Method for preparing 3, 4-dihydropyran by dehydrating tetrahydrofurfuryl alcohol under catalysis of modified aluminum oxide

Abstract

The invention relates to a method for preparing 3, 4-dihydropyran. According to the method, tetrahydrofurfuryl alcohol is adopted as a reactant, and under the catalytic action of a modified aluminum oxide catalyst, 3, 4-dihydropyran is prepared through a reaction. The reaction conditions are as follows: the reaction is carried out in a fixed bed reactor at normal pressure, the reaction temperature is 250-340 DEG C, and the feeding mass space velocity of tetrahydrofurfuryl alcohol is 0.1-2.0 h <-1 >. The method is characterized in that modified aluminum oxide is used as a catalyst, the catalyst is simple to prepare and relatively good in stability and can efficiently catalyze tetrahydrofurfuryl alcohol to selectively generate 3, 4-dihydropyran, and the conversion rate of the catalyst is gt; the selectivity of the 3, 4-dihydropyran is gt; 95%. The method has the beneficial effects that after being modified, the industrial activated aluminum oxide is moderate in acidity, tetrahydrofurfuryl alcohol is efficiently catalyzed to be dehydrated to prepare the 3, 4-dihydropyran, high-temperature carbonization inactivation of a product is effectively avoided, and the service life is greatly prolonged; and the catalyst is low in price and simple to prepare, and has a good industrial application prospect.

Description

Technical Field

[0001] The invention relates to a method for preparing 3,4-dihydropyran, and in particular to a method for preparing 3,4-dihydropyran by dehydrating tetrahydrofurfuryl alcohol using a modified alumina catalyst. Background Art

[0002] As the only renewable carbon resource in nature, biomass can be used to produce liquid fuels, platform chemicals, high value-added chemicals, etc. through the biorefining process. Furfural is one of the largest biomass-based platform chemicals today, with a global available production capacity of more than 600kt / a, and has the potential to become a major substitute for fossil resources. Furfural is hydrogenated in the gas phase to produce tetrahydrofurfuryl alcohol (THFA), which can be dehydrated in the gas phase to produce 3,4-dihydropyran (DHP). DHP is a six-membered oxygen-containing heterocyclic compound that can be used as a pharmaceutical intermediate and alcohol group protection reagent; it is widely used as a hydroxyl group protection reagent; DHP has active chemical properties and can be used to produce tetrahydropyran, pentanediol, glutaric acid, valerolactone, pentadiene and resin products through polymerization, hydrogenation, oxidation and other reactions. The preparation of DHP by dehydration of tetrahydrofurfuryl alcohol has important industrial significance in the fields of organic chemistry and polymer materials.

[0003] The existing DHP synthesis process mainly uses γ-alumina as a catalyst to make tetrahydrofurfuryl alcohol undergo ring expansion and dehydration at high temperature (usually above 280 degrees) to obtain it. However, studies have shown that the reaction of tetrahydrofurfuryl alcohol dehydration to 3,4-dihydropyran is easy to carry out, and the acidity of the catalyst is not high; and 3,4-dihydropyran is easy to carbonize and coke under strong acidic conditions, thereby deactivating the catalyst, so that the yield of DHP is only high in the initial stage (patent example); the catalyst needs to be regenerated repeatedly, resulting in high energy consumption of the entire process. Industrial activated alumina is inexpensive and has strong L acidity. It exhibits super catalytic performance for the dehydration of ethanol to olefins and is an ideal catalyst for dehydration reactions. Therefore, the purpose of this application is to modify industrial alumina appropriately to make it have moderate acidity and not easy to coke, so as to improve the stability of the catalyst in response to the current reaction needs of tetrahydrofurfuryl alcohol dehydration to DHP. Summary of the invention

[0004] The present invention aims to provide an industrial activated alumina catalyst modification method and a tetrahydrofurfuryl alcohol dehydration catalytic system for preparing DHP. The modified alumina catalyst prepared by the method can maintain high activity and long life operation and effectively reduce the regeneration frequency.

[0005] The objective of the present invention is achieved through the following technical scheme: a method for preparing 3,4-dihydropyran, characterized in that the raw material is tetrahydrofurfuryl alcohol, the catalyst is modified alumina, the product is 3,4-dihydropyran, and the reaction temperature is 250°C-350°C, preferably 280°C-300°C.

[0006] The modified alumina catalyst is prepared by an impregnation method: industrial activated alumina is impregnated with an alkaline compound solution, dried at 100°C-140°C, and then calcined at 300°C-600°C to obtain the modified activated alumina catalyst.

[0007] The alkaline compound impregnation solution is prepared by dissolving the alkaline compound in water. The mass of the alkaline compound, calculated as oxide, is 0.1%-20% of the total mass of the catalyst, preferably 5%-10%; the volume of the alkaline compound solution is 1.2 ml / g of the industrial activated alumina.

[0008] The alkaline compound is one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and cesium carbonate.

[0009] The device is a fixed bed reactor, and the reaction is carried out at normal pressure.

[0010] After the mesoporous silicon-based heteropolyacid-based catalyst is filled in the reaction tube, the reaction is placed in a fixed bed reactor for reaction.

[0011] The mass space velocity of tetrahydrofurfuryl alcohol feed is 0.1-3.0h -1 , the catalyst bed thickness is 10mm-50mm.

[0012] The method is characterized in that modified alumina is used as a catalyst, the catalyst preparation is simple, the catalyst has good stability, and the catalyst can efficiently catalyze tetrahydrofurfuryl alcohol to selectively generate 3,4-dihydropyran, with a conversion rate of >99% and a selectivity of 3,4-dihydropyran of >95%. The method is beneficial in that the industrial activated alumina has moderate acidity after modification, and can efficiently catalyze the dehydration of tetrahydrofurfuryl alcohol to generate 3,4-dihydropyran, effectively avoiding the high-temperature carbonization deactivation of the product, and greatly improving the service life; the catalyst is low in price, simple to prepare, and has good prospects for industrial application.

[0013] The beneficial effects of the present invention are:

[0014] (1) The modified alumina catalyst has moderate acidity and can efficiently catalyze the dehydration of tetrahydrofurfuryl alcohol to 3,4-dihydropyran, effectively avoiding the high-temperature carbonization and deactivation of the product, and greatly improving the service life of the industrial alumina catalyst; (2) The catalyst is inexpensive and easy to prepare, and has good prospects for industrial application. DETAILED DESCRIPTION

[0015] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The scope of protection required by the present invention is defined by the attached claims and their equivalents.

[0016] All raw materials of the present invention are not particularly limited in purity, and the reagents used in the following examples are all commercially available. Qualitative analysis of the reaction product: Agilent gas chromatography-mass spectrometry technology is used to perform qualitative analysis on the reaction product 1,5-pentanediol, which is confirmed by mass spectrometry library retrieval combined with standard substance retention time comparison. Quantitative analysis of the reaction product: Agilent gas chromatography-mass spectrometry technology is used to perform qualitative analysis on the reaction products 3,4-dihydropyran, tetrahydropyran, and 2-hydroxytetrahydropyran, which are confirmed by mass spectrometry library retrieval combined with standard substance retention time comparison. Quantitative analysis of the reaction product: Agilent gas chromatograph (chromatographic column is FFAP capillary column, with FID hydrogen ion flame detector) is used to perform quantitative analysis on the product by internal standard method, and the internal standard is N,N-dimethylformamide. Drawing of internal standard working curve:

[0017] Drawing of internal standard working curve: accurately weigh 4.0g of N,N-dimethylformamide, the standard substance of tetrahydrofurfuryl alcohol, 3,4-dihydropyran, tetrahydropyran, and 2-hydroxytetrahydropyran, to prepare the standard solution mother solution, then transfer 0.2g, 0.4g, 0.6g, 0.8g, and 1.0g from the mother solution respectively, dissolve 0.25N,N-dimethylformamide, add 1.5mL acetonitrile to make up the volume, and then perform gas phase analysis to record the analytes (tetrahydrofurfuryl alcohol, 3,4-dihydropyran, tetrahydropyran, and 2-hydroxytetrahydropyran) respectively. The peak area ratio of tetrahydrofurfuryl alcohol, 3,4-dihydropyran, tetrahydropyran, 2-hydroxytetrahydropyran) and standard N,N-dimethylformamide (Ai / As, where Ai represents the chromatographic peak area of ​​the analyte and As represents the chromatographic peak area of ​​the standard) is taken as the horizontal coordinate, and the mass ratio mi / ms of tetrahydrofurfuryl alcohol, 3,4-dihydropyran, tetrahydropyran, 2-hydroxytetrahydropyran and N,N-dimethylformamide in each solution is calculated as the vertical coordinate, and the standard working curve of the raw material and the product is drawn to calculate the yield of the product. In the following examples, the conversion rate of tetrahydrofurfuryl alcohol and the selectivity of 3,4-dihydropyran, tetrahydropyran and 2-hydroxytetrahydropyran are defined by the following formula:

[0018]

[0019]

[0020]

[0021]

[0022] 3,4-dihydropyran yield (%) = 3,4-dihydropyran selectivity * tetrahydrofurfuryl alcohol conversion rate * 100

[0023] Tetrahydropyran yield (%) = Tetrahydropyran selectivity * Tetrahydrofurfuryl alcohol conversion rate * 100

[0024] 2-Hydroxytetrahydropyran selectivity (%) = 2-Hydroxytetrahydropyran selectivity * tetrahydrofurfuryl alcohol conversion rate * 100

[0025] Example 1

[0026] Example 1: Weigh 3.7 g of potassium carbonate, prepare 60 ml of aqueous solution, weigh 50 g of industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-1#.

[0027] Example 2: Change in the amount of active ingredient

[0028] Weigh 0.073g potassium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 0.1 wt% was named catalyst-2#.

[0029] Example 3: Change in the amount of active ingredient

[0030] Weigh 0.37g potassium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 0.5 wt% was named catalyst-3#.

[0031] Example 4: Change in the amount of active ingredient

[0032] Weigh 0.73g potassium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 1.0 wt% was named catalyst-4#.

[0033] Example 5: Change in the amount of active ingredient

[0034] Weigh 7.3g potassium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 10.0 wt% was named catalyst-5#.

[0035] Example 6: Change in the amount of active ingredient

[0036] Weigh 11.0g potassium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 15.0 wt% was named catalyst-6#.

[0037] Example 7: Change in the amount of active ingredient

[0038] Weigh 14.4 g potassium carbonate, prepare 60 ml of aqueous solution, weigh 50 g of industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 20.0 wt% was named catalyst-7#.

[0039] Example 8: Types of active ingredients

[0040] Weigh 4.3g of sodium carbonate, prepare 60ml of aqueous solution, weigh 50g of industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven and dry for 24 hours, then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain Na 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-8#.

[0041] Example 9: Types of active ingredients

[0042] Weigh 6.2g lithium carbonate, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven and dry for 24 hours, then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain Li 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-9#.

[0043] Example 10: Types of active ingredients

[0044] Weigh 3.0g potassium hydroxide, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven for drying for 24 hours, and then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain K 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-10#.

[0045] Example 11: Types of active ingredients

[0046] Weigh 3.2g of sodium hydroxide, prepare 60ml of aqueous solution, weigh 50g of industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven and dry for 24 hours, then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst, and obtain Na 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-11#.

[0047] Example 12: Types of Active Ingredients

[0048] Weigh 1.9g lithium hydroxide, prepare 60ml aqueous solution, weigh 50g industrial activated alumina, add the prepared potassium carbonate solution to the alumina particles with a pipette until the particles are completely wetted, place at a constant temperature of 30 degrees Celsius for 5 hours, then transfer to a 120 degree Celsius oven and dry for 24 hours, then calcine in a muffle furnace at 600 degrees Celsius for 4 hours to obtain a modified alumina catalyst and obtain Li 2 The modified alumina catalyst with an O loading of 5.0 wt% was named catalyst-12#.

[0049] Examples 13-24

[0050] The prepared catalyst was applied to the reaction of catalyzing the dehydration of tetrahydrofurfuryl alcohol to 3,4-dihydropyran. The catalysts were pressed into tablets, and the catalysts with a mesh size of 20-40 were sieved and filled into a fixed bed reaction tube with an inner diameter of 6 mm and a length of 300 mm. The thickness of the catalyst bed was 20 mm. Before the reaction, the catalyst was pretreated in flowing nitrogen at 600 ° C for 1 h. After the pretreatment, the catalyst bed was cooled to a reaction temperature of 300 ° C, and the mass space velocity of tetrahydrofurfuryl alcohol was 0.5 h -1 , under normal pressure. Samples were taken every 2 hours for gas chromatography analysis. The conversion rate of tetrahydro alcohol and the selectivity of 3,4-dihydropyran are shown in Table 1.

[0051]

[0052]

[0053] Example 25-28 Reaction Temperature

[0054] Catalyst-1# was used in the reaction of catalyzing the dehydration of tetrahydrofurfuryl alcohol to 3,4-dihydropyran. The catalysts were pressed into tablets, and the catalysts with a mesh size of 20-40 were sieved and filled into a fixed bed reaction tube with an inner diameter of 6mm and a length of 300mm. The thickness of the catalyst bed was 20mm. Before the reaction, the catalyst was pretreated in flowing nitrogen at 600°C for 1h. After the pretreatment, the catalyst bed was cooled to a reaction temperature of 250-350°C, and the mass space velocity of tetrahydrofurfuryl alcohol was 0.5h -1 , under normal pressure. Samples were taken every 2 hours for gas chromatography analysis. The conversion rate of tetrahydro alcohol and the selectivity of 3,4-dihydropyran are shown in Table 2.

[0055]

[0056]

[0057] Comparative Example 1

[0058] Industrial activated alumina produced by Henan Sanyi Water Treatment Technology Co., Ltd. was used to catalyze the dehydration of tetrahydrofurfuryl alcohol to produce 3,4-dihydropyran. The catalyst was crushed and sieved to obtain a 20-40 mesh catalyst and filled into a fixed bed reaction tube with an inner diameter of 6mm and a length of 300mm. The catalyst bed thickness was 20mm. Before the reaction, the catalyst was pretreated in flowing nitrogen at 600°C for 1h. After the pretreatment, the catalyst bed was cooled to a reaction temperature of 280°C, and the mass space velocity of tetrahydrofurfuryl alcohol was 0.5h -1 , under normal pressure. Samples were taken every 2 hours for gas chromatography analysis. After 24 hours of continuous operation, the conversion rate of tetrahydrocarbol decreased from the initial 99% to 40%, and the selectivity of 3,4-dihydropyran decreased from more than 98% to 95%.

[0059] Comparative Example 2

[0060] The activated industrial alumina produced by Shandong Xiguan Alumina Technology Co., Ltd. was used to catalyze the dehydration of tetrahydrofurfuryl alcohol to produce 3,4-dihydropyran. The catalysts were pressed into tablets, and the catalysts with a mesh size of 20-40 were sieved and filled into a fixed bed tube reaction tube with an inner diameter of 6mm and a length of 300mm. The catalyst bed thickness was 20m. Before the reaction, the catalyst was pretreated in flowing nitrogen at 600℃ for 1h. After the pretreatment, the catalyst bed was cooled to a reaction temperature of 280℃, and the mass space velocity of tetrahydrofurfuryl alcohol was 0.5h -1 , under normal pressure. Samples were taken every 2 hours for gas chromatography analysis. After 72 hours of continuous operation, the conversion rate of tetrahydrocarbol decreased from the initial 95% to 80%, and the selectivity of 3,4-dihydropyran decreased from 99% to 98%.

Claims

1. A method for preparing 3,4-dihydropyran by dehydrating tetrahydrofurfuryl alcohol using modified alumina as catalyst, characterized in that: Using tetrahydrofurfuryl alcohol as a raw material and modified alumina as a catalyst, the product 3,4-dihydropyran is produced, and the reaction temperature is 250°C-350°C, preferably 280°C-300°C; The modified alumina catalyst is prepared by an impregnation method: industrial activated alumina is impregnated with an alkaline compound solution, dried, and then calcined at 300°C-600°C to obtain the modified alumina catalyst.

2. The method according to claim 1, characterized in that: The alkaline compound impregnation solution is prepared by dissolving the alkaline compound in water. The mass ratio of the alkaline compound to industrial alumina is 0.1%-20%, preferably 5%-10%, calculated as metal oxide. The volume of the alkaline compound solution is 0.8-1.5 ml / g of the industrial activated alumina, preferably 1.0-1.3 ml / (g of the industrial activated alumina).

3. The method according to claim 1 or 2, characterized in that: The impregnation temperature is 20-40°C (preferably 25-30°C), and the impregnation time is 1-24 hours (preferably 4-8 hours); the drying temperature is 100°C-140°C, the drying time is 4-48 hours (preferably 18-30 hours), and the roasting time is 2-12 hours (preferably 3-6 hours).

4. The method according to claim 1, characterized in that: The alkaline compound is one or more of lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate and cesium carbonate.

5. The method according to claim 1, characterized in that: The device is a fixed bed reactor, and the reaction is carried out at normal pressure.

6. The method according to claim 5, characterized in that: After the mesoporous silicon-based heteropolyacid-based catalyst is filled in the reaction tube, the reaction tube is placed in a fixed bed reactor for reaction.

7. The method according to claim 5 or 6, characterized in that: The mass space velocity of tetrahydrofurfuryl alcohol feed is 0.1-3.0h -1 , preferably 0.5-2.0h -1 ; The catalyst bed thickness is 10mm-50mm.

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