Composite solid acid catalyst, preparation method and method for synthesizing tetrahydrofuran from bdo raw material

Abstract

The present application relates to the technical field of organic synthesis, in particular to a composite solid acid catalyst, a preparation method and a method for synthesizing tetrahydrofuran from BDO raw materials. The present application discloses a composite solid acid catalyst, a preparation method and a method for synthesizing tetrahydrofuran from BDO raw materials, and a process for preparing high-purity tetrahydrofuran by dehydration and cyclization of 1,4-butanediol in a kettle reactor using the catalyst. By using a carbon-zirconium oxide high-specific-surface-area carrier, Ce to regulate acid sites and silane coupling agents to enhance the loading firmness, high conversion, high selectivity and high stability catalysis under mild conditions are realized; a nitrogen pressure-keeping, staged rectification and catalyst simple regeneration process are matched, and high-purity tetrahydrofuran with a purity of greater than or equal to 99.99wt% and solvent residue of less than or equal to 0.005wt% can be stably obtained, which is suitable for flexible production of small and medium-sized kettle devices.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a composite solid acid catalyst and its preparation method, and a method for synthesizing tetrahydrofuran from BDO raw materials, specifically a method for synthesizing tetrahydrofuran (THF) by catalytic dehydration and cyclization using a novel solid acid catalyst in a batch reactor. Background Technology

[0002] Tetrahydrofuran (THF), as an important organic solvent and chemical raw material, is widely used in the synthesis of polytetramethylene ether glycol (PTMEG), the preparation of pharmaceutical intermediates, and the processing of polymer materials. Currently, the mainstream industrial method for THF preparation is the 1,4-butanediol dehydration cyclization method. This method has advantages such as simple process and few byproducts, but existing technology still has many shortcomings: 1. Reactor type limitation: Existing technologies mostly use tubular fixed-bed reactors (such as CN202211622811.6, CN202510437924.6), which have problems such as uneven mass and heat transfer, easy carbon deposition and deactivation of catalysts, and large equipment investment, and are not suitable for small and medium-sized flexible production. 2. Catalyst performance defects: Traditional solid acid catalysts (such as modified silica-alumina molecular sieves and metal-doped alumina) have problems such as uneven distribution of acidic sites, insufficient selectivity, and poor thermal stability. Some catalysts are at risk of metal loss (such as the copper molybdate complex catalyst in CN202410806068.2), which leads to fluctuations in product purity and environmental pressure. 3. Harsh process conditions: Some processes require high pressure, high temperature or inert gas protection (such as CN202510437924.6 which requires high temperature reaction in air atmosphere), resulting in high energy consumption and increased operational complexity.

[0003] Therefore, developing a novel, efficient, stable, and environmentally friendly solid acid catalyst suitable for batch reactors, as well as an efficient synthesis process under mild conditions, has become an urgent technical problem to be solved. Summary of the Invention

[0004] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides a composite solid acid catalyst and its preparation method, as well as a method for synthesizing tetrahydrofuran from BDO raw materials. By designing a novel heteropolyacid-based composite solid acid catalyst and combining it with the mass transfer advantages of a batch reactor, efficient dehydration and cyclization of BDO can be achieved, solving problems such as poor catalyst stability, insufficient reactor adaptability, and high process energy consumption in existing technologies.

[0005] The above-mentioned objective is achieved through the following solution: A novel solid acid catalyst, comprising the following components in parts by weight: Carbon-zirconia composite carrier: 100 parts; Phosphotungstic acid (H3PW) 12 O 40 ): 15-30 servings; Cerium oxide (CeO2): 2-8 parts; Silane coupling agent (KH-550): 1~5 parts; The specific preparation method of the catalyst is as follows: The first aspect is the preparation method of the composite solid acid catalyst, which includes the following steps: (1) Preparation of carbon-zirconia support: Zirconium source and carbon source are mixed at a mass ratio of 1:0.8~1.2, water is added for dispersion, pH is adjusted to 3~5 (preferably 3.5~4.5, more preferably 3.8~4.2), hydrothermal reaction is carried out at 100~140℃ (preferably 110~130℃, more preferably 120~125℃) for 12~24h (preferably 15~21h, more preferably 18~20h), solid-liquid separation is performed, and then the solid is calcined at 500~600℃ in a nitrogen atmosphere for 4~6h (preferably 520~580℃, 4.5~5.5h, more preferably 550℃, 5h) to obtain carbon-zirconia support; (2) Preparation of modified phosphotungstic acid: Dissolve phosphotungstic acid in anhydrous ethanol, add cerium oxide powder, and stir and reflux at 60~80℃ (preferably 65~75℃, more preferably 70-72℃) for 2~4h (preferably 2.5~3.5h, more preferably 3h) to obtain Ce modified phosphotungstic acid solution; (3) Preparation of composite catalyst by loading: The carbon-zirconia support is immersed in the above solution and impregnated at 40~50℃ (preferably 42~48℃, more preferably 44~46℃) for 8~12h (preferably 9~11h, more preferably 9.5~10.5h) in equal volume. After filtration, it is dried at 110~130℃ (preferably 115~125℃, more preferably 120℃) for 6~8h (preferably 6.5~7.5h, more preferably 7h). An ethanol solution of silane coupling agent is added and stirred at room temperature for 2~3h (preferably 2.5-3h, more preferably 2.5h). After centrifugation, the solid is collected, dried at 100℃, and calcined in air at 150-300℃ (preferably 180-280℃, more preferably 200-250℃) for 2-8h (preferably 3-7h, more preferably 4-5h) to obtain the target Ce modified phosphotungstic acid / carbon-zirconia composite catalyst. In the above catalyst preparation process, the weight composition of each raw material is as follows: 100 parts of carbon-zirconium oxide support, 15-30 parts of phosphotungstic acid (preferably 18-28 parts, more preferably 20-25 parts), 2-8 parts of cerium oxide (preferably 3-7 parts, more preferably 4-6 parts), and 1-5 parts of silane coupling agent (preferably 2-4 parts, more preferably 2.5-3.5 parts).

[0006] Furthermore, the specific surface area of ​​the carbon-zirconia support is ≥350 m². 2 / g, pore volume ≥0.4cm 2 / g; In step (1), the zirconium source is one or more of zirconium chloride, zirconium acetate, zirconium silicate, and zirconium oxychloride; the carbon source is one or more of glucose, fructose, lactose, sucrose, and inulin. The pH is adjusted using one or more of the following substances: hydrochloric acid with a mass concentration of 26-28%, nitric acid with a mass concentration of 65-68%, sulfuric acid with a mass concentration of 98%, and acetic acid with a mass concentration of 99.5%. The amount of water used is 5-10 times that of the zirconium source. The zirconium source and carbon source are added to water and ultrasonically dispersed for 30-60 minutes (preferably 35-55 minutes, more preferably 40-50 minutes), and then the pH is adjusted. In step (1), the mass ratio of zirconium source to carbon source is 1:0.9~1.1 (preferably 1:0.95~1.05, more preferably 1:1.0); the hydrothermal reaction time is 12~18h (preferably 13~17h, more preferably 14~16h); and the calcination temperature is 530~580℃ (preferably 540~570℃, more preferably 550~560℃).

[0007] Furthermore, in step (2), the concentration of phosphotungstic acid in anhydrous ethanol is 0.15~0.30 g / mL (preferably 0.18~0.26 g / mL, more preferably 0.2~0.22 g / mL). The stirring and reflux temperature is 65~75℃ (preferably 68~72℃, more preferably 70℃), and the reflux time is 2.5~3.5h (preferably 2.8~3.2h, more preferably 3h).

[0008] Furthermore, the silane coupling agent in step (3) is one or more of KH-550, KH-560, KH-590, and KH-792; The mass concentration of the ethanol solution of the silane coupling agent is 5-15 wt%. The soaking time in step (3) is 9~11h (preferably 9.5~10.5h, more preferably 10h).

[0009] Secondly, the composite solid acid catalyst prepared by the method described above.

[0010] Thirdly, the method for synthesizing tetrahydrofuran from BDO feedstock utilizes the aforementioned composite solid acid catalyst to catalyze the catalytic dehydration and cyclization of 1,4-butanediol in a batch reactor, specifically including the following steps: S1. Reaction system configuration: Add 1,4-butanediol, composite solid acid catalyst and solvent to the batch reactor; S2. Reaction condition control: The reactor is sealed. After the atmosphere inside the reactor is replaced with nitrogen, the temperature is raised to the reaction temperature under stirring. Nitrogen is then added to the target reaction pressure. The pressure fluctuation is controlled to ≤±0.02MPa throughout the process by pressurizing and depressurizing. The reaction is kept at the temperature. S3. Product separation: After the reaction is completed, the temperature is lowered to 50-80℃ (preferably 50-75℃, more preferably 55-60℃), the catalyst is recovered by filtration, the reaction liquid is passed into a distillation column, the solvent is removed under normal pressure, and then the product is distilled under reduced pressure of 5-10 kPa (preferably 6-9 kPa, more preferably 7-8 kPa) to collect the fraction and obtain tetrahydrofuran product.

[0011] Furthermore, S4. Catalyst regeneration: The recovered catalyst is dried at 100~140℃ (preferably 100~130℃, more preferably 110~120℃) for 3~8h (preferably 4~7h, more preferably 4~6h), calcined at 300~400℃ (preferably 320~380℃, more preferably 340~360℃) for 1~4h (preferably 1.5~3.5h, more preferably 2~3h) and then recycled.

[0012] Furthermore, in step S1, the solvent is one or more of γ-butyrolactone, dichloromethane, acetone, and 1,2-dichloroethane.

[0013] Furthermore, in step S2, the reaction temperature is 120~160℃ (preferably 130~150℃, more preferably 135~145℃), the reaction pressure is 0.1~0.3MPa (preferably 0.15~0.25MPa, more preferably 0.18~0.22MPa), and the reaction time is 2~4h (preferably 2.5~3.5h, more preferably 3h). The mass ratio of the composite solid acid catalyst to 1,4-butanediol is 1:20~40 (preferably 1:25~35, more preferably 1:28~32), and the mass ratio of the solvent to 1,4-butanediol is 1:4~15 (preferably 1:6~12, more preferably 1:9~11).

[0014] Furthermore, the tetrahydrofuran product has a purity of ≥99.99%, a solvent content of ≤0.005% in impurities, and is free of methyltetrahydrofuran and succinic anhydride impurities.

[0015] The above technical solution has the following beneficial effects: 1. Novel Catalyst Design: Ce-modified phosphotungstic acid is supported on a carbon-zirconia composite support. The carbon phase enhances conductivity and resistance to carbon deposition, while zirconia provides a stable framework. 3+ By regulating the distribution of acidic sites, silane coupling agents enhance loading stability and achieve a precise match between acid strength and selectivity. 2. Adaptation to batch reactors: Taking advantage of the mixing capabilities of batch reactors, the catalyst particle size (50~100μm) and the flowability of the reaction system are optimized to solve the problem of uneven mass transfer in fixed beds. The system is flexible in operation and suitable for small and medium-scale production. 3. Mild and efficient process: The reaction temperature is 20-40℃ lower than that of the existing technology, the pressure is in the low pressure range, no need for continuous protection of inert gas is required, the cosolvent can be recycled, the catalyst regeneration is simple, and energy consumption is reduced by more than 30%. 4. High product purity: Through catalyst selectivity control and distillation process optimization, the THF product purity is ≥99.99wt%, free of impurities such as methyltetrahydrofuran and succinic anhydride, and the γ-butyrolactone content is ≤0.005wt%. Further explanation is provided below with reference to specific implementation methods. Detailed Implementation

[0016] Product testing methods: Gas chromatography was used to detect product purity and organic impurities. The chromatographic column was DB-624 (30m×0.32mm×1.8μm), and the detector was FID. The column temperature program was: 40℃ for 5 min, then ramped up to 120℃ at 10℃ / min and held for 2 min. The injection port temperature was 200℃ and the detector temperature was 250℃. External standard method was used for quantification.

[0017] Example 1 Preparation of catalyst 1 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then subjected to hydrothermal reaction at 120℃ for 18h. After filtration, the solid was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 380m²). 2 / g, pore volume 0.45cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 20g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain target catalyst 1.

[0018] Example 2 Preparation of catalyst 2 1. Preparation of carbon-zirconia support: 100g of zirconium acetate and 80g of fructose were added to 400mL of deionized water and ultrasonically dispersed for 30min. The pH was adjusted to 3 with nitric acid (65-68% by mass). The mixture was then hydrothermally reacted at 120℃ for 12h. After filtration, the solid was calcined at 500℃ under a nitrogen atmosphere for 4h to obtain a porous carbon-zirconia support (specific surface area 355m²). 2 / g, pore volume 0.41cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 15g of phosphotungstic acid in 80mL of anhydrous ethanol, add 2g of cerium oxide powder, and stir and reflux at 60℃ for 2h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 40℃ for 8h. After filtration, it was dried at 110℃ for 6h. 1g of KH-560 ethanol solution (concentration 10wt%) was added, stirred at room temperature for 2h, centrifuged, and the solid was collected, dried at 100℃, and calcined at 300℃ in air atmosphere for 2h to obtain target catalyst 2.

[0019] Example 3 Preparation of catalyst 3 1. Preparation of carbon-zirconia support: 100g of zirconium oxychloride and 120g of sucrose were added to 600mL of deionized water and ultrasonically dispersed for 60min. The pH was adjusted to 5 with 98% sulfuric acid, and the mixture was hydrothermally reacted at 120℃ for 24h. After filtration, the solid was calcined at 600℃ under a nitrogen atmosphere for 6h to obtain a porous carbon-zirconia support (specific surface area 392m²). 2 / g, pore volume 0.48cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 30g of phosphotungstic acid in 150mL of anhydrous ethanol, add 8g of cerium oxide powder, stir and reflux at 80℃ for 4h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 50℃ for 12h. After filtration, it was dried at 130℃ for 8h. 5g of KH-590 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 3h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 3h to obtain the target catalyst.

[0020] Example 4 Preparation of catalyst 4 1. Preparation of carbon-zirconia support: 100g of zirconium silicate and 90g of lactose were added to 500mL of deionized water and ultrasonically dispersed for 40min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then hydrothermally reacted at 120℃ for 15h. After filtration, the solid was calcined at 530℃ under a nitrogen atmosphere for 4.5h to obtain a porous carbon-zirconia support (specific surface area 368m²). 2 / g, pore volume 0.43cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 25g of phosphotungstic acid in 120mL of anhydrous ethanol, add 6g of cerium oxide powder, stir and reflux at 65℃ for 2.5h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 42℃ for 9h. After filtration, it was dried at 115℃ for 6.5h. 2g of KH-792 ethanol solution (concentration 10wt%) was added, stirred at room temperature for 2.2h, centrifuged, and the solid was collected, dried at 100℃, and calcined at 220℃ in air atmosphere for 2.5h to obtain the target catalyst.

[0021] Example 5 Preparation of catalyst 5 1. Preparation of carbon-zirconia support: 50g zirconium chloride + 50g zirconium acetate (total 100g zirconium source) and 110g inulin were added to 500mL of deionized water and ultrasonically dispersed for 50min. The pH was adjusted to 4 with nitric acid (65-68% by mass), and the mixture was hydrothermally reacted at 120℃ for 18h. After filtration, the solid was calcined at 580℃ under a nitrogen atmosphere for 5.5h to obtain a porous carbon-zirconia support (specific surface area 385m²). 2 / g, pore volume 0.46cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 22g of phosphotungstic acid in 110mL of anhydrous ethanol, add 4g of cerium oxide powder, and stir and reflux at 75℃ for 3.5h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 48℃ for 11h. After filtration, it was dried at 125℃ for 7.5h. 4g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.8h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 240℃ for 2.8h to obtain the target catalyst.

[0022] Example 6 Preparation of Catalyst 6 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with hydrochloric acid, and the mixture was hydrothermally reacted at 120℃ for 16h. After filtration, the solid was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 375m²). 2 / g, pore volume 0.44cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 18g of phosphotungstic acid in 90mL of anhydrous ethanol, add 3g of cerium oxide powder, and stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. A mixed ethanol solution of 2g KH-560 + 1g KH-792 (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 220℃ for 2.5h to obtain the target catalyst.

[0023] Example 7 Preparation of Catalyst 7 1. Preparation of carbon-zirconia support: 100g of zirconium oxychloride and 100g of fructose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with sulfuric acid, and the mixture was hydrothermally reacted at 120℃ for 14h. After filtration, the solid was calcined at 540℃ under a nitrogen atmosphere for 4.5h to obtain a porous carbon-zirconia support (specific surface area 362m²). 2 / g, pore volume 0.42cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 24g of phosphotungstic acid in 120mL of anhydrous ethanol, add 7g of cerium oxide powder, stir and reflux at 68℃ for 2.8h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 44℃ for 9.5h. After filtration, it was dried at 118℃ for 6.8h. 3g of KH-590 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.4h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 230℃ for 2.6h to obtain the target catalyst.

[0024] Example 8 Add 2 kg of 1,4-butanediol, 100 g of catalyst 1 prepared in Example 1, and 300 g of γ-butyrolactone to a 5 L batch reactor; purge the atmosphere inside the batch reactor with nitrogen three times, stir at 400 rpm, heat to 140 °C, replenish nitrogen to 0.2 MPa, and control the pressure fluctuation ≤ ±0.02 MPa throughout the process by pressurizing and depressurizing, and maintain the temperature for 3 h; then cool to 70 °C. Post-processing: The catalyst was recovered by filtration, and the reaction solution was passed into a distillation column to remove γ-butyrolactone at 90°C under normal pressure (288g recovered, recovery rate 96%). Then, it was distilled at 8 kPaG, and the fraction at 68°C was collected to obtain 1.42 kg of THF product; BDO ​​conversion rate 99.3%, THF selectivity 99.6%, product purity 99.992 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0025] Example 9 2 kg of 1,4-butanediol, 80 g of catalyst 2 prepared in Example 2, and 200 g of dichloromethane were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 350 rpm, the temperature was raised to 120 °C, and nitrogen was added to 0.1 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 2 h. The temperature was lowered to 60 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. Dichloromethane was removed at 40 °C under normal pressure (190 g was recovered, recovery rate 95%). Then, the product was distilled at 5 kPa, and the fraction at 66 °C was collected to obtain 1.38 kg of tetrahydrofuran product. The conversion rate of 1,4-butanediol was 98.5%, the selectivity of tetrahydrofuran was 99.4%, the purity of the product was 99.990 wt%, the impurity content of dichloromethane was 0.002 wt%, and the moisture content was 0.004 wt%.

[0026] Example 10 2 kg of 1,4-butanediol, 50 g of catalyst 3 prepared in Example 3, and 400 g of acetone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 450 rpm, the temperature was raised to 160 °C, and nitrogen was added to 0.3 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 4 h. The temperature was lowered to 75 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. Acetone was removed at 56 °C under normal pressure (384 g was recovered, recovery rate 96%). Then, the product was distilled at 10 kPa, and the fraction at 69 °C was collected to obtain 1.41 kg of tetrahydrofuran product. The conversion rate of 1,4-butanediol was 99.1%, the selectivity of tetrahydrofuran was 99.3%, the purity of the product was 99.991 wt%, the acetone impurity content was 0.004 wt%, and the water content was 0.003 wt%.

[0027] Example 11 2 kg of 1,4-butanediol, 100 g of catalyst 4 prepared in Example 4, and 333 g of 1,2-dichloroethane were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 130 °C, and nitrogen was added to 0.15 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 2.5 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. 1,2-dichloroethane was removed at 83 °C under normal pressure (319 g was recovered, recovery rate 96%). Then, the product was distilled at 7 kPa, and the fraction at 67 °C was collected to obtain 1.40 kg of tetrahydrofuran product. The conversion rate of 1,4-butanediol was 99.0%, the selectivity of tetrahydrofuran was 99.5%, the purity of the product was 99.991 wt%, the impurity content of 1,2-dichloroethane was 0.003 wt%, and the water content was 0.004 wt%.

[0028] Example 12 2 kg of 1,4-butanediol, 50 g of catalyst 5 prepared in Example 5, and 400 g of mixed solvent (γ-butyrolactone: acetone = 1:1) were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 380 rpm, the temperature was raised to 150 °C, and nitrogen was added to 0.25 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3.5 h. The temperature was lowered to 65 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. The mixed solvent was removed under normal pressure (380 g was recovered, recovery rate 95%), and then distilled at 9 kPa. The fraction at 68 °C was collected to obtain 1.39 kg of tetrahydrofuran product. The conversion rate of 1,4-butanediol was 98.8%, the selectivity of tetrahydrofuran was 99.4%, the purity of the product was 99.990 wt%, the total impurity content of the mixed solvent was 0.004 wt%, and the water content was 0.004 wt%.

[0029] Example 13 2 kg of 1,4-butanediol, 67 g of catalyst 4 prepared in Example 4, and 250 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 135 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was held at this temperature for 3 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. γ-butyrolactone was removed at 90 °C under normal pressure (240 g was recovered, recovery rate 96%). Then, the product was distilled at 8 kPaG, and the fraction at 68 °C was collected to obtain 1.42 kg of THF product. The BDO conversion rate was 99.4%, the THF selectivity was 99.5%, the product purity was 99.991 wt%, the γ-butyrolactone impurity content was 0.003 wt%, and the moisture content was 0.004 wt%.

[0030] Example 14 2 kg of 1,4-butanediol, 80 g of catalyst 6 prepared in Example 6, and 220 g of 1,2-dichloroethane were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 145 °C, and nitrogen was added to 0.2 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 2.8 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. 1,2-dichloroethane was removed at 80 °C under normal pressure (210 g was recovered, recovery rate 95%). Then, the product was distilled at 8 kPaG, and the fraction at 68 °C was collected to obtain 1.40 kg of THF product. The BDO conversion rate was 99.4%, the THF selectivity was 99.6%, the product purity was 99.992 wt%, the γ-butyrolactone impurity content was 0.003 wt%, and the moisture content was 0.003 wt%.

[0031] Example 15 2 kg of 1,4-butanediol, 57 g of catalyst 7 prepared in Example 7, and 300 g of acetone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 150 °C, and nitrogen was added to 0.25 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3.2 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. Acetone was removed at 60 °C under normal pressure (282 g recovered, recovery rate 94%). The product was then distilled at 8 kPaG, and the fraction at 68 °C was collected to obtain 1.4 kg of THF product. The BDO conversion rate was 99.0%, the THF selectivity was 99.4%, the product purity was 99.990 wt%, the γ-butyrolactone impurity content was 0.003 wt%, and the moisture content was 0.003 wt%.

[0032] Example 16: Cyclic Performance Test of Catalyst 1 The catalyst recovered in Example 8 was dried at 110°C for 4 hours and calcined at 350°C for 2 hours. The synthesis process of Example 8 was repeated for 5 consecutive cycles (the recovered catalyst was dried at 110°C for 4 hours and calcined at 250°C for 2 hours each time before being reused). The results are as follows: Table 1 shows the results after 5 iterations.

[0033] Example 17 1. Preparation of carbon-zirconia support: 100g of zirconium oxychloride and 90g of fructose were added to 500mL of deionized water and ultrasonically dispersed for 40min. The pH was adjusted to 3.8 with 65-68% nitric acid, and the mixture was hydrothermally reacted at 115℃ for 16h. After filtration, the mixture was calcined at 540℃ under a nitrogen atmosphere for 4.5h to obtain carbon-zirconia support (specific surface area 372m²). 2 / g, pore volume 0.43cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 22g of phosphotungstic acid in 110mL of anhydrous ethanol, add 4g of cerium oxide powder, and stir and reflux at 68℃ for 2.8h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 43℃ for 9.5h. After filtration, it was dried at 118℃ for 7h. 2.5g of KH-560 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.2h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 230℃ for 2.5h to obtain the target catalyst 17.

[0034] 2 kg of 1,4-butanediol, 100 g of catalyst 17 prepared in Example 17, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.2%, THF selectivity 99.5%, product purity 99.991 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0035] Example 18 1. Preparation of carbon-zirconia support: 100g of zirconium acetate and 110g of sucrose were added to 550mL of deionized water and ultrasonically dispersed for 50min. The pH was adjusted to 4.2 with hydrochloric acid, and the mixture was hydrothermally reacted at 125℃ for 20h. After filtration, the mixture was calcined at 570℃ under a nitrogen atmosphere for 5.5h to obtain carbon-zirconia support (specific surface area 386m²). 2 / g, pore volume 0.46cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 28g of phosphotungstic acid in 140mL of anhydrous ethanol, add 7g of cerium oxide powder, and stir and reflux at 72℃ for 3.2h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 47℃ for 10.5h. After filtration, it was dried at 122℃ for 7.5h. 4g of KH-792 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.8h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 240℃ for 3h to obtain the target catalyst 18.

[0036] 2 kg of 1,4-butanediol, 100 g of catalyst 18 prepared in Example 18, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.4%, THF selectivity 99.6%, product purity 99.992 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.004 wt%.

[0037] Example 19 1. Preparation of carbon-zirconia support: 100g of zirconium silicate and 95g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4.0 with 99.5% acetic acid, and the mixture was hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain carbon-zirconia support (specific surface area 358m²). 2 / g, pore volume 0.42cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 20g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 19.

[0038] 2 kg of 1,4-butanediol, 100 g of catalyst 19 prepared in Example 19, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.1%, THF selectivity 99.4%, product purity 99.991 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0039] Example 20 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 105g of fructose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4.5 with hydrochloric acid, and the mixture was hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 560℃ under a nitrogen atmosphere for 5h to obtain carbon-zirconia support (specific surface area 375m²). 2 / g, pore volume 0.44cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 20g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 20.

[0040] 2 kg of 1,4-butanediol, 100 g of catalyst 20 prepared in Example 20, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.3%, THF selectivity 99.5%, product purity 99.992 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0041] Example 21 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 380m²). 2 / g, pore volume 0.45cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 24g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, and stir and reflux at 68℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 21.

[0042] 2 kg of 1,4-butanediol, 100 g of catalyst 21 prepared in Example 21, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was held at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.2%, THF selectivity 99.5%, product purity 99.991 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0043] Example 22 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 380m²). 2 / g, pore volume 0.45cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 18g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, and stir and reflux at 72℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 10wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 22.

[0044] 2 kg of 1,4-butanediol, 100 g of catalyst 22 prepared in Example 22, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurizing and depressurizing. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.0%, THF selectivity 99.4%, product purity 99.991 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0045] Example 23 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 380m²). 2 / g, pore volume 0.45cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 18g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of KH-550 ethanol solution (concentration 8wt%) was added, and the mixture was stirred at room temperature for 2.5h. After centrifugation, the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 23.

[0046] 2 kg of 1,4-butanediol, 100 g of catalyst 23 prepared in Example 23, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.0%, THF selectivity 99.4%, product purity 99.991 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0047] Example 24 1. Preparation of carbon-zirconia support: 100g of zirconium chloride and 100g of glucose were added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid (26-28% by mass). The mixture was then hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a porous carbon-zirconia support (specific surface area 380m²). 2 / g, pore volume 0.45cm 3 / g); 2. Preparation of modified phosphotungstic acid: Dissolve 18g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 70℃ for 3h to obtain a solution; 3. Loading and modification: 100g of carbon-zirconia support was immersed in the above solution and impregnated at 45℃ for 10h. After filtration, it was dried at 120℃ for 7h. 3g of a mixed ethanol solution of KH-550 and KH-590 (mass ratio 1:1, concentration 12wt%) was added. The mixture was stirred at room temperature for 2.5h, centrifuged, and the solid was collected, dried at 100℃, and calcined in air at 250℃ for 2.5h to obtain the target catalyst 24.

[0048] 2 kg of 1,4-butanediol, 100 g of catalyst 24 prepared in Example 24, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.20 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.3%, THF selectivity 99.5%, product purity 99.992 wt%, γ-butyrolactone content 0.003 wt%, and moisture content 0.003 wt%.

[0049] Example 25 2 kg of 1,4-butanediol, 57 g of catalyst 1 prepared in Example 1, and 100 g of 1,2-dichloroethane were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 130 °C, and nitrogen was added to 0.15 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 2.5 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.0%, THF selectivity 99.4%, product purity 99.991 wt%, 1,2-dichloroethane 0.003 wt%, and moisture 0.003 wt%.

[0050] Example 26 2 kg of 1,4-butanediol, 80 g of catalyst 1 prepared in Example 1, and 250 g of acetone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 150 °C, and nitrogen was added to 0.25 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3.5 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.2%, THF selectivity 99.5%, product purity 99.991 wt%, acetone 0.003 wt%, and water 0.003 wt%.

[0051] Example 27 2 kg of 1,4-butanediol, 80 g of catalyst 1 prepared in Example 1, and 250 g of acetone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 150 °C, and nitrogen was added to 0.25 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3.5 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 99.2%, THF selectivity 99.5%, product purity 99.991 wt%, acetone 0.003 wt%, and water 0.003 wt%.

[0052] Comparative Example 1: Using ZSM-5 molecular sieve catalyst Following the process conditions of Example 8, the catalyst was replaced with an equal mass of ZSM-5 molecular sieve (silicon-to-aluminum ratio 50). The results showed that the BDO conversion rate was 89.5%, the THF selectivity was 75.2%, the product purity was 99.85 wt%, and the conversion rate dropped to 75.3% after the catalyst was used twice.

[0053] Comparative Example 2 Catalyst preparation: Except for step 2, where cerium oxide is not added, the rest of the process and conditions are the same as those in Example 1, Catalyst 1 preparation process, to obtain the catalyst.

[0054] 2 kg of 1,4-butanediol, 100 g of the above catalyst, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, and the reaction was carried out at 400 rpm, 140 °C, and 0.2 MPa for 3 h. The post-treatment was the same as in Example 8. Results: BDO conversion rate was 92.3%, THF selectivity was 88.7%, and product purity was 99.62 wt%. After two catalyst cycles, the conversion rate decreased to 66.3%.

[0055] Comparative Example 3 Catalyst preparation: Pure zirconium oxide support was used. Except for the absence of carbon source in step 1, the rest of the process and conditions were the same as those for catalyst 1 in Example 1.

[0056] Preparation of zirconia support: 100g of zirconium chloride was added to 500mL of deionized water and ultrasonically dispersed for 45min. The pH was adjusted to 4 with concentrated hydrochloric acid, and the mixture was hydrothermally reacted at 120℃ for 18h. After filtration, the mixture was calcined at 550℃ under a nitrogen atmosphere for 5h to obtain a zirconia support (specific surface area 80m²). 2 / g, pore volume 0.15cm 3 / g); 2 kg of 1,4-butanediol, 100 g of the above catalyst, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, and the reaction was carried out at 400 rpm, 140 °C, and 0.2 MPa for 3 h. The post-treatment was the same as in Example 8. Results: BDO conversion rate 75.6%, THF selectivity 62.3%, and product purity 98.77 wt%.

[0057] Comparative Example 4 Catalyst preparation: Except for step 3, which does not use a silane coupling agent, the rest of the process and conditions are the same as those for catalyst 1 in Example 1.

[0058] Loading and modification: 100g of carbon-zirconia support was immersed in the above solution, impregnated at 45℃ for 10h, filtered, dried at 120℃ for 7h, ethanol solution was added, stirred at room temperature for 2.5h, and calcined at 320℃ in air atmosphere for 2.5h to obtain the catalyst.

[0059] 2 kg of 1,4-butanediol, 100 g of the above catalyst, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, and the reaction was carried out at 400 rpm, 140 °C, and 0.2 MPa for 3 h. The post-treatment was the same as in Example 8. Results: BDO conversion rate was 63.2%, THF selectivity was 65.3%, and product purity was 96.9 wt%. After two catalyst cycles, the conversion rate decreased to 32.2%.

[0060] Comparative Example 5 2 kg of 1,4-butanediol, 100 g of catalyst 1 prepared in Example 1, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 110 °C, the pressure was controlled at 0.2 MPa, and the reaction was maintained at this temperature for 3 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. γ-butyrolactone was removed at 90 °C under normal pressure (288 g was recovered, recovery rate 96%). Then, the product was distilled at 8 kPaG, and the fraction at 68 °C was collected to obtain 0.98 kg of THF product. The BDO conversion rate was 70.6%, the THF selectivity was 95.3%, the product purity was 99.992 wt%, and the γ-butyrolactone impurity content was 0.003 wt%.

[0061] Comparative Example 6 2 kg of 1,4-butanediol, 30 g of catalyst 1 prepared in Example 1, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 110 °C, the pressure was controlled at 0.2 MPa, and the reaction was maintained at this temperature for 3 h. The temperature was lowered to 70 °C, the catalyst was recovered by filtration, and the reaction liquid was passed into a distillation column. γ-butyrolactone was removed at 90 °C under normal pressure (288 g was recovered, recovery rate 96%). Then, the product was distilled at 8 kPaG, and the fraction at 68 °C was collected to obtain 0.73 kg of THF product. The BDO conversion rate was 53.26%, the THF selectivity was 82.3%, the product purity was 99.992 wt%, and the γ-butyrolactone impurity content was 0.003 wt%.

[0062] Comparative Example 7 1. Preparation of carbon-zirconia support: The process and conditions are the same as in Example 1, except that 100g of zirconium chloride and 50g of glucose are used as raw materials, and the remaining preparation steps are the same as in step 1 of Example 1, resulting in a carbon-zirconia support (specific surface area 195m²). 2 / g, pore volume 0.21cm 3 / g); 2. Modified phosphotungstic acid and supported modification: Following the same procedures and conditions as steps 2 and 3 in Example 1, catalyst D7 was obtained.

[0063] 2 kg of 1,4-butanediol, 100 g of catalyst D7 prepared in Comparative Example 7, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 72.5%, THF selectivity was 78.1%, and product purity was 98.91 wt%. After two catalyst cycles, the conversion rate decreased to 54.8%.

[0064] Comparative Example 8 1. Preparation of carbon-zirconia support: The process and conditions are the same as in Example 1, except that: 100g of zirconium chloride and 100g of glucose are reacted hydrothermally for 8 hours, calcined at 450℃ under nitrogen atmosphere for 5 hours, and the remaining processes and conditions are the same as in Example 1, to obtain a carbon-zirconia support (specific surface area 220m²). 2 / g, pore volume 0.25cm 3 / g); 2. The subsequent preparation steps are the same as steps 2 and 3 in Example 1, and the catalyst D8 is obtained.

[0065] 2 kg of 1,4-butanediol, 100 g of catalyst D8 prepared in Comparative Example 8, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 78.3%, THF selectivity was 81.5%, and product purity was 99.12 wt%. After two catalyst cycles, the conversion rate decreased to 59.2%.

[0066] Comparative Example 9 1. Preparation of carbon-zirconia support: The process and conditions are the same as in Example 1, except that: 100g of zirconium chloride and 100g of glucose are taken, and the pH is adjusted to 2.2 with concentrated hydrochloric acid. The remaining steps are the same as in Example 1, to obtain a carbon-zirconia support (specific surface area 245m²). 2 / g, pore volume 0.28cm 3 / g); 2. The subsequent preparation steps are the same as steps 2 and 3 in Example 1, and the catalyst D9 is obtained.

[0067] 2 kg of 1,4-butanediol, 100 g of catalyst D9 prepared in Comparative Example 9, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to bring the pressure up to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurizing and depressurizing. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 76.8%, THF selectivity was 80.3%, and product purity was 99.05 wt%. After two catalyst cycles, the conversion rate decreased to 57.1%.

[0068] Comparative Example 10 1. Preparation of carbon-zirconia support: The process and conditions are the same as in Example 1, except that: 100g of zirconium chloride and 100g of glucose are taken, and the pH is adjusted to 5.8 with ammonia water. The remaining steps are the same as in Example 1, to obtain a carbon-zirconia support (specific surface area 270m²). 2 / g, pore volume 0.30cm 3 / g); 2. The subsequent preparation steps are the same as steps 2 and 3 in Example 1, and the catalyst D10 is obtained.

[0069] 2 kg of 1,4-butanediol, 100 g of catalyst D10 prepared in Comparative Example 10, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 79.4%, THF selectivity was 82.6%, and product purity was 99.18 wt%. After two catalyst cycles, the conversion rate decreased to 58.5%.

[0070] Comparative Example 11 1. Preparation of carbon-zirconia support: Same as step 1 in Example 1, procedure and conditions; 2. Preparation of modified phosphotungstic acid: Dissolve 10g of phosphotungstic acid in 100mL of anhydrous ethanol (concentration 0.10g / mL), add 5g of cerium oxide powder, and stir and reflux at 70℃ for 3h to obtain a solution; 3. The subsequent preparation steps are the same as step 3 in Example 1, and the catalyst D11 is obtained.

[0071] 2 kg of 1,4-butanediol, 100 g of catalyst D11 prepared in Comparative Example 11, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 74.2%, THF selectivity was 80.8%, and product purity was 99.01 wt%. After two catalyst cycles, the conversion rate decreased to 56.9%.

[0072] Comparative Example 12 1. Preparation of carbon-zirconia support: Same as step 1 in Example 1, procedure and conditions; 2. Preparation of modified phosphotungstic acid: Dissolve 20g of phosphotungstic acid in 100mL of anhydrous ethanol, add 5g of cerium oxide powder, stir and reflux at 50℃ for 1h to obtain a solution; 3. The subsequent preparation steps are the same as step 3 in Example 1, and the catalyst D12 is obtained.

[0073] 2 kg of 1,4-butanediol, 100 g of catalyst D12 prepared in Comparative Example 12, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 77.6%, THF selectivity was 80.8%, and product purity was 99.01 wt%. After two catalyst cycles, the conversion rate decreased to 56.9%.

[0074] Comparative Example 13 1. Preparation of carbon-zirconia support and modified phosphotungstic acid: Same as steps 1 and 2 in Example 1, and under the same conditions; 2. Loading and modification: Add an ethanol solution of KH-550 (concentration 3wt%), and follow the same procedures and conditions as in step 3 of Example 1 to obtain catalyst D13.

[0075] 2 kg of 1,4-butanediol, 100 g of catalyst D13 prepared in Comparative Example 13, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 73.8%, THF selectivity was 76.9%, and product purity was 98.79 wt%. After two catalyst cycles, the conversion rate decreased to 54.5%.

[0076] Comparative Example 14 1. Preparation of carbon-zirconia support and modified phosphotungstic acid: Same as steps 1 and 2 in Example 1, and under the same conditions; 2. Loading and modification: Add an ethanol solution of n-octyltriethoxysilane (concentration 20wt%), and follow the same procedures and conditions as in step 3 of Example 1 to obtain catalyst D14.

[0077] 2 kg of 1,4-butanediol, 100 g of catalyst D14 prepared in Comparative Example 14, and 300 g of γ-butyrolactone were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 140 °C, and nitrogen was added to 0.22 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate was 75.5%, THF selectivity was 78.2%, and product purity was 98.88 wt%. After two catalyst cycles, the conversion rate decreased to 55.7%.

[0078] Comparative Example 15 2 kg of 1,4-butanediol, 40 g of catalyst 1 prepared in Example 1, and 300 g of ethanol were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 100 °C, and nitrogen was added to 0.2 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the mixture was filtered and distilled. Results: BDO conversion rate 58.7%, THF selectivity 71.4%, product purity 98.26 wt%, and ethanol residue 0.12 wt%.

[0079] Comparative Example 16 2 kg of 1,4-butanediol, 133 g of catalyst 1 prepared in Example 1, and 300 g of ethyl acetate were added to a 5 L batch reactor. The atmosphere inside the batch reactor was purged with nitrogen three times, the stirring speed was 400 rpm, the temperature was raised to 170 °C, and nitrogen was added to 0.2 MPa. The pressure fluctuation was controlled to ≤ ±0.02 MPa throughout the process by pressurization and depressurization. The reaction was maintained at this temperature for 3 h. The temperature was then lowered to 70 °C, and the product was filtered and distilled. Results: BDO conversion rate was 99.5%, THF selectivity was 69.4%, product purity was 98.51 wt%, oligomers appeared in the product, and the color turned yellow.

[0080] Comparative Example 17 The catalyst recovered in Example 8 was dried at 80°C for 2 hours and calcined at 250°C for 0.5 hours. The synthesis process of Example 8 was repeated. The BDO conversion rate was 65.7%, the THF selectivity was 76.9%, and the product purity was 98.11 wt%.

[0081] Comparative Example 18 The catalyst recovered in Example 8 was dried at 160°C for 9 hours and calcined at 450°C for 5 hours. The synthesis process of Example 8 was repeated. The third cycle showed a BDO conversion of 74.1%, a THF selectivity of 82.3%, and a product purity of 98.92 wt%.

Claims

1. A method for preparing a composite solid acid catalyst, characterized in that, Includes the following steps: (1) Preparation of carbon-zirconia support: Zirconium source and carbon source are mixed at a mass ratio of 1:0.8~1.2, water is added for dispersion, pH is adjusted to 3~5, hydrothermal reaction is carried out at 100~140℃ for 12~24h, solid and liquid are separated, and then the solid is calcined at 500~600℃ under nitrogen atmosphere for 4~6h to obtain carbon-zirconia support; (2) Preparation of modified phosphotungstic acid: Dissolve phosphotungstic acid in anhydrous ethanol, add cerium oxide powder, stir and reflux at 60~80℃ for 2~4h to obtain Ce modified phosphotungstic acid solution; (3) Preparation of composite catalyst by loading: The carbon-zirconia support is immersed in the above solution and impregnated at 40~50℃ for 8~12h. After filtration, it is dried at 110~130℃ for 6~8h. An ethanol solution of silane coupling agent is added and stirred at room temperature for 2~3h. After centrifugation, the solid is collected, dried at 100℃, and calcined in air at 150-300℃ for 2-8h to obtain the target Ce modified phosphotungstic acid / carbon-zirconia composite catalyst. In the above catalyst preparation process, the weight composition of each raw material is as follows: 100 parts of carbon-zirconium oxide support, 15-30 parts of phosphotungstic acid, 2-8 parts of cerium oxide, and 1-5 parts of silane coupling agent.

2. The preparation method of the composite solid acid catalyst according to claim 1, characterized in that, The specific surface area of ​​the carbon-zirconia support is ≥350m². 2 / g, pore volume ≥0.4cm 2 / g; In step (1), the zirconium source is one or more of zirconium chloride, zirconium acetate, zirconium silicate, and zirconium oxychloride; the carbon source is one or more of glucose, fructose, lactose, sucrose, and inulin. The pH is adjusted using one or more of the following substances: hydrochloric acid with a mass concentration of 26-28%, nitric acid with a mass concentration of 65-68%, sulfuric acid with a mass concentration of 98%, and acetic acid with a mass concentration of 99.5%. The amount of water used is 5-10 times that of the zirconium source. Add the zirconium source and carbon source to the water and ultrasonically disperse for 30-60 minutes, then adjust the pH. In step (1), the mass ratio of zirconium source to carbon source is 1:0.9~1.1; the hydrothermal reaction time is 12~18h; and the calcination temperature is 530~580℃.

3. The method for preparing the composite solid acid catalyst according to claim 1, characterized in that, In step (2), the concentration of phosphotungstic acid in anhydrous ethanol is 0.15~0.30 g / mL; The stirring and reflux temperature is 65~75℃, and the reflux time is 2.5~3.5h.

4. The method for preparing the composite solid acid catalyst according to claim 1, characterized in that, The silane coupling agent in step (3) is one or more of KH-550, KH-560, KH-590, and KH-792; The mass concentration of the ethanol solution of the silane coupling agent is 5-15 wt%. The soaking time in step (3) is 9~11 hours.

5. The composite solid acid catalyst prepared by the method described in any one of claims 1-4.

6. A method for synthesizing tetrahydrofuran from BDO feedstock, characterized in that, Using the composite solid acid catalyst described in claim 5, the catalytic dehydration and cyclization of 1,4-butanediol in a batch reactor specifically includes the following steps: S1. Reaction system configuration: Add 1,4-butanediol, composite solid acid catalyst and solvent to the batch reactor; S2. Reaction condition control: The reactor is sealed. After the atmosphere inside the reactor is replaced with nitrogen, the temperature is raised to the reaction temperature under stirring. Nitrogen is then added to the target reaction pressure. The pressure fluctuation is controlled to ≤±0.02MPa throughout the process by pressurizing and depressurizing. The reaction is kept at the temperature. S3. Product separation: After the reaction is completed, the temperature is lowered to 50-80℃, the catalyst is recovered by filtration, the reaction liquid is passed into a distillation column, the solvent is removed under normal pressure, and then the product is distilled under reduced pressure of 5-10 kPa to collect the distillate to obtain tetrahydrofuran product.

7. The method for synthesizing tetrahydrofuran from BDO feedstock according to claim 6, characterized in that, S4. Catalyst regeneration: The recovered catalyst is dried at 100~140℃ for 3~8h, calcined at 300~400℃ for 1~4h, and then recycled.

8. The method for synthesizing tetrahydrofuran from BDO feedstock according to claim 6, characterized in that, The solvent in step S1 is one or more of γ-butyrolactone, dichloromethane, acetone, and 1,2-dichloroethane.

9. The method for synthesizing tetrahydrofuran from BDO feedstock according to claim 6, characterized in that, In step S2, the reaction temperature is 120~160℃, the reaction pressure is 0.1~0.3MPa, and the reaction time is 2~4h; The mass ratio of the composite solid acid catalyst to 1,4-butanediol is 1:20~40, and the mass ratio of the solvent to 1,4-butanediol is 1:4~15.

10. The method for synthesizing tetrahydrofuran from BDO feedstock according to claim 6, characterized in that, The tetrahydrofuran product has a purity of ≥99.99%, and the solvent content in the impurities is ≤0.005%. It does not contain methyltetrahydrofuran or succinic anhydride impurities.

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