Method for preparing tetrahydrofuran through liquid-phase catalytic hydrogenation of maleic anhydride

Abstract

The invention relates to a method for preparing tetrahydrofuran by liquid-phase catalytic hydrogenation of maleic anhydride. According to the method, maleic anhydride is used as a raw material and is subjected to one-step hydrogenation in a liquid-phase organic environment in the presence of a ternary metal silicide catalyst to prepare tetrahydrofuran. The ternary metal silicide is a Ti-Ni-Si series catalyst, the general formula of the ternary metal silicide is Ti < x > Ni < y > Si < z >, and x is equal to 1; y is equal to 1-3; z is equal to 1 to 1.5; and each represents the number of atoms of Ti, Ni, and Si. When 1, 4-dioxane is used as a solvent, the catalyst is used for maleic anhydride liquid phase hydrogenation, the conversion rate of maleic anhydride is close to 100% at the temperature of 200-300 DEG C and the pressure of 1-4 MPa, the selectivity of tetrahydrofuran is greater than 70%, high selectivity is shown, meanwhile, the catalyst has high corrosion resistance to an acid environment in a reaction system, and high stability is shown. And the preparation process is simple, the use of a noble metal catalyst is reduced, and the method has a better industrial application prospect.

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 taking maleic anhydride as raw material. Background Art

[0002] Tetrahydrofuran is an important organic solvent and intermediate. Due to its strong polarity, high solubility and low boiling point (66°C), it is used as a solvent and reaction medium in the synthesis of various drugs such as antibiotics and anticancer drugs. In particular, it can dissolve all polymers except polyethylene, polypropylene and fluororesins. Tetrahydrofuran is also used to produce polytetrahydrofuran (PTHF) and polytetrahydrofuran glycol (PTMEG). The latter is the basic raw material for producing high-elastic spandex, which is mainly used to produce high-elastic knitwear such as high-end sportswear and swimsuits. Due to the good performance of spandex, adding 3-5% spandex to many fabrics can greatly improve the wearing performance. Another important use of tetrahydrofuran is to manufacture functional materials, such as conductive polymers and nanomaterial dispersants, and as an electrolyte solvent and photoresist solvent in the electronics industry, it is widely used in lithium-ion batteries and semiconductor manufacturing. In recent years, with the gradual increase in the promotion and application of spandex in industries such as medical and health products, automobile decoration, and national defense, the spandex industry has developed rapidly, forming a new growth point for market demand. At the same time, with the rapid development of industries such as biodegradable plastic PBAT and lithium battery material N-methylpyrrolidone (NMP), the demand for tetrahydrofuran has increased accordingly, making it face 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 method and furfuryl alcohol hydrogenolysis method. 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 industrially built device is a "1,4-butanediol-tetrahydrofuran-polytetrahydrofuran" co-production device, which is currently the most mainstream production technology in the industry. It generally uses a catalyst containing an acidic component, such as the ZSM-5 molecular sieve catalyst reported in Chinese patent CN1283620; the strong acid ion exchange resin catalyst reported in CN101298444A, etc. However, the process reaction liquid is relatively acidic, so it has high requirements on the material of the reaction device. In addition, BDO as a raw material has been in high demand in recent years, and a large amount of imports are required every year to meet downstream industrial production. The price is relatively high, which further increases the production cost.

[0004] Furfuryl alcohol hydrogenolysis is a method for producing tetrahydrofuran from renewable resources. Furfuryl alcohol can be obtained by converting biomass (such as corn cobs or other crop wastes), and then undergoing hydrogenolysis reaction under the action of high-pressure hydrogen and catalyst to produce tetrahydrofuran. The main advantage of this process is that it can utilize renewable resources, which helps reduce dependence on petrochemical resources and reduces carbon footprint. However, the supply of furfuryl alcohol is unstable due to the seasonal and regional restrictions of crops. In addition, the furfuryl alcohol hydrogenolysis process usually requires higher temperatures and pressures, consumes more energy, and the catalyst is easily deactivated, which limits the large-scale application of this process.

[0005] In recent years, a catalytic hydrogenation method for maleic anhydride with obvious economic benefits has been developed. With the breakthrough of the process of producing maleic anhydride by butane oxidation, the price of maleic anhydride has declined, and many new and expanded devices have been built. With the rapid growth of maleic anhydride production capacity, maleic anhydride has seen a situation of excessively fast growth in production capacity and serious oversupply. In contrast, the development of maleic anhydride's downstream products still lags behind the pace of production capacity growth, and it is very necessary to strengthen the development of the market for maleic anhydride's downstream products. Therefore, the raw material maleic anhydride used in this process is widely available and inexpensive, and can be carried out under relatively mild conditions, reducing energy consumption and equipment corrosion, and to a certain extent avoiding the pollution problem of the furfuryl alcohol method and the shortage of raw material sources of the BDO catalytic dehydration cyclization method.

[0006] There are two main methods for preparing tetrahydrofuran from maleic anhydride: one is the esterification hydrogenation method, which was developed by UCC Company of the United States and Davy McKee Company of the United Kingdom. Maleic anhydride is first completely converted into dimethyl maleate, and then hydrogenated to produce tetrahydrofuran over a Cu-based catalyst: for example, Chinese patent CN1857771A reported that dimethyl maleate was directly hydrogenated to produce tetrahydrofuran over a CuO-ZnO-Al2O3 catalyst, but the process route of this method is relatively long; the other is the catalytic hydrogenation method 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, which uses ethanol as a maleic anhydride solvent (12:88, W / W) to carry out a gas-phase one-step hydrogenation reaction of maleic anhydride to produce tetrahydrofuran, and a high selectivity of tetrahydrofuran can be obtained at a pressure of 1 MPa and a temperature of 220-280°C. At the same time, the solvent ethanol reacts under the catalytic action of the catalyst to produce hydrogen, ethyl acetate and acetaldehyde as byproducts, and the process does not consider the stability of the catalyst in the reaction. The reaction liquid is highly acidic, which will corrode the catalyst, thereby affecting the service life of the catalyst. Chinese patent CN101168535A discloses a Cu-Zn-Ti-Ce series catalyst, which uses n-butanol as a solvent to carry out a gas-phase one-step hydrogenation reaction of maleic anhydride to produce tetrahydrofuran at a pressure of 1 MPa and a temperature of 265-280°C, and the yield is higher than 75%, and at the same time, n-butanol reacts 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 alcohol solvents reacting and consuming the solvent while producing more by-products. In addition, alcohols and water generated by hydrogenation of maleic anhydride to produce tetrahydrofuran easily form azeotropes, which makes separation difficult.

[0007] Maleic anhydride liquid phase hydrogenation mainly adopts precious metals such as Ru, Rh, Pd etc. in 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 is very low or even there is no generation of tetrahydrofuran. For example, Chinese patent CN 102229587A discloses a method for generating succinic anhydride by nano nickel catalytic hydrogenation of maleic anhydride, which has high activity, high selectivity and high yield to produce succinic anhydride, but is only used in autoclave batch reaction and cannot be continuously produced. CN106955710A discloses a maleic anhydride liquid phase hydrogenation catalyst, which consists of: nickel / zirconium oxide / aluminum oxide / silicon oxide, but the catalyst preparation process is complicated, and requires alcohol aqueous solution, and the catalyst cost is high. At present, there is no patent report on the method for preparing tetrahydrofuran by maleic anhydride liquid phase catalytic hydrogenation.

[0008] In view of the shortcomings of the above-mentioned prior art, we use the prepared ternary metal silicide Ti-Ni-Si series catalyst, use 1,4-dioxane as solvent to carry out liquid phase hydrogenation of maleic anhydride, combine the above hydrogenation with corrosion-resistant ternary metal silicide, so that it has strong acid corrosion resistance and high stability in a maleic anhydride organic solution with a high concentration, so that it has high stability and catalytic activity in the preparation of tetrahydrofuran by liquid phase hydrogenation of maleic anhydride. The technical process of the present invention can successfully prepare tetrahydrofuran by one-step hydrogenation in the liquid phase hydrogenation of maleic anhydride, and has the advantages of complete maleic anhydride conversion rate, high tetrahydrofuran selectivity, stable catalyst, etc., while avoiding the use of alcohol 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] With maleic anhydride as raw material and 1,4-dioxane as solvent, maleic anhydride is hydrogenated in liquid phase in one step to produce tetrahydrofuran 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 0.5wt%-10wt% maleic anhydride solution, 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 is 200-300°C, preferably 220-280°C; reaction pressure is 1-4MPa, preferably 1.5-2.5MPa; mass space velocity of maleic anhydride is 0.2-3.0h -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 a 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 mixed gas at a temperature of 400°C-700°C for 2-4 hours, 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 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 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 prior art of preparing tetrahydrofuran from maleic anhydride in liquid phase, and provides a new ternary metal silicide catalyst for the reaction of preparing tetrahydrofuran from maleic anhydride by liquid phase hydrogenation. When the catalyst of the present invention is used in the reaction of preparing tetrahydrofuran from maleic anhydride by liquid phase hydrogenation, under the above 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 shows 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 spectrum of Si7 catalyst.

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

[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 TiCl4 solution, 2.766g Ni(NO3)2·6H2O, and 1g SBA-15, dissolve them in 50ml 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, then take it out and evaporating it, place the sample in a muffle furnace at 600°C 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 (including 1.2g CaH2, 1.2g LiCl 0.6g), calcined at 5℃ / min to 600℃ for 2h in a tubular furnace under Ar / H2 atmosphere, and a black solid was obtained after being taken out; the black solid catalyst was washed with an acidic washing liquid 1mol / LNH4Cl solution to control the solution pH to 9-12, and then repeatedly washed with deionized water until neutral, centrifuged, and the sample was placed in a 70℃ oven and dried for 12h for use to obtain a Ti4Ni7Si4 ternary metal silicide catalyst.

[0033] Example 2: Preparation of ternary metal silicide TiNiSi catalyst

[0034] Prepare 3.157g TiCl4 solution, 4.840g Ni(NO3)2·6H2O, and 1g SBA-15, dissolve them in 50ml 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, then take it out and evaporation, place the sample in a muffle furnace at 600°C 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 CaH2 and 0.6g 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 for use, and obtain a TiNiSi ternary metal silicide catalyst.

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

[0036] Prepare 1.324g TiCl4 solution, 6.245g Ni(NO3)2·6H2O, and 1g SBA-15, dissolve them in 50ml 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, then take it out and evaporation it, place the sample in a muffle furnace at 600°C 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 CaH2 and 0.6g 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 for use, 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 TiCl4 solution, 11.063g Ni(NO3)2·6H2O, and 1g SBA-15 dissolved in 50ml 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, then take it out and evaporation, place the sample in a muffle furnace at 600°C 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 CaH2 and 0.6g 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 for use, 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 TiCl4 solution, 19.360g Ni(NO3)2·6H2O, and 1g SBA-15, dissolve them in 50ml 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, then take it out and evaporating it, place the sample in a muffle furnace at 600°C 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 (including 1.2g CaH2, 1.2g LiCl 0.6g), calcined at 5℃ / min to 600℃ for 2h in a tubular furnace under Ar / H2 atmosphere, and a black solid was obtained after being taken out; the black solid catalyst was washed with an acidic washing liquid 1mol / LNH4Cl solution to control the solution pH to 9-12, and then repeatedly washed with deionized water until neutral, centrifuged, and the sample was placed in a 70℃ oven and dried for 12h for use to obtain a Ti4Ni4Si ternary metal silicide catalyst.

[0041] Example 6: Using the ternary metal silicide Ti4Ni7Si4 catalyst of Example 1 to catalyze the liquid phase hydrogenation of maleic anhydride, with 2wt.% maleic anhydride (1,4-dioxane) solution as the substrate, the activity and selectivity for the target product of the Ti4Ni7Si4 ternary metal silicide catalyst prepared in Example 1 in the liquid phase hydrogenation of maleic anhydride to prepare tetrahydrofuran were investigated. The reaction was carried out in a fixed bed reaction, and the catalyst was activated in advance at 400°C and H2 atmosphere for 2h before the reaction. The process conditions are: 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 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 of the TiNiSi ternary metal silicide catalyst prepared in Example 1 in the reaction of preparing tetrahydrofuran by liquid phase hydrogenation of maleic anhydride were investigated using 2wt.% maleic anhydride (1,4-dioxane) solution as the substrate. The reaction was carried out in a fixed bed reaction. Before the reaction, the catalyst was activated at 400°C in a H2 atmosphere for 2h. The process conditions were: catalyst TiNiSi: 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.

[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 Liquid Phase Hydrogenation of Maleic Anhydride Catalyzed by Catalyst

[0047] Using 2 wt.% maleic anhydride (1,4-dioxane) solution as substrate, the Ti prepared in Example 1 was investigated. 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 reaction. The catalyst was activated at 400°C in a H2 atmosphere for 2 h 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] Using 2wt.% maleic anhydride (1,4-dioxane) solution as substrate, the Ti6Ni prepared in Example 1 was investigated. 16 The activity and selectivity of Si7 ternary metal silicide catalyst in the liquid phase hydrogenation of maleic anhydride to tetrahydrofuran were investigated. The reaction was carried out in a fixed bed reaction. The catalyst was activated at 400°C in a H2 atmosphere for 2 h 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 reaction of preparing tetrahydrofuran by liquid phase hydrogenation of maleic anhydride were investigated using 2wt.% maleic anhydride (1,4-dioxane) solution as substrate. The reaction was carried out in a fixed bed reaction. Before the reaction, the catalyst was activated at 400°C in a H2 atmosphere for 2h. 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 the overall material is conserved.

[0058] Based on the above data, among the ternary metal silicide catalysts, Ti6Ni 16 Due to its unique ratio and structure, Si7 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 silicides, the hydrogenation activity is weak, and the continuous hydrogenation effect on the C=O bond is not strong, which is difficult to achieve the same 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 technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and 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: With maleic anhydride as raw material and 1,4-dioxane as solvent, maleic anhydride is hydrogenated in liquid phase in a fixed bed reactor in the presence of Ti-Ni-Si ternary metal silicide catalyst under certain temperature and pressure conditions to produce tetrahydrofuran.

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 1-4MPa, mass space velocity of maleic anhydride of 0.2-3.0h -1 .

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

4. The method according to claim 1, characterized in that 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.

5. The method according to claim 4, characterized in that 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, and then mixed with a low eutectic point salt, calcined in a hydrogen-argon mixed gas at a temperature of 400°C-700°C for 2-4 hours, 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.

6. The method according to claim 5, characterized in that The silicon source is one of MCM-41, SAB-15 and SiO2.

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

8. The method according to claim 5, 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.

9. The method according to claim 5, characterized in that The mass ratio of the metal precursor salt to the low eutectic point salt is 1:1-3.

10. The method according to claim 5, characterized in that The certain acidity and alkalinity is pH=9-12.

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