A supported silver-based catalyst, its preparation method and use

Abstract

The application relates to the technical field of catalyst materials, and particularly discloses a supported silver-based catalyst, a preparation method and application thereof. The catalyst comprises a catalyst carrier, a main active component, an auxiliary active component and an auxiliary agent supported on the catalyst carrier; the main active component is elemental silver, the mass percentage of which is 2.5%-10%; the auxiliary active component is elemental nickel, the mass percentage of which is 0.5%-7%; and the auxiliary agent is elemental phosphorus, the mass percentage of which is 0.25%-1.5%; wherein the catalyst carrier is dendritic mesoporous silica microspheres. The catalyst carrier, the main active component, the auxiliary active component and the auxiliary agent are synergized in a specific proportion, the catalytic activity of the catalyst is significantly improved, the reaction rate under low-temperature conditions is accelerated, the reaction temperature is lowered, the time for reaching the reaction stable period is shortened, the use cost of the catalyst is effectively reduced, the green and environmental protection concept is met, and the practical value is extremely high.

Description

Technical Field

[0001] This invention relates to the field of catalyst materials technology, and in particular to a supported silver-based catalyst, its preparation method, and its application. Background Technology

[0002] Methyl glycolate is an important chemical product and intermediate widely used in numerous fields such as chemical engineering, pharmaceuticals, dyes, and pesticides. Methyl glycolate can undergo various reactions, including carbonylation, hydrolysis, and oxidation, thus serving as an intermediate in organic and pharmaceutical synthesis. Methyl glycolate hydrolyzes to glycolic acid, which, through polycondensation, can be converted into polyglycolic acid (PEG). PEG is a synthetic polymer with good biodegradability and biocompatibility, showing broad application prospects in biomedicine and ecology. Therefore, methyl glycolate, as an important raw material for chemical and pharmaceutical processes, possesses significant development value and a broad market prospect.

[0003] Currently, domestic research on catalysts for the hydrogenation of dimethyl oxalate to methyl glycolate mainly focuses on two major directions: copper-based catalysts and silver-based catalysts. Thomas et al. prepared a Cu / SiO2 catalyst using ion exchange technology for catalytic experiments on the hydrogenation of dimethyl oxalate. The authors found that this catalyst has good dispersibility and stability. Under reaction conditions of 0.6 MPa and 240 °C, although the conversion rate of dimethyl oxalate was greater than 99%, the main product was ethylene glycol, with a selectivity >85%, making it unsuitable for the hydrogenation of dimethyl oxalate to methyl glycolate. Yin et al. prepared an Ag / SiO2 catalyst using the sol-gel method. The 15Ag / SiO2 catalyst, under reaction conditions of 2.5 MPa, a hydrogen-to-ester molar ratio of 100:1, and a reaction temperature of 220 °C, achieved a methyl glycolate selectivity of 92% during catalytic hydrogenation. While silver-based catalysts are more suitable for the hydrogenation of dimethyl oxalate to methyl glycolate, silver is a precious metal, and its economic viability makes it difficult to apply to the large-scale industrial production of methyl glycolate. Furthermore, silver-based catalysts have poor stability. Therefore, how to improve the yield of methyl glycolate while reducing the cost of silver-based catalysts has become an urgent problem to be solved. Summary of the Invention

[0004] To address the problems of high cost and unsuitability for large-scale industrial production of currently used silver-based catalysts, as well as low methyl glycolate yields of other non-silver-based catalysts, this invention provides a supported silver-based catalyst, its preparation method, and its applications. This invention increases the loading of Ag and Ni by introducing phosphorus (P) as a promoter onto the surface of dendritic silica microspheres. Through the synergistic effect of Ag and Ni, the catalytic activity is significantly improved. Thus, while ensuring high activity of the supported catalyst, the amount of catalyst used and its cost are significantly reduced, demonstrating high practical value.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] On one hand, the present invention provides a supported silver-based catalyst, the catalyst comprising a catalyst support and a main active component, a co-active component, and an additive supported on the catalyst support; the main active component is elemental silver, with a mass percentage of 2.5%-10%; the co-active component is elemental nickel, with a mass percentage of 0.5%-7%; and the additive is elemental phosphorus, with a mass percentage of 0.25%-1.5%.

[0007] The catalyst support is dendritic mesoporous silica microspheres.

[0008] Compared to existing technologies, the supported silver-based catalyst provided by this invention uses dendritic silica microspheres as a support, which increases the specific surface area of ​​the catalyst, providing more reaction space. Furthermore, the three-dimensional radial channel structure and unique radially wrinkled internal structure of the dendritic silica microspheres facilitate uniform dispersion of the active components and active additives, and enhance the binding force between the active components and active additives and the support, preventing the easy loss of active components from the catalyst. The specific ratio of elemental nickel and elemental phosphorus with silver significantly increases the low-temperature activity of the catalyst, thereby helping to lower the reaction temperature. Simultaneously, the catalyst is easy to recycle and can maintain high catalytic activity even after multiple cycles, making it highly valuable for widespread application.

[0009] The supported silver-based catalyst provided in this invention significantly improves the catalytic activity of the catalyst by synergistically combining the catalyst support, main active component, co-active component, and promoter in a specific ratio. It can accelerate the reaction rate under low temperature conditions, thereby helping to reduce the reaction temperature, shorten the time to reach the reaction stability period, and effectively reduce the cost of catalyst use. It is in line with the concept of green environmental protection and has extremely high practical value.

[0010] Preferably, the catalyst support is KCC-1.

[0011] Furthermore, the particle size of the catalyst support is 400nm-600nm.

[0012] Secondly, the present invention also provides a method for preparing the above-mentioned supported silver-based catalyst, characterized by comprising the following steps:

[0013] Step a: Add dendritic mesoporous silica microspheres to a phosphate solution, disperse evenly, impregnate, and dry to obtain phosphorus-containing silica microspheres;

[0014] Step b: Immerse the phosphorus-containing silica microspheres in a mixed solution of silver salt and nickel salt, disperse them evenly, impregnate, and dry to obtain phosphorus-containing nickel-silver silica microspheres;

[0015] Step c: Under an air atmosphere, the phosphorus-containing nickel-silver silica microspheres are calcined and then reduced under a reducing atmosphere to obtain the supported silver-based catalyst.

[0016] The method for preparing the supported silver-based catalyst provided by this invention first introduces phosphate groups onto dendritic silica microspheres. Through the chemical bonding between phosphate groups and silver and nickel ions, more Ag and Ni are effectively loaded onto the silica microsphere support. Furthermore, the intermediate transition effect of phosphate groups effectively increases the binding force of Ag and Ni on the silica microsphere support, thereby significantly increasing the catalytic activity and stability of the catalyst. When applied to the hydrogenation of dimethyl oxalate to methyl glycolate at a reaction temperature of 160-180℃, the conversion rate of dimethyl oxalate can reach 98%-100%, and the selectivity of methyl glycolate can reach 96%-99%. Compared with the single-active-component Ag / KCC-1 catalyst, the yield of methyl glycolate is increased by more than ten percentage points.

[0017] The method for preparing the supported silver-based catalyst provided by the invention has a wide range of raw material sources, is simple and easy to operate, and is convenient for industrial production.

[0018] Preferably, in step a, the method for preparing the dendritic mesoporous silica microspheres includes the following steps:

[0019] Hexadecylpyridine bromide and urea were dissolved in water to obtain solution a; tetraethyl orthosilicate, cyclohexane and n-pentanol were dissolved in water to obtain solution b; solutions a and b were mixed evenly and stirred at 120℃-140℃ for 3-5 hours, the solid and liquid were separated, dried, and calcined at 400℃-600℃ for 4-6 hours to obtain the dendritic mesoporous silica microspheres.

[0020] For example, in conjunction with the above, the mass ratio of hexadecylpyridine bromide, urea and water is 1-2:1:50-100.

[0021] For example, in conjunction with the above, the mass ratio of tetraethyl orthosilicate, cyclohexane and n-pentanol is 1-3:20-40:1, and the volume ratio of cyclohexane and water is 1:1-1.2.

[0022] Preferably, the temperature is raised to 400℃-600℃ using a programmed temperature rise method. The specific temperature rise program is as follows: first, raise the temperature to 100-120℃ at a rate of 1℃ / min-3℃ / min, hold for 20min-40min, then continue to raise the temperature to 340℃-360℃, hold for 20min-40min, and then continue to raise the temperature to 400℃-600℃, hold for 4h-6h.

[0023] Furthermore, the temperature was first increased to 110℃ at a rate of 2℃ / min and held for 30min, then increased to 350℃ and held for 30min, and then increased to 550℃ and held for 6h.

[0024] The preferred programmed temperature calcination method can obtain dendritic silica microspheres with uniform morphology, improve the uniformity of Ag and Ni particle size, and the binding force between Ag, Ni and the support, thereby improving catalytic activity.

[0025] Preferably, in step a, the concentration of the phosphate solution is 0.05 mol / L to 0.35 mol / L.

[0026] Preferably, in step a, the phosphate solution is an ammonium dihydrogen phosphate solution.

[0027] Preferably, in step a, the mass ratio of phosphate to dendritic silica microspheres in the phosphate solution is 0.01-0.07:1.

[0028] Preferably, in step a, the immersion temperature is 20℃-40℃ and the immersion time is 20min-40min.

[0029] Preferably, in step b, the silver salt is silver nitrate and the nickel salt is nickel nitrate.

[0030] Further, in step b, the concentration of silver salt in the mixed solution is 0.15 mol / L-0.65 mol / L, and the concentration of nickel salt is 0.04 mol / L-0.70 mol / L.

[0031] In conjunction with the above, in step b, the mass ratio of silver salt, nickel salt and phosphorus-containing silica microspheres in the mixed solution is 0.04-0.18:0.02-0.35:1.

[0032] Furthermore, in step b, the immersion temperature is 20℃-40℃, and the immersion time is 20min-40min.

[0033] The optimized conditions of steps a and b can increase the loading of Ag and Ni on the support, thereby improving the catalytic activity of the catalyst.

[0034] Preferably, in step c, the calcination temperature is 400℃-500℃, and the calcination time is 4h-5h.

[0035] Preferably, in step c, the reduction temperature is 300℃-450℃, and the reduction time is 3h-4h.

[0036] It should be noted that the reducing atmosphere described in this invention can be a hydrogen atmosphere or a mixture of hydrogen and an inert gas.

[0037] Thirdly, the present invention also provides the application of the above-mentioned supported silver-based catalyst in the hydrogenation of dimethyl oxalate to prepare methyl glycolate.

[0038] Fourthly, the present invention also provides a method for preparing methyl glycolate by hydrogenation of dimethyl oxalate, comprising the following steps:

[0039] The supported silver-based catalyst described in any of the above items is packed into a fixed-bed reactor, and a reducing gas is introduced for reduction activation. Then, the hydrogenation reaction of dimethyl oxalate and hydrogen is carried out at 150℃-180℃ to obtain methyl glycolate.

[0040] Preferably, the hydrogenation reaction is carried out at a pressure of 2-3 MPa, the hydrogen-ester molar ratio is 80-110:1, and the liquid hourly space velocity (LISH) of dimethyl oxalate is 0.4 h⁻¹. -1 ~0.7h -1 .

[0041] This invention first modifies a dendritic silica support with phosphorus (P) to increase the effective loading of Ag and Ni on the support and enhance the bonding force between Ag and Ni and the support. Using elemental silver as the main active component and incorporating low-cost elemental Ni, the synergistic effect of Ag and Ni significantly improves the catalytic activity and selectivity of the hydrogenation reaction, while effectively reducing the cost of the catalyst. When applied to the hydrogenation of dimethyl oxalate to methyl glycolate at a reaction temperature of 160-180℃, the conversion rate of dimethyl oxalate can reach 98%-100%, and the selectivity of methyl glycolate can reach 96%-99%, with a significantly shortened time to reach the steady-state. This invention shows high promise for industrial application and is of great significance for the industrial application of the methyl glycolate process. Attached Figure Description

[0042] Figure 1 SEM image of the KCC-1a vector prepared in Example 1;

[0043] Figure 2 SEM image of the KCC-1b vector prepared in Example 2;

[0044] Figure 3 SEM image of the 6Ag-1.5Ni-0.25P / KCC-1 catalyst precursor prepared in Example 3;

[0045] Figure 4 SEM image of the 6Ag-1.5Ni-0.5P / KCC-1 catalyst precursor prepared in Example 5;

[0046] Figure 5SEM image of the 6Ag-1.5Ni-1.5P / KCC-1 catalyst precursor prepared in Example 6;

[0047] Figure 6 Nitrogen isothermal adsorption curves for Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors;

[0048] Figure 7 Pore ​​size distribution curves of Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors;

[0049] Figure 8 XPS spectra of Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors, where (a) Ag 3d, (b) Ni 2p, and (c) P 2p;

[0050] Figure 9 A comparison chart of the dimethyl oxalate conversion rates of Ag / KCC-1, Ag-Ni / KCC-1, and Ag-Ni-P / KCC-1 catalysts. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] To better illustrate the present invention, further examples are provided below.

[0053] Example 1

[0054] This invention provides a method for preparing dendritic silica microspheres (KCC-1a), comprising the following steps:

[0055] Take 0.026 mol of hexadecylpyridine bromide and 0.01 mol of urea, place them in a three-necked flask, add 30 mL of deionized water, stir to dissolve, and obtain solution a;

[0056] Take 0.012 mol of tetraethyl orthosilicate, 30 mL of n-pentanol and 1.5 mL of cyclohexane, place them in a beaker and stir to dissolve, to obtain solution b;

[0057] Solution b was slowly added dropwise to solution a, and stirred for 30 min. The mixture was then transferred to a hydrothermal reactor lined with polytetrafluoroethylene (PTFE). The temperature was increased to 120 °C at a rate of 1 °C / min, and the mixture was reacted for 2 h with stirring at 240 r / min. The mixture was then cooled to room temperature, centrifuged, and the resulting solid was washed three times each with ethanol and ethyl acetate. The solid was dried in a 60 °C oven for 12 h and then calcined in a muffle furnace. The calcination program was as follows: the temperature was increased to 110 °C at a rate of 2 °C / min and held for 30 min, then increased to 350 °C and held for 30 min, and then increased to 550 °C and held for 6 h to obtain a white solid powder, namely KCC-1a.

[0058] Example 2

[0059] This invention provides a method for preparing dendritic silica microspheres (KCC-1b), comprising the following steps:

[0060] Take 0.026 mol of hexadecylpyridine bromide and 0.01 mol of urea, place them in a three-necked flask, add 30 mL of deionized water, stir to dissolve, and obtain solution a;

[0061] Take 0.012 mol of tetraethyl orthosilicate, 30 mL of n-pentanol and 1.5 mL of cyclohexane, place them in a beaker and stir to dissolve, to obtain solution b;

[0062] Solution b was slowly added dropwise to solution a, and the mixture was stirred for 30 min. The mixture was then transferred to a hydrothermal reactor with a polytetrafluoroethylene liner. The temperature was increased to 120 °C at a rate of 1 °C / min, and the mixture was reacted for 2 h with stirring at 240 r / min. The mixture was then cooled to room temperature, centrifuged, and the resulting solid was washed three times with ethanol and ethyl acetate, respectively. The solid was then dried in an oven at 60 °C for 12 h and then calcined in a muffle furnace. The calcination program was as follows: the temperature was increased to 550 °C at a rate of 5 °C / min and held for 6 h to obtain a white solid powder, namely KCC-1b.

[0063] Example 3

[0064] This invention provides a method for preparing a supported silver-based catalyst (6Ag-1.5Ni-0.25P / KCC-1a), comprising the following steps:

[0065] Step a: Dissolve 0.066g of ammonium dihydrogen phosphate in 10mL of deionized water to obtain an ammonium dihydrogen phosphate solution; slowly add the ammonium dihydrogen phosphate solution dropwise to 5.982g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process. After the dropwise addition is completed, ultrasonically stir for 20min, then dry at room temperature for 24h, and place in an oven at 110℃ for 6h to obtain P / KCC-1a.

[0066] Step b: Dissolve 0.614 g of silver nitrate and 0.402 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to P / KCC-1a while stirring continuously during the dropwise addition process; after the dropwise addition is completed, sonicate and stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 400 °C at a rate of 2 °C / min, and calcine at this temperature for 4 h to obtain the 6Ag-1.5Ni-0.25P / KCC-1a catalyst precursor.

[0067] Step c: The 6Ag-1.5Ni-0.25P / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 1.

[0068] Example 4

[0069] Following the exact same method as in Example 3, a 6Ag-1.5Ni-0.25P / KCC-1b catalyst was prepared using the KCC-1b prepared in Example 2 as the support. The hydrogenation of dimethyl oxalate to methyl glycolate was then carried out following the exact same method as in Example 3.

[0070] Example 5

[0071] This invention provides a method for preparing a supported silver-based catalyst (6Ag-1.5Ni-0.5P / KCC-1a), comprising the following steps:

[0072] Step a: Dissolve 0.133g of ammonium dihydrogen phosphate in 10mL of deionized water to obtain an ammonium dihydrogen phosphate solution; slowly add the ammonium dihydrogen phosphate solution dropwise to 5.965g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process. After the dropwise addition is completed, ultrasonically stir for 20min, then dry at room temperature for 24h, and place in an oven at 110℃ for 6h to obtain P / KCC-1.

[0073] Step b: Dissolve 0.614 g of silver nitrate and 0.402 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to P / KCC-1a while stirring continuously during the dropwise addition. After the dropwise addition is completed, sonicate and stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 450 °C at a rate of 2 °C / min, and calcine at this temperature for 4.5 h to obtain the 6Ag-1.5Ni-0.5P / KCC-1a catalyst precursor.

[0074] Step c: The 6Ag-1.5Ni-0.5P / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 300℃ and 3MPa for 4 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 1.

[0075] Example 6

[0076] This invention provides a method for preparing a supported silver-based catalyst (6Ag-1.5Ni-1.5P / KCC-1a), comprising the following steps:

[0077] Step a: Dissolve 0.403g of ammonium dihydrogen phosphate in 10mL of deionized water to obtain an ammonium dihydrogen phosphate solution; slowly add the ammonium dihydrogen phosphate solution dropwise to 5.893g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process. After the dropwise addition is completed, ultrasonically stir for 40min, then dry at room temperature for 24h, and place in an oven at 110℃ for 6h to obtain P / KCC-1a.

[0078] Step b: Dissolve 0.614 g of silver nitrate and 0.402 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to P / KCC-1a while stirring continuously during the dropwise addition process. After the dropwise addition is completed, sonicate and stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 500 °C at a rate of 2 °C / min, and calcine at this temperature for 4 h to obtain the 6Ag-1.5Ni-1.5P / KCC-1 catalyst precursor.

[0079] Step c: The 6Ag-1.5Ni-1.5P / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 450℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 1.

[0080] Example 7

[0081] This invention provides a method for preparing a supported silver-based catalyst (10Ag-0.5Ni-0.5P / KCC-1a), comprising the following steps:

[0082] Step a: Dissolve 0.133g of ammonium dihydrogen phosphate in 10mL of deionized water to obtain an ammonium dihydrogen phosphate solution; slowly add the ammonium dihydrogen phosphate solution dropwise to 5.965g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process, and then ultrasonically stir for 30min after the dropwise addition is completed, then dry at room temperature for 24h, and then place in an oven at 110℃ for 6h to obtain P / KCC-1.

[0083] Step b: Dissolve 1.058 g of silver nitrate and 0.139 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to P / KCC-1a while stirring continuously during the dropwise addition. After the dropwise addition is completed, sonicate and stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 400 °C at a rate of 2 °C / min, and calcine at this temperature for 4 h to obtain the 10Ag-0.5Ni-0.5P / KCC-1a catalyst precursor.

[0084] Step c: The 10Ag-0.5Ni-0.5P / KCC-1a catalyst precursor was ground, pressed into tablets, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 1.

[0085] Example 8

[0086] This invention provides a method for preparing a supported silver-based catalyst (2.5Ag-7Ni-0.5P / KCC-1a), comprising the following steps:

[0087] Step a: Dissolve 0.133g of ammonium dihydrogen phosphate in 10mL of deionized water to obtain an ammonium dihydrogen phosphate solution; slowly add the ammonium dihydrogen phosphate solution dropwise to 5.965g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process. After the dropwise addition is completed, ultrasonically stir for 20min, then dry at room temperature for 24h, and place in an oven at 110℃ for 6h to obtain P / KCC-1a.

[0088] Step b: Dissolve 0.263g of silver nitrate and 1.928g of nickel nitrate hexahydrate in 10mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to P / KCC-1 while stirring continuously during the dropwise addition; after the dropwise addition is completed, sonicate and stir for 20min, then dry at room temperature for 24h, place in an oven at 110℃ for 6h, transfer to a muffle furnace and heat to 400℃ at a rate of 2℃ / min, and calcine at this temperature for 4h to obtain the 2.5Ag-7Ni-0.5P / KCC-1a catalyst precursor.

[0089] Step c: The 2.5Ag-7Ni-0.5P / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 1.

[0090] Comparative Example 1

[0091] This comparative example provides a method for preparing a 2.5Ag / KCC-1a catalyst, comprising the following steps:

[0092] Step a: Dissolve 0.243g of silver nitrate in 10mL of deionized water to obtain a silver nitrate solution; slowly add the silver nitrate solution dropwise to 6g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process; after the dropwise addition is completed, ultrasonically stir for 20min, then dry at room temperature for 24h, place in an oven at 110℃ for 6h, transfer to a muffle furnace and heat to 400℃ at a rate of 2℃ / min, and calcine at this temperature for 4h to obtain a 2.5Ag / KCC-1a catalyst precursor.

[0093] Step b: The 2.5Ag / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 hours. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 2.

[0094] Comparative Example 2

[0095] This comparative example provides a method for preparing a 7.5Ag / KCC-1a catalyst, comprising the following steps:

[0096] Step a: Dissolve 0.768g of silver nitrate in 10mL of deionized water to obtain a silver nitrate solution; slowly add the silver nitrate solution dropwise to 6g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process; after the dropwise addition is completed, ultrasonically stir for 20min, then dry at room temperature for 24h, place in an oven at 110℃ for 6h, transfer to a muffle furnace and heat to 400℃ at a rate of 2℃ / min, and calcine at this temperature for 4h to obtain a 7.5Ag / KCC-1a catalyst precursor.

[0097] Step b: The 7.5Ag / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 hours. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 2.

[0098] Comparative Example 3

[0099] This comparative example provides a method for preparing a 6Ag-1.5Ni / KCC-1a catalyst, specifically including the following steps:

[0100] Step a: Dissolve 0.614 g of silver nitrate and 0.402 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to 6 g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process; after the dropwise addition is completed, ultrasonically stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 400 °C at a rate of 2 °C / min, and calcine at this temperature for 4 h to obtain the 6Ag-1.5Ni / KCC-1a catalyst precursor.

[0101] Step b: The 6Ag-1.5Ni / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 3.

[0102] Comparative Example 4

[0103] This comparative example provides a method for preparing a 2.5Ag-5Ni / KCC-1a catalyst, specifically including the following steps:

[0104] Step a: Dissolve 0.256 g of silver nitrate and 1.340 g of nickel nitrate hexahydrate in 10 mL of deionized water to obtain a mixed salt solution; slowly add the mixed salt solution dropwise to 6 g of KCC-1a prepared in Example 1, stirring continuously during the dropwise addition process; after the dropwise addition is completed, ultrasonically stir for 20 min, then dry at room temperature for 24 h, place in an oven at 110 °C for 6 h, transfer to a muffle furnace and heat to 400 °C at a rate of 2 °C / min, and calcine at this temperature for 4 h to obtain the 2.5Ag-5Ni / KCC-1a catalyst precursor.

[0105] Step b: The 2.5Ag-5Ni / KCC-1a catalyst precursor was ground, pressed, pulverized, and sieved to obtain 40-60 mesh particles. 0.2 g of these particles were loaded into a fixed-bed reactor and reduced with hydrogen at 420℃ and 3MPa for 3 h. The temperature was then lowered to 160℃, maintaining a hydrogen-to-ester molar ratio of 100:1 and a liquid hourly space velocity (LHSV) of 0.5 h⁻¹ for dimethyl oxalate. -1 The reaction was sampled every 1 hour and analyzed by gas chromatography. The results are shown in Table 3.

[0106] Table 1 Results after the Ag-Ni-P / KCC-1 catalyst reaction stabilized.

[0107]

[0108] Table 2 Results after the Ag / KCC-1 catalyst reaction stabilized.

[0109]

[0110] Table 3 Results after the Ag-Ni / KCC-1 catalyst reaction stabilized.

[0111]

[0112] Material characterization

[0113] SEM image of the KCC-1a vector prepared in Example 1 is shown below. Figure 1 As shown in the figure, the KCC-1a prepared in Example 1 exhibits a three-dimensional central radial channel structure and a unique radial fold internal structure, with a uniform morphology.

[0114] SEM image of the KCC-1b vector prepared in Example 2 is shown below. Figure 2 As shown in the figure, the KCC-1b prepared in Example 2 also exhibits a certain three-dimensional radial pore structure, but its radial fold structure is relatively blurred, some folds have collapsed and there are uneven blocky deposits on the outer surface, which have a certain impact on its pore structure.

[0115] SEM images of the Ag-Ni-P / KCC-1 catalyst precursors prepared in Examples 3, 5, and 6 are shown below. Figures 3-5 As shown in the figure, the Ag-Ni-P / KCC-1 catalyst precursor retains the dendritic structure of the KCC-1 support.

[0116] Nitrogen isothermal adsorption curves and pore size distributions of Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors are shown in the figure. Figure 6 and Figure 7 As shown, from Figure 6As can be seen, both the Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors exhibit Langmuir type IV adsorption isotherms and possess H3-type hysteresis loops at relative pressures P / P0 > 0.5, indicating that the addition of P did not microscopically alter the structural characteristics of the catalysts. Figure 7 As can be seen, when the loading of P is less than 0.5 wt%, the post-mesoporous peak shifts towards a smaller pore size relative to the mesoporous peak of the 6Ag-1.5Ni / KCC-1 catalyst, indicating that the addition of an appropriate amount of P will not block the pores of KCC-1. However, as the loading of P continues to increase, the peak intensity of the Ag-Ni-P / KCC-1 catalyst continues to decrease, and the pore size distribution becomes more dispersed.

[0117] XPS spectra of Ag-Ni / KCC-1 and Ag-Ni-P / KCC-1 catalyst precursors are as follows: Figure 8 As shown in the figure, for the Ag-Ni-P / KCC-1 catalyst, the two peaks near 368.5 eV and 374.5 eV are attributed to Ag 3d5 / 2 and Ag 3d3 / 2, respectively. After adding P to the 6Ag-1.5Ni / KCC-1 catalyst, the binding energy of Ni 2p orbitals fluctuates around 856 eV, the binding energy of P 2p orbitals fluctuates around 133 eV, and the binding energy of Ag 3d orbitals gradually decreases, all of which are lower than those of the 6Ag-1.5Ni / KCC-1 catalyst. This suggests that electron transfer may have occurred from P to Ag or to Ag and Ni, indicating an interaction between P and Ag and Ni.

[0118] A comparison of the dimethyl oxalate conversion rates of Ag / KCC-1, Ag-Ni / KCC-1, and Ag-Ni-P / KCC-1 catalysts is shown in the figure below. Figure 9 As shown in the figure, the conversion rate of dimethyl oxalate by the Ag-Ni-P / KCC-1 catalyst is significantly better than that of the Ag / KCC-1 and Ag-Ni / KCC-1 catalysts.

[0119] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a supported silver-based catalyst in the hydrogenation of dimethyl oxalate to methyl glycolate, characterized in that, The supported silver-based catalyst comprises a catalyst support and a main active component, a co-active component, and an additive supported on the catalyst support; the main active component is elemental silver, with a mass percentage of 2.5%-10%; the co-active component is elemental nickel, with a mass percentage of 0.5%-7%; and the additive is elemental phosphorus, with a mass percentage of 0.25%-1.5%. The catalyst support is dendritic mesoporous silica microspheres; The reaction temperature for preparing methyl glycolate is 150℃-180℃; The preparation method of the supported silver-based catalyst includes the following steps: Step a: Add dendritic mesoporous silica microspheres to a phosphate solution, disperse evenly, impregnate, and dry to obtain phosphorus-containing silica microspheres; Step b: Immerse the phosphorus-containing silica microspheres in a mixed solution of silver salt and nickel salt, disperse them evenly, impregnate, and dry to obtain phosphorus-containing nickel-silver silica microspheres; Step c: Under an air atmosphere, the phosphorus-containing nickel-silver silica microspheres are calcined and then reduced under a reducing atmosphere to obtain the supported silver-based catalyst.

2. The application as described in claim 1, characterized in that, The particle size of the catalyst support is 400nm-600nm.

3. The application as described in claim 1, characterized in that, In step a, the preparation method of the dendritic mesoporous silica microspheres includes the following steps: Hexadecylpyridine bromide and urea were dissolved in water to obtain solution a; tetraethyl orthosilicate, cyclohexane and n-pentanol were dissolved in water to obtain solution b; solutions a and b were mixed evenly and stirred at 120℃-140℃ for 3-5 hours, solid-liquid separation was performed, and the mixture was dried. Then, the temperature was first increased to 100-120℃ at a rate of 1℃ / min-3℃ / min and calcined for 20-40 minutes. Then, the temperature was further increased to 340℃-360℃ and calcined for 20-40 minutes. Finally, the temperature was increased to 400℃-600℃ and calcined for 4-6 hours to obtain the dendritic mesoporous silica microspheres.

4. The application as described in claim 1, characterized in that, In step a, the concentration of the phosphate solution is 0.05 mol / L to 0.35 mol / L; and / or In step a, the phosphate solution is an ammonium dihydrogen phosphate solution; and / or In step a, the mass ratio of phosphate to dendritic silica microspheres in the phosphate solution is 0.01-0.07:1; and / or In step a, the immersion temperature is 20℃-40℃ and the immersion time is 20min-40min.

5. The application as described in claim 1, characterized in that, In step b, the silver salt is silver nitrate, and the nickel salt is nickel nitrate; and / or In step b, the concentration of silver salt in the mixed solution is 0.15 mol / L-0.65 mol / L, and the concentration of nickel salt is 0.04 mol / L-0.70 mol / L; and / or In step b, the mass ratio of silver salt, nickel salt, and phosphorus-containing silica microspheres in the mixed solution is 0.04-0.18:0.02-0.35:1; and / or In step b, the immersion temperature is 20℃-40℃, and the immersion time is 20min-40min; and / or In step c, the calcination temperature is 400℃-500℃, and the calcination time is 4h-5h; and / or In step c, the reduction temperature is 300℃-450℃, and the reduction time is 3h-4h.

6. The application as described in claim 1, characterized in that, The method for preparing methyl glycolate by hydrogenation of dimethyl oxalate includes the following steps: The supported silver-based catalyst was loaded into a fixed-bed reactor, and a reducing gas was introduced for reduction and activation. Then, the hydrogenation reaction of dimethyl oxalate and hydrogen was carried out at 150℃-180℃ to obtain methyl glycolate.

7. The application as described in claim 6, characterized in that, The hydrogenation reaction was carried out at a pressure of 2-3 MPa, with a hydrogen-to-ester molar ratio of 80-110:1 and a liquid hourly space velocity (LISH) of 0.4 h⁻¹ for dimethyl oxalate. -1 ~0.7h -1 .

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