes are 5 - 25 nm for TiO2 and 10 - 70 nm for Cu / TiO2.

[0102] Scanning transmission electron microscope (STEM) and EDX images of the Cu / TiO2 nanoparticles of the present invention highlight copper / copper oxide clusters on the TiO2 surface with diameters of 1 - 3 nm.

[0103] Synthesis by impregnation on a TiO2 support: The metal (oxide) / TiO2 photocatalyst of the present invention may also be synthesized by impregnating a metal via a metal precursor onto a TiO2 support. This TiO2 support may be commercially available or may be obtained by laser pyrolysis of the above TiO2 or the like. An example using copper as the metal is shown below.

[0104] 500 mg of TiO2 obtained by laser pyrolysis was dissolved in 50 mL of distilled water, and 43.3 mg of copper acetylacetonate Cu(acac)2 (purity = 97%), which is a copper precursor, was added thereto (2.00 wt%). The metal precursor is not limited to this compound in the case of copper, and may be, for example, copper acetate (anhydrous or hydrated) or copper nitrate. Optionally, one or more organic solvents such as ethanol may be added to disperse the precursor in an ultrasonic bath. Once the precursor is completely dissolved, the mixture is transferred to a 50 mL flat-bottom flask and heated to 70 °C in a water bath. The stirred mixture is evaporated using a magnetic bar for 12 hours, and the residual powder is dried in an oven at 120 °C.

[0105] Next, the impregnated powder is -1 calcined at 450 °C for 6 hours in a reactor in a tubular oven under an air flow of 100 mL / min.

[0106] The main physicochemical properties of the TiO2 support obtained by laser pyrolysis are described, and the physicochemical properties of the Cu IMP / TiO2 photocatalyst synthesized by impregnation are shown in Table 3 below.

[0107]

Table 3

[0108] It should be noted that the copper content in the Cu / TiO2 material synthesized by impregnation was measured to be 2.15% m by inductively coupled plasma spectroscopy (ICP), which is very similar to the ratio (2.00% m) introduced into the flask for impregnation of the TiO2 support.

[0109] Example 3: Photocatalysis of Propanoic Acid Photocatalyst TiO2 (reference outside the present invention) and Cu / TiO2 (Example 2, Part 1) were introduced into 100 mL of an aqueous solution at a concentration of 0.5 g·L containing 1% by volume of propanoic acid -1 and introduced into the above-mentioned photocatalytic reactor (Figure 1). It was fixed for 6 hours with an argon flow of 70 mL / min, the air was expelled from the photocatalytic reactor, and it was exchanged with a neutral argon atmosphere. After complete purging, the argon flow was stopped and the photocatalytic reactor was separated. The photo-generated gaseous compounds were taken out from the headspace of the reactor and sent to GC / FID and GC / PDHID.

[0110] Figure 2 shows ethylene produced from propanoic acid (1% by volume in H2O) under UVA irradiation centered at 370 nm using TiO2 and Cu / TiO2 photocatalysts. The ethylene obtained by photocatalysis with TiO2 reached a production rate of 2 ppmv / h, and with Cu / TiO2 it reached 214 ppmv / h. This production is linear and the photocatalyst does not lose its activity during the 910-minute irradiation.

[0111] Table 4 below shows the gas production amounts per hour obtained in this reaction, as well as the [compound] / Σ[C x H y O z (where x and y are 1 or more) calculated according to the quotient of selectivity.

[0112]

Table 4

[0113] Considering that the photodecomposed propanoic acid molecules form ethane radicals and CO2 molecules, and the ethane radicals can form ethylene or ethane molecules, the ethylene yield calculated by the ratio [C2H4 / CO2] is 1.0% for TiO2 and 85.0% for Cu / TiO2 after 910 minutes of irradiation.

[0114] Similarly, the photocatalysis was carried out using an impregnated photocatalyst (Example 2, Part 2).

[0115] Cu IMP The Cu / TiO₂ impregnated photocatalyst was introduced into the above-mentioned photocatalytic reactor (Figure 1) at a concentration of 0.5 g·L⁻¹ containing 1 vol% propanoic acid in 100 mL of aqueous solution. The synthesis of ethylene by photocatalysis was carried out under the same conditions as above.

[0116] Figure 3 shows ethylene produced from propanoic acid (1 volume% in H₂O) under UVA irradiation centered at 370 nm using photocatalytic TiO₂ (obtained by laser pyrolysis and irradiated for 910 minutes) and Cu IMP / TiO₂ (obtained by impregnating the above TiO₂ support with irradiation for 3250 minutes, i.e., more than 54 hours). The ethylene synthesized by photocatalysis using TiO₂ was 2 ppmv / h, and Cu IMP / TiO₂ achieved a production rate of 218 ppmv / h. This production was linear, and the photocatalyst did not lose its activity over 3250 minutes of irradiation.

[0117] Table 5 below shows the gas production amounts per hour obtained in this reaction, as well as the selectivity calculated according to the quotient of [compound] / Σ[C x H y O z (where x and y are 1 or more).

[0118]

Table 5

[0119] The ethylene yield after 910 minutes of irradiation was 1.0% for TiO₂ and 86.5% for Cu IMP / TiO₂.

[0120] Example 4: Photocatalysis of Ethanol An ethanol concentration of 1 mass% (i.e., 1.27 volume%) was used. The 2% Cu / TiO₂ catalyst was added to 100 mL of solution obtained under an inert atmosphere (argon) at 0.5 g catIt was introduced at a concentration of / L. Further, under an inert atmosphere, UV irradiation (UVA with a center of 370 nm) was carried out at room temperature (20 - 25 °C) for about 650 minutes. The gaseous products were monitored in the same manner as in Example 3, i.e., by kinetic monitoring using GC - FID and GC - PDHID, and by identification and calibration of the products using standards.

[0121] Results: After 600 minutes of irradiation, H2, CO2, ethylene C2H4, acetaldehyde CH3CHO, methane CH4, and trace amounts of CO and ethane were obtained.

[0122] Figure 4 shows the formation of these species over the irradiation time, and Figure 5 shows the selectivity obtained.

[0123] The results show excellent selectivity for ethylene compared to other C x H y O z products (x, y ≥ 1). The molar selectivities for ethylene and acetaldehyde are 51% and 38% respectively. Thus, ethylene is the majority of the C x H y O z (x, y ≥ 1) product.

[0124] Neither acetone nor ethyl acetate was detected.

Claims

1. Formula (I)R ａ - At least one carboxylic acid of formula (II) R in the COOH group ｂ A TiO2 system for obtaining at least one alkene from at least one alcohol of the -OH group by photocatalysis, wherein at least a portion of the surface is supported with a metal M and / or an oxide of metal M (where M is selected from the group including Cu, Zn, Fe, Mo, W, and Ni). ２ The use of particles consisting of or containing, where R ａ and R ｂ The group used may be independently selected from linear, branched, or cyclic alkyl groups and may be substituted with at least one group X selected from arenes, where X is in particular a phenyl group.

2. Formula (I) R ａ -COOH and / or at least one carboxylic acid of formula (II) R ｂ -OH, a method for obtaining at least one alkene, comprising supporting metal M and / or an oxide of metal M (M is selected from the group consisting of Cu, Zn, Fe, Mo, W and Ni) on at least a part of the surface, TiO ２ consisting of or comprising particles thereof, or in the presence of a catalyst comprising the same, subjecting at least one carboxylic acid and / or at least one alcohol to photocatalysis by UV and / or visible light irradiation in step (i), wherein R ａ and R ｂ are independently selected from linear, branched or cyclic alkyl groups and may be substituted with at least one group X selected from arenes, X being in particular a phenyl group.

3. -TiO ２ The particles consist of or contain such particles, and the maximum number average dimension of the particles is 1 to 100 nm; and / or -TiO ２ The method according to claim 2, wherein the particles, consisting of or containing the, are spherical, spheroidal, rod-shaped, wire-shaped, tubular, and / or platelet-shaped, and the particles are optionally arranged in a chain.

4. The TiO ２ The method according to claim 2, wherein the substance is in the form of anatase, rutile, or a mixture of anatase and rutile, and the anatase / rutile ratio is 0.80 to 2.

33.

5. -TiO ２ The content of metal M and / or oxides of metal M relative to is 0.01 to 50% by mass; and / or - The metal M and / or an oxide of the metal M are at least TiO ２ The method according to claim 2, wherein the particles consist of or contain the same, and exist on the surface of the particles in the form of particles having a maximum number average particle size of 0.1 to 50 nm.

6. The method according to claim 2, for obtaining at least one alkene from at least one carboxylic acid, particularly propanoic acid, acetic acid, phenylpropanoic acid, n-butyric acid, n-valeric acid or pivalic acid, or from at least one alcohol which is ethanol or cyclohexanol, and / or the at least one alkene is ethylene.

7. Step (i) is, - In an atmosphere containing less than 1% oxygen by volume; - Under a nitrogen, helium and / or argon atmosphere; and / or - In a nitrogen, helium and / or argon atmosphere, in a flow of 1 to 500 mL / min; or - The method according to claim 2, which is carried out in the absence of a continuous flow of inert gas.

8. The method according to claim 2, wherein the at least one carboxylic acid and / or the at least one alcohol is present in a composition further comprising a solvent, the solvent being water, and the concentration of one or more alcohols and / or one or more carboxylic acids in the composition being 0.0001% by volume or more and / or less than 100% by volume, or the at least one carboxylic acid and / or the at least one alcohol is not present in the presence of the solvent.

9. The method according to claim 2, wherein the catalyst is present in a composition comprising the at least one carboxylic acid and / or the at least one alcohol and the solvent, or in the absence of the solvent, in the at least one carboxylic acid and / or the at least one alcohol, at a concentration of 0.01 to 50 g / L.

10. - Step (i) is carried out at a temperature of 10 to 200°C, or 40 to 200°C, and / or - The method according to claim 2, wherein the irradiation is UV-A, UV-B, UV-C and / or visible light irradiation with a wavelength of 350 to 400 nm.

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