Application of rare earth metal doped modified clay mesoporous composite as carrier of ethanol dehydrogenation catalyst

Abstract

The application belongs to the field of chemical catalysis technology, and specifically discloses application of a rare earth metal doped modified white clay mesoporous composite material as an ethanol dehydrogenation catalyst carrier. The preparation method of the rare earth metal doped modified white clay mesoporous composite material comprises the following steps: after alkali modification of active white clay powder, the active white clay powder is dispersed in silica sol, an aqueous solution of a rare earth metal salt is added dropwise, and then hydrothermal crystallization treatment and calcination treatment are performed to obtain the rare earth metal doped modified white clay mesoporous composite material. The modified white clay-mesoporous silica composite substrate is selected, and the rare earth metal is chemically bonded to the interface of the composite substrate to form an inlaid cross-linked multi-level pore network, thereby breaking through the limitation of a conventional porous carrier that relies on physical adsorption to load active metals. The prepared ethanol dehydrogenation catalyst reduces carbon deposition by virtue of the rare earth interface modification, greatly delays the rapid deactivation rate of the catalyst, significantly enhances the operation stability of the catalyst and prolongs the service life, and meets the needs of industrial continuous production.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalysis technology, specifically to the field of low-carbon alcohol dehydrogenation catalysts, and specifically relates to the application of rare earth metal-doped modified clay mesoporous composite materials as a catalyst support for ethanol dehydrogenation. Background Technology

[0002] Acetaldehyde is an important organic chemical intermediate, widely used in the production of organic compounds such as acetic acid, vinyl acetate, pentaerythritol, pyridine and its derivatives. It is also used as a basic raw material for manufacturing fine organic chemical products such as fragrances, dyes, and pharmaceuticals. With the growth of downstream demand, developing an economically feasible ethanol-to-acetaldehyde process has promising market prospects.

[0003] Currently, the main synthetic routes for acetaldehyde include ethylene oxidation, acetylene liquid-phase hydration, acetic acid reduction, ethane oxidation, and C3 / C4 alkane oxidative dehydrogenation. Among these, direct ethanol dehydrogenation is considered an important future route for acetaldehyde production, as ethanol, the raw material, has advantages such as large annual output, wide distribution, and renewability. This method offers advantages such as simple process, easy product separation, high atom economy, and few side reactions, thus attracting the attention and research of scientists. Traditional catalyst systems used in the direct dehydrogenation of ethanol, such as Au, Ag, and Au-Cu alloys, exhibit good performance, but their high cost limits large-scale industrial application. Although inexpensive copper can be used as the active component to reduce costs, copper-based catalysts suffer from poor acetaldehyde selectivity, low stability, and easy deactivation, making it difficult to meet the requirements of industrial production for efficient and stable catalysts.

[0004] In recent years, some researchers have attempted to optimize the catalytic performance of copper-based catalysts by controlling the type and structure of the support, thereby applying them to the catalytic dehydrogenation of ethanol to acetaldehyde. For example, using oxides (such as SiO₂)... 2、 Catalysts such as copper-based catalysts (e.g., Al2O3), Cu-mesoporous carbon, Cu / C / SiC, and Pt-Cu-molecular sieves, while exhibiting good catalytic activity in ethanol dehydrogenation, deactivate within tens of hours due to poor stability, making them unsuitable for industrial production. Cu / ZrO2 catalysts, when applied to ethanol dehydrogenation, achieve 81% selectivity for ethyl acetate, but not for the target product acetaldehyde, which clearly does not meet the reaction requirements for acetaldehyde production from ethanol dehydrogenation. Although the aforementioned supports provide high active sites, poor diffusion effects of reactants and products during the reaction result in low acetaldehyde selectivity. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the existing technology by providing a rare earth metal-doped modified clay mesoporous composite material as a catalyst support for ethanol dehydrogenation. This invention uses a modified clay-mesoporous silica composite substrate, where rare earth metals are chemically bonded to form an embedded cross-linked hierarchical porous network at the substrate interface. This overcomes the limitation of conventional porous supports relying on physical adsorption to load active metals. The prepared ethanol dehydrogenation catalyst, through rare earth interface modification, reduces carbon deposition and significantly improves the catalyst's operational stability.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: The preparation method of rare earth metal doped modified clay mesoporous composite material includes the following steps: S1. Add activated clay powder to an alkaline aqueous solution and stir at 50-70℃ for 1-3.5 hours to obtain alkali-modified clay; S2. Disperse the template agent in ethanol, add ammonia to adjust the pH to 9-11, slowly add the silicon source, and stir continuously for 3-5 hours to obtain silica sol; S3. Disperse the alkali-modified clay in the silica sol to form alkali-modified clay. A silica sol suspension system was prepared by adding an aqueous solution of rare earth metal salts dropwise into the suspension system and stirring at 30-50℃ for 5-7 hours. The resulting slurry was then transferred to a hydrothermal reactor and hydrothermally crystallized at 100-120℃ for 20-28 hours. The resulting solid product was washed, dried, and then calcined in a muffle furnace to obtain a rare earth metal-doped modified clay mesoporous composite material.

[0007] According to the above scheme, in step S1, the alkaline aqueous solution is either ammonia or an organic alkali aqueous solution. When ammonia is used, its concentration is 10-15 mol / L, and the mass ratio of activated clay to ammonia is 1:(5-25). When an organic alkali aqueous solution is used, its concentration is 0.2-1.0 mol / L, and the mass ratio of activated clay to organic alkali is 1:(10-25). The organic alkali is at least one of tetraethylammonium hydroxide (TEAOH) or tetrapropylammonium hydroxide (TPAOH). By controlling the amount of activated clay added and the concentration of the alkaline aqueous solution, impurities are dissolved to improve the purity of the clay and achieve the effect of pore expansion.

[0008] According to the above scheme, in step S2, the template agent is one or more of the following: hexadecyltrimethylammonium bromide (CTAB), polyethylene oxide-polypropylene oxide block copolymer (P123), sodium dodecylbenzenesulfonate (SDBS), polyvinylpyrrolidone (PVP, K90); and the silicon source is one or more of the following: methyl orthosilicate (TMOS), ethyl orthosilicate (TEOS), propyl orthosilicate (TPOS).

[0009] According to the above scheme, in step S2, the mass ratio of template agent, ethanol and silicon source is 1:(50-70):(0.5-4).

[0010] According to the above scheme, in step S3, the rare earth metal salt is one or more of cerium nitrate, lanthanum nitrate, scandium nitrate, etc.; the concentration of the aqueous solution of the rare earth metal salt is 3-8 mg / mL.

[0011] According to the above scheme, in step S3, the mass ratio of alkali-modified clay, silica sol and rare earth metal salt is 1:(2-10):(0.02-1); the calcination conditions are that the muffle furnace is heated at a rate of 4-6℃ / min to 500-600℃ and calcined for 4-6 hours.

[0012] Based on the above, the present invention provides a copper-based catalyst for the dehydrogenation of ethanol to acetaldehyde, comprising the rare earth metal-doped modified clay mesoporous composite material (as a support), and an active component Cu supported on the support; wherein the loading of the active component Cu is 3-15% of the total mass of the catalyst, with the remainder being the support. Further, the loading of the active component Cu is preferably 6-10 wt% of the total mass of the catalyst.

[0013] The above-mentioned copper-based catalyst for the dehydrogenation of ethanol to acetaldehyde was prepared by the ammonia stripping method. The specific preparation method is as follows: (1) Weigh out copper salt and mix it with ammonia and alcohol to prepare a copper ammonia alcohol solution; (2) The rare earth metal doped modified clay mesoporous composite material is completely immersed in the above copper ammonia solution, placed in an oil bath at 40-60℃ for 1.5-2.5 hours to evaporate ammonia, then the temperature is raised to 75-85℃ and the evaporation continues for 2-4 hours until the pH of the system is less than 8, then the evaporation ends. (3) The solid product after ammonia stripping is filtered, dried and calcined to obtain the copper-based catalyst for ethanol dehydrogenation to acetaldehyde.

[0014] According to the above scheme, the copper salt is any one or a mixture of several soluble copper salts such as copper nitrate, copper chloride, and copper acetate in any proportion; the alcohol is any one or a mixture of several methanol, ethanol, isopropanol, and butanol in any proportion.

[0015] According to the above scheme, the copper ammonia alcohol solution is formed by adding copper salt to a solvent alcohol and dissolving it, then adding ammonia water to adjust the pH to 9-11 and continuously stirring to form a copper ammonia complex solution; wherein, the concentration of copper salt added to the alcohol is 3-10 mg / mL.

[0016] According to the above scheme, the mass ratio of the modified clay mesoporous composite material to the copper amino alcohol solution is 1:(100-150).

[0017] According to the above scheme, the filtration and washing process involves filtration and water washing, the drying temperature is 60-80℃, and the time is 10-12 hours; the calcination temperature is 500-600℃, and the time is 4-6 hours.

[0018] In the above-mentioned method for preparing the copper-based catalyst for ethanol dehydrogenation to acetaldehyde, the theoretical loading of Cu species in the rare earth metal-doped modified clay mesoporous composite material can be controlled by controlling the concentration of the copper ammonia solution and the amount of rare earth metal-doped modified clay mesoporous composite material added.

[0019] A third aspect of this invention provides a method for using the aforementioned copper-based catalyst for ethanol dehydrogenation to acetaldehyde, specifically comprising: packing the copper-based catalyst for ethanol dehydrogenation to acetaldehyde into a fixed-bed reactor, reducing it under a reducing atmosphere to obtain an activated catalyst; then, under dehydrogenation reaction conditions, ethanol is vaporized and carried by a carrier gas into the solid-bed reactor, where it is dehydrogenated to produce acetaldehyde under the action of the activated catalyst. The carrier gas is an inactive gas and will not chemically react with the catalyst, ethanol, or acetaldehyde.

[0020] Furthermore, in the specific application method, the reducing atmosphere is a mixture of H2 / N2 gas, with a volume ratio of H2 to N2 of 1:(8-10); the reduction is carried out at 250-300℃ for 2-5 hours.

[0021] Furthermore, in the specific application method, the reaction conditions are: atmospheric pressure, liquid hourly space velocity 2.0-3.6 h⁻¹. -1 Temperature 200-280℃.

[0022] Compared with the prior art, the technical effects of the present invention are as follows: 1. This invention uses rare earth metal-doped modified clay mesoporous composite material as a catalyst support for ethanol dehydrogenation. First, modified clay-mesoporous silica is selected as the composite substrate. Rare earth metals are chemically bonded to the interface of the composite substrate to form an embedded cross-linked hierarchical porous network, which breaks through the limitation of conventional porous supports relying on physical adsorption to load active metals. Moreover, the rare earth metals are site-specifically bonded and modified at the interface of the modified clay-mesoporous silica two-phase system to construct oxygen vacancy synergistic sites and reduce carbon deposition during dehydrogenation.

[0023] 2. This invention uses a rare-earth metal-doped modified clay mesoporous composite material as a catalyst support for ethanol dehydrogenation. This material exhibits excellent pore accessibility, and through the synergistic effect of the mesoporous structure and hierarchical pore system, it significantly optimizes the molecular diffusion effect, efficiently promoting the entire process of reactant molecule diffusion, adsorption, decomposition, and desorption. When this rare-earth metal-doped modified clay mesoporous composite material is used as a catalyst support for loading active metal components, its unique confinement effect promotes high dispersion of active sites on the support surface and pore walls, thereby ensuring that the prepared ethanol dehydrogenation to acetaldehyde catalyst possesses excellent catalytic activity.

[0024] 3. This invention uses a rare-earth metal-doped modified clay mesoporous composite material as a support to prepare an ethanol dehydrogenation to acetaldehyde catalyst via an ammonia stripping method. Copper ammonia complex ions are chemically bonded to the rare-earth metal-doped modified clay mesoporous composite material, further strengthening the bond between copper species and the support. Simultaneously, this preparation method reduces the aggregation, sintering, and carbon deposition of copper nanoclusters during the reaction, significantly slowing down the rapid deactivation rate of the catalyst, significantly enhancing its operational stability and extending its service life, thus enabling the catalyst to better meet the needs of continuous industrial production applications.

[0025] 4. The copper-based catalyst for ethanol dehydrogenation to acetaldehyde provided by this invention has significant advantages in terms of preparation and usage costs. The preparation conditions are mild, the synthesis steps are easy to control, and the product reproducibility is excellent. When this catalyst is applied to a fixed-bed reactor for the direct dehydrogenation of ethanol to acetaldehyde, it exhibits excellent dehydrogenation performance with an acetaldehyde selectivity of up to 95%, and has high industrial application prospects and value. Attached Figure Description

[0026] Figure 1 This is a scanning electron microscope image of the rare earth metal-doped modified clay mesoporous composite material prepared in Example 1 of this invention.

[0027] Figure 2 (a) is a diagram showing the N2 isothermal adsorption-desorption of the rare earth metal-doped modified clay mesoporous composite material prepared in Example 1 of this invention, and (b) is a diagram showing the average pore size distribution.

[0028] Figure 3 This is a comparison of the Fourier transform infrared spectra of the rare earth metal-doped modified clay mesoporous composite material prepared in Example 1 of this invention and the modified clay.

[0029] Figure 4 The stability test curve of the copper-based catalyst prepared in Example 1 of this invention for the dehydrogenation of ethanol to acetaldehyde is shown. Detailed Implementation

[0030] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0031] In the following examples and comparative examples, the specific surface area, pore volume, and pore size distribution of the samples were determined using the BET method; microstructure characterization was performed on a field emission scanning electron microscope (SEM) model JSM 6510LV purchased from Beijing Euroton Optical Technology Co., Ltd.; and Fourier transform infrared spectroscopy analysis was performed on an infrared spectrometer model Nicolet Is10 purchased from Thermo Fisher Scientific.

[0032] In the following examples and comparative examples, the formulas for calculating ethanol conversion, ethanol selectivity, and single-pass yield are as follows: ; ; .

[0033] Example 1 (1) A method for preparing rare earth metal-doped modified clay mesoporous composite materials, specifically including the following steps: S1. Weigh 1g of activated clay powder and fully disperse it in 10g of 10mol / L ammonia solution. Stir at 50℃ for 3.5 hours for modification treatment. After filtration and washing, the solid powder is dried, which is alkali-modified clay.

[0034] S2. Weigh 1g of cetyltrimethylammonium bromide (CTAB) and dissolve it in 50g of ethanol. Add 10mol / L ammonia solution to adjust the pH to 10. Add 0.5g of tetraethyl orthosilicate (TEOS) dropwise and stir continuously for 5 hours to obtain silica sol.

[0035] S3. Take 5g of alkali-modified clay and disperse it in the above 10g silica sol. Then slowly add 20mL of cerium nitrate aqueous solution with a concentration of 5mg / mL. Stir vigorously at a constant temperature of 40℃ for 6 hours. Transfer the resulting slurry to a hydrothermal reactor and hydrothermally crystallize at 100℃ for 24 hours. Cool and filter out the solid product. Wash it three times with deionized water and dry it at 60℃ for 12 hours. Then transfer it to a muffle furnace and heat it to 500℃ at a rate of 5℃ / min. Calcine it for 6 hours to obtain rare earth metal doped modified clay mesoporous composite material.

[0036] Tests showed that the specific surface area of ​​the above-mentioned rare earth metal-doped modified clay mesoporous composite material is approximately 478.9 m². 2 / g, average pore volume is 0.4 cm³. 3 / g.

[0037] Figure 1 This is a SEM microstructure image of the rare earth metal-doped modified clay mesoporous composite material prepared in Example 1.

[0038] Figure 2 (a) is the N2 isotherm diagram of the rare earth metal-doped modified clay mesoporous composite material prepared in Example 1 of this invention. The curve shows that the composite material has significant nitrogen adsorption-desorption capacity. (b) is its average pore size distribution diagram. Figure 2 It can be seen that the pore size of the composite material is mainly distributed between 3.6 nm and 19.2 nm. The synergistic effect of the mesoporous structure and the hierarchical pore system can accelerate the diffusion rate of reactants in the dehydrogenation reaction, ensure the stability of catalytic performance, and improve the selectivity of acetaldehyde.

[0039] Figure 3 This is a comparison of FTIR images of the rare earth metal-doped modified clay mesoporous composite material (a) and alkali-modified clay (b) prepared in Example 1. The images show that, compared to alkali-modified clay, the rare earth metal-doped modified clay mesoporous composite material (a) exhibits better performance in the 3450-3500 cm⁻¹ range. -1 The presence of more pronounced hydroxyl characteristic peaks at the specified wavelength indicates that the catalyst has a richer number of active binding sites, which helps to increase the copper loading and thus improve the reaction conversion rate. At the same time, it also helps to disperse the copper active centers and significantly extend the catalyst's lifespan.

[0040] (2) Preparation of catalyst for ethanol dehydrogenation to acetaldehyde A copper-based catalyst for the dehydrogenation of ethanol to acetaldehyde was prepared by loading copper onto the above-mentioned rare earth metal-doped modified clay mesoporous composite material through ammonia stripping. The specific preparation method is as follows: 1.0 g of copper nitrate was dispersed in 100 g of ethanol, and the pH was adjusted to 10 with 10 mol / L ammonia water to obtain a copper-amine alcohol solution. 3 g of rare earth metal-doped modified clay mesoporous composite material was completely dispersed in the 100 g copper-amine alcohol solution and reacted in an oil bath at 50 °C for 2 hours. The temperature was then raised to 80 °C, and ammonia was further evaporated until the pH of the mixture was less than 8. After ammonia evaporation, the mixture was washed with deionized water, and the filter cake was dried at 60 °C for 12 hours, then calcined at 500 °C for 6 hours to obtain a catalyst for the dehydrogenation of ethanol to acetaldehyde, wherein the active component Cu was loaded at approximately 10% of the total catalyst mass.

[0041] (3) Evaluation of the catalytic performance of the catalyst in online reduction and ethanol dehydrogenation reaction In this invention, the ethanol dehydrogenation to acetaldehyde reaction is carried out in a fixed-bed reactor. 1.0 g of the ethanol dehydrogenation to acetaldehyde catalyst is compressed into a tablet and loaded into the reactor. Reduction is performed in an atmosphere with a H2:N2 volume ratio of 1:10, a gas flow rate of 40 ml / min, and the temperature is increased from room temperature to 300°C at a rate of 5°C / min, maintained for 4 hours to obtain the activated catalyst. Then, the catalyst is further activated under atmospheric pressure and an ethanol liquid hourly space velocity of 3.6 h⁻¹. -1 At a temperature of 260℃, ethanol was vaporized and carried by nitrogen gas into a solid-bed reactor, where it was dehydrogenated to produce acetaldehyde under the action of the activated catalyst. Gas chromatography was used to analyze the products and obtain the ethanol conversion rate and acetaldehyde selectivity. The catalyst performance evaluation results are shown in Table 1.

[0042] Figure 4This is a stability test curve of the catalyst prepared in Example 1 of this invention for the dehydrogenation of ethanol to acetaldehyde, with a test duration of 500 hours. The results show that the catalyst has a stable activity level. Data fitting yielded an average acetaldehyde selectivity of y (average selectivity) = 94.73 ± 0.285x and an average ethanol conversion of y (average conversion) = 36.75 ± 0.247x. This not only demonstrates good ethanol conversion but also maintains a stable acetaldehyde selectivity of around 94%, significantly reduces reaction byproducts, and achieves an average yield of over 33% per pass, reflecting the excellent long-term operational stability of the catalyst.

[0043] Example 2-3 In the preparation of rare earth metal-doped modified clay mesoporous composite materials, the only difference between Example 2 and Example 1 is that 20g of a 0.3 mol / L tetraethylammonium hydroxide (TEAOH) aqueous solution is used as the alkali treatment agent in step S1; the only difference between Example 3 and Example 1 is that 15g of a 0.8 mol / L tetrapropylammonium hydroxide (TPAOH) aqueous solution is used as the alkali treatment agent in step S1. All other preparation processes, reagents, temperatures, and times are the same as in Example 1.

[0044] The preparation, reduction, and catalytic performance evaluation of the catalyst for the dehydrogenation of ethanol to acetaldehyde were carried out in accordance with Example 1.

[0045] Examples 4-7 In the preparation process of rare earth metal doped modified clay mesoporous composite materials, the only difference between Example 4 and Example 1 is that the template agent used in step S2 is sodium dodecylbenzenesulfonate (SDBS); the only difference between Example 5 and Example 1 is that the template agent used in step S2 is polyvinylpyrrolidone (PVP, K90); the only difference between Example 6 and Example 1 is that tetraethyl orthosilicate is replaced with methyl orthosilicate (TMOS); the only difference between Example 7 and Example 1 is that tetraethyl orthosilicate is replaced with propyl orthosilicate (TPOS).

[0046] The preparation, reduction, and catalytic performance evaluation of the catalyst for the dehydrogenation of ethanol to acetaldehyde were carried out in accordance with Example 1.

[0047] Examples 8-9 In the preparation process of rare earth metal doped modified clay mesoporous composite material, the only difference between Example 8 and Example 1 is that 20 mL of cerium nitrate aqueous solution with a concentration of 5 mg / mL is replaced with 20 mL of lanthanum nitrate aqueous solution with a concentration of 8 mg / mL; the only difference between Example 9 and Example 1 is that 20 mL of cerium nitrate aqueous solution with a concentration of 5 mg / mL is replaced with 20 mL of scandium nitrate aqueous solution with a concentration of 6 mg / mL.

[0048] The preparation, reduction, and catalytic performance evaluation of the catalyst for the dehydrogenation of ethanol to acetaldehyde were carried out in accordance with Example 1.

[0049] Examples 10-11 The rare earth metal doped modified clay mesoporous composite material was prepared according to the examples.

[0050] In the preparation of the catalyst for the dehydrogenation of ethanol to acetaldehyde, the only difference between Example 10 and Example 1 is that 0.55g of copper chloride is used instead of 1.0g of copper nitrate; the only difference between Example 11 and Example 1 is that 0.5g of copper acetate is used instead of 1.0g of copper nitrate. The reduction and catalytic performance evaluation of the catalyst were carried out in accordance with Example 1.

[0051] Comparative Example 1 This comparative example uses alkali-modified clay to compare with the example. The alkali-modified clay was prepared according to step S1 of Example 1.

[0052] A copper-modified clay catalyst for the dehydrogenation of ethanol to acetaldehyde was prepared by loading copper onto the aforementioned alkali-modified clay via ammonia stripping. The specific preparation method was as follows: 1.0 g of copper nitrate was dispersed in 100 g of ethanol, and the pH was adjusted to 10 with 10 mol / L ammonia water to obtain a copper-amine alcohol solution. 3 g of alkali-modified clay was completely dispersed in 100 g of the copper-amine alcohol solution, and the mixture was reacted in an oil bath at 50°C for 2 hours. The temperature was then raised to 80°C, and ammonia was stripped until the pH of the mixture was less than 8. After ammonia stripping, the mixture was washed with deionized water, and the filter cake was dried at 60°C for 12 hours, followed by calcination at 500°C for 6 hours to obtain the ethanol-acetaldehyde dehydrogenation catalyst. The reduction and catalytic performance evaluation of the catalyst were conducted according to Example 1.

[0053] Comparative Example 2 This comparative example uses a modified clay mesoporous composite material, which is compared with the example. The preparation method specifically includes the following steps: S1. Alkali-modified clay was prepared according to Example 1.

[0054] S2. Prepare silica sol according to Example 1.

[0055] S3. Disperse 5g of alkali-modified clay in the above 10g silica sol, and stir vigorously at a constant temperature of 40℃ for 6 hours; transfer the resulting slurry to a hydrothermal reactor, and hydrothermally crystallize at 100℃ for 24 hours. After cooling and filtration, the solid product is washed three times with deionized water, dried at 60℃ for 12 hours, and then transferred to a muffle furnace and heated to 500℃ at a rate of 5℃ / min for calcination for 6 hours to obtain the modified clay mesoporous composite material. The preparation, reduction, and catalytic performance evaluation of the ethanol dehydrogenation to acetaldehyde catalyst are carried out in accordance with Example 1.

[0056] The performance evaluation results of the ethanol dehydrogenation to acetaldehyde catalysts prepared in each embodiment are shown in Table 1.

[0057] Table 1

[0058] As shown in Table 1, compared with the comparative examples, the ethanol dehydrogenation to acetaldehyde catalyst prepared using the rare earth metal-doped modified clay mesoporous composite material described in this invention as a support, when applied to the direct dehydrogenation of ethanol to acetaldehyde, achieved excellent catalytic effects in both ethanol conversion and acetaldehyde selectivity. Furthermore, analysis of Example 1 and Comparative Examples 1 and 2 shows that when the catalyst support is a rare earth metal-doped modified clay mesoporous composite material, the catalyst effect is significantly improved. Examples 1, 4, 5, 6, and 7 reveal that when the template agent is hexadecyltrimethylammonium bromide (CTAB) and the silicon source is tetraethyl orthosilicate (TEOS), the catalyst performance is significantly improved. Comparison of Examples 1, 8, and 9 shows that different types of rare earth metals produce different electronic effects, leading to changes in conversion and selectivity; cerium nitrate exhibits relatively better catalytic effects. In addition, the test results of Examples 1, 10, and 11 show that copper nitrate is more suitable as a Cu precursor salt solution for preparing copper-based catalysts, which can optimize the distribution and dispersion of active sites, thereby improving the catalyst activity level.

[0059] Clearly, this invention effectively increases the specific surface area of ​​the rare earth metal-doped modified clay mesoporous composite material by controlling the material composition and ratio, thereby improving the pore structure and molecular diffusion effect of the mesoporous material. The introduction of rare earth metals effectively constructs oxygen vacancy cooperative sites, reducing carbon deposition and extending service life. Using this composite material as a carrier to load copper components, the resulting catalyst, even with a low metal loading, achieves excellent catalytic performance in the direct dehydrogenation of ethanol to acetaldehyde, exhibiting superior ethanol conversion and acetaldehyde selectivity.

[0060] The above are preferred embodiments of the present invention. If those skilled in the art are inspired by this and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. The application of rare earth metal-doped modified clay mesoporous composite materials as a catalyst support for ethanol dehydrogenation, characterized in that, The preparation method of the rare earth metal doped modified clay mesoporous composite material includes the following steps: S1. Add activated clay powder to an alkaline aqueous solution, heat and stir to obtain alkali-modified clay; S2. Disperse the template agent in ethanol, add ammonia to adjust the pH to 9-11, add the silicon source and stir continuously to obtain silica sol; S3. Disperse the alkali-modified clay in the silica sol, add an aqueous solution of rare earth metal salt dropwise and stir thoroughly. Then, after hydrothermal crystallization and calcination, a rare earth metal-doped modified clay mesoporous composite material is obtained.

2. The application of the rare earth metal-doped modified clay mesoporous composite material according to claim 1 as a catalyst support for ethanol dehydrogenation, characterized in that, In step S1, the alkaline aqueous solution is ammonia or an organic base aqueous solution, the heating temperature is 50-70℃, and the stirring time is 1-3.5 hours.

3. The application of the rare earth metal-doped modified clay mesoporous composite material according to claim 2 as a catalyst support for ethanol dehydrogenation, characterized in that, When using ammonia water, the concentration of ammonia water is 10-15 mol / L, and the mass ratio of activated clay powder to ammonia water is 1:(5-25); when using an organic base aqueous solution, the concentration of the organic base aqueous solution is 0.2-1.0 mol / L, and the mass ratio of activated clay powder to organic base aqueous solution is 1:(10-25); wherein, the organic base is tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

4. The application of the rare earth metal-doped modified clay mesoporous composite material according to claim 1 as a catalyst support for ethanol dehydrogenation, characterized in that, In step S2, the mass ratio of template agent, ethanol and silicon source is 1:(50-70):(0.5-4), and the stirring time is 3-5 hours.

5. The application of the rare earth metal-doped modified clay mesoporous composite material according to claim 1 as a catalyst support for ethanol dehydrogenation, characterized in that, In step S2, the template agent is one or more of hexadecyltrimethylammonium bromide, polyethylene oxide-polypropylene oxide block copolymer, sodium dodecylbenzenesulfonate, and polyvinylpyrrolidone; the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate.

6. The application of the rare earth metal doped modified clay mesoporous composite material according to claim 1 as a catalyst support for ethanol dehydrogenation, wherein in step S3, the mass ratio of alkali-modified clay, silica sol and rare earth metal salt is 1:(2-10):(0.02-1); the temperature for thorough stirring is 30-50℃, and the stirring time is 5-7 hours; the temperature for hydrothermal crystallization is 100-120℃, and the time is 20-28 hours.

7. The application of the rare earth metal doped modified clay mesoporous composite material according to claim 1 as a catalyst support for ethanol dehydrogenation, wherein in step S3, the rare earth metal salt is one or more of cerium nitrate, lanthanum nitrate, and scandium nitrate; the concentration of the aqueous solution of the rare earth metal salt is 3-8 mg / mL; and the calcination conditions are as follows: the temperature is increased to 500-600℃ at a rate of 4-6℃ / min in a muffle furnace, and calcined for 4-6 hours.

8. A copper-based catalyst for the dehydrogenation of ethanol to acetaldehyde, characterized in that, The rare earth metal doped modified clay mesoporous composite material described in claim 1 is used as a carrier to load the active component Cu.

9. The method for preparing the copper-based catalyst for ethanol dehydrogenation to acetaldehyde according to claim 8, characterized in that, Includes the following steps: (1) Weigh out copper salt and mix it with ammonia and alcohol to prepare a copper ammonia alcohol solution; (2) The rare earth metal doped modified clay mesoporous composite material is completely immersed in the above copper ammonia alcohol solution, placed in an oil bath at 40-60℃ for 1.5-2.5 hours to evaporate ammonia, then the temperature is raised to 75-85℃ and the ammonia is evaporated for 2-4 hours until the pH of the system is less than 8, then the ammonia evaporation is finished. (3) The solid product after ammonia stripping is filtered, dried and calcined to obtain the copper-based catalyst for ethanol dehydrogenation to acetaldehyde.

10. The method of using the copper-based catalyst for ethanol dehydrogenation to acetaldehyde according to claim 8, characterized in that, The copper-based catalyst for ethanol dehydrogenation to acetaldehyde was packed into a fixed-bed reactor and reduced under a reducing atmosphere to obtain an activated catalyst. Then, under dehydrogenation reaction conditions, ethanol was vaporized and carried into the fixed-bed reactor by a carrier gas, where it was dehydrogenated to produce acetaldehyde under the action of the activated catalyst.

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