Preparation method of high-dispersion copper-based silicon oxide catalyst for coal-to-ethylene glycol

Abstract

The application discloses a preparation method of a high-dispersion copper-based silicon oxide catalyst for coal-based ethylene glycol, which comprises the following steps: dissolving a silicon source and polyacrylamide in water, adding inorganic acid to finely control an acidification process, and preparing modified silica gel; then, preparing a copper-ammonia mixed solution adsorbed by carbon powder by mixing nano carbon powder, copper salt, auxiliary metal salt and ammonia water; finally, performing an adsorption reaction on the modified silica gel and the copper-ammonia mixed solution adsorbed by carbon powder, and preparing a rasching ring copper-based silicon oxide catalyst after ammonia removal, washing, drying, shaping and calcination. The method can significantly improve the dispersity and stability of the active components of the copper-based silicon oxide catalyst by preparing the modified silica gel rich in silicon oxygen groups through the acidification of the silicon source and then loading the active metal and the auxiliary metal co-doped with the nano carbon. When the catalyst is applied to a reaction of preparing ethylene glycol by coal-based dimethyl oxalate hydrogenation, the conversion rate of the dimethyl oxalate is more than 99%, the selectivity of the ethylene glycol is more than 97%, the stable operation time is more than 5000 hours, and the catalyst has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol production. Background Technology

[0002] Ethylene glycol (EG) is a colorless, odorless, sweet-tasting viscous liquid with a boiling point of 197.3℃ and a melting point of -12.9℃. It is miscible with water and many organic solvents and possesses properties such as a high boiling point, low freezing point, good hygroscopicity, and chemical stability. It is an important raw material or additive in the fields of lubricants, adhesives, coatings, cosmetics, pharmaceuticals, and rubber. Due to its polyol structure (two hydroxyl groups), which provides chemical reactivity, ethylene glycol is also a key monomer in bulk plastic products such as polyester fiber (polyester), polyethylene terephthalate (PET), and polyurethane, with an annual domestic consumption exceeding 20 million tons. Therefore, ethylene glycol is not only a fundamental chemical in modern industry but also an important material basis for ensuring economic security and promoting sustainable development.

[0003] While the ethylene glycol production process using ethylene oxide hydration is technically mature, it is heavily reliant on petroleum. In contrast, the coal gasification followed by catalytic hydrogenation of oxalate esters (such as dimethyl oxalate) to produce ethylene glycol not only yields high-purity ethylene glycol but also achieves clean and efficient coal conversion, leading to rapid development in China. Compared to the relatively mature upstream catalytic coupling technology, the low-temperature, high-selectivity reaction of dialkyl oxalate hydrogenation and the long-term stability of copper catalysts are the core challenges most difficult to overcome and optimize in the industrialization of coal-to-ethylene glycol technology. In the 1970s and 80s, a series of patents from Ube Industries in Japan (Sho 57-122939, Sho 57-122946, Sho 57-123127, etc.) investigated copper-supported Al₂O₃ and other oxide catalysts, discovering that product selectivity could be directionally controlled by adding different additives: zinc (Zn) additives improved ethylene glycol selectivity, while silver (Ag) additives facilitated the formation of methyl glycolate. Simultaneously, adjusting reaction conditions (temperature, pressure, etc.) could flexibly alter product distribution. Research in US patent US54112245 by ARCO Company in the United States confirmed that Cu-Cr system catalysts have hydrogenation activity, but the early yield is low (11.7% to 18.9%), and they face elimination due to the highly toxic pollution problem of chromium.

[0004] As research progresses, the copper-silicon system has become a research hotspot for oxalate hydrogenation catalysts due to its excellent hydrogenation selectivity and relatively mild reaction conditions. Patent CN102091650A reports a copper-silicon catalyst for oxalate hydrogenation and its preparation method. The method involves flowing an aqueous solution of copper salt into a reaction vessel containing metered silica-alumina molecular sieves, adding silicate esters or silica sol, then adding a precipitant solution. After aging, the precipitate is washed, dried, calcined, and reduced to obtain the catalyst. The feed conversion rate can reach up to 99.7%, but it suffers from poor ethylene glycol selectivity. Patent CN109482185B reports a method for preparing a copper-silicon catalyst for selective hydrogenation of dimethyl oxalate. This method utilizes a mixed sol-gel reaction between copper ion-grafted polymer micelles and an alcohol solution of alkyl silicates to obtain a supported Cu / gco-SiO2 catalyst with uniformly dispersed active components. Although the ethylene glycol selectivity is higher than 96%, the synthesis process is complex, requiring a large amount of expensive organic reagents, resulting in high costs. Patent CN101856615B reports a catalyst and its preparation method for the hydrogenation of oxalate to ethylene glycol. Zirconia is added to a copper-silicon catalyst in the form of zirconium gel, giving copper high dispersibility and anti-sintering ability. The oxalate hydrogenation reaction runs for 3200 h, but the ethylene glycol selectivity remains low. Patent CN115709065B reports a catalyst and its preparation method for the hydrogenation of dimethyl oxalate to ethylene glycol. It uses a hydrothermal / solvothermal method to pretreat the silica support and loads the active component using a traditional precipitation method. However, this catalyst still suffers from sintering and deactivation of the active component under high temperature and high pressure conditions. The long-term stability of the catalyst was not investigated, and the solvothermal treatment step is complex and energy-intensive.

[0005] In summary, copper-silicon systems are commonly used as catalysts for coal-to-ethylene glycol production. However, these systems suffer from drawbacks such as low copper dispersion, susceptibility to sintering, rapid deactivation, low selectivity, and poor stability. Improving the long-term operational stability of these catalysts while maintaining high conversion rates and selectivity remains a critical technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0006] To address the technical shortcomings of existing copper-silicon catalysts for coal-to-ethylene glycol production, such as low dispersion of active components, easy sintering, and poor long-term stability, this invention provides a method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol production. Through the synergistic innovation of in-situ construction of a silica-rich oxygen-based silica support, in-situ introduction of nano-carbon-doped active metals, and a stepwise reduction activation process, the dispersion of copper active components and the structural stability of the catalyst are significantly improved, thereby enhancing the catalytic performance and reaction stability of the catalyst, making it suitable for the industrial conditions of dimethyl oxalate hydrogenation to ethylene glycol production.

[0007] The method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol provided by this invention specifically includes the following steps:

[0008] Step 1: Dissolve the silicon source and polyacrylamide with a mass-average molecular weight of 2 million to 15 million in distilled water at 20 to 90°C according to a mass ratio of polyacrylamide to SiO2 of 0.1 to 5:30, to prepare a silica gel solution with a SiO2 mass concentration of 1% to 20%. Under the conditions of stirring speed of 100 to 2000 r / min and heating temperature of 20 to 90°C, add 0.01 to 1 mol / L inorganic acid aqueous solution dropwise to the above silica gel solution, control the pH of the system between 3 and 8, and add the solution over a time of 30 to 100 min to obtain a modified sol with a surface rich in siloxy groups and capable of anchoring copper active species.

[0009] Step 2: Dissolve copper salt and auxiliary metal salt in deionized water, and add nano-sized carbon powder to prepare a mixed solution with a total metal ion concentration of 0.02-2 mol / L; under the condition of 5-50℃, add 5%-25% ammonia solution dropwise to the mixed solution and stir evenly to obtain a suspension with pH of 9-12, in which the nano-sized carbon powder pre-adsorbs copper ammonia complex ions and can form a spatial isolation barrier for subsequent copper grains.

[0010] Step 3: The modified sol obtained in Step 1 and the suspension obtained in Step 2 are simultaneously added dropwise to deionized water at 5-50℃ and stirred for adsorption for 1-10 hours. Then, the temperature is increased to 80-180℃ at a rate of 5-30℃ / min and held for 1-10 hours until the pH of the system is lower than 7, resulting in a blue precipitate. The precipitate is washed with deionized water until the conductivity of the filtrate is 50-800 μS / cm. The precipitate is then dried at 80-200℃ for 6-20 hours. The dried material is mixed with 1%-5% of guar gum powder by mass, and deionized water is added to adjust it to a plastic state. The mixture is then extruded to obtain Raschig rings with an outer diameter × height × inner diameter of 5-8 mm × 5-10 mm × 1-3 mm. The rings are then placed in a muffle furnace and calcined at 300-500℃ for 2-10 hours to obtain the catalyst precursor.

[0011] Step 4: The catalyst precursor obtained in Step 3 is loaded into a continuous atmosphere furnace, and hydrogen-nitrogen mixed gases of different concentrations are introduced. A segmented reduction and activation mode of low-temperature pre-reduction, gradient heating, and staged hydrogen extraction is adopted to control the reduction rate of copper species and avoid local overheating that could lead to copper grain agglomeration and sintering. The segmented reduction and activation procedure is as follows: First, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 1% to 5%. The temperature is increased to 80 to 160°C at a rate of 5 to 25°C / min and held for 2 to 10 hours. Then, the temperature is increased to 160 to 300°C at a rate of 0.5 to 10°C / min. Subsequently, under isothermal conditions, the hydrogen volume concentration is gradually increased in three stages, successively adjusted to 5% to 20%, 30% to 50%, and 60% to 100%, with each stage held at a constant temperature for 2 to 10 hours. Finally, the temperature is allowed to cool naturally to room temperature to obtain a copper-based silicon oxide catalyst.

[0012] Further, in step 1 above, it is preferable to dissolve the silicon source and polyacrylamide with a mass-average molecular weight of 4 million to 10 million in distilled water at 30 to 60°C according to a mass ratio of polyacrylamide to SiO2 in the silicon source of 0.1 to 2:30, so as to prepare a silica gel solution with a SiO2 mass concentration of 2% to 10%.

[0013] Furthermore, in step 1 above, the silicon source is preferably one or more of water glass, tetraethyl silicate, tetrabutyl silicate, sodium silicate sol, and ammonia silica sol.

[0014] Furthermore, in step 1 above, the polyacrylamide is one or more of anionic, cationic, and nonionic types.

[0015] Further, in step 1 above, preferably, under the conditions of stirring speed of 200-1000 r / min and heating temperature of 20-50℃, 0.05-0.5 mol / L inorganic acid aqueous solution is added dropwise to the above silica gel solution, the pH of the system is controlled between 4 and 7, and the dropwise addition time is 50-80 min, to obtain the modified sol.

[0016] Furthermore, in step 1 above, the inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid.

[0017] Further, in step 2 above, copper salt and auxiliary metal salt are preferably dissolved in deionized water, and nano-sized carbon powder is added to prepare a mixed solution with a total metal ion concentration of 0.05 to 1 mol / L; under the condition of 10 to 40°C, an ammonia solution with a mass concentration of 8% to 15% is added dropwise to the mixed solution and stirred evenly to obtain a suspension with a pH of 9 to 12.

[0018] Furthermore, in step 2 above, the nano-sized carbon powder is one or more of coke powder, graphite carbon powder, and bamboo charcoal powder, with a particle size D50 of 50-200 nm, a purity of 98%-99%, and a graphite crystal form; the copper salt is a soluble copper salt, such as copper nitrate or copper acetate; and the auxiliary metal salt is any one or more soluble salts of Ni, Co, and Zn.

[0019] Further, in step 3 above, preferably, the modified sol obtained in step 1 and the suspension obtained in step 2 are simultaneously added dropwise to deionized water at 10-40°C and stirred for adsorption for 2-8 hours; then the temperature is increased to 90-120°C at a rate of 10-20°C / min and held for 2-6 hours until the pH of the system is lower than 6.5, resulting in a blue precipitate; the precipitate is washed with deionized water until the conductivity of the filtrate is 50-300 μS / cm, and then dried at 100-150°C for 6-8 hours. The dried material is mixed with 2%-4% of its mass of guar gum powder, and deionized water is added to adjust it to a plastic state. The mixture is then extruded to obtain Raschig rings with an outer diameter × height × inner diameter of 6-8 mm × 6-8 mm × 2-3 mm. The rings are then placed in a muffle furnace and calcined at 350-450°C for 4-6 hours to obtain the catalyst precursor.

[0020] Furthermore, in step 4 above, it is preferable to load the catalyst precursor obtained in step 3 into a continuous atmosphere furnace for staged reduction and activation: first, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 2% to 3%. The temperature is increased to 100 to 140°C at a heating rate of 10 to 15°C / min and held for 2 to 4 hours; then, the temperature is increased to 200 to 250°C at a rate of 1 to 5°C / min; subsequently, the hydrogen volume concentration is gradually increased in three stages under constant temperature conditions, successively adjusted to 5% to 10%, 30% to 40%, and 80% to 100%, with each stage held at a constant temperature for 2 to 6 hours. Further, in step 4 above, the catalyst uses metallic Cu as the active component, one or more of Ni, Co, and Zn, and nano-carbon powder as auxiliary agents, and silicon oxide as a support; the mass content of metallic Cu in the catalyst is 5%–50%, the total mass content of Ni, Co, and Zn is 0.5%–10%, the mass content of nano-carbon powder is 0.01%–1%, and the balance is silicon oxide. Preferably, the mass content of metallic Cu in the catalyst is 10%–30%, the total mass content of Ni, Co, and Zn is 1%–5%, the mass content of nano-carbon powder is 0.05%–0.3%, and the balance is silicon oxide.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention uses silicon source and polyacrylamide to prepare silica-oxygen-rich modified silica sol carrier in situ under the fine control of inorganic acid. The carrier surface has abundant silanol anchoring sites, which can form strong chemical bonds with copper species, inhibiting the migration and sintering of copper particles from the source, and significantly improving the dispersion and structural stability of active components.

[0023] 2. In this invention, nano-sized carbon powder is introduced in situ during the active metal loading stage. After adsorbing copper ammonia complex ions, the carbon powder is uniformly dispersed on the surface of the carrier. After reduction, a co-doped structure of metallic copper and nano-carbon is formed. The physical isolation effect of nano-carbon effectively blocks direct contact and agglomeration between copper particles, and has both spatial confinement and electronic synergy effects, further enhancing the anti-sintering ability of the active component.

[0024] 3. This invention employs a multi-stage programmed temperature rise and gradient hydrogen concentration reduction process. Through segmented control of "low-temperature pre-reduction → gradual temperature rise → gradient hydrogen extraction", it achieves precise regulation of the reduction kinetics of copper species, avoiding local overheating and copper particle aggregation caused by rapid exothermic reaction in the traditional one-step reduction method. This is beneficial for obtaining active copper crystals with uniform particle size and high dispersion.

[0025] 4. The present invention shapes the catalyst into a Raschig ring structure, which has low bed pressure drop, good air permeability, and high mass transfer efficiency, making it more suitable for the fluid dynamic requirements of industrial fixed bed reactors and conducive to large-scale continuous production.

[0026] 5. When the catalyst of this invention is applied to the hydrogenation reaction of dimethyl oxalate to ethylene glycol, the conversion rate of dimethyl oxalate exceeds 99%, the selectivity of ethylene glycol exceeds 97%, the stable operating time exceeds 5000 hours, the activity loss rate is low, and the copper loss rate is significantly lower than that of existing technologies, showing good prospects for industrial application. Attached Figure Description

[0027] Figure 1 This is a transmission electron microscope (TEM) comparison image of 18Cu1.5Ni-0.08C / SiO2-LSN in Example 11 and commercial 18%Cu / SiO2 in Comparative Example 1.

[0028] Figure 2 These are X-ray diffraction (XRD) comparison images of 18Cu1.5Ni-0.08C / SiO2-LSN in Example 11, commercial 18%Cu / SiO2 in Comparative Example 1, and 30%Cu-5%V / SiO2 in patent CN115709065B. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0030] The catalyst described in the examples is referred to as xCuyNi-nC / SiO2-MM catalyst, where x, y, and n are the mass contents of the active component copper, the auxiliary metal, and the nano-sized carbon powder, respectively, and MM is an abbreviation for silicon source or inorganic acid.

[0031] Example 1

[0032] Step 1: Dissolve 200g of ammoniacal silica sol (30% SiO2, pH=10.5) and 2g of nonionic polyacrylamide (mass-average molecular weight of 6 million) completely in distilled water at 60℃ to form a silica solution with a SiO2 mass concentration of 5%; then, under the conditions of stirring speed of 500r / min and heating at 30℃, add 0.15mol / L nitric acid aqueous solution dropwise to the above silica solution, controlling the pH of the system to be 6.5 during the dropwise addition process, and the dropwise addition time to be 45min, to obtain the modified sol.

[0033] Step 2: Dissolve 40.74g of copper nitrate trihydrate, 3.54g of nickel nitrate hexahydrate, and 0.04g of coke powder (D50 of 200nm) in deionized water to prepare a mixed solution with a total metal ion concentration of 0.5mol / L; add 15% ammonia solution dropwise to the mixed solution at 30℃ and stir vigorously until homogeneous to obtain a suspension with a pH of 10.5.

[0034] Step 3: The modified sol obtained in Step 1 and the suspension obtained in Step 2 are simultaneously added dropwise to deionized water while stirring and controlling the temperature at 20℃. After the addition is completed, stirring and adsorption continue for 3 hours. Then, the temperature is increased to 100℃ at a rate of 10℃ / min to evaporate ammonia until the pH is less than 6.5, resulting in a blue precipitate. The precipitate is washed with deionized water until the conductivity of the filtrate is less than 100μS / cm. It is then dried in an oven at 120℃ for 8 hours. 3% of its mass of guar gum powder is added and mixed. The mixture is adjusted to a plastic state with deionized water and extruded into Raschig rings with an outer diameter × height × inner diameter of 5mm × 5mm × 2mm. Finally, the rings are calcined in a muffle furnace at 400℃ for 4 hours to obtain a green catalyst precursor.

[0035] Step 4: The catalyst precursor obtained in Step 3 is loaded into a continuous atmosphere furnace for staged reduction and activation: First, a mixture of hydrogen and nitrogen is introduced, controlling the hydrogen volume concentration at 2%, and the temperature is increased to 140℃ at a rate of 10℃ / min, and held for 2 hours; then, the temperature is increased to 240℃ at a rate of 2℃ / min, and subsequently, the hydrogen volume concentration is gradually increased in three stages at this temperature, successively adjusted to 5%, 30%, and 100%, with each stage held at a constant temperature for 2 hours. Finally, the temperature is allowed to cool naturally to room temperature to obtain a copper-based silica catalyst. Based on 100% by mass, the obtained copper-based silica catalyst contains 15% Cu, 1% Ni, and 0.05% coke powder, with the remainder being silica support, denoted as 15Cu1Ni-0.05C / SiO2-LS, where LS is an abbreviation for ammonia-type silica sol.

[0036] The prepared copper-based silica catalyst was packed into a fixed-bed reactor, and dimethyl oxalate was preheated to 150°C before being introduced into the reactor at a flow rate of 0.6 h. -1 The hydrogenation reaction was initiated in the reactor at a mass hourly space velocity (MHSV). The hydrogenation reaction temperature was controlled at 180℃, the pressure at 3 MPa, and the hydrogen-ester molar ratio at 90. The reaction products were quantitatively analyzed by gas chromatography. The conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The dispersion of metallic Cu in the catalyst was determined by N₂O chemisorption, and the activity loss rate was calculated based on 5000h long-term operation data. The results are shown in Table 1. The copper content in the catalyst before and after the reaction was determined by ICP-AES, and the copper loss rate was calculated. The specific surface area was measured using a nitrogen adsorption-desorption analyzer. The results are shown in Table 2.

[0037] Example 2

[0038] In step 1 of this embodiment, 214.4g of water glass with a modulus of 1.8 and a SiO2 content of 28% and 2g of nonionic polyacrylamide (mass-average molecular weight of 4 million) are completely dissolved in distilled water at 60°C to form a silica gel solution with a SiO2 mass concentration of 15%. In step 2, coke powder is replaced with an equal mass of graphite carbon powder. In step 4, the catalyst precursor obtained in step 3 is loaded into a continuous atmosphere furnace for staged reduction and activation: first, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 2%. The temperature is increased to 140°C at a rate of 10°C / min and held for 2 hours. Then, the temperature is increased to 220°C at a rate of 1°C / min. Subsequently, the hydrogen volume concentration is gradually increased in three stages at this temperature, successively adjusted to 5%, 35%, and 100%, and each stage is kept at a constant temperature for 4 hours. Other steps are the same as in Example 1. The obtained copper-based silica catalyst is denoted as 15Cu1Ni-0.05C / SiO2-WG, where WG is the abbreviation for water glass.

[0039] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0040] Example 3

[0041] In step 1 of this embodiment, 200g of sodium silicate sol (20% SiO2, pH=11) and 3g of cationic polyacrylamide (mass-average molecular weight of 3 million) are completely dissolved in distilled water at 60°C to form a silica gel solution with a SiO2 mass concentration of 10%. Then, under the conditions of stirring speed of 500r / min and heating at 25°C, 0.25mol / L nitric acid aqueous solution is added dropwise to the above silica gel solution, controlling the pH of the system to be 4.5 during the dropwise addition process, and the dropwise addition time to be 60min, to obtain the modified sol. In step 4, the catalyst precursor obtained in step 3 is loaded into a continuous atmosphere furnace for staged reduction and activation: first, a mixture of hydrogen and nitrogen is introduced, controlling the hydrogen volume concentration to be 2%, and the temperature is raised to 140°C at a heating rate of 10°C / min and held for 2h; then, the temperature is raised to 230°C at a rate of 1°C / min, and then the hydrogen volume concentration is gradually increased in three stages at this temperature, successively adjusted to 5%, 30%, and 100%, and each stage is kept at a constant temperature for 4h. The other steps are the same as in Example 1. The resulting copper-based silica catalyst is denoted as 15Cu1Ni-0.05C / SiO2-LSN, where LSN is an abbreviation for sodium silicate sol.

[0042] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The methods for testing the dispersion of metallic Cu in the catalyst, the activity loss rate, the copper loss rate in the catalyst before and after the reaction, and the specific surface area were the same as those in Example 1, and the results are shown in Tables 1 and 2.

[0043] Example 4

[0044] In step 1 of this embodiment, 163.3g of tetraethyl silicate (28% SiO2, purity 98%) and 3.5g of cationic polyacrylamide (mass-average molecular weight 4 million) are completely dissolved in distilled water at 60°C to form a silica gel solution with a SiO2 mass concentration of 15%. Then, under the conditions of stirring speed of 800r / min and heating at 25°C, 0.3mol / L nitric acid aqueous solution is added dropwise to the above silica gel solution, controlling the pH of the system to be 6.0 during the dropwise addition process, and the dropwise addition time to be 80min, to obtain a modified sol. In step 4, the catalyst precursor obtained in step 3 is loaded into a continuous atmosphere furnace for segmented reduction and activation: first, a mixture of hydrogen and nitrogen is introduced, controlling the hydrogen volume concentration to be 2%, at a speed of 10°C / min. The temperature was increased to 140°C and held for 4 hours; then increased to 200°C at a rate of 1°C / min. Subsequently, the hydrogen volume concentration was gradually increased in three stages at this temperature, successively adjusted to 5%, 40%, and 100%, with each stage held at a constant temperature for 6 hours. Other steps were the same as in Example 1. The resulting copper-based silicon oxide catalyst was designated 15Cu1Ni-0.05C / SiO2-TE, where TE is the abbreviation for tetraethyl orthosilicate.

[0045] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0046] Example 5

[0047] In step 2 of this embodiment, 40.74g of copper nitrate, 3.25g of zinc nitrate, and 0.06g of coke powder (D50 of 100nm) are dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.15mol / L. A 25% ammonia solution is added dropwise to the mixed solution at 40°C and stirred vigorously to obtain a suspension with a pH of 10.7. In step 4, the catalyst precursor obtained in step 3 is loaded into a continuous atmosphere furnace for staged reduction and activation: first, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 3%. The temperature is increased to 120°C at a rate of 10°C / min and held for 2 hours. Then, the temperature is increased to 200°C at a rate of 3°C / min. Subsequently, the hydrogen volume concentration is gradually increased in three stages at this temperature, successively adjusted to 5%, 30%, and 100%, and each stage is kept at a constant temperature for 6 hours. The other steps are the same as in Example 1, and the resulting copper-based silicon oxide catalyst is denoted as 15Cu1Zn-0.05C / SiO2-LS.

[0048] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0049] Example 6

[0050] In step 2 of this embodiment, 40.74g of copper nitrate, 3.53g of cobalt nitrate, and 0.06g of coke powder (D50 of 100nm) were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.6mol / L. A 15% ammonia solution was then added dropwise to this mixed solution at 30°C, and the mixture was vigorously stirred until homogeneous, resulting in a suspension with a pH of 10.7. The other steps were the same as in Example 1, and the obtained copper-based silica catalyst was designated as 15Cu1Co-0.05C / SiO2-LS.

[0051] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The test methods for the dispersion of metallic Cu in the catalyst and the activity loss rate were the same as those in Example 1, and the results are shown in Table 1.

[0052] Example 7

[0053] In step 1 of this embodiment, under the conditions of stirring speed of 600 r / min and heating at 40°C, 0.3 mol / L hydrochloric acid aqueous solution is added dropwise to the silica gel solution, controlling the pH of the system to be 5.5 during the dropwise addition process, and the dropwise addition time is 50 min. The other steps are the same as in Example 1, and a copper-based silica catalyst is obtained, denoted as 15Cu1Ni-0.05C / SiO2-HA, where HA is the abbreviation for hydrochloric acid.

[0054] The prepared copper-based silica catalyst was packed into a fixed-bed reactor, and dimethyl oxalate was preheated to 140°C before being discharged at a flow rate of 0.72 h. -1 The hydrogenation reaction was initiated in the reactor at a mass hourly space velocity (MHSV). The hydrogenation reaction temperature was controlled at 180 °C, the pressure at 2 MPa, and the hydrogen-to-ester molar ratio at 100. The reaction products were quantitatively analyzed by gas chromatography. The conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0055] Example 8

[0056] In step 1 of this embodiment, under the conditions of stirring speed of 750 r / min and heating at 30°C, a 0.2 mol / L aqueous phosphoric acid solution is added dropwise to the silica gel solution, controlling the pH of the system to be 6.5 during the dropwise addition process, and the dropwise addition time is 70 min. The other steps are the same as in Example 1, and a copper-based silica catalyst is obtained, denoted as 15Cu1Ni-0.05C / SiO2-HP, where HP is the abbreviation for phosphoric acid.

[0057] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The test methods for the dispersion of metallic Cu in the catalyst and the activity loss rate were the same as those in Example 1, and the results are shown in Table 1.

[0058] Example 9

[0059] In step 2 of this embodiment, 41.25g of copper nitrate, 6.58g of zinc nitrate, and 0.07g of graphite carbon powder (D50=150nm) were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.5mol / L. A 15% ammonia solution was then added dropwise to this mixed solution at 60°C, and the mixture was vigorously stirred until homogeneous, resulting in a suspension with a pH of 10.7. The other steps were the same as in Example 5, and the obtained copper-based silicon oxide catalyst was designated as 15Cu2Zn-0.1C / SiO2-LS.

[0060] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0061] Example 10

[0062] In step 2 of this embodiment, 41.75g ​​of copper nitrate, 9.99g of zinc nitrate, and 0.15g of bamboo charcoal powder (D50=200nm) were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.5mol / L. A 13% ammonia solution was then added dropwise to this mixed solution at 40°C, and the mixture was vigorously stirred until homogeneous, resulting in a suspension with a pH of 10.2. The other steps were the same as in Example 5, and the obtained copper-based silica catalyst was designated as 15Cu3Zn-0.2C / SiO2-LS.

[0063] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1.

[0064] Example 11

[0065] In step 2 of this embodiment, 51.06g of copper nitrate, 5.54g of nickel nitrate, and 0.06g of bamboo charcoal powder (D50=200nm) were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.4mol / L. A 15% ammonia solution was then added dropwise to this mixed solution at 40°C, and the mixture was vigorously stirred until homogeneous, resulting in a suspension with a pH of 10.0. The other steps were the same as in Example 3, and the obtained copper-based silica catalyst was designated as 18Cu1.5Ni-0.08C / SiO2-LSN.

[0066] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The methods for testing the copper loss rate and specific surface area in the catalyst before and after the reaction were the same as in Example 1, and the results are shown in Table 2. TEM and XRD results are shown in Table 2. Figure 1 and 2 As shown.

[0067] Example 12

[0068] In step 2 of this embodiment, 101.33g of copper nitrate, 10.12g of nickel nitrate, and 0.14g of bamboo charcoal powder (D50=200nm) were dissolved in deionized water to prepare a mixed solution with a total metal ion concentration of 0.5mol / L. A 15% ammonia solution was then added dropwise to this mixed solution at 30°C, and the mixture was vigorously stirred until homogeneous, resulting in a suspension with a pH of 10.0. The other steps were the same as in Example 5, and the obtained copper-based silica catalyst was designated as 30Cu2.3Ni-0.16C / SiO2-LS.

[0069] The catalytic performance evaluation conditions of the obtained copper-based silica catalyst were the same as those in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The test methods for the dispersion of metallic Cu in the catalyst and the activity loss rate were the same as those in Example 1, and the results are shown in Table 1.

[0070] Comparative Example 1

[0071] A commercially available 18% Cu / SiO2 catalyst precursor with a columnar diameter × height of 5 mm × 5 mm was loaded into a continuous atmosphere furnace for staged reduction and activation: First, a mixture of hydrogen and nitrogen was introduced, and the hydrogen volume concentration was controlled at 1%. The temperature was increased to 150 °C at a rate of 4 °C / min and held for 2 h. Then, the temperature was increased to 220 °C at a rate of 1 °C / min. Subsequently, the hydrogen volume concentration was gradually increased in three stages at this temperature, successively adjusted to 5%, 10%, and 100%. Each stage was kept at a constant temperature for 1 h. Finally, the temperature was allowed to cool naturally to room temperature to obtain the 18% Cu / SiO2 catalyst.

[0072] The catalytic performance evaluation conditions of the obtained 18% Cu / SiO2 catalyst were the same as in Example 1. The reaction products were analyzed by gas chromatography, and the conversion rate of dimethyl oxalate and the selectivity of ethylene glycol are shown in Table 1. The methods for testing the dispersion of metallic Cu in the catalyst and the copper loss rate in the catalyst before and after the reaction were the same as in Example 1, and the results are shown in Table 1. TEM and XRD results are shown in Table 1. Figure 1 and 2 As shown.

[0073] Table 1

[0074]

[0075] Table 2

[0076]

[0077] Table 1 shows the performance test results, indicating that the catalyst of this invention exhibits superior dimethyl oxalate conversion and ethylene glycol selectivity compared to the commercial 18% Cu / SiO2 catalyst. The catalytic performance of Examples 1 and 3 is comparable to or slightly better than the 30% Cu-5% V / SiO2 catalyst reported in Comparative Example 2, but with lower activity loss after 5000 hours of long-term operation. Table 2 shows the characterization results, indicating that the catalyst of this invention has higher initial copper dispersion, and the copper loss rate and specific surface area decay after 1000 hours of operation are significantly lower than those of the commercial catalyst. TEM and XRD patterns show that the copper grain size in the 18Cu1.5Ni-0.08C / SiO2-LSN catalyst prepared in Example 11 is only 2–3 nm, with uniform grain dispersion, effectively suppressing particle agglomeration. Therefore, the catalyst preparation method of this invention can effectively refine grains, improve dispersion, and significantly enhance the hydrogenation performance and long-term stability of the catalyst.

Claims

1. A method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol production, characterized in that, Includes the following steps: Step 1: Dissolve the silicon source and polyacrylamide with a mass average molecular weight of 2 million to 15 million in distilled water at 20 to 90°C according to a mass ratio of polyacrylamide to SiO2 of 0.1 to 5:30, to prepare a silica gel solution with a SiO2 mass concentration of 1% to 20%. Under the conditions of stirring speed of 100 to 2000 r / min and heating temperature of 20 to 90°C, add 0.01 to 1 mol / L inorganic acid aqueous solution dropwise to the above silica gel solution, controlling the pH of the system between 3 and 8 during the dropwise addition process, and the dropwise addition time is 30 to 100 min, to obtain the modified sol. Step 2: Dissolve copper salt and auxiliary metal salt in deionized water, and add nano-sized carbon powder to prepare a mixed solution with a total metal ion concentration of 0.02–2 mol / L; under conditions of 5–50℃, add 5%–25% ammonia solution dropwise to the mixed solution and stir until homogeneous to obtain a suspension with pH of 9–12 in which the nano-sized carbon powder adsorbs copper ammonia complex ions; the auxiliary metal salt is any one or more soluble salts of Ni, Co, and Zn; Step 3: The modified sol obtained in Step 1 and the suspension obtained in Step 2 are simultaneously added dropwise to deionized water at 5-50℃ and stirred for adsorption for 1-10 hours; then the temperature is increased to 80-180℃ at a rate of 5-30℃ / min and held for 1-10 hours until the pH of the system is lower than 7, resulting in a blue precipitate; the precipitate is washed with deionized water until the conductivity of the filtrate is 50-800 μS / cm, and then dried at 80-200℃ for 6-20 hours. The dried material is mixed with 1%-5% of guar gum powder by mass, and deionized water is added to adjust it to a plastic state. The mixture is then extruded to obtain Raschig rings with an outer diameter × height × inner diameter of 5-8 mm × 5-10 mm × 1-3 mm. The rings are then placed in a muffle furnace and calcined at 300-500℃ for 2-10 hours to obtain the catalyst precursor. Step 4: The catalyst precursor obtained in Step 3 is loaded into a continuous atmosphere furnace for staged reduction and activation: First, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 1% to 5%. The temperature is increased to 80 to 160°C at a rate of 5 to 25°C / min and held for 2 to 10 hours. Then, the temperature is increased to 160 to 300°C at a rate of 0.5 to 10°C / min. Subsequently, the hydrogen volume concentration is gradually increased in three stages under isothermal conditions, successively adjusted to 5% to 20%, 30% to 50%, and 60% to 100%. Each stage is kept at a constant temperature for 2 to 10 hours. Finally, the temperature is allowed to drop naturally to room temperature to obtain the copper-based silicon oxide catalyst. The copper-based silica catalyst uses metallic Cu as the active component, one or more of Ni, Co, and Zn and nano-carbon powder as additives, and silica as the support. The mass content of metallic Cu in the catalyst is 5% to 50%, the total mass content of Ni, Co, and Zn is 0.5% to 10%, the mass content of nano-carbon powder is 0.01% to 1%, and the balance is silica.

2. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that, In step 1, the silicon source and polyacrylamide with a mass average molecular weight of 4 million to 10 million are dissolved in distilled water at 30 to 60°C, according to the mass ratio of polyacrylamide to SiO2 in the silicon source being 0.1 to 2:30, to prepare a silica gel solution with a SiO2 mass concentration of 2% to 10%.

3. The method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1 or 2, characterized in that, In step 1, the silicon source is one or more of water glass, tetraethyl silicate, tetrabutyl silicate, sodium silicate sol, and ammonia silica sol; the polyacrylamide is one or more of anionic, cationic, and nonionic types.

4. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that, In step 1, under the conditions of stirring speed of 200-1000 r / min and heating temperature of 20-50℃, 0.05-0.5 mol / L inorganic acid aqueous solution is added dropwise to the above silica gel solution, the pH of the system is controlled between 4 and 7, and the dropwise addition time is 50-80 min, to obtain modified sol.

5. The method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1 or 4, characterized in that, In step 1, the inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid.

6. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that, In step 2, copper salt and auxiliary metal salt are dissolved in deionized water, and nano-sized carbon powder is added to prepare a mixed solution with a total metal ion concentration of 0.05-1 mol / L. Under the condition of 10-40℃, the mixed solution is added dropwise to an ammonia solution with a mass concentration of 8%-15% and stirred evenly to obtain a suspension with a pH of 9-12.

7. The method for preparing a highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1 or 6, characterized in that, In step 2, the nano-sized carbon powder is one or more of coke powder, graphite carbon powder, and bamboo charcoal powder, with a particle size D50 of 50-200 nm; the copper salt is copper nitrate or copper acetate.

8. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that, In step 3, the modified sol and suspension are simultaneously added dropwise to deionized water at 10–40°C and stirred for adsorption for 2–8 hours. Then, the temperature is increased to 90–120°C at a rate of 10–20°C / min and held for 2–6 hours until the pH of the system is below 6.5, resulting in a blue precipitate. The precipitate is washed with deionized water until the conductivity of the washing solution is 50–300 μS / cm, and then dried at 100–150°C for 6–8 hours. The dried material is mixed with 2%–4% of guar gum powder by mass, and deionized water is added to adjust it to a plastic state. The mixture is then extruded to obtain Raschig rings with an outer diameter × height × inner diameter of 6–8 mm × 6–8 mm × 2–3 mm. The Raschig rings are calcined at 350–450°C for 4–6 hours to obtain the catalyst precursor.

9. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that, In step 4, the catalyst precursor is loaded into a continuous atmosphere furnace for staged reduction and activation: First, a mixture of hydrogen and nitrogen is introduced, and the hydrogen volume concentration is controlled at 2%–3%. The temperature is increased to 100–140°C at a rate of 10–15°C / min and held for 2–4 hours. Then, the temperature is increased to 200–250°C at a rate of 1–5°C / min. Subsequently, under constant temperature conditions, the hydrogen volume concentration is gradually increased in three stages, successively adjusted to 5%–10%, 30%–40%, and 80%–100%, with each stage held at a constant temperature for 2–6 hours.

10. The method for preparing the highly dispersed copper-based silica catalyst for coal-to-ethylene glycol according to claim 1, characterized in that: In step 4, the catalyst contains 10% to 30% Cu by mass, 1% to 5% Ni, Co and Zn by mass, 0.05% to 0.3% nano-sized carbon powder by mass, and the remainder is silicon oxide.

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