CN101386608A - A kind of method for preparing tetrahydrofuran by gas-phase hydrogenation of maleic anhydride - Google Patents

Abstract

The invention relates to a method for preparing tetrahydrofuran. The method uses ethanol as a maleic anhydride solvent, and adopts Cu-Zn-Zr series catalysts to hydrogenate maleic anhydride in one-step gas phase to prepare tetrahydrofuran. The catalyst has the following general formula: CuZn _a Zr _b O _X , wherein a=0-2, b=0-2, representing the atomic numbers of Zn and Zr respectively. X is the number of oxygen atoms required to satisfy the valence requirements of other elements. When ethanol is used as the maleic anhydride solvent, the catalyst can be used to carry out gas-phase hydrogenation of maleic anhydride, and a higher tetrahydrofuran yield can be obtained in one step. At the same time, ethanol reacts under the action of catalyst to generate hydrogen, ethyl acetate and acetaldehyde. The hydrogen removed from ethanol can be used as raw material for hydrogenation of maleic anhydride.

Description

A kind of method for preparing tetrahydrofuran by gas-phase hydrogenation of maleic anhydride

Technical field:

The invention relates to a method for preparing tetrahydrofuran, in particular to preparing tetrahydrofuran by using ethanol as a maleic anhydride solvent and adopting a Cu-Zn-Zr catalyst to hydrogenate maleic anhydride in one step in gas phase.

Background technique

Tetrahydrofuran is an excellent low-boiling point (66°C) solvent that can dissolve all polymers except polyethylene, polypropylene, and fluororesin, and is especially suitable for PVC, polyvinylidene fluoride resin, and butylaniline. At the same time, it can be used as an intermediate to produce polyurethane elastomer, spandex elastic fiber, etc.

The industrial production of tetrahydrofuran includes various industrial production methods such as furfural method, 1,4-butanediol catalytic dehydration and cyclization method, butadiene chlorination method and butadiene acetoxylation method. In recent years, a maleic anhydride catalytic hydrogenation method with obvious economic benefits has been developed. The maleic anhydride catalytic hydrogenation method avoids the pollution problem of the furfural method and the shortage of raw material sources such as the catalytic dehydration and cyclization method of 1,4-butanediol. There are two main methods for preparing THF from maleic anhydride: US Stand Oil Company adopts Cu/Zn/Cr catalyst to carry out gas-phase hydrogenation of maleic anhydride at 1.5-5MPa and 200-325°C to obtain a higher THF yield, but The Cr component is easy to cause environmental pollution. The second is to adopt 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 diethyl maleate, and then hydrogenated by a copper-based catalyst to produce tetrahydrofuran. However, the reaction route of this method is relatively long.

In the presence of copper-based catalysts, monohydric saturated alcohols can react to synthesize esters with a corresponding carbon number of 2n, while by-product hydrogen.

We choose Cu-Zn-Zr series catalysts, and use ethanol as maleic anhydride solvent for maleic anhydride hydrogenation reaction. By adjusting the reaction parameters, a higher THF yield can be obtained. At the same time, ethanol reacts under the action of catalyst to generate hydrogen, ethyl acetate and acetaldehyde. The hydrogen removed from ethanol can be used as raw material for hydrogenation of maleic anhydride.

Contents of the invention

The purpose of the present invention is to propose a new gas-phase hydrogenation method for preparing tetrahydrofuran, that is, adopt Cu-Zn-Zr catalyst and use ethanol as solvent maleic anhydride to prepare tetrahydrofuran by one-step gas-phase hydrogenation.

The method for preparing tetrahydrofuran by gas-phase hydrogenation of maleic anhydride in the present invention is to use a saturated hydroxyl alcohol as a solvent for maleic anhydride, and adopt a Cu-Zn-Zr catalyst to produce tetrahydrofuran by one-step gas-phase hydrogenation of maleic anhydride;

Catalyst used in the present invention can be represented by following general formula: Cu Zn _a Zr _b O _X

Among them, a and b represent the atomic numbers of Zn and Zr respectively, and the control range is: a=0~2; b=0~2;

X is the number of oxygen atoms required to satisfy the valence requirements of other elements.

The preparation method of catalyzer of the present invention is coprecipitation method, and this method comprises the following steps:

(1) According to the composition requirements of the catalyst, dissolve Cu, Zn, Zr salts, preferably Cu, Zn, Zr nitrates in distilled water to form a mixed solution. Put the mixed solution and lye into the sedimentation tank in parallel, the lye is preferably NaCO ₃ solution. The heating temperature of the water bath is maintained at about 60-90°C, and the pH of the reaction solution is controlled between 8-9. After the precipitation is complete, rinse repeatedly with distilled water until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 400-500°C for 2-4h. The samples were pressed into tablets and sieved to make Cu-Zn-Zr catalyst precursor.

(2) Reducing the catalyst precursor at 250-300° C. for 2-6 hours in hydrogen or hydrogen diluted with inert gas under a pressure of 0.1 MPa.

The method for producing tetrahydrofuran by gas-phase hydrogenation of maleic anhydride of the present invention comprises the following steps:

A fixed-bed reactor is used, the catalyst loading amount is 5ml, the raw material is maleic anhydride/ethanol solution (12:88, W/W), and after gasification, it enters a stainless steel tubular reactor (20cm long and 0.8cm internal diameter), and the molar ratio of hydrogen anhydride is 50/ 1. The space velocity of the liquid phase is 0.2h ^-1 . Regulate the reaction pressure at 1MPa through the pressure stabilizing valve, and the reaction temperature is 220-280°C. Continuously sample for 1 hour at a given temperature, and collect the product by condensation in a water bath. The product was quantitatively detected and analyzed by Shanghai Tianmei GC7890 II gas chromatograph, and the chromatographic data was processed by Zhejiang Zhida N2000 chromatographic workstation. The products of maleic anhydride hydrogenation include tetrahydrofuran, γ-butyrolactone and diethyl succinate; the products of ethanol dehydrogenation include acetaldehyde and ethyl acetate.

One of the remarkable features of the present invention is that the catalyst activity is relatively high. For example, using maleic anhydride dissolved in ethanol as a raw material, using the catalyst of the present invention, under the above reaction conditions, the conversion of maleic anhydride is close to 100%, and the selectivity of THF can be as high as 92%.

Another remarkable feature of the present invention is that ethanol as maleic anhydride solvent reacts simultaneously to generate hydrogen, ethyl acetate and acetaldehyde. The hydrogen generated from ethanol can also be used as a raw material for the hydrogenation of maleic anhydride. If maleic anhydride is dissolved in ethanol to make a maleic anhydride/ethanol mixture (12:88, W/W), the hydrogen consumption of maleic anhydride can be saved by 20% to 110% according to material calculation.

Detailed ways

The present invention will be further described below in conjunction with specific embodiment:

Example 1

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O, 40.6 g of Zn(NO ₃ ) ₂ ·6H ₂ O, and 29.4 g of Zr(NO ₃ ) ₄ ·5H ₂ O were dissolved in distilled water to prepare a mixed liquid. Using two constant-current pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 60°C. Stir vigorously while adjusting the flow rate of the constant flow pump to keep the pH of the reaction solution around 8. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 400°C for 2h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₂ Zr ₁ O ₅ .

A fixed-bed reactor is used, the catalyst loading amount is 5ml, the raw material is maleic anhydride/ethanol solution (12:88, W/W), and after gasification, it enters a stainless steel tubular reactor (20cm long and 0.8cm internal diameter), and the molar ratio of hydrogen anhydride is 50/ 1. The liquid phase space velocity is 0.2h ^-1 Before the activity test, the catalyst is first reduced and activated with H ₂ -N ₂ (10:90, V/V, 250ml/min) mixed gas, under 0.1MPa pressure, at 1.5 °C/min program temperature up to 200 °C, then 1.0 °C/min program temperature up to 250 °C, while _H2 volume fraction slowly increased to 30%. Reduction at a constant temperature of 250°C for 2h.

Regulate the reaction pressure at 1MPa through the pressure stabilizing valve, and the reaction temperature is 220, 240, 260, 280°C. Continuously sample at a given temperature for 1h, and collect the product by condensation in a water bath.

The product was quantitatively detected by Shanghai Tianmei GC7890 II gas chromatograph, and analyzed by normalization, and the chromatographic data was processed by Zhejiang Zhida N2000 chromatographic workstation. The products of maleic anhydride hydrogenation include tetrahydrofuran, γ-butyrolactone and diethyl succinate; the products of ethanol dehydrogenation include acetaldehyde and ethyl acetate. The test results are shown in Table 1.

Example 2

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O, 40.6 g of Zn(NO ₃ ) ₂ ·6H ₂ O, and 58.8 g of Zr(NO ₃ ) ₄ ·5H ₂ O were dissolved in distilled water to prepare a mixed solution. Using two constant flow pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 75°C. Stir vigorously while adjusting the flow rate of the constant flow pump to keep the pH of the reaction solution around 8.3. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 450°C for 3h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₂ Zr ₂ O ₇ .

A fixed-bed reactor is used, the catalyst loading amount is 5ml, the raw material is maleic anhydride/ethanol solution (12:88, W/W), and after gasification, it enters a stainless steel tubular reactor (20cm long and 0.8cm internal diameter), and the molar ratio of hydrogen anhydride is 50/ 1. The liquid phase space velocity is 0.2h ^-1 Before the activity test, the catalyst is first reduced and activated with H ₂ -N ₂ (10:90, V/V, 250ml/min) mixed gas, under 0.1MPa pressure, at 1.5 °C/min program temperature up to 200 °C, then 1.0 °C/min program temperature up to 280 °C, while _H2 volume fraction slowly increased to 30%. Reduction at a constant temperature of 280°C for 4h.

Regulate the reaction pressure at 1MPa through the pressure stabilizing valve, and the reaction temperature is 220, 240, 260, 280°C. Continuously sample at a given temperature for 1h, and collect the product by condensation in a water bath.

Adopt the same gas chromatography method as example 1 to carry out the detection of product, test result table 1.

Example 3

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O, 20.3 g of Zn(NO ₃ ) ₂ ·6H ₂ O, and 14.7 g of Zr(NO ₃ ) ₄ ·5H ₂ O were dissolved in distilled water to prepare a mixed solution. Using two constant-current pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 90°C. Stir vigorously while adjusting the flow rate of the constant-current pump to keep the pH of the reaction solution around 9. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 500°C for 4h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₁ Zr _0.5 O ₃ .

A fixed-bed reactor is used, the catalyst loading amount is 5ml, the raw material is maleic anhydride/ethanol solution (12:88, W/W), and after gasification, it enters a stainless steel tubular reactor (20cm long and 0.8cm internal diameter), and the molar ratio of hydrogen anhydride is 50/ 1. The liquid phase space velocity is 0.2h ^-1 Before the activity test, the catalyst is reduced and activated with H ₂ -N ₂ (10:90, V/V, 250ml/min) mixed gas, and the temperature is programmed at 1.5°C/min to 200°C, and then the temperature was programmed to 300°C at 1.0°C/min, while the volume fraction of _H2 was slowly increased to 30%. Reduction at a constant temperature of 300°C for 6h. Regulate the reaction pressure at 1MPa through the pressure stabilizing valve, and the reaction temperature is 220, 240, 260, 280°C. Continuously sample at a given temperature for 1h, and collect the product by condensation in a water bath.

Adopt the same gas chromatography method as example 1 to carry out the detection of product, test result table 1.

Example 4

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O, 20.3 g of Zn(NO ₃ ) ₂ ·6H ₂ O, and 29.4 g of Zr(NO ₃ ) ₄ ·5H ₂ O were dissolved in distilled water to prepare a mixed liquid. Using two constant flow pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 75°C. Stir vigorously while adjusting the flow rate of the constant flow pump to keep the pH of the reaction solution around 8.3. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 450°C for 2h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₁ Zr ₁ O ₄ .

Adopt the same method as Example 1 to carry out the reduction activation and activity test of the catalyst. The product was collected by condensation in a water bath. Adopt the same gas chromatography method as example 1 to carry out the detection of product, test result table 1.

Example 5

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O and 14.7 g of Zr(NO ₃ ) ₄ ·5H ₂ O were dissolved in distilled water to prepare a mixed solution. Using two constant flow pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 75°C. Stir vigorously while adjusting the flow rate of the constant flow pump to keep the pH of the reaction solution around 8.3. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 450°C for 2h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₀ Zr _0.5 O ₂ .

Adopt the same method as Example 1 to carry out the reduction activation and activity test of the catalyst. The product was collected by condensation in a water bath. Adopt the same gas chromatography method as example 1 to carry out the detection of product, test result table 1.

Example 6

16.5 g of Cu(NO ₃ ) ₂ ·3H ₂ O and 20.3 g of Zn(NO ₃ ) ₂ ·6H ₂ O were dissolved in distilled water to prepare a mixed liquid. Using two constant flow pumps, pour the mixed solution and saturated NaCO ₃ solution into a 1000ml beaker in parallel, and heat it in a water bath, maintaining the temperature of the water bath at about 75°C. Stir vigorously while adjusting the flow rate of the constant flow pump to keep the pH of the reaction solution around 8.3. After the precipitation is complete, repeatedly wash with distilled water, decant, and suction filter until the conductivity of the filtrate no longer changes, about 2mS/m. The samples were dried at 120°C for 12h and calcined at 450°C for 2h. The samples were pressed into tablets and sieved to make 20-40 mesh granules for later use. The catalyst is CuZn ₁ Zr ₀ O ₂

Adopt the same method as Example 1 to carry out the reduction activation and activity test of the catalyst. The product was collected by condensation in a water bath. Adopt the same gas chromatography method as example 1 to carry out the detection of product, test result table 1.

Table 1. Activity test analysis table

Note:

(1) MA—maleic anhydride, THF—tetrahydrofuran, GBL—γ-butyrolactone, DS—diethyl succinate, ET—ethanol, AD—acetaldehyde, EA—ethyl acetate.

(2) When calculating the ethanol conversion rate, the amount of ethanol consumed to generate diethyl succinate is not considered.

(3) H%=(the amount of hydrogen gas taken off by ethanol/the amount of hydrogen gas consumed by the hydrogenation of maleic anhydride)×100%

Claims (4)

1. a kind of method that maleic anhydride gas-phase hydrogenation prepares tetrahydrofuran is characterized in that, with a hydroxyl saturated alcohol as maleic anhydride solvent, adopts Cu-Zn-Zr catalyst maleic anhydride one-step gas-phase hydrogenation to prepare tetrahydrofuran; Said catalyzer has The general formula is as follows: CuZn _a Zr _b O _x , where a=0~2, b=0~2, representing the atomic numbers of Zn and Zr respectively, and X is the number of oxygen atoms required to meet the valence requirements of other elements. 2. the method for preparing THF by maleic anhydride gas-phase hydrogenation according to claim 1, is characterized in that, said one hydroxyl saturated alcohol is ethanol. 3. the method for preparing tetrahydrofuran (THF) by maleic anhydride gas-phase hydrogenation according to claim 1, is characterized in that, said catalyst is made by co-precipitation method, specifically: According to the composition requirements of the catalyst, dissolve Cu, Zn, Zr nitrates in distilled water to make a mixed solution; add the mixed solution and saturated NaCO ₃ into the sedimentation tank, maintain the temperature of the water bath at 60-90°C, and control the pH of the reaction solution At 8~9; after the precipitation is complete, rinse with distilled water repeatedly until the conductivity of the filtrate no longer changes, dry the sample at 120°C for 12h, roast at 400~500°C for 2~4h, press the sample into tablets, and sieve to make Cu -Zn-Zr catalyst precursor; reducing the catalyst precursor at 250-300° C. for 2-6 hours under a pressure of 0.1 MPa in hydrogen or hydrogen diluted with an inert gas. 4. the method for preparing tetrahydrofuran by maleic anhydride gas-phase hydrogenation according to claim 1 is characterized in that, specifically: adopt fixed-bed reactor, catalyst loading 5ml, raw material is weight ratio 12:88 maleic anhydride/ethanol solution, After gasification, enter the stainless steel tubular reactor, the molar ratio of hydrogen anhydride is 50/1, the liquid space velocity is 0.2h ^-1 , the reaction pressure is stable at 1MPa, the reaction temperature is 220-280°C, continuous sampling at a given temperature for 1h, and condensed in a water bath Collect the product.