CN114700114A - Water-phase bifunctional catalyst and method for preparing dihydric alcohol by using same in external loop reaction process - Google Patents

Abstract

The invention provides an aqueous phase bifunctional catalyst and a method for preparing a dihydric alcohol in an outer loop reaction process, belonging to the technical field of dihydric alcohol preparation. The method for preparing diol in an outer loop reaction process with an aqueous bifunctional catalyst adopts an outer loop reactor, utilizes an aqueous bifunctional catalyst, at a reaction pressure of 0.3-3.0 MPa and a reaction pressure of 50-150 MPa. At the reaction temperature of ℃, carbon dioxide, alkylene oxide and water are used as raw materials for reaction preparation. The outer loop reaction process of the invention can effectively strengthen the gas-liquid mass transfer and improve the reaction efficiency. The aqueous heteronuclear bimetallic catalyst has better water solubility, higher catalyzing efficiency of the hydration reaction of alkylene oxide, and can realize high-efficiency reaction under low concentration of alkylene oxide. The reaction can be carried out at lower carbon dioxide pressure and mild reaction temperature. The problems of insufficient reactivity and poor selectivity in the prior art are solved, and the invention has good industrial application value.

Description

A kind of water-phase bifunctional catalyst and method for preparing dihydric alcohol in outer loop reaction process

technical field

The invention belongs to the technical field of carbonate preparation, and relates to a method for preparing a dihydric alcohol with an aqueous heteronuclear bimetallic complex bifunctional catalyst combined with an outer loop process. alcohol method.

Background technique

Monoglycols such as ethylene glycol (EG) and 1,2-propanediol (PG) are a class of widely used basic chemical raw materials. For example, EG is mainly used in the production of polyester fibers, polyethylene terephthalate plastics and resins, and as surfactants, plasticizers, glycol ethers, glyoxal, oxalic acid and other chemical products raw material. In addition, it is also used as a high-boiling polar solvent, an antifreeze for automobile radiators and a refrigerant for engines, etc.

At present, the traditional ethylene oxide (EO) hydration process is still mainly used for the industrial production of diols. However, due to the high reaction temperature (180-200°C) of this technical route, the water ratio is large (H ₂ O/EO=20～20°C). 25:1), poor EG selectivity (88%-91%), resulting in complicated subsequent separation and purification steps, long process flow, high energy consumption and high production cost.

Because alkylene oxide and carbon dioxide can synthesize the corresponding cyclic carbonate with high selectivity under the action of a suitable catalyst, and the formed cyclic carbonate is easily hydrolyzed to diol with high selectivity. The technical route of carbonate hydrolysis to synthesize diols has attracted much attention. EP 776890, JP 5690029, JP 57106631, GB2098895A, GB 2107712, US 4400559, US 4508927, CN 1955152A, CN 1850755A, CN101121641A, CN 10123808, etc. It discloses a kind of indirect 10206 water catalyzed by CN Ethane and carbon dioxide are used as raw materials to generate ethylene carbonate through a cycloaddition reaction, and then ethylene carbonate is hydrolyzed with water to prepare ethylene glycol. The molar ratio of water and ethylene oxide can be reduced to less than 5:1. The selectivity of diols can reach 98%. As in EP776890 the gas from the ethylene oxide reactor is supplied to an absorber where the absorption liquid mainly contains ethylene carbonate and ethylene glycol. The ethylene oxide in the absorption solution is supplied to the reactor and converted into ethylene carbonate under the action of a catalyst. The ethylene carbonate in the absorption solution is then supplied to the hydrolysis reactor along with the added water for final conversion to ethylene glycol. CN 101238087 discloses that in the presence of carbon dioxide, a combined catalyst of halide, molybdate and macrocyclic crown ether is used for the hydrolysis of alkylene oxide to prepare alkylene glycol, and the molar ratio in water/alkylene oxide is 4, mono-di The selectivity to alcohol is up to 98%. CN 102060657A describes the preparation of cyclic carbonate by catalyzing the cycloaddition reaction of carbon dioxide and epoxy compounds with a catalytic system composed of metal salts, ionic liquids and quaternary ammonium salts. The cyclic carbonate after separating the catalyst is hydrolyzed into the corresponding dihydric alcohol by using the supported alkaline ionic liquid catalyst, and the selectivity is ≥98%.

In recent years, we have also used different bifunctional catalysts and heterogeneous catalysts to conduct high-selective hydrolysis of alkylene oxides with carbon dioxide to synthesize diols (CN 102936181, CN 103100422 and CN 102921468), mainly to solve the problems of water and epoxy in previous technical solutions. The defects of high molar ratio of alkanes, large energy consumption and many by-products. However, similar to other methods, there is a problem of adding alkylene oxide at one time to achieve high-efficiency reaction. Since epoxy is a macromolecular internal energy substance, the reaction exotherm is violent, this method cannot be applied in actual production, and the reaction process depends on high CO ₂ pressure or high CO ₂ dosage can improve the reactivity and diol product selectivity, but there is a shortage.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a water-phase high-activity heteronuclear bimetallic complex bifunctional catalyst, which can enhance gas-liquid mass transfer by combining the catalyst with an outer loop reaction process, and efficiently realize the hydration of alkylene oxide to synthesize glycol. method.

Technical scheme of the present invention:

An aqueous bifunctional catalyst, wherein the aqueous bifunctional catalyst is a heteronuclear bimetallic complex, and the structure is:

In the formula: X ^- is OH ^-1 , HCO ₃ ^- or OCH ₃ ^- anion, preferably X is OH ^-1 .

The method for preparing diol in an outer loop reaction process with an aqueous bifunctional catalyst adopts an outer loop reactor, utilizes an aqueous bifunctional catalyst, at a reaction pressure of 0.3-3.0 MPa and a reaction pressure of 50-150 MPa. Under the reaction temperature of ℃, carbon dioxide, alkylene oxide and water are used as raw materials for reaction preparation, and the reaction equation is:

The reaction process can be divided into one-pot method and two-step method.

The one-pot reaction process is as follows: adding an aqueous solution containing an aqueous bifunctional catalyst to the outer loop reactor; heating the starting material to the reaction temperature through a heat exchanger, and feeding carbon dioxide to the reaction system pressure to complete the preparation stage ; Then feed the alkylene oxide into the outer loop reactor for reaction; after the feeding of the alkylene oxide is completed, continue the reaction until it is completely consumed, and the pressure will no longer change, and then the material is transferred to the flash tank by cooling down and depressurizing, removing the After the carbon dioxide is removed, the diol product can be obtained by separating the water and the water-phase bifunctional catalyst by distillation.

The two-step reaction process is as follows: adding an aqueous solution containing an aqueous bifunctional catalyst to the outer loop reactor; heating the starting material to the reaction temperature through a heat exchanger, and feeding carbon dioxide to the reaction system pressure to complete the preparation stage ; In the first stage of the reaction, the alkylene oxide is introduced into the outer loop reactor for the reaction, and carbon dioxide is added to maintain the reaction pressure constant until the alkylene oxide feed ends; the second stage continues to react and discharges _CO2 to maintain a constant pressure. , until the pressure no longer changes, the reaction is completed. After cooling down and depressurizing, the material is transferred to the flash tank, and after carbon dioxide is removed, the diol product can be obtained by separating the water and the water-phase bifunctional catalyst by distillation.

In the method for preparing dihydric alcohol in an outer loop reaction process with an aqueous bifunctional catalyst, the reaction pressure is preferably 0.6-1.2MPa, and the reaction temperature is preferably 80-120°C.

In the method for preparing diol in an outer loop reaction process with an aqueous bifunctional catalyst, the molar ratio of the alkylene oxide to the aqueous bifunctional catalyst is 500-50000:1.

The molar ratio of water to alkylene oxide is 1:1 to 5:1.

The alkylene oxide is propylene oxide, ethylene oxide, epichlorohydrin, styrene oxide, phenyl glycidyl ether or epoxy cyclohexane.

The outer loop reactors include spray and jet reactors.

Beneficial effects of the present invention:

(1) The outer loop reaction process can effectively strengthen the gas-liquid mass transfer and improve the reaction efficiency.

(2) The aqueous heteronuclear bimetallic catalyst has better water solubility, higher catalyzed alkoxyalkane hydration reaction efficiency, and can realize high-efficiency reaction at low alkylene oxide concentration.

(3) The reaction can be carried out under lower carbon dioxide pressure and mild reaction temperature.

(4) It solves the problems of insufficient reactivity and poor selectivity in the prior art, and has good industrial application value.

Description of drawings

Fig. 1 is the schematic diagram of the outer loop reaction process system of the present invention.

Detailed ways

The technical solutions of the present invention are further described below through the examples.

Example 1: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst ⁽ X- is OH ^-1 ) in an outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 100° C., and carbon dioxide was introduced into the reaction system until the pressure was 0.8 MPa. Then feed ethylene oxide into the outer loop reactor for reaction, the reaction process controls the epoxy feed rate so that the reaction pressure is not less than 0.5MPa, consumes 4.4kg of ethylene oxide in 5 hours, and stops adding epoxy. The pressure did not change after continuing the reaction for 1.5 h. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was 98%, the ethylene carbonate content was 1%, the material weighed about 6.2kg, and the epoxy conversion rate was greater than 99.5%.

Example 2: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst (X ^- is OH ^-1 ) in the outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 100° C., and carbon dioxide was introduced into the reaction system until the pressure was 0.8 MPa. Then feed 4.4kg of ethylene oxide at a speed of 0.88kg/h to carry out the reaction, and supplement CO ₂ to maintain the reaction pressure of not less than 0.8MPa until the end of ethylene oxide feeding. After feeding, the _CO2 feeding was stopped. At this time, the hydrolysis reaction of ethylene carbonate was carried out in the system. It was necessary to continuously discharge _CO2 to the outside to maintain a constant pressure of 0.8 MPa. After continuing the reaction for 45 min, the pressure did not change. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was 99%, the ethylene carbonate content was less than 0.5%, the material weighed about 6.2kg, and the epoxy conversion rate was greater than 99.5%.

Example 3: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst (X ^- is OH ^-1 ) in the outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 100°C, and carbon dioxide was introduced into the reaction system until the pressure was 1.2 MPa. Then feed 4.4kg of ethylene oxide at a speed of 0.88kg/h to carry out the reaction, and supplement CO ₂ to maintain the reaction pressure of not less than 1.2MPa until the end of ethylene oxide feeding. After the feeding, the _CO2 feeding was stopped. At this time, the hydrolysis reaction of ethylene carbonate was carried out in the system, and _CO2 was continuously discharged to the outside to maintain the pressure of 1.2MPa, and the pressure did not change after continuing the reaction for 30min. After cooling and depressurizing to remove carbon dioxide and epoxy, sampling is carried out for gas chromatography column detection. The ethylene glycol selectivity is greater than 99.5%, the ethylene carbonate content is less than 0.5%, the material weighs about 6.2kg, and the epoxy conversion rate is greater than 99.5%.

Example 4: Add 1.8 kg of deionized water containing 0.05 mol of a water ^- phase bifunctional catalyst (X- is OH ^-1 ) in an outer loop jet reactor with an effective volume of 10 L; start the reaction device, and pass the heat exchanger The starting material was heated to 100° C., and carbon dioxide was introduced into the reaction system until the pressure was 3.0 MPa. Then feed 4.4kg of ethylene oxide at a speed of 0.88kg/h to carry out the reaction, and supplement CO ₂ to maintain the reaction pressure of not less than 3.0MPa until the end of ethylene oxide feeding. After the feeding, the CO ₂ feeding was stopped. At this time, the hydrolysis reaction of ethylene carbonate was carried out in the system. It was necessary to continuously discharge CO ₂ to the outside to maintain the pressure of 3.0 MPa, and the pressure did not change after continuing the reaction for 30 min. After cooling and depressurizing to remove carbon dioxide and epoxy, sampling is carried out for gas chromatography column detection. The ethylene glycol selectivity is greater than 99.5%, the ethylene carbonate content is less than 0.5%, the material weighs about 6.2kg, and the epoxy conversion rate is greater than 99.5%.

Example 5: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst ⁽ X- is OH ^-1 ) in the outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 100° C., and carbon dioxide was introduced into the reaction system until the pressure was 0.3 MPa. Then feed 4.4kg of ethylene oxide at a speed of 0.5kg/h to carry out the reaction, and supplement CO ₂ to maintain the reaction pressure of not less than 0.3MPa until the end of ethylene oxide feeding. After the feeding, the CO ₂ feeding was stopped. At this time, the hydrolysis reaction of ethylene carbonate was carried out in the system. It was necessary to continuously discharge CO ₂ to the outside to maintain the pressure of 0.3MPa, and the pressure did not change after continuing the reaction for 3h. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was 96%, the ethylene carbonate content was 2%, the material weighed about 6.2kg, and the epoxy conversion rate was greater than 99.5%.

Example 6: Add 1.8kg deionized water containing 0.002mol aqueous bifunctional catalyst ⁽ X- is OH ^-1 ) in an outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 150° C., and carbon dioxide was introduced into the reaction system until the pressure was 1.5 MPa. Then feed ethylene oxide into the outer loop reactor for reaction, and the reaction process controls the epoxy feed rate so that the reaction pressure is not lower than 1.2MPa, consumes 4.4kg of ethylene oxide in 8 hours, and stops adding epoxy. The pressure did not change after continuing the reaction for 2 h. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was 90%, the ethylene carbonate content was 5%, the material weighed about 6.26kg, and the epoxy conversion rate was about 99%.

Example 7: Add 1.8 kg of deionized water containing 0.2 mol of water ^- phase bifunctional catalyst (X- is OH ^-1 ) in an outer loop jet reactor with an effective volume of 10 L; start the reaction device, and pass the heat exchanger The starting material was heated to 50°C, and carbon dioxide was introduced into the reaction system until the pressure was 1.5 MPa. Then feed ethylene oxide into the outer loop reactor for reaction, the reaction process controls the epoxy feed rate so that the reaction pressure is not less than 1.2MPa, consumes 4.4kg of ethylene oxide in 10 hours, and stops adding epoxy. The pressure did not change after continuing the reaction for 1.5 h. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was 99%, the ethylene carbonate content was less than 0.5%, the material weighed about 6.2kg, and the epoxy conversion rate was greater than 99.5%.

Example 8: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst ⁽ X- is OH ^-1 ) in the outer loop jet reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 100° C., and carbon dioxide was introduced into the reaction system until the pressure was 1.2 MPa. Then feed ethylene oxide into the outer loop reactor to carry out the reaction. The reaction process controls the epoxy feed rate so that the reaction pressure is not lower than 0.8 MPa, and consumes 2.2 kg of ethylene oxide in 2 hours. The pressure did not change after continuing the reaction for 30 min. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The ethylene glycol selectivity was greater than 99.5%, the ethylene carbonate content was less than 0.5%, the material weighed 4.0kg, and the epoxy conversion rate was greater than 99.5%.

Example 9: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst (X ^- is OH ^-1 ) in the outer loop spray reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 120° C., and carbon dioxide was introduced into the reaction system until the pressure was 1.2 MPa. Then feed propylene oxide into the outer loop reactor for reaction, the reaction process controls the epoxy feed rate to make the reaction pressure not less than 0.8MPa, consumes 5.8kg of propylene oxide in 6.5 hours, and continues the reaction after the epoxy is stopped. The pressure did not change after 1.5h. After cooling and depressurizing to remove carbon dioxide and epoxy, sampling is carried out for gas chromatography column detection. The selectivity of propylene glycol is 99%, the content of propylene carbonate is less than 0.5%, the material weighs 7.6kg, and the epoxy conversion rate is greater than 99.5%.

Example 10: Add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst ⁽ X- is OH ^-1 ) in an outer loop spray reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 120° C., and carbon dioxide was introduced into the reaction system until the pressure was 1.5 MPa. Then feed propylene oxide into the outer loop reactor for reaction, the reaction process controls the epoxy feed rate so that the reaction pressure is not less than 1.2MPa, consumes 2.9kg of propylene oxide in 3 hours, and continues the reaction after stopping the addition of epoxy The pressure did not change after 45min. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The selectivity of propylene glycol was greater than 99.5%, the content of propylene carbonate was less than 0.5%, the weight of the material was 4.7kg, and the epoxy conversion rate was greater than 99.5%.

Embodiment 11: add 1.8kg deionized water containing 0.05mol aqueous bifunctional catalyst (X ^- is OCH ₃ ^- ) in an outer loop spray reactor with an effective volume of 10L; start the reaction device, and pass the heat exchanger The starting material was heated to 120° C., and carbon dioxide was introduced into the reaction system until the pressure was 1.5 MPa. Then feed epichlorohydrin into the outer loop reactor to react, and the reaction process controls the epoxy feed rate so that the reaction pressure is not less than 1.2MPa, consumes 4.6kg of propylene oxide in 5 hours, and continues after the epoxy is stopped. The pressure did not change after 1 h of reaction. After cooling and depressurizing to remove carbon dioxide and epoxy, samples were taken for gas chromatography column detection. The diol selectivity was greater than 99.5%, the cyclic carbonate content was less than 0.5%, the material weighed 6.4kg, and the epoxy conversion rate was greater than 99.5%.

Claims (6)

1. The water-phase bifunctional catalyst is characterized by being a heteronuclear bimetallic complex and having the structure as follows:

in the formula: x^-Is OH^-1、HCO₃ ^-Or OCH₃ ^-And (4) negative ions.

2. The method for preparing dihydric alcohol by using the aqueous phase bifunctional catalyst in the external loop reaction process as claimed in claim 1, wherein the external loop reactor is adopted, the aqueous phase bifunctional catalyst is used, carbon dioxide, alkylene oxide and water are used as raw materials to carry out reaction preparation under the reaction pressure of 0.3-3.0 MPa and the reaction temperature of 50-150 ℃, and the reaction equation is as follows:

3. the method for preparing dihydric alcohol by using the aqueous phase bifunctional catalyst in the external loop reaction process as claimed in claim 2, wherein the method can be divided into a one-pot method and a two-step method;

the one-pot reaction process comprises the following steps:

adding an aqueous solution containing a water-phase bifunctional catalyst into the outer loop reactor; heating the initial material to the reaction temperature through a heat exchanger, and introducing carbon dioxide until the pressure of the reaction system is the reaction pressure to complete the preparation stage; then introducing alkylene oxide into the outer loop reactor for reaction; after the alkylene oxide feeding is finished, continuously reacting until the alkylene oxide is completely consumed, the pressure is not changed, then cooling and discharging pressure to transfer the material to a flash tank, removing carbon dioxide, and separating the water-phase dual-function catalyst by distillation to obtain a dihydric alcohol product;

the two-step reaction process comprises the following steps:

adding an aqueous solution containing a water-phase bifunctional catalyst into an outer loop reactor; heating the initial material to the reaction temperature through a heat exchanger, and introducing carbon dioxide until the pressure of the reaction system is the reaction pressure to complete the preparation stage; in the first stage of reaction, introducing alkylene oxide into an outer loop reactor for reaction, and supplementing carbon dioxide to maintain the reaction pressure constant until the alkylene oxide feeding is finished; the second stage continues the reaction and discharges CO₂Maintaining the pressure constant until the pressure is not changed any more, and finishing the reaction; and then cooling and discharging pressure to transfer the material to a flash tank, removing carbon dioxide, and separating the water-water phase dual-function catalyst by distillation to obtain a dihydric alcohol product.

4. The method for preparing the dihydric alcohol by using the water-phase bifunctional catalyst in the outer loop reaction process according to the claims 2 and 3, wherein the reaction pressure is 0.6-1.2 MPa, and the reaction temperature is 80-120 ℃.

5. The method for preparing the dihydric alcohol by using the aqueous phase bifunctional catalyst in the outer loop reaction process as claimed in claims 2 and 3, wherein the molar ratio of the alkylene oxide to the aqueous phase bifunctional catalyst is 500-50000: 1; the molar ratio of the water to the alkylene oxide is 1: 1-5: 1.

6. The method for preparing dihydric alcohol by using the aqueous phase bifunctional catalyst in the outer loop reaction process according to the claims 2 and 3, wherein the alkylene oxide is propylene oxide, ethylene oxide, epichlorohydrin, styrene oxide, phenyl glycidyl ether or cyclohexene oxide; the external loop reactor comprises a spraying reactor and a spraying reactor.

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