A method for purifying a by-product of transesterification of 1,2-propanediol

Abstract

The application discloses a purification method of 1,2-propanediol by-produced in transesterification, which comprises the following steps: contacting and reacting 1,2-propanediol by-produced in transesterification with hydrogen, so as to obtain purified 1,2-propanediol; the 1,2-propanediol by-produced in transesterification contains propylene carbonate impurities; and the reaction temperature is 190-230 DEG C. The method has the advantages of simplicity, low cost and high product purity.

Description

TECHNICAL FIELD

[0001] The application relates to a purification method of 1,2-propanediol by-produced in ester exchange, and belongs to the technical field of chemical synthesis. BACKGROUND

[0002] 1,2-propanediol is a widely used non-toxic chemical raw material. Propylene glycol is a main raw material in the production of unsaturated polyesters. In the food and daily chemical industry, 1,2-propanediol can be used as an extraction solvent of natural flavors, a moisturizing and softening agent for bread and meat, and a solvent for various flavors, pigments and preservatives. In addition, it can also be used as a solvent, softening agent and moisturizing agent in the pharmaceutical industry, cosmetic industry and tobacco industry. Since propylene glycol is widely used in the food industry, the product quality of propylene glycol is divided into industrial grade, pharmaceutical grade and company grade according to purity, color and odor. The pharmaceutical grade propylene glycol has a higher purity of 99.5% or above and no irritating odor. The product produced by the ester exchange method in the domestic process cannot directly reach a high product quality, and cannot meet the standard requirements of the pharmaceutical, food and cosmetic industries. Therefore, it is of great significance to improve the odor of the product and increase the purity of the product.

[0003] At present, the domestic refining method of propylene glycol mainly starts from extraction decolorization, adsorption decolorization and extraction rectification. The extraction decolorization reaction process is too long, and the extractant needs to be further separated, which increases the equipment investment; the adsorption decolorization cannot handle the colority to the pharmaceutical grade standard due to the cost problem; the extraction rectification can handle the colority to the standard above, but it does not solve the odor problem of the product. Foreign refining processes are learned from the treatment process of 1,3-propanediol, mainly including azeotropic rectification, strong alkaline anion refining and vacuum batch rectification. The azeotropic rectification uses ethylbenzene as the azeotropic agent, and the product yield is improved compared with ordinary rectification. If the odor of the product needs to be removed, a deodorizing agent and desalted water need to be added for rectification. The product purity after strong alkaline anion refining is high, but the equipment cost is high and a large amount of dilution water is needed, and the water content in the product is high, which is difficult to remove. The colority of the product refined by vacuum rectification is low, and the purity is high, reaching the pharmaceutical grade standard. The process is simple, but it is a batch reaction and cannot realize continuous production. The application studies the impurities in the product, prepares a high-efficiency and stable catalyst for fixed-bed continuous catalytic reaction, improves the product purity and solves the odor problem caused by impurities. SUMMARY

[0004] A purification method of 1,2-propanediol by-produced in ester exchange, wherein the 1,2-propanediol crude by-produced in ester exchange is contacted with hydrogen to react, and 1,2-propanediol after purification is obtained.

[0005] The 1,2-propanediol crude by-produced in ester exchange contains propylene carbonate impurities.

[0006] The content of 1,2-propanediol in the crude 1,2-propanediol obtained from the transesterification by-product is 99.2-99.6wt%, and the content of propylene carbonate impurity is 0.3-0.7wt%;

[0007] The content of 1,2-propanediol in the purified 1,2-propanediol is 98%.

[0008] The temperature of the reaction is 190-230℃.

[0009] The space velocity of the reaction is 0.2-0.5h -1 .

[0010] Optionally, the space velocity of the reaction is 0.35-0.5h -1 .

[0011] Optionally, the space velocity of the reaction is any value among 0.35h -1 ,0.4h -1 ,0.45h -1 ,0.5h -1 or a range value between any two of them.

[0012] The pressure of the reaction is 2-5MPa.

[0013] Optionally, the pressure of the reaction is 3-5MPa.

[0014] Optionally, the pressure of the reaction is any value among 3MPa, 4MPa, 5MPa or a range value between any two of them.

[0015] The reaction is carried out in a fixed bed reactor.

[0016] The reaction further comprises a catalyst.

[0017] The catalyst is selected from a nickel-based catalyst or a copper-based catalyst.

[0018] The nickel-based catalyst is selected from Ni / Al2O3;

[0019] The copper-based catalyst is selected from Cu / SiO2, Cu / MgO.

[0020] The advantages of the present application are:

[0021] The method of the present application is simple, low in cost, and can also ensure the purity of the product. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1Schematic diagram of the device used in Example 1, wherein 1, nitrogen or hydrogen; 2, raw material bottle; 3, high-pressure constant flow pump; 4, stop valve; 5, pressure reducing valve; 6, hydrogen mass flow meter; 7, check valve; 8, mixed preheater; 9, fixed bed reactor; 10, condenser; 11, gas-liquid separator; 12, back pressure valve; 13, product outlet. DETAILED DESCRIPTION

[0023] The present application will be described in detail below with reference to examples, but the present application is not limited to these examples.

[0024] The raw materials and catalysts in the examples of the present application are all purchased through commercial channels unless otherwise specified.

[0025] Comparative Example 1

[0026] First, the hydrogenation catalyst Cu / SiO2 was loaded, then the experimental device was purged with nitrogen to blow out all the air in the experimental device, the hydrogen valve was slowly opened, the nitrogen valve was gradually closed, after the hydrogen valve was fully opened, the nitrogen valve was fully closed; the 1,2-propanediol crude product obtained by ester exchange by-product was introduced, the pressure was controlled at 3 MPa, the space velocity was 0.5 h -1 , the reaction temperature was 110°C, the hydrogenated material was collected, and the content of each component was analyzed by gas chromatography. The content of 1,2-propanediol after hydrogenation was 99.17%, the content of impurity 1 was 0.3734%, the content of 1,2-propanediol in the raw material was 99.48%, the content of impurity 1 was 0.3994%, the content of 1,2-propanediol after hydrogenation and the content of impurity 1 were reduced but not obvious, the hydrogenation effect was not good, and there was no obvious change in the irritating odor after hydrogenation.

[0027] Figure 1 Schematic diagram of the device used in Example 1, wherein 1, nitrogen or hydrogen; 2, raw material bottle; 3, high-pressure constant flow pump; 4, stop valve; 5, pressure reducing valve; 6, hydrogen mass flow meter; 7, check valve; 8, mixed preheater; 9, fixed bed reactor; 10, condenser; 11, gas-liquid separator; 12, back pressure valve; 13, product outlet.

[0028] Example 1

[0029] First, the hydrogenation catalyst Cu / SiO2 was loaded, then the experimental device was purged with nitrogen to blow out all the air in the experimental device, the hydrogen valve was slowly opened, the nitrogen valve was gradually closed, after the hydrogen valve was fully opened, the nitrogen valve was fully closed; the 1,2-propanediol crude product obtained by ester exchange by-product was introduced, the pressure was controlled at 3 MPa, the space velocity was 0.5 h -1, reaction temperature 210℃, the hydrogenated material was collected, and the content of each component was analyzed using gas chromatography. After hydrogenation, the content of 1,2-propanediol was 97.67%, and the content of impurity 1 was 0.0607%. In the raw material, the content of 1,2-propanediol was 99.48%, and the content of impurity 1 was 0.3994%. After hydrogenation, the content of 1,2-propanediol was significantly reduced, and the content of impurity 1 was significantly reduced. The hydrogenation effect was good, and there was no irritating odor after hydrogenation.

[0030] Example 2

[0031] First, the hydrogenation catalyst Cu / SiO2 was loaded, and then the experimental device was purged with nitrogen to blow out all the air in the experimental device. The hydrogen valve was slowly opened, the nitrogen valve was gradually closed, and after the hydrogen valve was fully opened, the nitrogen valve was fully closed. The 1,2-propanediol crude product obtained by ester exchange by-product was introduced, the pressure was controlled at 3 MPa, the space velocity was 0.5 h -1 , reaction temperature 210℃, the hydrogenated material was collected, and the content of each component was analyzed using gas chromatography. After hydrogenation, the content of 1,2-propanediol was 97.67%, and the content of impurity 1 was 0.0607%. In the raw material, the content of 1,2-propanediol was 99.48%, and the content of impurity 1 was 0.3994%. After hydrogenation, the content of 1,2-propanediol was significantly reduced, and the content of impurity 1 was significantly reduced. The hydrogenation effect was good, and there was no irritating odor after hydrogenation.

[0032] Example 3

[0033] First, the hydrogenation catalyst Cu / SiO2 was loaded, and then the experimental device was purged with nitrogen to blow out all the air in the experimental device. The hydrogen valve was slowly opened, the nitrogen valve was gradually closed, and after the hydrogen valve was fully opened, the nitrogen valve was fully closed. The 1,2-propanediol crude product obtained by ester exchange by-product was introduced, the pressure was controlled at 5 MPa, the space velocity was 0.5 h -1 , reaction temperature 210℃, the hydrogenated material was collected, and the content of each component was analyzed using gas chromatography. After hydrogenation, the content of 1,2-propanediol was 97.67%, and the content of impurity 1 was 0.0607%. In the raw material, the content of 1,2-propanediol was 99.48%, and the content of impurity 1 was 0.3994%. After hydrogenation, the content of 1,2-propanediol was significantly reduced, and the content of impurity 1 was significantly reduced. The hydrogenation effect was good, and there was no irritating odor after hydrogenation.

[0034] Example 4

[0035] First, the hydrogenation catalyst Cu / SiO2 was loaded, and then the experimental device was purged with nitrogen to blow out all the air in the experimental device. The hydrogen valve was slowly opened, the nitrogen valve was gradually closed, and after the hydrogen valve was fully opened, the nitrogen valve was fully closed. The 1,2-propanediol crude product obtained by ester exchange by-product was introduced, the pressure was controlled at 3 MPa, the space velocity was 0.5 h -1The reaction temperature was 190℃, the hydrogenated material was collected, and the content of each component was analyzed by gas chromatography. The content of 1,2-propanediol after hydrogenation was 98.9%, the content of impurity 1 was 0.0365%, the content of 1,2-propanediol in the raw material was 99.48%, the content of impurity 1 was 0.3994%, the content of 1,2-propanediol after hydrogenation did not change significantly, the content of impurity 1 decreased significantly, the hydrogenation effect was good, and there was no irritating odor after hydrogenation.

[0036] The experimental data is shown in Table 1

[0037] Table 1

[0038]

[0039] Therefore, it can be seen that the method of the present application can effectively purify the 1,2-propanediol crude product obtained by ester exchange by-product.

[0040] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed as above, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, which are equivalent to equivalent embodiments, and all belong to the scope of the technical solution.

Claims

1. A method for purifying 1,2-propanediol, a byproduct of transesterification, characterized in that, The crude 1,2-propanediol obtained as a byproduct of transesterification was reacted with hydrogen in the presence of a copper-based catalyst to obtain purified 1,2-propanediol. The crude 1,2-propanediol obtained as a byproduct of the transesterification process contains propylene carbonate impurities. The reaction temperature is 190~230℃; The reaction pressure is 2~5 MPa; The space velocity of the reaction is 0.2~0.5 h⁻¹. -1 .

2. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The crude 1,2-propanediol obtained as a byproduct of transesterification contains 99.2-99.6 wt% 1,2-propanediol and 0.3-0.7 wt% propylene carbonate impurities.

3. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The purified 1,2-propanediol contained 98% 1,2-propanediol.

4. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The space velocity of the reaction is 0.35~0.5 h⁻¹. -1 .

5. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The space velocity of the reaction is 0.4~0.45 h⁻¹. -1 .

6. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The reaction is carried out at a pressure of 3-5 MPa.

7. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 1, is characterized in that, The reaction is carried out at a pressure of 3-4 MPa.

8. The purification method for 1,2-propanediol byproduct of transesterification according to claim 1, characterized in that, The reaction is carried out in a fixed-bed reactor.

9. The purification method for 1,2-propanediol, a byproduct of transesterification, according to claim 8, is characterized in that, The catalyst is selected from Cu / SiO2 and Cu / MgO catalysts.

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