A hierarchical porous Cu / SiO2 catalyst modified with carbon-metal oxide layers and reinforced with carbon fibers, its preparation method and application

Abstract

This invention provides a carbon-metal oxide layer-modified, carbon fiber-reinforced hierarchical porous Cu / SiO2 catalyst, its preparation method, and its applications, belonging to the field of catalyst technology. The catalyst contains 27%–30% copper, 7.3%–12.6% carbon, and 1%–3% total metal oxide content (based on metal content), with the remainder being SiO2. The catalyst surface contains a carbon-metal oxide layer with a thickness of 1 nm–2 nm. The catalyst exhibits a hierarchical porous distribution and a specific surface area of ​​180 m². 2 / g~320 m 2 / g, pore volume 0.31cm 3 / g~0.45cm 3 The catalyst exhibits a pore size distribution in two ranges: 2 nm to 10 nm and 30 nm to 120 nm. This invention's catalyst effectively inhibits sintering and carbon deposition of the active component, effectively improves the activity and selectivity of cyclohexanone dehydrogenation to produce cyclohexanone and other alcohols, while extending the catalyst's lifespan.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst, its preparation method and application. Background Technology

[0002] Cu-based catalysts are an important and widely used class of catalysts in alcohol dehydrogenation reactions. They work through active sites (such as Cu). 0 Cu + Cu-based catalysts promote the breaking of CH and OH bonds in alcohols, achieving dehydrogenation. Under the action of Cu-based catalysts, primary alcohols can be dehydrogenated to the corresponding aldehydes, such as methanol dehydrogenation to formaldehyde, ethanol dehydrogenation to acetaldehyde, and n-butanol dehydrogenation to butyraldehyde; secondary alcohols can be dehydrogenated to the corresponding ketones, such as isopropanol dehydrogenation to acetone, cyclohexanol dehydrogenation to cyclohexanone, and phenylethanol dehydrogenation to acetophenone; diols can be dehydrogenated to hydroxy aldehydes, lactones, or diketones, such as 1,2-propanediol dehydrogenation to hydroxyacetone and methylglyoxal, 1,4-butanediol dehydrogenation to γ-butyrolactone, and ethylene glycol dehydrogenation to glycolaldehyde and glyoxal. The research and development of highly efficient Cu-based catalysts has always attracted much attention.

[0003] Taking cyclohexanone dehydrogenation as an example, cyclohexanone is an important intermediate in the production of caprolactam and adipic acid, and its downstream applications include the synthesis of nylon 6 (PA6) and nylon 66 (PA66). Cyclohexanone is also used in the pharmaceutical field as a raw material for methadone, trihexyphenidyl hydrochloride, and ketoconazole. Currently, the industrial synthesis routes of cyclohexanone mainly focus on two methods: oxidative dehydrogenation of cyclohexanone and direct dehydrogenation of cyclohexanone. The direct dehydrogenation method of cyclohexanone has gradually become the mainstream method for industrial synthesis of cyclohexanone due to its advantages of not introducing additional oxidants, low cost, few byproducts, and simple operation.

[0004] In the 1970s, copper-based catalysts capable of direct dehydrogenation at low temperatures were gradually developed. Patent CN200810234492.5 reported a catalyst for the dehydrogenation of cyclohexanol to cyclohexanone, mainly comprising copper oxide, zinc oxide, and aluminum oxide, with rare metal compounds and alkali metal compounds serving as structural and active agents, respectively. CN200810234493.X reported a method for preparing a copper-zinc-aluminum catalyst by co-precipitating a mixed solution of copper nitrate, zinc nitrate, and aluminum nitrate with a precipitant and then modifying it with additives. CN201110210438.9 reported a catalyst for the dehydrogenation of cyclohexanol to cyclohexanone and its preparation method, with CuO, ZnO, and ZrO2 as the main components.

[0005] In recent years, Cu / SiO2 catalysts with superior performance have been reported. Patent CN 106890641 A reports a method for preparing a cyclohexanol dehydrogenation catalyst. First, a support (silica sol) is precipitated, then the precursors of the active component Cu and promoters (oxides of modulating promoters Na and K, and structural promoters Ce and Mn) are precipitated on the support, resulting in a copper-based catalyst with good cyclohexanone selectivity. Patent CN 112387288 B uses silica as a support and simultaneously supports a composite oxide of copper, zinc, and calcium, obtaining a copper-silicon catalyst that significantly improves cyclohexanone selectivity. Patent CN 108722498 A reports a method for expanding the pores of a silica support. By impregnating a copper ammonia solution onto the expanded silica support, a catalyst for the cyclohexanol dehydrogenation reaction is obtained, exhibiting high cyclohexanone selectivity. Patent CN 117504881 A provides a two-step preparation method combining silica alkaline etching and copper precipitation. This method can effectively increase the mesoporous specific surface area of ​​the support and the pore size of the catalyst, thereby improving the selectivity of cyclohexanone.

[0006] However, due to the low melting point of Cu (1083 °C), the corresponding Hüttig temperature (174 °C) and Tammann temperature (405 °C) are also relatively low. At the typical reaction temperature for alcohol dehydrogenation (200-300 °C), surface Cu atoms already exhibit high mobility. Small Cu nanoparticles aggregate into larger particles through surface migration or atom / particle migration, leading to a sharp decrease in the active specific surface area and a reduction in the number of active sites (especially coordinatingly unsaturated sites), resulting in irreversible degradation of catalyst activity. On the other hand, reactants such as alcohols or their dehydrogenation products (aldehydes, ketones) undergo excessive dehydrogenation, polymerization, and condensation side reactions on the catalyst surface, forming high molecular weight compounds that cover active sites, causing catalyst deactivation due to carbon deposition. This remains a significant challenge hindering the long-term reaction performance of catalysts. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by providing a carbon-metal oxide layer-modified, carbon fiber-reinforced hierarchical porous Cu / SiO2 catalyst, its preparation method, and its application. This invention effectively solves the problems of catalyst sintering and carbon deposition in the cyclohexanol dehydrogenation reaction of copper-based catalysts.

[0008] This invention is achieved through the following technical solution: According to the first aspect of the invention: A multi-level porous Cu / SiO2 catalyst modified with a carbon-metal oxide layer and reinforced with carbon fibers is provided. It is composed of copper, carbon, metal oxides and SiO2. Based on the total mass of the catalyst, the copper content is 27% to 30%, the carbon content is 7.3% to 12.6%, the total content of metal oxides is 1% to 3% based on metal content, and the remainder is SiO2. The metal oxide is an oxide of at least one metal selected from Mn, Ce, Ca, Mg and La.

[0009] Furthermore, the surface of the carbon-metal oxide layer-modified, carbon fiber-reinforced hierarchical porous Cu / SiO2 catalyst is a carbon-metal oxide layer with a thickness of 1 nm to 2 nm; this catalyst exhibits a hierarchical pore distribution and a specific surface area of ​​180 m². 2 / g~320 m 2 / g, pore volume 0.31cm 3 / g ~ 0.45cm 3 / g, exhibiting two pore size distributions: 2 nm to 10 nm and 30 nm to 120 nm.

[0010] Furthermore, the carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst tablet is a columnar structure with a height × diameter of (3 mm to 5 mm) × (3 mm to 5 mm) and a radial strength ≥300 N.

[0011] According to a second aspect of the invention: The preparation method of the carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst includes the following steps: Step 1: Dissolve copper nitrate trihydrate in an appropriate amount of deionized water under strong stirring at room temperature, and add a mixture of ammonia, ammonium citrate, ammonium carbonate and urea. Stir at 20℃~40℃ for 30min~180min to form a copper ammonia mixed solution.

[0012] Step 2: Add silica sol and template agent to the copper-ammonia mixed solution prepared in Step 1, and continue stirring at 20℃~40℃ for 30min~180min. Raise the temperature to 65℃~105℃ for ammonia stripping treatment for 2h~30h. Filter off the solution, wash the precipitate with deionized water to remove impurities, and then dry it at 60℃~150℃ for 3h~24h. Calcine it in a muffle furnace at 400℃~600℃ for 3h~8h to obtain the copper-silicon catalyst precursor.

[0013] Step 3: Place the above copper-silicon catalyst precursor into a ball mill, and add silane coupling agent, anhydrous ethanol, metal additive, and asphalt to it. Ball mill the copper-silicon catalyst precursor, then dry it at 60℃~120℃ for 8h~24h, and calcine it in a muffle furnace at 300℃~550℃ for 2h~6h under the condition of oxygen content of 3%~10% to obtain catalyst powder.

[0014] Step 4: Add graphite powder, hydroxymethyl cellulose, and carbon fiber to the catalyst raw powder obtained by calcination, mix evenly, and then compress into tablets using a tablet press to obtain the tablet material.

[0015] Step 5: The tablet material obtained in Step 4 is loaded into an atmosphere furnace, and H2 / Ar mixed gas is introduced to raise the temperature and reduce it, thereby obtaining the carbon-metal oxide layer modified and carbon fiber reinforced multi-level porous Cu / SiO2 catalyst.

[0016] Furthermore, in step one of the above preparation method, the mass of copper nitrate trihydrate weighed per liter of the copper-ammonia mixed solution is 63.2 g to 96.5 g, the mass of ammonia water is 58.7 g to 87.8 g, the mass of ammonium citrate is 0.5 g to 20.8 g, the mass of ammonium carbonate is 0.5 g to 24.2 g, and the mass of urea is 1.5 g to 26.8 g.

[0017] Furthermore, in step two of the above preparation method, the silica sol used is a sodium-type silica sol with a SiO2 concentration of 28% to 30%, and the added mass is 11.9% to 13.2% of the mass of the copper ammonia mixed solution; the added template agent is PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride), with a diameter of 20 nm to 50 nm, and the added amount is calculated as 3 g to 25.2 g per liter of copper ammonia mixed solution; the preferred ammonia stripping temperature is 85℃ to 105℃, the preferred drying temperature is 110℃ to 130℃, and the preferred calcination temperature is 400℃ to 500℃.

[0018] Furthermore, in step three of the above preparation method, the metal additive is one of Mn, Ce, Ca, Mg, and La, added in the form of a nitrate of the metal additive, and the amount of metal added is 1.0% to 3.4% of the copper-silicon catalyst precursor; the silane coupling agent is one of γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane, added in an amount of 1% to 2% of the copper-silicon catalyst precursor; the asphalt is petroleum asphalt, added in an amount of 1.5% to 2.5% of the copper-silicon catalyst precursor; the amount of anhydrous ethanol added is 5% to 8.3% of the copper-silicon catalyst precursor; the drying temperature is preferably 100℃ to 120℃, the calcination temperature is preferably 400℃ to 500℃; and the oxygen content in the muffle furnace is preferably 3% to 8%.

[0019] Furthermore, in step four of the above preparation method, the amounts of graphite powder, hydroxymethyl cellulose, and carbon fiber added are 5%–8%, 6%–13%, and 2%–5% of the weight of the original catalyst powder, respectively.

[0020] Furthermore, in step five of the above preparation method, the temperature reduction conditions are: 200℃~350℃, H2:Ar=1:9~1:4 (LHSV=200h) -1 ~300h -1 Reduction was carried out under a certain atmosphere for 1.5 to 5 hours, followed by switching to pure H2 (LHSV = 150 h). -1 ~400h -1 Reduction time: 0.5h to 1.5h.

[0021] According to a third aspect of the invention: The application of the carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst in alcohol dehydrogenation reactions, especially in the dehydrogenation of cyclohexanol to cyclohexanone.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The preparation method of the copper-silicon catalyst precursor in this invention adopts the ammonia stripping method, and introduces ammonium citrate, ammonium carbonate and urea in the preparation process. On the one hand, ammonium ions are added, which increases the stability of the copper-ammonia complex and helps to form a unique layered copper silicate structure. On the other hand, the presence of various organic anions, with their steric hindrance effect, makes the layered copper silicate more dispersed. Finally, silicon and copper are connected by Si-O-Cu bonds, while the bonds between copper atoms are broken, forming a stable curved structure. This structure has a large specific surface area and a strong confinement effect, which is beneficial to the dispersion of copper species and their stability in the reaction process, and effectively inhibits the aggregation and growth of copper species.

[0023] (2) In this invention, the copper-silicon catalyst precursor is modified by adding metal additives, pitch, and silane coupling agents during ball milling and then calcining under low oxygen content to form a carbon-metal oxide layer. Specifically, the silane coupling agent is chemically bonded to the surface of the support to form an inorganic interface layer; the pitch penetrates under mechanical force and combines with the silane organic chain through hydrophobic interaction / π-π stacking to form an organic carbon precursor intermediate layer, which is transformed into an organic carbon film tightly bonded to copper silicate during calcination under low oxygen content. At the same time, the metal additives are decomposed into corresponding oxides by heating, which together with the organic carbon film form a surface modification layer. The presence of this modification layer, on the one hand, confines Cu species, further inhibiting the aggregation and growth of copper species; on the other hand, the metal oxide plays a role in modulating the surface properties, making the catalyst surface weakly alkaline, inhibiting carbon deposition and deactivation caused by the polymerization of alcohols, ketones, etc., present in acidic centers.

[0024] (3) In step two of the preparation method of this invention, a template agent is introduced. PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) can form a pore structure of 2 nm to 10 nm. Further, hydroxymethyl cellulose (CMC) is added during the tableting process in step four. The hydroxyl groups (-OH) and carboxymethyl groups (-CH2COOH) on the CMC molecular chain form hydrogen bonds with the surface of the catalyst particles. This not only enhances the binding force between powder particles during tableting and prevents cracking or edge breakage during tableting, but more importantly, CMC pyrolyzes at 200℃ to 300℃ to generate gases such as CO2 and H2O, forming through-pores of 30 nm to 120 nm. This multi-level pore structure with pores of different sizes not only ensures the full exposure of the active components and makes the catalyst highly active, but more importantly, the presence of macropores is conducive to the diffusion of the reaction and inhibits the polymerization of reaction molecules, especially the aldehyde / ketone molecules generated in the reaction, caused by prolonged residence in the pores, further reducing catalyst deactivation caused by carbon buildup and blockage.

[0025] (4) The carbon fibers added during the tableting process interweave into a three-dimensional network, acting as "reinforcing ribs" to improve compressive strength and reduce catalyst edge breakage. This process fundamentally solves the pulverization phenomenon caused by mechanical force during catalyst use, further extending catalyst life.

[0026] (5) Based on the multiple advantages of the structure, the catalyst of the present invention exhibits excellent activity, selectivity and service life in alcohol dehydrogenation. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The XRD patterns of catalysts #1, #3, and #5 in Examples of this invention are shown.

[0029] Figure 2 The N2 adsorption-desorption isotherms are shown for catalysts #1, #3, and #5 in Examples of the present invention.

[0030] Figure 3 The pore size distribution diagrams are for catalysts #1, #3, and #5 in Examples of the present invention.

[0031] Figure 4 This is an HRTEM image of catalyst #1 in Example 1 of the present invention. Detailed Implementation

[0032] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore merely examples and should not be used to limit the scope of protection of the present invention. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0033] This invention provides a hierarchical porous Cu / SiO2 catalyst modified with a carbon-metal oxide layer and reinforced with carbon fibers, which is composed of copper, carbon, metal oxides and SiO2; based on the total mass of the catalyst, the copper content is 27% to 30%, the carbon content is 7.3% to 12.6%, the total content of metal oxides is 1% to 3% based on metal content, and the remainder is SiO2; wherein, the metal oxide is an oxide of at least one metal selected from Mn, Ce, Ca, Mg and La.

[0034] The carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst has a carbon-metal oxide layer on its surface with a thickness of 1 nm to 2 nm; the catalyst exhibits a hierarchical pore distribution and a specific surface area of ​​180 m². 2 / g~320m 2 / g, pore volume 0.31cm 3 / g ~ 0.45cm 3 / g, exhibiting two pore size distributions: 2 nm to 10 nm and 30 nm to 120 nm.

[0035] The carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst tablet is a columnar structure with a height × diameter of (3 mm to 5 mm) × (3 mm to 5 mm) and a radial strength ≥300 N.

[0036] This invention also provides a method for preparing the above-mentioned carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst, comprising the following steps: Step 1: Dissolve copper nitrate trihydrate in an appropriate amount of deionized water under strong stirring at room temperature, and add a mixture of ammonia, ammonium citrate, ammonium carbonate and urea. Stir at 20℃~40℃ for 30min~180min to form a copper ammonia mixed solution.

[0037] In the copper-ammonia mixed solution, the mass of copper nitrate trihydrate weighed per liter of solution is 63.2 g to 96.5 g, the mass of ammonia water is 58.7 g to 87.8 g, the mass of ammonium citrate is 0.5 g to 20.8 g, the mass of ammonium carbonate is 0.5 g to 24.2 g, and the mass of urea is 1.5 g to 26.8 g.

[0038] Step 2: Add silica sol and template agent to the copper-ammonia mixed solution prepared in Step 1, and continue stirring at 20℃~40℃ for 30min~180min. Raise the temperature to 65℃~105℃ for ammonia stripping treatment for 2h~30h. Filter off the solution, wash the precipitate with deionized water to remove impurities, and then dry it at 60℃~150℃ for 3h~24h. Calcine it in a muffle furnace at 400℃~600℃ for 3h~8h to obtain the copper-silicon catalyst precursor.

[0039] The silica sol used is a sodium-type silica sol with a SiO2 concentration of 28% to 30%, and the mass added is 11.9% to 13.2% of the mass of the copper ammonia mixed solution. The template agent added is PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride), with a diameter of 20 nm to 50 nm, and the amount added is calculated as 3 g to 25.2 g per liter of copper ammonia mixed solution. The preferred ammonia stripping temperature is 85℃ to 105℃, the preferred drying temperature is 110℃ to 130℃, and the preferred calcination temperature is 400℃ to 500℃.

[0040] Step 3: Place the above copper-silicon catalyst precursor into a ball mill, and add silane coupling agent, anhydrous ethanol, metal additive, and asphalt to it. Ball mill the copper-silicon catalyst precursor, then dry it at 60℃~120℃ for 8h~24h, and calcine it in a muffle furnace at 300℃~550℃ for 2h~6h under the condition of oxygen content of 3%~10% to obtain catalyst powder.

[0041] The metal additive is one of Mn, Ce, Ca, Mg, and La, added in the form of a nitrate of the metal additive, with an addition amount of 1.0% to 3.4% of the copper-silicon catalyst precursor; the silane coupling agent is one of γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane, added with an addition amount of 1% to 2% of the copper-silicon catalyst precursor; the asphalt is petroleum asphalt, added with an addition amount of 1.5% to 2.5% of the copper-silicon catalyst precursor; the anhydrous ethanol is added with an addition amount of 5% to 8.3% of the copper-silicon catalyst precursor; the drying temperature is preferably 100℃ to 120℃, and the calcination temperature is preferably 400℃ to 500℃; the oxygen content in the muffle furnace is preferably 3% to 8%.

[0042] Step 4: Add graphite powder, hydroxymethyl cellulose, and carbon fiber to the catalyst raw powder obtained by calcination, mix evenly, and then compress into tablets using a tablet press to obtain the tablet material.

[0043] The amounts of graphite powder, hydroxymethyl cellulose, and carbon fiber added are 5%–8%, 6%–13%, and 2%–5% of the weight of the original catalyst powder, respectively.

[0044] Step 5: The tablet material obtained in Step 4 is loaded into an atmosphere furnace, and H2 / Ar mixed gas is introduced to raise the temperature and reduce it, thereby obtaining the carbon-metal oxide layer modified and carbon fiber reinforced multi-level porous Cu / SiO2 catalyst.

[0045] The temperature-reduction conditions are: 200℃~350℃, H2:Ar=1:9~1:4 (LHSV=200h) -1 ~300h -1 Reduction was carried out under a certain atmosphere for 1.5 to 5 hours, followed by switching to pure H2 (LHSV = 150 h). -1 ~400h -1 Reduction time: 0.5h to 1.5h.

[0046] This invention also provides the application of the above-mentioned carbon-metal oxide layer-modified, carbon fiber-reinforced hierarchical porous Cu / SiO2 catalyst in alcohol dehydrogenation reactions, particularly in the dehydrogenation of cyclohexanol to cyclohexanone. This catalyst exhibits excellent catalytic performance in the dehydrogenation of cyclohexanol to cyclohexanone, with a liquid hourly space velocity (LHSV) of 0.55 h⁻¹. -1 ~0.65h -1 At reaction temperatures of 200℃~230℃, the conversion rate of cyclohexanol reaches 57.1%~58.6%, and the selectivity of cyclohexanone is 99.5%~99.8%. Furthermore, this catalyst is also suitable for various other alcohol dehydrogenation reactions, such as the dehydrogenation of sec-butanol to methyl ethyl ketone, the dehydrogenation of 1,4-butanediol to γ-butyrolactone, and the dehydrogenation of diethylene glycol to dioxane.

[0047] The following are several specific examples of preparing the carbon-metal oxide layer-modified, carbon fiber-reinforced hierarchical porous Cu / SiO2 catalyst to further illustrate the technical solution of the present invention: Example 1

[0048] 63.2 g of copper nitrate trihydrate was dissolved in 300 mL of deionized water to prepare a copper nitrate aqueous solution. 0.5 g of ammonium citrate, 24.2 g of ammonium carbonate, and 1.5 g of urea solution were dissolved in 200 mL of deionized water, and then 58.7 g of 25% ammonia solution was added to prepare an ammonia solution. The ammonia solution was then added to the copper nitrate aqueous solution, and deionized water was added to bring the volume to 1 L. The mixture was stirred at 20°C for 180 min to form a copper-ammonia mixed solution. Then, 119.3 g of sodium silica sol with a SiO2 content of 28%–30% and 3.0 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 20°C for 180 min, heated to 65°C for ammonia removal treatment for 30 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 60°C for 24 h, and calcined in a muffle furnace at 400°C for 8 h to obtain the copper-silicon catalyst precursor.

[0049] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 1.0 g of γ-aminopropyltriethoxysilane, 1.5 g of petroleum asphalt, 5.0 g of anhydrous ethanol, and 3.4 g of cerium nitrate hexahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 60 °C for 24 h and calcined at 300 °C for 6 h in a muffle furnace with an oxygen content of 3% to obtain the original catalyst powder.

[0050] Take 100 g of catalyst powder, add 5.0 g of graphite powder, 6.0 g of hydroxymethyl cellulose and 2.0 g of carbon fiber, mix evenly and then compress into tablets using a tablet press.

[0051] The obtained tableting material was loaded into an atmosphere furnace and heated to 200°C with an H2:Ar ratio of 1:9 (LHSV = 300 h). -1 Reduction was carried out under a certain atmosphere for 2 hours, followed by switching to pure H2 (LHSV=150 h). -1 After reduction for 1.5 h, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #1. Example 2

[0052] 71.7 g of copper nitrate trihydrate was dissolved in 300 mL of deionized water to prepare a copper nitrate aqueous solution. 4.6 g of ammonium citrate, 19.2 g of ammonium carbonate, and 6.8 g of urea solution were dissolved in 200 mL of deionized water, and then 64.1 g of 25% ammonia solution was added to prepare an ammonia solution. The ammonia solution was then added to the copper nitrate aqueous solution, and deionized water was added to bring the volume to 1 L. The mixture was stirred at 25°C for 150 min to form a copper-ammonia mixed solution. Then, 123.1 g of sodium silica sol with a SiO2 content of 28%–30% and 7.5 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 25°C for 150 min, heated to 75°C for ammonia removal treatment for 25 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 80°C for 20 h, and calcined in a muffle furnace at 450°C for 7 h to obtain the copper-silicon catalyst precursor.

[0053] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 1.5 g of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, 1.8 g of petroleum asphalt, 6.1 g of anhydrous ethanol, and 9.5 g of manganese nitrate hexahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 80 °C for 20 h and calcined at 400 °C for 5 h in a muffle furnace with an oxygen content of 4% to obtain the original catalyst powder.

[0054] Take 100 g of catalyst powder, add 6.5 g of graphite powder, 7.7 g of hydroxymethyl cellulose and 3.2 g of carbon fiber, mix evenly and then compress into tablets using a tablet press to obtain the tablet material.

[0055] The obtained tableting material was loaded into an atmosphere furnace and heated to 250°C with an H2:Ar ratio of 1:4 (LHSV = 200 h⁻¹). -1 Reduction was carried out under a certain atmosphere for 5 hours, followed by switching to pure H2 (LHSV=200 h). -1 After reduction for 1 hour, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #2. Example 3

[0056] Dissolve 80.5 g of copper nitrate trihydrate in 300 mL of deionized water to prepare a copper nitrate aqueous solution. Dissolve 9.6 g of ammonium citrate, 14.4 g of ammonium carbonate, and 11.6 g of urea solution in 200 mL of deionized water, then add 69.9 g of 25% ammonia solution to prepare an ammonia solution. Add the ammonia solution to the copper nitrate aqueous solution and then add deionized water to bring the volume to 1 L. Stir at 30°C for 120 min to form a copper-ammonia mixed solution. Then, 129.0 g of sodium silica sol with a SiO2 content of 28%–30% and 12.0 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 30°C for 120 min, heated to 85°C for ammonia removal treatment for 20 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 90°C for 18 h, and calcined in a muffle furnace at 500°C for 6 h to obtain the copper-silicon catalyst precursor.

[0057] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 2.0 g of γ-glycidyl etheroxypropyltrimethoxysilane, 1.9 g of petroleum asphalt, 7.1 g of anhydrous ethanol, and 17.7 g of calcium nitrate tetrahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 90 °C for 16 h and calcined at 450 °C for 4 h in a muffle furnace with an oxygen content of 6% to obtain the original catalyst powder.

[0058] Take 100 g of catalyst powder, add 7.5 g of graphite powder, 8.6 g of hydroxymethyl cellulose and 3.8 g of carbon fiber, mix evenly and then compress into tablets using a tablet press to obtain the tablet material.

[0059] The obtained tableting material was loaded into an atmosphere furnace and heated at 350°C with an H2:Ar ratio of 1:8 (LHSV = 300 h). -1 Reduction was carried out under a certain atmosphere for 1.5 hours, followed by switching to pure H2 (LHSV=400 h). -1 After reduction for 0.5 h, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #3. Example 4

[0060] 81.3 g of copper nitrate trihydrate was dissolved in 300 mL of deionized water to prepare a copper nitrate aqueous solution. 14.6 g of ammonium citrate, 10.2 g of ammonium carbonate, and 16.7 g of urea solution were dissolved in 200 mL of deionized water, and then 75.78 g of 25% ammonia solution was added to prepare an ammonia solution. The ammonia solution was then added to the copper nitrate aqueous solution, and deionized water was added to bring the volume to 1 L. The mixture was stirred at 35°C for 90 min to form a copper-ammonia mixed solution. Then, 128.8 g of sodium silica sol with a SiO2 content of 28%–30% and 16.5 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 35°C for 90 min, heated to 95°C for ammonia removal treatment for 15 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 110°C for 12 h, and calcined in a muffle furnace at 550°C for 4 h to obtain the copper-silicon catalyst precursor.

[0061] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 2.0 g of γ-aminopropyltriethoxysilane, 2.1 g of petroleum asphalt, 8.3 g of anhydrous ethanol, and 21.1 g of magnesium nitrate hexahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 105 °C for 12 h and calcined at 500 °C for 3 h in a muffle furnace with an oxygen content of 6% to obtain the original catalyst powder.

[0062] Take 100 g of catalyst powder, add 7.5 g of graphite powder, 10.1 g of hydroxymethyl cellulose and 4.1 g of carbon fiber, mix evenly and then compress into tablets using a tablet press to obtain the tablet material.

[0063] The obtained tableting material was loaded into an atmosphere furnace and heated to 200°C with an H2:Ar ratio of 1:5 (LHSV = 200 h). -1 Reduction was carried out under a certain atmosphere for 5 hours, followed by switching to pure H2 (LHSV=300 h). -1 After reduction for 1.5 h, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #4. Example 5

[0064] 90.1 g of copper nitrate trihydrate was dissolved in 300 mL of deionized water to prepare a copper nitrate aqueous solution. 18.8 g of ammonium citrate, 5.2 g of ammonium carbonate, and 21.6 g of urea solution were dissolved in 200 mL of deionized water, and then 81.6 g of 25% ammonia solution was added to prepare an ammonia solution. The ammonia solution was then added to the copper nitrate aqueous solution, and deionized water was added to bring the volume to 1 L. The mixture was stirred at 40°C for 30 min to form a copper-ammonia mixed solution. Then, 131.3 g of sodium silicate sol with a SiO2 content of 28%–30% and 20.0 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 40°C for 30 min, heated to 100°C for ammonia removal treatment for 10 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 130°C for 9 h, and calcined in a muffle furnace at 600°C for 3 h to obtain the copper-silicon catalyst precursor.

[0065] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 1.8 g of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, 2.2 g of petroleum asphalt, 8.1 g of anhydrous ethanol, and 6.7 g of lanthanum nitrate hexahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 120 °C for 8 h and calcined at 550 °C for 2 h in a muffle furnace with an oxygen content of 7% to obtain the original catalyst powder.

[0066] Take 100 g of catalyst powder, add 7.8 g of graphite powder, 12.2 g of hydroxymethyl cellulose and 4.7 g of carbon fiber, mix evenly and then compress into tablets using a tablet press to obtain the tablet material.

[0067] The obtained tableting material was loaded into an atmosphere furnace and heated to 250°C with an H2:Ar ratio of 1:7 (LHSV = 250 h). -1 Reduction was carried out under a certain atmosphere for 3 hours, followed by switching to pure H2 (LHSV=300 h). -1 After reduction for 1 hour, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #5. Example 6

[0068] Dissolve 96.5 g of copper nitrate trihydrate in 300 mL of deionized water to prepare a copper nitrate aqueous solution. Dissolve 20.8 g of ammonium citrate, 0.5 g of ammonium carbonate, and 26.8 g of urea solution in 200 mL of deionized water, then add 87.8 g of 25% ammonia solution to prepare an ammonia solution. Add the ammonia solution to the copper nitrate aqueous solution and then add deionized water to bring the volume to 1 L. Stir at 40°C for 60 min to form a copper-ammonia mixed solution. Then, 132.0 g of sodium silicate sol with a SiO2 content of 28%–30% and 25.2 g of PMMA (polymethyl methacrylate) microspheres modified with DMC (methacryloyloxyethyltrimethylammonium chloride) were added to the prepared copper-ammonia mixed solution. The mixture was stirred at 40°C for 60 min, heated to 105°C for ammonia removal treatment for 2 h, the solution was filtered off, the precipitate was washed with deionized water to remove impurities, dried at 150°C for 3 h, and calcined in a muffle furnace at 600°C for 3 h to obtain the copper-silicon catalyst precursor.

[0069] 100 g of the above copper-silicon catalyst precursor was placed in a ball mill, and 1.8 g of γ-glycidyl etheroxypropyltrimethoxysilane, 2.5 g of petroleum asphalt, 8.0 g of anhydrous ethanol, and 10.3 g of lanthanum nitrate hexahydrate were added. The catalyst precursor was then ball-milled. Subsequently, it was dried at 110 °C for 12 h and calcined at 450 °C for 4 h in a muffle furnace with an oxygen content of 8% to obtain the original catalyst powder.

[0070] Take 100 g of catalyst powder, add 8.0 g of graphite powder, 13.0 g of hydroxymethyl cellulose and 4.9 g of carbon fiber, mix evenly and then compress into tablets using a tablet press to obtain the tablet material.

[0071] The obtained tableting material was loaded into an atmosphere furnace and heated to 250°C with an H2:Ar ratio of 1:9 (LHSV = 300 h). -1 Reduction was carried out under a certain atmosphere for 3 hours, followed by switching to pure H2 (LHSV=400 h). -1 After reduction for 0.5 h, a multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement was obtained, which was designated as catalyst #6.

[0072] Furthermore, the catalysts No. 1 to No. 6 prepared in Examples 1 to 6 above are analyzed and described in detail as follows: Tables 1 and 2 show the composition and physicochemical properties of catalysts #1 to #6, respectively.

[0073] Table 1-Composition of Catalyst #1 to #6

[0074] Table 2 - Physicochemical properties of catalysts #1 to #6

[0075] Figure 1 The XRD patterns are for catalysts #1, #3, and #5. Figure 2 The N2 adsorption-desorption isotherms are shown for catalysts #1, #3, and #5. Figure 3 The diagram shows the pore size distribution of catalysts #1, #3, and #5. Figure 4 This is a high-resolution electron microscope (HRTEM) image of catalyst #1.

[0076] Combine Table 1 and Table 2 Figure 1 , Figure 2 , Figure 3 , Figure 4 As can be seen, the catalyst of this invention is a hierarchical porous Cu / SiO2 catalyst modified with a carbon-metal oxide layer and reinforced with carbon fibers. Based on 100% of the total mass of the catalyst, its composition includes: 27%–30% copper, 7.3%–12.6% carbon, and an oxide of at least one metal selected from Mn, Ce, Ca, Mg, and La, with a total metal content of 1%–3%, and the remainder being SiO2. The catalyst surface contains a carbon-metal oxide layer with a thickness of 1 nm–2 nm. The catalyst exhibits a hierarchical porous distribution and a specific surface area of ​​180 m². 2 / g~320 m 2 / g, pore volume 0.31cm 3 / g ~ 0.45cm 3 The catalyst exhibits a pore size distribution in two ranges: 2 nm to 10 nm and 30 nm to 120 nm. After compression, the catalyst forms a columnar tablet with dimensions of 3 mm to 5 mm in height and 3 mm to 5 mm in diameter, and a radial strength ≥300 N. This structure effectively inhibits sintering and carbon deposition of the active component. It effectively improves the activity and selectivity of cyclohexanone dehydrogenation to cyclohexanone while extending the catalyst's lifespan.

[0077] The activity of catalyst samples 1 through 6 was evaluated in a fixed-bed reactor with an inner diameter of 10 mm, with a feedstock cyclohexanol space velocity of 0.55 h⁻¹. -1 ~0.65 h -1 The activity was evaluated under controlled reaction temperatures of 200 ℃~230 ℃, and the evaluation results are shown in Table 3. Table 3-1 Evaluation results of cyclohexanol dehydrogenation of catalysts #1 to #6

[0078] As shown in Table 3, the catalyst prepared according to the method of this invention exhibits excellent catalytic performance in the dehydrogenation reaction of cyclohexanol: the conversion rate of cyclohexanol is 57.1%–58.6%, reaching the thermodynamic equilibrium conversion rate at this reaction temperature; the selectivity of cyclohexanone is as high as 99.5%–99.8%, with only a very small amount of byproducts (such as cyclohexene and phenol) generated. After continuous operation for 3000 hours, thermogravimetric analysis showed that the content of polymerized organic matter on the surface of the catalyst was less than 1%, demonstrating outstanding resistance to carbon deposition. Based on the above results, the service life of the catalyst under industrial conditions is expected to reach more than 20 months.

[0079] Table 4-1 Evaluation results of catalysts #1 to #6 in other alcohol dehydrogenation reactions

[0080] The catalyst prepared according to the method described in this invention was further applied to the dehydrogenation reactions of various alcohols, including sec-butanol, 1,4-butanediol, and diethylene glycol. Table 4 shows that the evaluation results indicate that this catalyst exhibits excellent catalytic activity and good product selectivity in most alcohol dehydrogenation systems, demonstrating broad applicability and stable catalytic performance.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A multi-level porous Cu / SiO2 catalyst modified with a carbon-metal oxide layer and reinforced with carbon fibers, characterized in that, It is composed of copper, carbon, metal oxides and SiO2; based on the total mass of the catalyst, the copper content is 27% to 30%, the carbon content is 7.3% to 12.6%, the total content of metal oxides is 1% to 3% based on metal content, and the remainder is SiO2; among which, the metal oxides are oxides of at least one metal selected from Mn, Ce, Ca, Mg and La.

2. The multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement according to claim 1, characterized in that: The catalyst surface consists of a carbon-metal oxide layer with a thickness of 1 nm to 2 nm; the catalyst exhibits a hierarchical porous distribution and a specific surface area of ​​180 m². 2 / g~320 m 2 / g, pore volume 0.31cm 3 / g ~ 0.45cm 3 / g, exhibiting two pore size distributions: 2 nm to 10 nm and 30 nm to 120 nm.

3. The multi-level porous Cu / SiO2 catalyst with carbon-metal oxide layer modification and carbon fiber reinforcement according to claim 2, characterized in that: The catalyst tablets are columnar with a height × diameter of (3 mm to 5 mm) × (3 mm to 5 mm) and a radial strength ≥ 300 N.

4. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst as described in claim 3, characterized in that, Includes the following steps: Step 1: Dissolve copper nitrate trihydrate in an appropriate amount of deionized water under strong stirring at room temperature, and add a mixture of ammonia, ammonium citrate, ammonium carbonate and urea. Stir at 20℃~40℃ for 30 min~180 min to form a copper ammonia mixed solution. Step 2: Add silica sol and template agent to the copper-ammonia mixed solution prepared in Step 1, stir at 20℃~40℃ for 30 min~180 min, heat to 65℃~105℃ for ammonia stripping treatment for 2 h~30 h, filter off the solution, wash the precipitate with deionized water to remove impurities, then dry at 60℃~150℃ for 3 h~24 h, and calcine in a muffle furnace at 400℃~600℃ for 3 h~8 h to obtain the copper-silicon catalyst precursor; Step 3: Place the above copper-silicon catalyst precursor into a ball mill and add silane coupling agent, anhydrous ethanol, metal additive, and asphalt to it. Ball mill the copper-silicon catalyst precursor, then dry it at 60℃~120℃ for 8 h~24 h, and calcine it at 300℃~550℃ for 2 h~6 h in a muffle furnace with an oxygen content of 3%~10% to obtain the catalyst powder. Step 4: Add graphite powder, hydroxymethyl cellulose, and carbon fiber to the catalyst raw powder obtained by calcination treatment, mix evenly, and then compress into tablets using a tablet press to obtain the tablet material; Step 5: The tablet material obtained in Step 4 is loaded into an atmosphere furnace, and H2 / Ar mixed gas is introduced to raise the temperature and reduce it, thereby obtaining the carbon-metal oxide layer modified and carbon fiber reinforced multi-level porous Cu / SiO2 catalyst.

5. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to claim 4, characterized in that: In step one, the following amounts of copper nitrate trihydrate are weighed per liter of the copper-ammonia mixed solution: 63.2 g to 96.5 g, ammonia water: 58.7 g to 87.8 g, ammonium citrate: 0.5 g to 20.8 g, ammonium carbonate: 0.5 g to 24.2 g, and urea: 1.5 g to 26.8 g.

6. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to claim 4, characterized in that: In step two, the silica sol used is a sodium-type silica sol with a SiO2 concentration of 28%–30%, and the added mass is 11.9%–13.2% of the mass of the copper-ammonia mixed solution; the added template agent is polymethyl methacrylate microspheres modified with methacryloyloxyethyltrimethylammonium chloride, with a diameter of 20 nm–50 nm, and the added amount is calculated as 3 g–25.2 g per liter of copper-ammonia mixed solution; the preferred ammonia stripping temperature is 85℃–105℃, the preferred drying temperature is 110℃–130℃, and the preferred calcination temperature is 400℃–500℃.

7. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to claim 4, characterized in that: In step three, the metal additive is one of Mn, Ce, Ca, Mg, and La, added in the form of a nitrate of the metal additive, with the amount of metal added being 1.0% to 3.4% of the copper-silicon catalyst precursor; the silane coupling agent is one of γ-aminopropyltriethoxysilane, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane, added with the amount added being 1% to 2% of the copper-silicon catalyst precursor; the asphalt is petroleum asphalt, added with the amount added being 1.5% to 2.5% of the copper-silicon catalyst precursor; the amount of anhydrous ethanol added is 5% to 8.3% of the copper-silicon catalyst precursor; the drying temperature is preferably 100℃ to 120℃, the calcination temperature is preferably 400℃ to 500℃; and the oxygen content in the muffle furnace is preferably 3% to 8%.

8. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to claim 4, characterized in that: In step four, the amounts of graphite powder, hydroxymethyl cellulose, and carbon fiber added are 5%–8%, 6%–13%, and 2%–5% of the weight of the original catalyst powder, respectively.

9. The method for preparing a carbon-metal oxide layer modified, carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to claim 4, characterized in that: In step five, the temperature reduction conditions are: 200℃~350℃, H2:Ar=1:9~1:4 (LHSV=200h) -1 ~300h -1 Reduction was carried out under a certain atmosphere for 1.5 to 5 hours, followed by switching to pure H2 (LHSV = 150 h). -1 ~400h -1 Reduction time: 0.5h to 1.5h.

10. The application of the carbon-metal oxide layer modified and carbon fiber reinforced hierarchical porous Cu / SiO2 catalyst according to any one of claims 1-3 in alcohol dehydrogenation reaction.

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