A method for preparing tetrahydrofuran by liquid-phase catalytic hydrogenation of maleic anhydride

Abstract

A method for preparing tetrahydrofuran by liquid-phase catalytic hydrogenation of maleic anhydride. Maleic anhydride is used as a raw material, and tetrahydrofuran is prepared by hydrogenation of maleic anhydride in a liquid organic environment in the presence of a ternary metal silicide catalyst. The ternary metal silicide is a Ti-Ni-Si series catalyst with the general formula Ti x Ni y Si z , where x = 1; y = 1-3; and z = 1-1.5, representing the number of Ti, Ni, and Si atoms, respectively. When using 1,4-dioxane as the solvent, the catalyst for liquid-phase hydrogenation of maleic anhydride achieves a maleic anhydride conversion of nearly 100% at a temperature of 200-300°C and a pressure of 1-4 MPa, with a tetrahydrofuran selectivity exceeding 70%. This catalyst exhibits high selectivity, strong corrosion resistance to the acidic environment in the reaction system, and high stability. The preparation process is simple, reducing the use of precious metal catalysts, and has promising prospects for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of new catalytic materials and fine chemical industry, and relates to a method for preparing tetrahydrofuran by using maleic anhydride as a raw material. Background Art

[0002] Tetrahydrofuran (THF) is an important organic solvent and intermediate. Due to its strong polarity, high solvency, and low boiling point (66°C), it is used as a solvent and reaction medium in the synthesis of various drugs, including antibiotics and anticancer drugs. In particular, it can dissolve all polymers except polyethylene, polypropylene, and fluororesins. THF is also used to produce polytetrahydrofuran (PTHF) and polytetrahydrofuran glycol (PTMEG). The latter is the basic raw material for the production of high-elasticity spandex, which is mainly used in the production of high-elasticity knitwear such as high-end sportswear and swimwear. Due to its excellent performance, adding 3-5% spandex to many fabrics can greatly improve their wearing properties. Another important use of THF is in the manufacture of functional materials, such as conductive polymers and nanomaterial dispersants. In the electronics industry, it is used as an electrolyte solvent and photoresist solvent, and is widely used in lithium-ion battery and semiconductor manufacturing. In recent years, with the gradual promotion and application of spandex in industries such as medical and sanitary products, automotive decoration, and national defense, the spandex industry has developed rapidly, forming a new growth point for market demand. At the same time, the rapid development of industries such as biodegradable plastic PBAT and lithium battery material N-methylpyrrolidone (NMP) has led to a corresponding increase in demand for tetrahydrofuran, which has brought it huge market opportunities.

[0003] Industrial green and low-carbon transformation and industrial empowerment of green development are important directions for my country's industrial transformation. Traditional industrial production methods of tetrahydrofuran mainly rely on a variety of production methods such as 1,4-butanediol (BDO) dehydration cyclization and furfuryl alcohol hydrogenolysis. Among them, the BDO catalytic dehydration method is currently the main industrial technology route for the production of tetrahydrofuran. According to different synthesis routes, the BDO dehydration cyclization method can be divided into the Reppe method, the PBT / PBAT by-product route and the LBDO purification method. The Reppe method uses high-purity BDO as raw material. It was developed by Dr. Reppe of Germany in 1930 and was first industrialized by BASF of Germany in 1940. The industrial device built is the "1,4-butanediol-tetrahydrofuran-polytetrahydrofuran" co-production device, which is currently the most mainstream production technology in the industry. This process generally uses catalysts containing acidic components, such as the ZSM-5 molecular sieve catalyst reported in Chinese patent CN1283620 and the strongly acidic ion exchange resin catalyst reported in CN101298444A. However, the reaction liquid in this process is highly acidic, placing high demands on the materials used in the reaction equipment. Furthermore, BDO, as a raw material, has seen strong demand in recent years, requiring large quantities to be imported annually to meet downstream industrial production. This high price further increases production costs.

[0004] Furfuryl alcohol hydrogenolysis is a method for producing tetrahydrofuran (THF) from renewable resources. Furfuryl alcohol can be obtained by converting biomass (such as corn cobs or other crop waste), and then undergoing a hydrogenolysis reaction under the action of high-pressure hydrogen and a catalyst to produce tetrahydrofuran. The main advantage of this process is that it can utilize renewable resources, helping to reduce dependence on petrochemical resources and lowering the carbon footprint. However, the supply of furfuryl alcohol is limited by the seasonality and regionality of crops, resulting in unstable supply. In addition, the furfuryl alcohol hydrogenolysis process generally requires high temperatures and pressures, consumes a lot of energy, and the catalyst is easily deactivated, limiting the large-scale application of this process.

[0005] In recent years, the catalytic hydrogenation of maleic anhydride has been developed, offering significant economic benefits. With breakthroughs in butane oxidation to maleic anhydride, maleic anhydride prices have declined, leading to a surge in new and expanded facilities. With the rapid growth of maleic anhydride production capacity, maleic anhydride production has seen rapid capacity growth, resulting in a severe oversupply. In contrast, the development of maleic anhydride's downstream products continues to lag behind this growth, necessitating increased market development. This process utilizes a widely available and inexpensive raw material, maleic anhydride, which can be operated under relatively mild conditions, reducing energy consumption and equipment corrosion. This, to a certain extent, avoids the pollution issues associated with the furfuryl alcohol process and the raw material shortages associated with BDO catalytic dehydration cyclization.

[0006] There are two main methods for producing tetrahydrofuran from maleic anhydride. One is the esterification hydrogenation method, developed by UCC in the United States and Davy McKee in the United Kingdom. Maleic anhydride is first completely converted into dimethyl maleate, which is then hydrogenated over a Cu-based catalyst to produce tetrahydrofuran. For example, Chinese patent CN1857771A reports the direct hydrogenation of dimethyl maleate to tetrahydrofuran using a CuO-ZnO-Al2O3 catalyst, but this method has a relatively long process route. The other is the catalytic hydrogenation of maleic anhydride, which includes gas-phase hydrogenation and liquid-phase hydrogenation of maleic anhydride. For example, Chinese patent CN101386608A discloses a Cu-Zn-Zr series catalyst for producing tetrahydrofuran by vapor-phase one-step hydrogenation of maleic anhydride using ethanol as the solvent (12:88, w / w). High tetrahydrofuran selectivity is achieved at a pressure of 1 MPa and a temperature of 220-280°C. Simultaneously, the ethanol solvent reacts under the catalytic action of the catalyst to produce hydrogen, with ethyl acetate and acetaldehyde as byproducts. Furthermore, this process fails to consider the stability of the catalyst in the reaction, resulting in a highly acidic reaction solution that corrodes the catalyst, thereby shortening its service life. Chinese patent CN101168535A discloses a Cu-Zn-Ti-Ce series catalyst for producing tetrahydrofuran by vapor-phase one-step hydrogenation of maleic anhydride using n-butanol as the solvent at a pressure of 1 MPa and a temperature of 265-280°C. The yield is greater than 75%, with n-butanol reacting under the catalytic action of the catalyst to produce hydrogen, butyl butyrate, and n-butanol. Therefore, in the gas-phase hydrogenation of maleic anhydride, alcohol solvents are generally used in the gasification process, resulting in the reaction process where the alcohol solvents react and consume the solvent while producing more by-products. In addition, alcohols and water generated by hydrogenation of maleic anhydride to produce tetrahydrofuran easily form azeotropes, making separation difficult.

[0007] Liquid-phase hydrogenation of maleic anhydride mainly adopts precious metals such as Ru, Rh, Pd, etc. among transition metals, and also non-precious metals such as Ni and Co. At present, the products of existing patent reports liquid-phase hydrogenation are mostly gamma-butyrolactone or succinic anhydride, and the selectivity to tetrahydrofuran (THF) is very low or even no tetrahydrofuran (THF) is generated. For example, Chinese patent CN 102229587A discloses a method for producing succinic anhydride by nano-nickel catalytic hydrogenation of maleic anhydride, which has high activity, high selectivity and high yield for producing succinic anhydride, but is only used in autoclave batch reactions and cannot be produced continuously. CN 106955710A discloses a maleic anhydride liquid-phase hydrogenation catalyst, which is composed of nickel / zirconium oxide / aluminum oxide / silicon oxide, but the catalyst preparation process is complicated and requires an alcohol aqueous solution, resulting in a high catalyst cost. At present, there is no patent report on the method for producing tetrahydrofuran (THF) by liquid-phase catalytic hydrogenation of maleic anhydride.

[0008] To address the shortcomings of the aforementioned prior art, we employ a prepared ternary intermetallic silicide Ti-Ni-Si catalyst series in the liquid-phase hydrogenation of maleic anhydride using 1,4-dioxane as a solvent. Combining this hydrogenation with the corrosion-resistant ternary metal silicide results in enhanced acid corrosion resistance and stability in relatively high-concentration maleic anhydride organic solutions, thereby enhancing stability and catalytic activity in the liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran. The process of the present invention enables the successful production of tetrahydrofuran through a single-step hydrogenation of maleic anhydride in the liquid-phase hydrogenation of maleic anhydride, and exhibits advantages such as complete maleic anhydride conversion, high tetrahydrofuran selectivity, and catalyst stability, while avoiding the use of alcoholic solvents and precious metal catalysts. Summary of the Invention

[0009] The purpose of the present invention is to provide a new technology for preparing tetrahydrofuran by liquid phase hydrogenation.

[0010] A method for preparing tetrahydrofuran by liquid-phase catalytic hydrogenation of maleic anhydride, comprising the following steps:

[0011] Tetrahydrofuran is prepared by one-step liquid-phase hydrogenation of maleic anhydride using maleic anhydride as raw material and 1,4-dioxane as solvent in the presence of Ti-Ni-Si ternary metal silicide catalyst under certain temperature and pressure conditions.

[0012] The maleic anhydride hydrogenation reaction is carried out in a fixed bed reactor.

[0013] The raw material is a maleic anhydride solution with a concentration of 0.5wt%-10wt%, which is pumped into a fixed bed reactor, mixed with hydrogen, and enters a reaction section for liquid phase hydrogenation reaction.

[0014] The reaction conditions of the liquid phase hydrogenation reaction are: reaction temperature of 200-300°C, preferably 220-280°C; reaction pressure of 1-4 MPa, preferably 1.5-2.5 MPa; mass space velocity of maleic anhydride of 0.2-3.0 h -1 , preferably 0.8-2h -1 .

[0015] The general formula of Ti-Ni-Si ternary metal silicide catalyst is: Ti x Ni y Si z , x, y, z represent the atomic numbers of Ti, Ni and Si respectively, and the control range is: x=1; y=1-3; z=1-1.5.

[0016] The Ti-Ni-Si ternary metal silicide catalyst is synthesized by the low-temperature molten salt method, and the steps are as follows:

[0017] The silicon source and the metal precursor salt are mixed and impregnated to form a catalyst precursor, and then mixed with a low eutectic point salt, calcined in a hydrogen-argon mixture at a temperature of 400°C-700°C for 2-4 hours, and then washed with an acidic solvent to a certain acidity and alkalinity, and then washed with deionized water to neutrality, and dried to obtain a Ti-Ni-Si ternary metal silicide catalyst.

[0018] The silicon source is one of MCM-41, SAB-15 and SiO2.

[0019] The metal precursor salts are metal nickel salts and titanium salts.

[0020] The metal nickel salt is Ni(NO3)·6H2O and / or NiCl2.

[0021] The metal titanium salt is TiCl4 and / or TiO2.

[0022] The low eutectic point salt is one of KCl-KI, NaCl-CaH2, KCl-CaH2, and CaH2-LiCl, and the mass ratio of the two metal salts in the low eutectic point salt is 1:0.5-2.

[0023] The mass ratio of the metal precursor salt to the low eutectic point salt is 1:1-3.

[0024] The certain acidity and alkalinity is pH=9-12.

[0025] The beneficial effects of the present invention are as follows: (1) The present invention solves the problem of low selectivity of tetrahydrofuran in the liquid-phase preparation of tetrahydrofuran from maleic anhydride in the prior art, and provides a new ternary metal silicide catalyst for the liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran. When the catalyst of the present invention is used in the liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran, under the above-mentioned reaction conditions, the maleic anhydride conversion rate is close to 100%, and the selectivity of tetrahydrofuran is greater than 70%. While showing high selectivity, the catalyst also has strong corrosion resistance to the acid environment in the reaction system and exhibits high stability.

[0026] (2) The preparation process of the present invention is simple, the catalyst is inexpensive, the use of precious metal catalysts is reduced, and the reaction process is optimized. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a ternary metal silicide Ti6Ni 16 XRD diffraction pattern of Si7 catalyst.

[0028] Figure 2 It is a ternary metal silicide Ti6Ni 16 Conversion and selectivity of Si7-catalyzed liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran.

[0029] Figure 3 It is a ternary metal silicide Ti6Ni 16 Stability of Si7-catalyzed liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran. DETAILED DESCRIPTION

[0030] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0031] Example 1: Preparation of Ternary Metal Silicide Ti4Ni7Si4 Catalyst

[0032] Prepare 1.804g of TiCl4 solution, 2.766g of Ni(NO3)2·6H2O, and 1g of SBA-15 dissolved in 50ml of deionized water to make a mixed solution, add it to a 100ml flask, heat it in a water bath, maintain the temperature at 110℃ for 14h, then take it out and evaporation, place the sample in a muffle furnace at 600℃ for 2h to obtain a green solid catalyst; grind the above green solid catalyst, take 0.4g of the catalyst and mix it with low-temperature molten salt in a certain proportion and grind it. The catalyst was calcined at 5°C / min to 600°C for 2 h in a tubular furnace under an Ar / H2 atmosphere to obtain a black solid. The black solid catalyst was washed with an acidic detergent solution of 1 mol / L NH4Cl solution to control the pH of the solution to 9-12, and then repeatedly washed with deionized water until neutral, and centrifuged. The sample was placed in a 70°C oven and dried for 12 h to obtain a Ti4Ni7Si4 ternary metal silicide catalyst.

[0033] Example 2: Preparation of Ternary Metal Silicide TiNiSi Catalyst

[0034] Prepare a mixture of 3.157 g of TiCl4 solution, 4.840 g of Ni(NO3)2·6H2O, and 1 g of SBA-15 dissolved in 50 ml of deionized water. The mixture was added to a 100 ml flask, heated in a water bath, maintained at 110°C for 14 h, and then removed and rotary evaporated. The sample was placed in a muffle furnace and calcined at 600°C for 2 h to obtain a green solid catalyst. After grinding the above green solid catalyst, 0.4 g of the catalyst was mixed with a low-temperature molten salt in a certain proportion (including 1.2 g of CaH2 and 0.6 g of LiCl) and ground. The mixture was heated to 600°C at 5°C / min in a tube furnace under an Ar / H2 atmosphere for 2 h, and a black solid was obtained after removal. The above black solid catalyst was washed with an acidic detergent 1 mol / L NH4Cl solution to control the solution pH to 9-12, then repeatedly washed with deionized water until neutral, centrifuged, and the sample was placed in a 70°C oven and dried for 12 h to obtain a TiNiSi ternary metal silicide catalyst.

[0035] Example 3: Ternary Metal Silicide Ti13 Ni 40 Si 31 Catalyst preparation

[0036] Prepare 1.324g of TiCl4 solution, 6.245g of Ni(NO3)2·6H2O, and 1g of SBA-15, dissolve them in 50ml of deionized water to make a mixed solution, add it to a 100ml flask, heat it in a water bath, maintain the temperature at 110°C for 14h, take it out and evaporation, place the sample in a muffle furnace at 600°C and calcine for 2h to obtain a green solid catalyst; grind the above green solid catalyst, take 0.4g of the catalyst and mix it with low-temperature molten salt in a certain proportion (including 1.2g of CaH2 and 0.6g of LiCl), and calcine it at 600°C at 5°C / min in a tubular furnace Ar / H2 atmosphere for 2h, and take it out to obtain a black solid; wash the above black solid catalyst with an acidic detergent 1mol / LNH4Cl solution to control the solution pH to 9-12, then wash it repeatedly with deionized water until neutral, centrifuge, place the sample in a 70°C oven, dry it for 12h, and obtain Ti 13 Ni 40 Si 31 Ternary metal silicide catalyst.

[0037] Example 4: Ternary Metal Silicide Ti6Ni 16 Preparation of Si7 catalyst

[0038] Prepare 2.706g of TiCl4 solution, 11.063g of Ni(NO3)2·6H2O, and 1g of SBA-15 dissolved in 50ml of deionized water to make a mixed solution, add it to a 100ml flask, heat it in a water bath, maintain the temperature at 110°C for 14h, take it out and evaporation, place the sample in a muffle furnace at 600°C and calcine for 2h to obtain a green solid catalyst; grind the above green solid catalyst and take 0.4g of the catalyst and mix it with low-temperature molten salt in a certain proportion (including 1.2g of CaH2 and 0.6g of LiCl) and grind it, raise the temperature to 600°C at 5°C / min in a tubular furnace Ar / H2 atmosphere and calcine it for 2h, take it out to obtain a black solid; wash the above black solid catalyst with an acidic detergent 1mol / LNH4Cl solution to control the solution pH to 9-12, then wash it repeatedly with deionized water until neutral, centrifuge, place the sample in a 70°C oven, dry it for 12h, and obtain Ti6Ni 16 Si7 ternary metal silicide catalyst, the XRD diffraction pattern of the obtained catalyst is as follows Figure 1 shown.

[0039] Example 5: Preparation of Ternary Metal Silicide Ti4Ni4Si Catalyst

[0040] Prepare 12.628g of TiCl4 solution, 19.360g of Ni(NO3)2·6H2O, and 1g of SBA-15 dissolved in 50ml of deionized water to make a mixed solution, add it to a 100ml flask, heat it in a water bath, maintain the temperature at 110℃ for 14h, then take it out and evaporation, place the sample in a muffle furnace at 600℃ for 2h to obtain a green solid catalyst; grind the above green solid catalyst, take 0.4g of the catalyst and mix it with low-temperature molten salt in a certain proportion and grind it. The catalyst was calcined at 5°C / min to 600°C for 2 h in a tubular furnace under an Ar / H2 atmosphere to obtain a black solid. The black solid catalyst was washed with an acidic detergent 1 mol / L NH4Cl solution to control the pH of the solution to 9-12, and then repeatedly washed with deionized water until neutral, centrifuged, and the sample was placed in a 70°C oven and dried for 12 h to obtain a Ti4Ni4Si ternary metal silicide catalyst.

[0041] Example 6: The ternary metal silicide Ti4Ni7Si4 catalyst prepared in Example 1 was used to catalyze the liquid-phase hydrogenation of maleic anhydride. A 2wt.% maleic anhydride (1,4-dioxane) solution was used as a substrate to investigate the activity and selectivity of the Ti4Ni7Si4 ternary metal silicide catalyst prepared in Example 1 in the liquid-phase hydrogenation of maleic anhydride to produce tetrahydrofuran. The reaction was carried out in a fixed-bed reaction. Prior to the reaction, the catalyst was pre-activated at 400°C in an H2 atmosphere for 2h. The process conditions were: catalyst Ti4Ni7Si4: 0.1g (diluted to 4ml with quartz sand), temperature 260°C, pressure 2MPa, maleic anhydride mass space velocity 0.4h -1 , the ratio of hydrogen to maleic anhydride solution is 350.

[0042] The products were analyzed by G7890Ⅱ gas chromatography and high performance liquid chromatography with a differential detection detector. The reaction results are shown in Table 1.

[0043] Example 7: Liquid-Phase Hydrogenation of Maleic Anhydride Catalyzed by the Ternary Metal Silicide TiNiSi Catalyst of Example 2

[0044] The activity and selectivity for the target product of the TiNiSi ternary metal silicide catalyst prepared in Example 1 in the liquid-phase hydrogenation of maleic anhydride to tetrahydrofuran were investigated using a 2 wt.% maleic anhydride (1,4-dioxane) solution as the substrate. The reaction was carried out in a fixed-bed reactor, and the catalyst was pre-activated at 400°C in a H2 atmosphere for 2 hours prior to the reaction. The process conditions were: catalyst TiNiSi: 0.1 g (diluted with quartz sand to 4 ml), temperature 260°C, pressure 2 MPa, and maleic anhydride mass space velocity of 0.4 h / min. -1 , the ratio of hydrogen to maleic anhydride solution is 350.

[0045] The product was detected by the same gas chromatography method and liquid chromatography method as in Example 6. The reaction results are shown in Table 1.

[0046] Example 8: Using the ternary metal silicide Ti of Example 3 13 Ni 40 Si 31 Catalyzed Liquid Phase Hydrogenation of Maleic Anhydride

[0047] The Ti prepared in Example 1 was investigated using 2 wt.% maleic anhydride (1,4-dioxane) solution as a substrate. 13 Ni 40 Si 31 The activity and selectivity of ternary metal silicide catalysts in the liquid phase hydrogenation of maleic anhydride to tetrahydrofuran were investigated. The reaction was carried out in a fixed bed reactor. The catalyst was pre-activated at 400°C in a H2 atmosphere for 2 hours before the reaction. The process conditions were: catalyst Ti 13 Ni 40 Si 31 : 0.1g (diluted with quartz sand to 4ml), temperature 260℃, pressure 2MPa, maleic anhydride mass space velocity 0.4h -1 , the ratio of hydrogen to maleic anhydride solution is 350.

[0048] The product was detected by the same gas chromatography method and liquid chromatography method as in Example 6. The reaction results are shown in Table 1.

[0049] Example 9: Using the ternary metal silicide Ti6Ni of Example 4 16 Liquid Phase Hydrogenation of Maleic Anhydride Catalyzed by Si7 Catalyst

[0050] The Ti6Ni prepared in Example 1 was investigated using 2 wt.% maleic anhydride (1,4-dioxane) solution as a substrate. 16 The activity and selectivity of Si7 ternary metal silicide catalyst in the liquid phase hydrogenation of maleic anhydride to tetrahydrofuran were studied. The reaction was carried out in a fixed bed reactor. The catalyst was pre-activated at 400°C in a H2 atmosphere for 2 hours before the reaction. The process conditions were: catalyst Ti6Ni 16 Si7: 0.1 g (diluted with quartz sand to 4 ml), temperature 260 ° C, pressure 2 MPa, maleic anhydride mass space velocity 0.4 h -1 , the ratio of hydrogen to maleic anhydride solution is 350.

[0051] The product was detected by the same gas chromatography method and liquid chromatography method as in Example 6. The reaction results are shown in Table 1.

[0052] Example 10: Liquid-Phase Hydrogenation of Maleic Anhydride Catalyzed by the Ternary Metal Silicide Ti4Ni4Si Catalyst of Example 5

[0053] The activity and selectivity of the Ti4Ni4Si ternary metal silicide catalyst prepared in Example 1 in the liquid phase hydrogenation of maleic anhydride to tetrahydrofuran were investigated using a 2 wt.% maleic anhydride (1,4-dioxane) solution as the substrate. The reaction was carried out in a fixed bed reactor. The catalyst was pre-activated at 400°C in a H2 atmosphere for 2 h before the reaction. The process conditions were as follows: the catalyst Ti6Ni4Si 16 Si7: 0.1 g (diluted with quartz sand to 4 ml), temperature 260 ° C, pressure 2 MPa, maleic anhydride mass space velocity 0.4 h -1 , the ratio of hydrogen to maleic anhydride solution is 350.

[0054] The product was detected by the same gas chromatography method and liquid chromatography method as in Example 6. The reaction results are shown in Table 1.

[0055] Table 1 Effect of different catalyst compositions on catalytic activity

[0056]

[0057] Note: Others include succinic acid, succinic anhydride, butyric acid, propionic acid, etc., and overall material conservation is maintained.

[0058] Based on the above data, among the ternary metal silicide catalysts, Ti6Ni 16 Si7, due to its unique ratio and structure, greatly reduces the activation energy of the intermediate product γ-butyrolactone hydrogenation to tetrahydrofuran, making it show excellent C=O hydrogenation activity. For other ratios of Ti-Ni-Si ternary metal silicide, the hydrogenation activity is weak, and the continuous hydrogenation effect on the C=O bond is not strong, and it is difficult to achieve the same level as Ti6Ni 16 Si7 catalyst has the same catalytic effect.

[0059] The description of the above embodiments is only used to help understand the method of the present invention and its core concept. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing tetrahydrofuran by liquid-phase catalytic hydrogenation of maleic anhydride, characterized in that: Here are the steps: Tetrahydrofuran is produced by one-step liquid-phase hydrogenation of maleic anhydride in a fixed-bed reactor using maleic anhydride as raw material and 1,4-dioxane as solvent in the presence of a Ti-Ni-Si ternary metal silicide catalyst under certain temperature and pressure conditions. The general formula of the Ti-Ni-Si ternary metal silicide catalyst is: Ti x Ni y Si z , x, y, z represent the atomic numbers of Ti, Ni and Si respectively, and the control range is: x=1; y=1-3; z=1-1.5; The Ti-Ni-Si ternary metal silicide catalyst is synthesized by a low-temperature molten salt method, and the steps are as follows: The silicon source and the metal precursor salt are mixed and impregnated to form a catalyst precursor, which is then mixed with a low eutectic point salt and calcined in a hydrogen-argon mixture at a temperature of 400°C-700°C for 2-4 hours. After that, the catalyst is washed with an acidic solvent to a certain acidity and alkalinity, and then washed with deionized water to neutrality and dried to obtain a Ti-Ni-Si ternary metal silicide catalyst.

2. The method according to claim 1, characterized in that The reaction conditions of the liquid phase hydrogenation reaction are: reaction temperature of 200-300 ° C, reaction pressure of 1-4 MPa, mass space velocity of maleic anhydride of 0.2-3.0 h -1 .

3. The method according to claim 1, characterized in that The raw material is a 0.5 wt%-10 wt% maleic anhydride solution, which is pumped into a fixed bed reactor, mixed with hydrogen, and then enters a reaction zone for liquid-phase hydrogenation reaction.

4. The method according to claim 1, wherein The silicon source is one of MCM-41, SAB-15 and SiO2.

5. The method according to claim 1, wherein The metal precursor salts are metal nickel salts and titanium salts; the metal nickel salts are Ni(NO3)·6H2O and / or NiCl2; and the metal titanium salts are TiCl4 and / or TiO2.

6. The method according to claim 1, characterized in that The low eutectic point salt is one of KCl-KI, NaCl-CaH2, KCl-CaH2, and CaH2-LiCl, and the mass ratio of the two metal salts in the low eutectic point salt is 1:0.5-2.

7. The method according to claim 1, characterized in that The mass ratio of the metal precursor salt to the low eutectic point salt is 1:1-3.

8. The method according to claim 1, characterized in that The certain acidity and alkalinity is pH=9~12.

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