Catalysts, preparation methods and applications for photothermal catalytic methane coupling reaction

Abstract

This invention relates to a catalyst for photothermal catalytic methane coupling reaction, its preparation method, and its application. The catalyst comprises a titanium dioxide support and metal particles; the titanium dioxide support has anatase phase crystal structure; the metal particles, based on 100% of the total mass of the catalyst, have a mass percentage content greater than 0 and less than or equal to 0.12 wt%; the metal element in the metal particles is selected from Pd or Pt; the metal particles are loaded onto the titanium dioxide support via photodeposition, specifically: under an inert gas atmosphere, using methanol as a sacrificial agent, photogenerated electrons are used to reduce metal ions to zero-valent metal atoms in situ, which are then deposited on reduction sites on the surface of the titanium dioxide support. This invention's catalyst, by controlling the support crystal structure and metal-support interface, achieves efficient conversion of methane to ethane under mild conditions, avoiding over-oxidation, and exhibits excellent catalytic activity and stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal catalytic materials and energy chemical engineering, and specifically relates to a catalyst for photothermal catalytic methane coupling reaction, a preparation method thereof, and an application thereof. Background Technique

[0002] In the context of the global energy structure transformation towards low-carbon and clean energy and the continuous promotion of the "dual-carbon" goal, greenhouse gas emission reduction and efficient resource utilization have become the core research topics in the fields of energy chemical engineering and catalytic science. Methane (CH4), as the main component of natural gas, is a clean energy source with abundant reserves. Compared with oil and coal, natural gas produces fewer pollutants such as sulfur dioxide and nitrogen oxides during combustion, and has a higher calorific value, so it has become the cleanest fossil energy. However, methane is also the second-largest greenhouse gas after carbon dioxide, and its global warming potential on a centennial time scale is about 28 times that of CO2, and even as high as 81 times on a twenty-year time scale. Effective control and resource utilization of methane emissions are of great significance for alleviating global climate change and promoting the low-carbon transformation of the energy system.

[0003] From the perspective of chemical industry, methane is not only an energy carrier, but also an ideal carbon- and hydrogen-containing basic raw material. As a crucial C1 basic unit in the chemical industry, converting methane into high-value-added multi-carbon chemicals is the "holy grail" of the chemical community. However, the methane molecular structure is highly symmetric, and its C-H bond energy is as high as 438 - 439 kJ·mol -1 , with extremely high thermodynamic and kinetic stability, making it difficult to be activated under mild conditions. Traditional methane conversion processes mostly rely on high-temperature thermal (700 - 1000 °C or >1 MPa) catalytic paths, which not only consume huge amounts of energy, but also easily cause problems such as carbon deposition, catalyst sintering, and loss of reaction selectivity, seriously restricting the sustainable development of related technologies. Therefore, exploring new catalytic paths that can achieve methane dehydrogenation coupling under mild conditions has important scientific value and engineering significance.

[0004] Among various methane activation reactions, the methane coupling reaction stands out because it can directly obtain valuable C2+ hydrocarbons. Currently, methane coupling reactions are mainly divided into two categories: oxidative coupling of methane (OCM) and non-oxidative coupling of methane (NOCM). OCM (4CH4 + O2→2C2H6 + 2H2O, = -320 kJ·mol -1 ), although more thermodynamically favorable, brings challenges due to the production of peroxidation by-products such as carbon dioxide due to the presence of oxygen. In contrast, NOCM (2CH4→2C2H6+ H2, = +68.6 kJ·mol -1This process generates ethane / long-chain alkanes and hydrogen without the need for an oxidant, avoiding over-oxidation. It boasts significant advantages such as high atom utilization, high carbon efficiency, and the production of clean hydrogen as a byproduct, making it considered one of the ideal reaction pathways for efficient methane utilization. The generated ethane can serve as an important chemical intermediate, further converting to ethylene through dehydrogenation, thus indirectly converting methane into high-value-added hydrocarbon chemicals. Therefore, developing efficient NOCM technology will significantly improve methane utilization efficiency. Group VIII transition metals exhibit excellent photo-driven catalytic performance and possess the unique ability to convert light energy into heat energy, indicating that transition metals can be utilized to design highly efficient photothermal-driven methane coupling catalysts. Noble metals such as gold, platinum, and palladium are often used as co-catalysts to modify photothermal catalysts and enhance photothermal catalytic methane coupling reactions.

[0005] Photothermal catalysis technology provides a novel energy supply method for methane conversion processes, distinct from traditional high-temperature thermocatalysis, by converting solar energy into a synergistic input of chemical and thermal energy. Compared to reaction systems that rely on overall high-temperature energy supply, photothermal catalysis can effectively activate methane under ambient temperature and pressure or medium-low temperature conditions, thereby significantly reducing reaction energy consumption and mitigating engineering problems caused by high-temperature operation, such as catalyst sintering, carbon deposition, and equipment load.

[0006] In the methane dehydrogenation coupling reaction, the photothermal catalytic pathway can directly generate ethane and hydrogen without the addition of an external oxidant. This not only improves carbon atom utilization efficiency but also produces clean hydrogen as a byproduct, demonstrating great potential. The technical route exhibits significant advantages in terms of mild reaction conditions, low carbon emission intensity, and high energy utilization efficiency, aligning with the development needs of green chemistry and "dual carbon" (carbon dioxide, carbon emissions, and carbon emissions). Therefore, the photothermal catalytic methane dehydrogenation coupling reaction provides an important technological reserve for constructing a new process for the high-value utilization of methane with low energy consumption and low emissions, and has promising application prospects.

[0007] Titanium dioxide (TiO2) has become one of the most widely used semiconductor materials in the field of photothermal catalysis due to its advantages such as good chemical stability, low cost, and non-toxicity and environmental friendliness. However, pure titanium dioxide has inherent defects: firstly, it has a wide band gap (about 3.2 eV), which can only respond to ultraviolet light, which accounts for less than 5% of solar energy, resulting in extremely low spectral utilization; secondly, the photogenerated electron-hole pair recombination rate is fast, and the carrier separation efficiency is low, which leads to its photothermal catalytic methane conversion efficiency remaining at a low level of μmol·g⁻¹ for a long time. -1 ·h -1 Thirdly, the surface active sites are limited to a single type, and the activity level of methane CH bonds is low (bond energy 438.8~439.3 kJ·mol⁻¹). -1 Its activation ability is limited, and the product selectivity is poor, making it prone to over-oxidation or deep dehydrogenation.

[0008] To improve the photothermal catalytic performance of titanium dioxide, existing technologies often employ strategies such as doping, constructing heterojunctions, or supporting metals. However, these approaches still have shortcomings: doping elements can easily lead to an increase in lattice defects, which in turn accelerates carrier recombination; heterojunction interfaces have poor compatibility and high charge transfer resistance; metal particles prepared by traditional supporting methods (such as impregnation and calcination) are unevenly dispersed, have large particle sizes, and exhibit weak interactions with the support, making them prone to detachment or aggregation, resulting in insufficient catalyst stability. Furthermore, existing methane dehydrogenation coupling catalysts generally suffer from low selectivity for the target product (ethane), demanding reaction conditions (requiring high temperature or high pressure), dependence on precious metals, and large quantities, making it difficult to meet the needs of industrial applications.

[0009] Based on this, a titanium dioxide-based photothermal catalytic material with simple preparation process, uniform metal dispersion, wide photoresponse range, high carrier separation efficiency, and excellent catalytic activity and stability is developed to achieve efficient dehydrogenation coupling conversion of methane under mild conditions. This invention is proposed. Summary of the Invention

[0010] The purpose of this invention is to provide a catalyst for photothermal catalysis of methane coupling reaction, in order to solve the problems of high energy consumption, easy deactivation at high temperature and low efficiency of existing titanium dioxide photocatalysts in traditional methane conversion.

[0011] The technical solution adopted by this invention to solve its technical problem is:

[0012] A catalyst for photothermal catalytic methane coupling reaction comprises a titanium dioxide support and metal particles; the titanium dioxide support is in the anatase phase; the metal particles, based on 100% of the total mass of the catalyst, have a mass percentage greater than 0 and less than or equal to 0.12 wt%; the metal element in the metal particles is selected from Pd or Pt; the metal particles are loaded onto the titanium dioxide support by photodeposition, specifically: under an inert gas atmosphere, using methanol as a sacrificial agent, photogenerated electrons are used to reduce metal ions to zero-valent metal atoms in situ, and the atoms are deposited on the reduction sites on the surface of the titanium dioxide support.

[0013] The catalyst described in this invention for photothermal catalytic methane coupling reaction can be used as a catalyst in photothermal catalytic methane coupling reaction, which can improve the conversion rate of raw materials and improve the selectivity of target products.

[0014] The catalyst of this invention is a titanium dioxide-supported metal catalyst, with the metal distributed on the surface of the titanium dioxide. The metal particles are basically uniformly distributed on the surface of the titanium dioxide.

[0015] Preferably, based on the total mass of the catalyst (100%), the mass percentage of the metal particles is 0.02 wt% to 0.08 wt%. More preferably, it is 0.04 wt% to 0.06 wt%.

[0016] A method for preparing the catalyst according to the present invention includes the following steps: S1: a titanium source is dropped into water, stirred, aged, washed, and dried, and then calcined in air at 300 ℃ to 800 ℃ to obtain the anatase phase titanium dioxide support; S2: using the titanium dioxide support obtained in S1 as a carrier, it is mixed with a metal precursor solution, a sacrificial agent, and water, and photodeposited under an inert gas atmosphere by irradiation with a light source and stirring; after deposition, it is washed and dried to obtain the catalyst; wherein the sacrificial agent is anhydrous methanol.

[0017] This invention employs photodeposition to reduce metal ions in a precursor solution into metals, which are then deposited onto the surface of titanium dioxide to enhance photoresistivity and thus exhibit excellent photothermal catalytic performance. This material benefits from the ionization of the metal precursor in the solution into metal cations. These cations capture photogenerated electrons on the TiO2 surface and are reduced to zero-valent metal atoms. n+ + ne - (CB) → M 0 These metal atoms aggregate and nucleate at specific sites (such as defect sites and oxygen vacancies) on the TiO2 surface, eventually growing into nanoparticles. They generally have a narrow band gap or abundant surface defects, thus exhibiting a wide spectral absorption rate and good photogenerated carrier separation efficiency, ultimately demonstrating excellent photothermal catalytic performance.

[0018] This invention has found that in the preparation of titanium dioxide support, it is necessary to control the amount of water and the temperature range. If the amount of water and the temperature range are not within the scope of this invention, it will be detrimental to the formation of a catalyst for photothermal catalytic methane coupling.

[0019] This invention reveals that the calcination time, whether too short or too long, affects the formation of the anatase phase catalyst. Similarly, the photodeposition temperature, whether too high or too low, also influences the formed catalyst.

[0020] Preferably, in step S1, the titanium source is tetrabutyl titanate, and the volume ratio of the titanium source to water is 1:9-10; the titanium source is added to the water dropwise, and after the addition is complete, stirring is continued at room temperature and the mixture is allowed to stand for aging; the drying is carried out at a temperature below 100 ℃.

[0021] Preferably, in step S2, the solute in the metal precursor solution is selected from any one of chloroplatinic acid, palladium nitrate, ruthenium chloride, nickel nitrate, copper nitrate, and cobalt chloride; and the light source is a xenon lamp.

[0022] Preferably, in step S2, the volume ratio of the sacrificial agent to water is 1:5 to 1:15, preferably 1:9. Preferably, in step S2, the ratio of the titanium dioxide carrier, the sacrificial agent, and the water is: 100 mg of titanium dioxide carrier corresponds to 10 mL of anhydrous methanol and 90 mL of water.

[0023] Preferably, in step S1, the heating rate of calcination is 100 ℃ / h; in both steps S1 and S2, the washing is performed with deionized water until neutral.

[0024] Preferably, in step S1, the calcination temperature is 300℃~500℃ and the time is 1-2 hours.

[0025] Application of the catalyst described in this invention in the photothermal catalytic non-oxidative coupling reaction of methane.

[0026] Preferably, the application specifically includes: placing the catalyst in a photothermal catalytic reactor, introducing methane as the reaction gas, and carrying out the reaction under light source irradiation; the target products of the methane non-oxidative coupling reaction are ethane and hydrogen.

[0027] The beneficial effects of this invention are:

[0028] This invention abandons the traditional impregnation method and employs a photodeposition method using anhydrous methanol as a sacrificial agent under an inert gas atmosphere. Utilizing the extremely strong reducing power of photogenerated electrons in TiO2, metal ions in solution are reduced in situ to zero-valent metal atoms, which are then precisely and uniformly anchored at reduction sites (such as defect sites and oxygen vacancies) on the TiO2 surface. This unique preparation process creates a very strong interfacial interaction between the ultrafine metal nanoparticles and the TiO2 support, greatly promoting the spatial separation and directional migration of photogenerated carriers, thereby significantly improving the reaction efficiency of photothermal catalytic methane coupling to ethane.

[0029] This invention prepares a pure anatase-phase TiO2 support by strictly controlling the hydrolysis ratio of tetrabutyl titanate and a specific calcination temperature of 300 ℃ to 800 ℃. Compared with rutile phase, anatase TiO2 has a superior band structure and a higher specific surface area, which is more conducive to the separation of photogenerated electrons and holes. The synergistic effect of these two factors results in an ethane yield (up to 1.66 μmol·g) of the catalysts of this invention (such as anatase Pd / TiO2). -1 It exhibits a precipitous lead over rutile catalysts (only 0.26 μmol·g). -1 This completely solved the problem of low efficiency caused by improper crystal form selection.

[0030] The catalyst of this invention achieves extremely high catalytic activity while its metal loading is strictly controlled within an ultra-low range of greater than 0 and less than or equal to 0.12 wt% (preferably, the Pd loading is only 0.04 wt% to 0.06 wt%). This ultra-low loading not only effectively avoids the agglomeration of metal particles and exposes more active edge sites, but also greatly reduces the cost of using precious metals. It breaks the industry's technical prejudice that high-efficiency catalysts must rely on high consumption of precious metals, and has extremely high economic benefits and industrial promotion value.

[0031] The catalyst of this invention fully utilizes the photothermal synergistic effect, enabling the non-oxidative coupling (NOCM) reaction of methane to be driven under mild conditions ranging from ambient temperature and pressure to low to medium temperatures. This process requires no external oxidant, fundamentally blocking the side reaction pathway of excessive methane oxidation to produce the greenhouse gas CO2, and exhibits high selectivity for the target product (ethane). Simultaneously, it produces clean hydrogen as a byproduct, with no carbon buildup, perfectly aligning with the principles of green chemistry and the global "dual carbon" goal. Attached Figure Description

[0032] Figure 1 This is the X-ray diffraction pattern of the catalyst prepared in Example 1 of this invention;

[0033] Figure 2 This is a SEM image of the catalyst prepared in Example 1 of this invention;

[0034] Figure 3 This is a TEM image of the catalyst prepared in Example 1 of this invention;

[0035] Figure 4 This is the X-ray diffraction pattern of the catalyst prepared in Example 2 of this invention;

[0036] Figure 5 This is a SEM image of the catalyst prepared in Example 2 of this invention;

[0037] Figure 6 This is the X-ray diffraction pattern of the catalyst prepared in Example 3 of this invention;

[0038] Figure 7 This is a SEM image of the catalyst prepared in Example 3 of this invention;

[0039] Figure 8 These are X-ray diffraction patterns of the catalysts prepared in Examples 4, 5, 6, 7, and 8 of this invention;

[0040] Figure 9 This is the X-ray diffraction pattern of the catalyst prepared in Comparative Example 1 of the present invention;

[0041] Figure 10This is the X-ray diffraction pattern of the catalyst prepared in Comparative Example 2 of the present invention;

[0042] Figure 11 This is a SEM image of the catalyst prepared in Comparative Example 2 of the present invention;

[0043] Figure 12 This is a TEM image of the catalyst prepared in Comparative Example 2 of the present invention;

[0044] Figure 13 This is a bar chart showing the ethane yield from the performance test of methane coupling to ethane. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0046] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0047] Unless otherwise specified, the reagents used in the following examples can be purchased from a regular biochemical reagent store.

[0048] <Analytical Methods>

[0049] The analytical methods or analytical devices used in the embodiments and comparative examples of the present invention are described below:

[0050] X-ray diffraction pattern: The image was obtained using a Rigaku SmartLab SE AutoMATE II X-ray powder diffractometer.

[0051] SEM images: A Regulus 8100 scanning electron microscope manufactured by HITACHI Corporation, Japan was used. Test conditions: After drying the sample, it was sputter-coated with gold to increase conductivity. The accelerating voltage of the analytical electron microscope was 20.0 kV, and the magnification was 30-110 K.

[0052] TEM image: A ThermoFisher Talos F200X field emission transmission electron microscope was used. Test conditions: The sample was dispersed in ethanol and dropped onto an ultrathin carbon film. The accelerating voltage of the analytical electron microscope was 20.0 kV, and the magnification was 1-20 K.

[0053] Elemental analysis: The metal atom content in the molecular sieve was determined using an Agilent 5110 inductively coupled plasma atomic emission spectrometer (ICP-OES). Prior to characterization, the samples were digested by acid dissolution at room temperature.

[0054] Example 1

[0055] Tetrabutyl titanate and deionized water were mixed and stirred at room temperature for 24 h, then allowed to stand for 24 h to allow for complete hydrolysis, yielding titanium dioxide precipitate. The volume ratio of tetrabutyl titanate to deionized water was 1:10. The obtained titanium dioxide precipitate was centrifuged, washed, dried at 80 °C, and calcined at 500 °C for 1 h in air at a heating rate of 100 °C / h to obtain TiO2.

[0056] Prepare 10 mL of 4 mM palladium nitrate solution. Weigh 7.09 mg of palladium precursor palladium nitrate dihydrate (Pd(NO3)2·2H2O) and dissolve it in 10 mL of deionized water by stirring at room temperature. Place 100 mg of titanium dioxide support, 189.83 μL of palladium nitrate solution, 10 mL of anhydrous methanol, and 90 mL of water in a photodeposition reactor. Stir at 200 r / min for 30 min with argon gas, and the photodeposition stirring time is 1 h. Wash the sample 6 times with deionized water. Dry the deposited sample in a forced-air drying oven. A Pd / TiO2 catalyst with a palladium loading of 0.04 wt% is obtained.

[0057] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 1 As shown, by Figure 1 The diffraction pattern shows that the catalyst is anatase titanium dioxide, with no characteristic diffraction peaks corresponding to palladium, indicating that the Pd content in the synthesized sample is low or that large Pd particles have not formed. Figure 2 and Figure 3 As can be seen, the catalyst obtained in this embodiment has a uniform morphology. The catalyst surface is smooth and free of obvious particulate matter. Metallic Pd nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.04 wt%.

[0058] Example 2

[0059] Except for the following parameters and settings, the rest are the same as in Example 1: the obtained titanium dioxide precipitate is centrifuged and washed, dried at 80°C, and calcined at 300°C for 1 h in air atmosphere at a heating rate of 100°C / h to obtain TiO2.

[0060] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 4 As shown, by Figure 4 It can be seen that the diffraction pattern shows anatase-phase titanium dioxide, without any characteristic diffraction peaks corresponding to palladium element. From Figure 5 It can be seen that the morphology of the obtained catalyst is uniform. The surface of the catalyst is smooth, without obvious particulate substances. Metal Pd nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. By elemental analysis, the content of metal Pd element in the catalyst is 0.04 wt%.

[0061] Example 3

[0062] Except for the following parameters and settings, the rest are the same as in Example 1: The obtained titanium dioxide precipitate was centrifuged and washed, dried at 80 °C, and calcined at 800 °C for 1 h in an air atmosphere at a heating rate of 100 °C / h to obtain TiO2. 100 mg of titanium dioxide support, 142.37 μL of palladium nitrate solution, 10 mL of anhydrous methanol, and 90 mL of water were placed in a photoreduction reactor, argon was passed for 30 min, the stirring speed was 200 r / min, and the photoreduction stirring time was 1 h;

[0063] The X-ray diffraction pattern of the catalyst prepared in this example is as Figure 6 shown. From Figure 6 It can be seen that the diffraction pattern shows rutile-phase titanium dioxide, without any characteristic diffraction peaks corresponding to palladium element. From Figure 7 It can be seen that the morphology of the obtained catalyst is uniform. The surface of the catalyst is smooth, without obvious particulate substances. Metal Pd nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. By elemental analysis, the content of metal Pd element in the catalyst is 0.06 wt%.

[0064] Example 4

[0065] Except for the following parameters and settings, the rest are the same as in Example 1: 10 mL of 0.0413 M chloroplatinic acid solution was prepared, 0.2134 g of platinum precursor chloroplatinic acid hexahydrate was weighed and placed in 10 mL of deionized water, and it was stirred at room temperature until fully dissolved. 100 mg of titanium dioxide support, 14.26 μL of chloroplatinic acid solution, 10 mL of anhydrous methanol, and 90 mL of water were placed in a photoreduction reactor, argon was passed at a flow rate of 80 mL / min for 30 min, the photoreduction stirring and illumination were with a xenon lamp source, and it was stirred at a constant speed for 1 h; the washing was carried out 6 times with deionized water; the deposited sample was dried in a blast drying oven. A Pt / TiO2 catalyst with a platinum loading of 0.09 wt% was prepared.

[0066] The X-ray diffraction pattern of the catalyst prepared in this example is as Figure 8 shown. From Figure 8The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to platinum, indicating a uniform catalyst morphology. The catalyst surface is smooth and free of obvious particulate matter. Metallic Pt nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. Elemental analysis revealed that the content of metallic Pt in the catalyst is 0.09 wt%.

[0067] Example 5

[0068] Except for the following parameters and settings, the rest are the same as in Example 1: Prepare 150 mL of 858.4 mg / 150 mL ruthenium chloride solution, weigh 0.8584 mg of ruthenium chloride precursor, and place it in 150 mL of deionized water, stirring until fully dissolved at room temperature. Place 100 mg of titanium dioxide support, 13.44 μL of ruthenium chloride solution, 10 mL of anhydrous methanol, and 90 mL of water in a photodeposition reactor, purge with argon gas at a rate of 80 mL / min for 30 min, use a xenon lamp as the photodeposition illumination, and stir at a constant speed for 1 h; the washing is performed by washing 6 times with deionized water; dry the deposited sample in a forced-air drying oven. A Ru / TiO2 catalyst with a ruthenium loading of 0.05 wt% is obtained.

[0069] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 8 As shown, by Figure 8 The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to ruthenium. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter. Metallic Ru nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. Elemental analysis shows that the content of metallic Ru in the catalyst is 0.05 wt%.

[0070] Example 6

[0071] Except for the following parameters and settings, everything else is the same as in Example 1: Prepare 100 mL of 10.282 g / L nickel nitrate solution, weigh 1.0282 g of nickel precursor nickel nitrate hexahydrate (Ni(NO3)2·6H2O), and place it in 100 mL of deionized water, stirring until fully dissolved at room temperature. Place 100 mg of titanium dioxide support, 38.95 μL of nickel nitrate solution, 10 mL of anhydrous methanol, and 90 mL of water in a photodeposition reactor, purge with argon gas at a rate of 80 mL / min for 30 min, use a xenon lamp as the photodeposition illumination, and stir at a constant speed for 1 h; the washing is performed 6 times with deionized water; the deposited sample is dried in a forced-air drying oven. A Ni / TiO2 catalyst with a nickel loading of 0.03 wt% is obtained.

[0072] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 8 As shown, by Figure 8 The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to nickel. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter. Metallic Ni nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. Elemental analysis shows that the content of metallic Ni in the catalyst is 0.03 wt%.

[0073] Example 7

[0074] Except for the following parameters and settings, everything else is the same as in Example 1: Prepare 100 mL of 10.904 g / L copper nitrate solution. Weigh 1.0904 g of copper precursor copper nitrate trihydrate (Cu(NO3)2·3H2O), and place it in 100 mL of deionized water. Stir until fully dissolved at room temperature. Place 100 mg of titanium dioxide support, 52.83 μL of copper nitrate solution, 10 mL of anhydrous methanol, and 90 mL of water in a photodeposition reactor. Pour argon gas at a rate of 80 mL / min for 30 min. Use a xenon lamp as the photodeposition irradiation source and stir at a constant speed for 1 h. Wash the sample 6 times with deionized water. Dry the deposited sample in a forced-air drying oven. A Cu / TiO2 catalyst with a copper loading of 0.12 wt% is obtained.

[0075] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 8 As shown, by Figure 8 The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to copper. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter. Metallic Cu nanoparticles are uniformly distributed on the surface of the titanium dioxide support and at reduction sites. Elemental analysis shows that the content of metallic Cu in the catalyst is 0.12 wt%.

[0076] Example 8

[0077] Except for the following parameters and settings, everything else is the same as in Example 1: Prepare 50 mL of a 10.403 g / L cobalt chloride solution. Weigh 2.1 g of the cobalt precursor cobalt chloride hexahydrate (CoCl2·6H2O) and place it in 50 mL of deionized water. Stir until fully dissolved at room temperature. Place 100 mg of titanium dioxide support, 6.07 μL of cobalt chloride solution, 10 mL of anhydrous methanol, and 90 mL of water in a photodeposition reactor. Pour argon gas at a rate of 80 mL / min for 30 min. Use a xenon lamp as the photodeposition illumination source and stir at a constant speed for 1 h. Wash the sample 6 times with deionized water. Dry the deposited sample in a forced-air drying oven. A Co / TiO2 catalyst with a cobalt loading of 0.01 wt% is obtained.

[0078] The X-ray diffraction pattern of the catalyst prepared in this embodiment is as follows: Figure 8 As shown, by Figure 8 The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to cobalt. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter. Metallic Co nanoparticles are uniformly distributed on the reduction sites of the titanium dioxide support surface. Elemental analysis shows that the content of metallic Co in the catalyst is 0.01 wt%.

[0079] Comparative Example 1

[0080] Except for the following parameters and settings, everything else is the same as in Example 1: no palladium nitrate solution is added, and the titanium dioxide prepared in Example 1 is used directly.

[0081] The X-ray diffraction pattern of the catalyst prepared in this comparative example is shown below. Figure 9 As shown. By Figure 9 The diffraction pattern shows anatase titanium dioxide with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter.

[0082] Comparative Example 2

[0083] 100 mg of titanium dioxide prepared in Example 1 and 142.37 μL of palladium nitrate solution were mixed thoroughly by stirring at room temperature for 1 h. The resulting mixture of titanium dioxide and palladium nitrate solution was dried at 80 °C, and then reduced at 300 °C for 1 h under a hydrogen atmosphere with a heating rate of 100 °C / h. A Pd / TiO2 catalyst with a palladium loading of 0.06 wt% was obtained.

[0084] The X-ray diffraction pattern of the catalyst obtained in this comparative example is as follows: Figure 10 As shown, by Figure 10As can be seen, the diffraction pattern shows anatase titanium dioxide, with no characteristic diffraction peaks corresponding to palladium. The obtained catalyst has a uniform morphology, a smooth surface, and no obvious particulate matter. Metallic Pd nanoparticles are uniformly distributed on the surface of the titanium dioxide support. Elemental analysis shows that the content of metallic Pd in ​​the catalyst is 0.06 wt%.

[0085] The SEM image of the catalyst prepared in this embodiment is shown below. Figure 11 TEM image Figure 12 .

[0086] Application Example - Used for photothermal catalytic methane coupling reaction

[0087] The catalysts of Examples 1, 2, 3, 4, 5, 6, 7, 8 and Comparative Examples 1 and 2 were used to test the photothermal catalytic methane coupling reaction.

[0088] The specific test conditions were as follows: 5 mg of catalyst was dispersed in 0.5 mL of water and dropped onto FTO glass using a dropper. The sample was dried at 60 °C. The FTO loaded with catalyst was placed in a photothermal catalytic reactor. Methane was then introduced into the reactor as a reaction gas. The reactor was then placed under a PLS-SMR300 xenon lamp light source with a focusing plate and a current of 15 A. The reaction was carried out for 6 h under these conditions.

[0089] The reaction temperature for Examples 1, 2, 3, 4, 5, 6, 7, 8 and Comparative Examples 1 and 2 was 150°C, and the reaction time was 6 h.

[0090] Detection method: Samples were taken after the reaction was completed, and the composition of the products was analyzed by gas chromatography. The yield of ethane was then calculated. Results are shown below. Figure 13 .

[0091] Depend on Figure 13 As shown, under the same photothermal catalytic reaction conditions, the catalysts prepared in Examples 1-8 and Comparative Examples 1-2 were tested for their methane coupling to ethane production performance. The results showed that different catalysts had significant differences in ethane production.

[0092] Examples 1-3 are palladium-supported titanium dioxide catalysts, wherein the ethane yields of the anatase Pd / TiO2 catalysts prepared in Examples 1 and 2 are 1.66 μmol·g. -1 and 1.20 μmol·g -1 This is significantly higher than the 0.26 μmol·g of the rutile Pd / TiO2 catalyst in Example 3. -1 This indicates that the crystal structure of the titanium dioxide support has a significant impact on the photothermal catalysis of the methane coupling reaction, and that anatase titanium dioxide is more conducive to the occurrence of this reaction.

[0093] To investigate the effects of different metals, Examples 4-8 used Pt, Ru, Ni, Cu, and Co as loading metals for comparison. The experimental results show (see...) Figure 13 The ethane yields of these metal-supported catalysts were all significantly lower than those of the palladium (Pd)-supported catalyst in Example 1. Notably, the catalytic activity of Ru, Ni, Cu, and Co supported (Examples 5-8) was even lower than that of the unsupported pure titanium dioxide support (Comparative Example 1), indicating that not all transition metals can promote this photothermal catalytic reaction. This strongly demonstrates that Pd metal possesses unique catalytic activity in this specific support and reaction system, which is crucial for achieving efficient methane coupling.

[0094] Further comparison of Example 1 and Comparative Example 2 reveals that although the palladium loading in Example 1 is lower than that in Comparative Example 2, and no obvious palladium metal characteristic diffraction peaks were detected by XRD, the ethane yield of the Pd / TiO2 catalyst prepared by photodeposition (Example 1) was significantly higher than that of the Pd / TiO2 catalyst prepared by the conventional impregnation method (Comparative Example 2). This indicates that photodeposition is more conducive to constructing a highly efficient metal-support interface structure, thereby significantly improving the catalytic performance of the photothermal catalytic methane coupling reaction. This invention, by controlling the crystal phase of the titanium dioxide support and using photodeposition to load palladium metal, can significantly improve the reaction efficiency of photothermal catalytic methane coupling to ethane, demonstrating significant technical effects and application advantages.

[0095] To determine the actual metal loading of all catalysts, ICP-OES analysis was performed. As shown in Table 1, ICP testing revealed different actual metal loadings during photodeposition, possibly due to variations in affinity and interfacial bonding between the metals and the titanium dioxide support. Although the Pd / TiO2 catalyst prepared by impregnation (Comparative Example 2) had a slightly higher palladium content, its ethane production was lower than that of the catalyst prepared by photodeposition (Example 1), indicating that catalytic performance is not determined by metal loading but is closely related to the metal-support interface structure. Catalysts prepared by different methods but with similar Pd loadings exhibited significantly different catalytic performances. Furthermore, compared to rutile titanium dioxide, anatase titanium dioxide is more conducive to the separation and migration of photogenerated carriers, thereby significantly improving the photothermal catalytic performance of methane coupling.

[0096] Table 1

[0097]

[0098] In summary, the catalyst of this invention achieves efficient conversion of methane to ethane under mild conditions by controlling the crystal form of the support and the metal-support interface, while avoiding excessive oxidation, and exhibits excellent catalytic activity and stability.

[0099] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A catalyst for photothermal catalytic methane coupling reaction, characterized in that, The catalyst comprises a titanium dioxide support and metal particles; the titanium dioxide support has an anatase phase crystal structure; the metal particles, based on the total mass of the catalyst (100%), have a mass percentage content greater than 0 and less than or equal to 0.12 wt%; the metal element in the metal particles is selected from Pd or Pt; the metal particles are loaded onto the titanium dioxide support by photodeposition, specifically: under an inert gas atmosphere, using methanol as a sacrificial agent, photogenerated electrons are used to reduce metal ions to zero-valent metal atoms in situ, and deposited on the reduction sites on the surface of the titanium dioxide support.

2. The catalyst according to claim 1, characterized in that, Based on the total mass of the catalyst being 100%, the mass percentage of the metal particles is 0.02 wt% to 0.08 wt%.

3. A method for preparing the catalyst as described in claim 1, characterized in that, The method includes the following steps: S1: Titanium source is dropped into water, stirred, aged, washed, and dried, and then calcined in air at 300 ℃~800 ℃ to obtain the anatase phase titanium dioxide support; S2: Using the titanium dioxide support obtained in S1 as a carrier, it is mixed with a metal precursor solution, a sacrificial agent, and water, and photodeposited under an inert gas atmosphere by irradiation with a light source and stirring; after deposition, it is washed and dried to obtain the catalyst; wherein, the sacrificial agent is anhydrous methanol.

4. The preparation method according to claim 3, characterized in that, In step S1, the titanium source is tetrabutyl titanate, and the volume ratio of the titanium source to water is 1:9-10; the titanium source is added to the water dropwise, and after the addition is complete, stirring is continued at room temperature and the mixture is allowed to stand and age; the drying is carried out at a temperature below 100 ℃.

5. The preparation method according to claim 3, characterized in that, In step S2, the solute in the metal precursor solution is selected from any one of chloroplatinic acid, palladium nitrate, ruthenium chloride, nickel nitrate, copper nitrate, and cobalt chloride; the light source is a xenon lamp.

6. The preparation method according to claim 3, characterized in that, In step S2, the volume ratio of the sacrificial agent to water is 1:5 to 1:

15.

7. The preparation method according to claim 3, characterized in that, In step S2, the ratio of the titanium dioxide carrier, the sacrificial agent, and the water is: 100 mg of titanium dioxide carrier corresponds to 10 mL of anhydrous methanol and 90 mL of water.

8. The preparation method according to claim 3, characterized in that, In step S1, the heating rate of calcination is 100 ℃ / h; in both steps S1 and S2, the washing is performed with water until neutral.

9. The application of a catalyst as described in claim 1 or 2 in the photothermal catalytic non-oxidative coupling reaction of methane.

10. The application according to claim 9, characterized in that, The specific application includes: placing the catalyst in a photothermal catalytic reactor, introducing methane as the reaction gas, and carrying out the reaction under the irradiation of a light source; the target products of the methane non-oxidative coupling reaction are ethane and hydrogen.

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