CN101168536A - A kind of method for preparing tetrahydrofuran - Google Patents

Abstract

The invention relates to a method for preparing tetrahydrofuran, which uses reactive distillation technology to use tungsten-doped phosphomolybdenum heteropoly acid as a catalyst to catalyze the cyclodehydration of 1,4-butanediol to prepare tetrahydrofuran, and firstly adopts the classic ether extraction method to prepare tungsten-doped Phosphomolybdenum heteropolyacid uses the prepared phosphomolybdotungstic heteropolyacid as a catalyst, and adopts reactive distillation technology to catalyze the cyclodehydration of 1,4-butanediol to prepare tetrahydrofuran. The reaction conditions are as follows, calculated by mass ratio, the ratio of 1,4-butanediol:catalyst = ^1: 10-4-1: ^10-3 , reaction temperature: 190-230°C, reaction time: 15-90min. The tetrahydrofuran prepared by the invention has high selectivity, high yield, high purity, little pollution, easy control of reaction conditions and simple and convenient production process.

Description

A kind of method for preparing tetrahydrofuran

technical field

The present invention relates to a method for preparing tetrahydrofuran, specifically refers to doped tungsten phosphomolybdenum heteropoly acid H ₃ PMo _12-n W _n O ₄₀ ·XH ₂ O (n=1～11) as a catalyst, using reactive distillation technology to catalyze 1 , A method for preparing tetrahydrofuran through cyclodehydration of 4-butanediol.

Background technique

Tetrahydrofuran (THF) is a low-toxicity solvent with high polarity, low boiling point and excellent performance. It is widely used as a solvent for surface coatings, anti-corrosion coatings and film coatings. Its main purpose is to produce polytetramethylene ether glycol (PTMEG), polyurethane elastomer and polyurethane artificial leather, etc. It is also used as a solvent in esterification and polymerization reactions, and as a raw material for the synthesis of some hormone drugs in medicine. But the production capacity of tetrahydrofuran in my country is not high. With the domestic consumption of polyurethane elastic fibers, elastomers, and spandex increasing, the demand for tetrahydrofuran will also increase rapidly.

In my country, the furfural method is mainly used to produce tetrahydrofuran. This method consumes a lot of raw materials, the process is complicated, the scale of the device is small, the output is small, and the environmental pollution is serious. Traditional strong protonic acids such as phosphoric acid, sulfuric acid, and nitric acid are used as catalysts, and 1,4-butanediol (BDO) is used as raw material to prepare tetrahydrofuran by liquid-phase cyclodehydration. Acid catalysts and product separation difficulties pollute the environment. As the main component of green catalysis, heteropolyacid catalyst is becoming a research hotspot in environment-friendly chemistry.

Li Haixia, Yin Hengbo, Hu Tongjie, etc. published an article entitled "Supported silicotungstic acid catalyzes the cyclodehydration of 1,4-butanediol to prepare tetrahydrofuran" in the second issue of 2005, and studied the support type of the supported heteropolyacid catalyst. , the interaction between the carrier and the heteropoly acid, the acid strength and acid content of the catalyst and other factors on the catalytic 1,4-butanediol cyclodehydration to prepare THF, and this patent adopts reactive distillation technology to dope tungsten, phosphomolybdenum The use of acid as a catalyst is different for the cyclodehydration of 1,4-butanediol to produce tetrahydrofuran.

Contents of the invention

The object of the present invention is to provide a method for preparing tetrahydrofuran, that is, to prepare tetrahydrofuran by adopting reactive distillation technology and using tungsten-doped phosphomolybdic acid as a catalyst to prepare tetrahydrofuran through cyclodehydration of 1,4-butanediol.

Specifically:

The preparation method of the catalyst adopts the classic ether extraction method, and the prepared tungsten-doped phosphomolybdenum heteropolyacid is proved by ICP, IR, TG-DSC, XRD and other characterization means that the prepared heteropolyacid belongs to the A-type Keggin structure heteropolyacid , the expressions are: H ₃ PMo _10.6 W _1.1 O ₄₀ · 22H ₂ O, H ₃ PMo _8.7 W ₃ O ₄₀ · 19H ₂ O, H ₃ PMo _6.5 W _4.8 O ₄₀ · 12H ₂ O, H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O, H ₃ PMo _3.3 W _8.5 O ₄₀ ·11H ₂ O, H ₃ PMo _1.2 W _10.6 O ₄₀ ·12H ₂ O.

Using the prepared phosphomolybdenum tungsten heteropoly acid as a catalyst, reactive distillation technology is used to catalyze the cyclodehydration of 1,4-butanediol to prepare tetrahydrofuran. The reaction conditions are as follows, calculated by mass ratio, the ratio of 1,4-butanediol:catalyst = ^1: 10-4-1: ^10-3 , reaction temperature: 190-230°C, reaction time: 15-90min.

The invention adopts reactive rectification technology, and the doped heteropolyacid has better catalytic activity than the pure heteropolyacid catalyst as well as the loaded heteropolyacid catalyst.

Description of drawings

Figure 1: Activity test of catalyst H ₃ PMo _10.6 W _1.1 O ₄₀ ·22H ₂ O in catalyzing 1,4-butanediol to tetrahydrofuran.

Figure 2: Activity test of catalyst H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O catalyzing 1,4-butanediol to prepare tetrahydrofuran.

Figure 3: Activity test of catalyst H ₃ PMo _1.2 W _10.6 O ₄₀ ·12H ₂ O catalyzed 1,4-butanediol to prepare tetrahydrofuran.

Figure 4: TG-DSC spectrum of H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O as an example.

Wherein the number of moles of each catalyst in Fig. 1 is 0.075mmol, the number of moles of each catalyst in Fig. 2 is 0.227mmol, and the number of moles of each catalyst in Fig. 3 is 0.378mmol. The catalysts corresponding to each icon in each figure are:

■ indicates H ₃ PMo ₁₂ O ₄₀ 11H ₂ O, ▲ indicates H ₃ PMo _10.6 W _1.1 O ₄₀ 22H ₂ O, ● indicates H ₃ PMo _8.7 W ₃ O ₄₀ 19H ₂ O, □ indicates H ₃ PMo _6.5 W _4.8 O ₄₀ · 12H ₂ O, △ represents H ₃ PMo _4.8 W _6.8 O ₄₀ · 15H ₂ O, ○ represents H ₃ PMo _3.3 W _8.5 O ₄₀ · 11H ₂ O, ◇ represents H ₃ PMo _1.2 W _10.6 O ₄₀ · 12H ₂ O

Detailed ways

Below in conjunction with specific implementation examples the present invention will be further described:

Example 1

Preparation and catalytic activity test of H ₃ PMo _10.6 W _1.1 O ₄₀ ·22H ₂ O catalyst:

First weigh 8.95g of Na ₂ HPO ₄ 12H ₂ O and 66.54g of Na ₂ MoO ₄ 2H ₂ O, dissolve them in 25ml and 80ml of water respectively, stir and react at a reaction temperature of 90°C for 30min, then add 8.25g 100ml of Na ₂ WO ₄ ·2H ₂ O aqueous solution, continue to stir and react at 90°C for 30 minutes, after cooling to room temperature, add concentrated H ₂ SO ₄ (98%) dropwise to acidify while stirring, and adjust the pH value to 1.5-2. Concentrated sulfuric acid (98%) was used in an amount of about 15ml. During the addition of sulfuric acid, the reaction temperature was maintained below 50°C. After adding sulfuric acid, the reaction temperature was 90°C and continued to stir for 8h, cooled to room temperature, and left overnight. After the reaction, the reactant was transferred to a separatory funnel, and 100ml of ether was added to shake fully, then 20ml of 1:1 H ₂ SO ₄ was added in portions, shaken, allowed to stand, and the yellow oily substance in the lower layer was separated, and the separated substance was blown off with flowing air. Diethyl ether in the yellow oily substance, dissolve the remaining solid in water (about 30ml of water), concentrate the crystals with concentrated sulfuric acid in a vacuum desiccator, obtain bright yellow-green crystals after filtration, wash with water, and dry in the air. H ₃ PMo _10.6 W _1.1 O ₄₀ ·22H ₂ O was obtained and stored in a desiccator for later use.

Catalyst activity test method: Take 100ml of 1,4-butanediol and heat it to 230°C when it boils, add 0.378mmol (57mg) of H ₃ PMo _10.6 W _1.1 O ₄₀ ·22H ₂ O as a catalyst for rectification reaction, and use gas phase The chromatographic analysis method analyzes the concentration of the rectified product and 1,4-butanediol and tetrahydrofuran in the reactor, and calculates the conversion rate. As shown in Figure 1, the conversion rate of the catalyst has reached over 90% when the reaction time is 18 minutes.

Example 2

Preparation and catalytic activity test of H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O catalyst:

First weigh 8.95g of Na ₂ HPO ₄ ·12H ₂ O and 30.24g of Na ₂ MoO ₄ ·2H ₂ O, dissolve them in 25ml and 80ml of water respectively, stir and react at a reaction temperature of 90°C for 30min, then add 57.72g 100ml of Na ₂ WO ₄ ·2H ₂ O aqueous solution, continue to stir and react at 90°C for 30 minutes, after cooling to room temperature, add concentrated H ₂ SO ₄ (98%) dropwise to acidify while stirring, and adjust the pH value to 1.5-2. Concentrated sulfuric acid (98%) was used in an amount of about 15ml. During the addition of sulfuric acid, the reaction temperature was maintained below 50°C. After adding sulfuric acid, the reaction temperature was 90°C and continued to stir for 8h, cooled to room temperature, and left overnight. After the reaction, the reactant was transferred to a separatory funnel, and 100ml of ether was added to shake fully, and then 20ml of 1:1 H ₂ SO ₄ was added in portions, shaken, left to stand, and the yellow oily substance in the lower layer was separated, and blown off with flowing air. Diethyl ether in the isolated yellow oily substance was dissolved in water (approximately 30ml of water), and the crystals were concentrated with concentrated sulfuric acid in a vacuum desiccator. After filtration, bright yellow-green crystals were obtained, washed with water, and dried in the air. The resulting H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O is stored in a desiccator for later use.

Catalyst activity test method: Take 100 ml of 1,4-butanediol and heat it to 230 ° C. When it boils, add 0.227 mmol (40.2 mg) of H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O as a catalyst for rectification reaction, and The concentration of 1,4-butanediol and tetrahydrofuran in the rectified product and the reactor was analyzed by gas chromatography analysis method, and the conversion rate was calculated. As shown in Fig. 2, when 0.227 mmol of H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O is used as a catalyst, the conversion rate of the catalyst can reach 94% after a reaction time of 19 minutes.

As shown in Figure 4, taking H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O as an example, the H ₃ PMo _4.8 W _6.8 O ₄₀ ·15H ₂ O heteropoly acid loses crystal water in the first step, with a weight loss of 7.58%. Correspondingly, there is an endothermic peak at 88.8°C in the DSC curve, which corresponds to the loss of physically adsorbed (zeolitic) water. What the second step loses is bound water, which is 3.54% in weight loss. The mass lost corresponds to the number of water molecules lost by each Keggin structural unit. These water molecules are connected with acidic protons through hydrogen bonds in heteropolyacids. Polyacid crystals exist in the state of protonated hydronium ions (H ₅ O ₂ ⁺ orH ₃ O ⁺ ), correspondingly there is an endothermic peak at 158°C on the DSC curve. In the third step, structural water is lost, with a weight loss of 1.15%, corresponding to an exothermic peak at 496°C in the DSC curve. The loss of this part of water indicates that the tungsten-doped phosphomolybdenum heteropoly acid loses all the acidic protons and the thermal decomposition of the Keggin structure begins, and the Keggin structure of the heteropoly acid completely decomposes to form a mixed oxide. In addition, as shown in Table 1, combined with the data of TG-DSC characterization, the exothermic peak temperature of each catalyst increases with the increase of tungsten content, indicating that the thermal stability of the catalyst increases with the increase of tungsten content.

Table 1: TG-DSC analysis results of each catalyst:

HPAs Endothermic 1 Endothermic 2 Exothermic T(°C) -H ₂ O T(°C) -H ₂ O T(°C) -H ₂ O

H ₃ PMo ₁₂ O ₄₀ 12H ₂ O 74.9 7.17 116.7 4.85 416.0 1.54 H ₃ PMo _10.6 W _1.1 O ₄₀ 22H ₂ O 98.2 13.36 117.0 8.64 435.0 1.53 H ₃ PMo _8.7 W ₃ O ₄₀ 19H ₂ O 91.9 10.94 121.8 8.06 457.0 1.48 H ₃ PMo _6.5 W _4.8 O ₄₀ 12H ₂ O 85.1 6.22 127.1 6.10 469.0 1.51 H ₃ PMo _4.8 W _6.8 O ₄₀ 15H ₂ O 88.8 10.22 158.0 4.78 496.0 1.52 H ₃ PMo _3.3 W _8.5 O ₄₀ 11H ₂ O 72.0 6.90 161.8 4.1 518.9 1.52 H ₃ PMo _1.2 W _10.6 O ₄₀ 12H ₂ O 68.1 7.18 169.1 4.82 561.1 1.54

Example 3

Preparation and catalytic activity test of H ₃ PMo _1.2 W _10.6 O ₄₀ ·12H ₂ O catalyst:

First weigh 8.95g of Na ₂ HPO ₄ ·12H ₂ O and 6.05g of Na ₂ MoO ₅ ·2H ₂ O, dissolve them in 25ml and 80ml of water respectively, stir and react at a reaction temperature of 90°C for 30min, then add 90.71g 100ml of Na ₂ WO ₄ ·2H ₂ O aqueous solution, continue to stir and react at 90°C for 30 minutes, after cooling to room temperature, add concentrated H ₂ SO ₄ (98%) dropwise to acidify while stirring, and adjust the pH value to 1.5-2. Concentrated sulfuric acid (98%) was used in an amount of about 15ml. During the addition of sulfuric acid, the reaction temperature was maintained below 50°C. After adding sulfuric acid, the reaction temperature was 90°C and continued to stir for 8h, cooled to room temperature, and left overnight. After the reaction, the reactant was transferred to a separatory funnel, and 100ml of ether was added to shake fully, then 30ml of 1:1 H ₂ SO ₄ was added in portions, shaken, allowed to stand, and the yellow oily substance in the lower layer was separated, and the separated substance was blown off with flowing air. Diethyl ether in the yellow oily substance, dissolve the remaining solid in water (about 30ml of water), concentrate the crystals with concentrated sulfuric acid in a vacuum desiccator, obtain bright yellow-green crystals after filtration, wash with water, and dry in the air. H ₃ PMo _1.2 W _10.6 O ₄₀ ·12H ₂ O is obtained. Store in a desiccator for later use.

Catalyst activity test method: Take 100 ml of 1,4-butanediol and heat it to 230 ° C. When it boils, add 0.075 mmol (15 mg) of H ₃ PMo _1.2 W _10.6 O ₄₀ ·12H ₂ O as a catalyst for rectification reaction, and use The gas chromatographic analysis method analyzes the concentration of 1,4-butanediol and tetrahydrofuran in the rectified product and the reactor, and calculates the conversion rate, as shown in Figure 3, 0.075mmol of H ₃ PMo _1.2 W _10.6 O ₄₀ 12H ₂ When O is used as a catalyst, the conversion rate of the raw material reaches more than 96% in a reaction time of 20 minutes.

Therefore, it can be seen from the activity test results of a series of tungsten-doped phosphomolybdenum heteropolyacids (H ₃ PMo _12-n W _n O ₄₀ n=1～11) that when the catalyst has an equimolar With the increase of the amount of tungsten, the activity and reaction rate of the catalyst increase accordingly. This is the result of modulating the physicochemical properties of the catalyst. The substitution of W ⁶⁺ for Mo ⁶⁺ significantly improves the catalytic activity of the catalyst for the cyclodehydration reaction of 1,4-butanediol, and the reactive distillation technology can better separate the product tetrahydrofuran and water.

Claims (3)

1. mix the tungsten phosphato-molybdic heteropolyacid as the application of catalyzer at the preparation tetrahydrofuran (THF), promptly at first adopt phosphato-molybdic heteropolyacid is mixed the tungsten modification, prepare difference and mix the heteropoly phosphorus molybdenum tungstic acid of tungsten amount, adopt reaction rectification technique separated product tetrahydrofuran (THF) and water again, with the heteropoly phosphorus molybdenum tungstic acid is catalyzer, catalysis 1, the cyclodehydration of 4-butyleneglycol prepares tetrahydrofuran (THF).

2. the described tungsten phosphato-molybdic heteropolyacid of mixing of claim 1 is as the application of catalyzer at the preparation tetrahydrofuran (THF), be specially: at first adopt classical extracted with diethyl ether legal system to be equipped with the different tungstenic phosphato-molybdic heteropolyacids of tungsten amount of mixing, be catalyzer with the heteropoly phosphorus molybdenum tungstic acid of preparing again, adopt reaction rectification technique catalysis 1, the cyclodehydration of 4-butyleneglycol prepares tetrahydrofuran (THF); Reaction conditions is as follows: presses mass ratio and calculates, and 1, the 4-butyleneglycol: the ratio of catalyzer is=1: 10 ^-4-1: 10 ^-3, temperature of reaction: 190-230 ℃, the reaction times: 15-90min.

3. the described tungsten phosphato-molybdic heteropolyacid of mixing of claim 2 is as the application of catalyzer at the preparation tetrahydrofuran (THF), and it is characterized in that: classical extracted with diethyl ether method is specially: the mol ratio that adds tungsten and phosphorus according to molybdenum is 12: 1 a ratio, takes by weighing Na earlier ₂HPO ₄12H ₂O and Na ₂MoO ₄2H ₂O, soluble in water respectively, at 90 ℃ of following stirring reaction 30min, add the Na of stoichiometric ratio ₂WO ₄2H ₂The aqueous solution of O, 90 ℃ are continued stirring reaction 30min down, behind the cool to room temperature, drip dense H while stirring ₂SO ₄PH value to 1.5～2 are regulated in acidifying, add in the sulfuric acid process temperature of reaction and keep below 50 ℃, add sulfuric acid after, be to continue stirring reaction 6-10h under 90 ℃ again in temperature of reaction, be cooled to room temperature, placement is spent the night; Reaction finishes the back and mixes the tungsten phosphato-molybdic heteropolyacid with extracted with diethyl ether, utilize flowing air stream to blow down ether in the isolated yellow oily material then, remaining solids is water-soluble, condensing crystal, filtration, wash, dry, must mix the tungsten phosphato-molybdic heteropolyacid, store in the moisture eliminator standby.

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