Purification method of 1, 2-propylene glycol prepared by transesterification method and obtained product

Abstract

The invention provides a purification method of 1, 2-propylene glycol prepared by a transesterification method and an obtained product, and belongs to the technical field of refining and purification. The purification method comprises the following steps: 1) carrying out primary molecular distillation on a 1, 2-propylene glycol crude product to obtain light component removed 1, 2-propylene glycol; (2) carrying out secondary molecular distillation on the 1, 2-propylene glycol to obtain 1, 2-propylene glycol without heavy components; and (3) filtering the 1, 2-propylene glycol subjected to heavy component removal by adopting an activated carbon fiber membrane to obtain the purified 1, 2-propylene glycol. The 1, 2-propylene glycol obtained by the purification method provided by the invention has the advantages of low chromaticity, small odor, simple process, mild reaction conditions and less three wastes, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of refining and purification, and particularly relates to a purification method of 1,2 - propanediol prepared by transesterification and the obtained product. Background Art

[0002] 1,2 - propanediol is a widely used chemical raw material and is widely used in industries such as food. The product quality of propanediol is divided into industrial grade, pharmaceutical grade, and electronic grade according to purity, chromaticity, and odor. Pharmaceutical - grade propanediol has a higher purity, reaching 99.5% and above, and has no pungent odor.

[0003] At present, the production processes of 1,2 - propanediol can be divided into two types: "hydration method" and "transesterification method". The "hydration method" process uses propylene oxide and water as raw materials, reacts under the action of no catalyst or an acidic catalyst, and then obtains 1,2 - propanediol through refining and purification. The "hydration method" process is simple, has a short process flow, and the produced 1,2 - propanediol product has good quality. The "transesterification method" production process uses propylene carbonate and methanol as raw materials and sodium methoxide as a catalyst to produce dimethyl carbonate and co - produce 1,2 - propanediol. Since the "transesterification method" is a co - production process, a set of devices produces two products, dimethyl carbonate and 1,2 - propanediol, simultaneously, which has an obvious cost advantage. However, there are problems such as a longer process flow and more side reactions. Therefore, the 1,2 - propanediol product produced by the "transesterification method" is prone to discoloration, has a strong pungent odor, and the quality of the propanediol product is poor. At present, the products of propanediol produced by the transesterification method in China cannot meet the standard requirements of industries such as medicine, food, essence, spice, cosmetics, and high - grade resins. Therefore, improving the odor of the product and increasing the product purity are of great significance.

[0004] At present, the domestic refining methods for propanediol mainly start from extraction decolorization, adsorption decolorization, and extractive distillation. The extraction decolorization reaction process is too long, and the extractant needs to be further separated, increasing equipment investment; considering cost issues, adsorption decolorization cannot process the chromaticity to the pharmaceutical - grade standard; extractive distillation can process the chromaticity to above the standard, but does not solve the product odor problem. Patent CN101906020A discloses a new purification process for 1,2 - propanediol by transesterification. In this scheme, a deodorant is added to reduce the odor. Although it can reduce the product odor, it will introduce new substances, and the trace impurities in the product are more complex. Summary of the Invention

[0005] The present invention provides a purification method of 1,2 - propanediol prepared by transesterification and the obtained product. The 1,2 - propanediol obtained by the purification method provided by the present invention has low chromaticity, small odor, a simple process, mild reaction conditions, and less generation of three wastes, and is suitable for industrial production.

[0006] To achieve the above object, the present invention provides a purification method of 1,2 - propanediol prepared by transesterification, comprising the following steps:

[0007] 1) Performing primary molecular distillation on the crude 1,2 - propanediol to obtain light - removed 1,2 - propanediol;

[0008] 2) Performing secondary molecular distillation on the said 1,2 - propanediol to obtain heavy - removed 1,2 - propanediol;

[0009] 3) Filtering the said heavy - removed 1,2 - propanediol with an activated carbon fiber membrane to obtain purified 1,2 - propanediol.

[0010] Preferably, in step 1), the temperature during the primary molecular distillation is 55 - 75°C, and the vacuum degree is 0.1 - 10 Pa.

[0011] Preferably, in step 2), the temperature during the secondary molecular distillation is 75 - 100°C, and the vacuum degree is 0.1 - 10 Pa.

[0012] Preferably, in step 3), nitrogen is introduced into the filtering device, and filtration is carried out under slightly positive pressure.

[0013] Preferably, the pressure during filtration is 0.01 - 0.1 MPa.

[0014] Preferably, in step 3), the thickness of the activated carbon fiber membrane used for filtration is 4 - 40 cm, and the pore diameters of the filter membranes before and after the activated carbon fiber membrane are 0.22 - 1 μm.

[0015] Preferably, in step 3), the flow rate of the material during filtration is 1 - 5 Kg / h.

[0016] Preferably, by weight percentage, the purity of the crude 1,2 - propanediol in step 1) is ≥95%.

[0017] The present invention provides 1,2 - propanediol obtained by any of the above purification methods. By weight percentage, the purity of the 1,2 - propanediol is ≥99.99%, and the transmittance at 220 nm is >55.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0019] The purification method provided by this application uses a two-stage molecular distillation technology to remove the light components and heavy components in the crude 1,2-propanediol in sequence, and then uses an activated carbon fiber membrane for filtration to further remove trace impurities and odors in the product, obtaining high-purity 1,2-propanediol. The method provided by this application does not introduce new substances additionally, has high product purity, mild reaction conditions, simple process, and less three wastes, is suitable for industrial production, and the product can be used in high-end fields such as daily chemical fragrances and unsaturated resins. Description of the Drawings

[0020] Figure 1 It is a gas chromatograph-mass spectrometry analysis comparison diagram of the industrial product of 1,2-propanediol in Example 2 and the purified 1,2-propanediol. Detailed Embodiments

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] The present invention provides a purification method for 1,2-propanediol prepared by a transesterification method, comprising the following steps:

[0023] 1) Performing first-stage molecular distillation on the crude 1,2-propanediol to obtain light-component-removed 1,2-propanediol;

[0024] 2) Performing second-stage molecular distillation on the 1,2-propanediol to obtain heavy-component-removed 1,2-propanediol;

[0025] 3) Filtering the heavy-component-removed 1,2-propanediol with an activated carbon fiber membrane to obtain purified 1,2-propanediol.

[0026] The present invention performs first-stage molecular distillation on the crude 1,2-propanediol to obtain light-component-removed 1,2-propanediol. In the present invention, the crude 1,2-propanediol is 1,2-propanediol prepared by a transesterification method. In the present invention, by weight percentage, the purity of the crude 1,2-propanediol is preferably ≥95%. In the present invention, the temperature during the first-stage molecular distillation is preferably 55-75°C, and the vacuum degree is preferably 0.1-10 Pa, more preferably 0.5-5 Pa. In the present invention, by performing first-stage molecular distillation, light-component impurities in the crude 1,2-propanediol can be removed.

[0027] After obtaining the light - removed 1,2 - propanediol, the present invention subjects the 1,2 - propanediol to secondary molecular distillation to obtain heavy - removed 1,2 - propanediol. In the present invention, the temperature during the secondary molecular distillation is preferably 75 - 100 °C, and the vacuum degree is preferably 0.1 - 10 Pa, more preferably 0.5 - 5 Pa. In the present invention, by performing secondary molecular distillation, the heavy - component impurities in the light - removed 1,2 - propanediol can be removed.

[0028] After obtaining the heavy - removed 1,2 - propanediol, the present invention filters the heavy - removed 1,2 - propanediol with an activated carbon fiber membrane to obtain purified 1,2 - propanediol. In the present invention, the thickness of the activated carbon fiber membrane used for filtration is preferably 4 - 40 cm, and the pore size of the filter membranes before and after the activated carbon fiber membrane is 0.22 - 1 μm. Filtering with an activated carbon fiber membrane can further remove trace impurities in the product, reduce the product odor, and improve the product light transmittance. In the present invention, membranes numbered 1 - 9 produced by Beijing Rixin Yuanwang Company are used, preferably membranes numbered 1, 5, and 8.

[0029] In the present invention, it is preferred to introduce nitrogen gas into the filtration equipment and perform filtration under slightly positive pressure. In the present invention, the pressure during filtration is preferably controlled at 0.01 - 0.1 MPa. Since the activated carbon fiber membrane used is relatively thick and the raw material to be filtered is not easily permeated, in the present invention, introducing nitrogen gas into the filtration equipment and performing filtration under slightly positive pressure can promote product filtration. In the present invention, the flow rate of the material during filtration is preferably 1 - 5 Kg / h.

[0030] The present invention provides 1,2 - propanediol obtained by any of the above purification methods, and the purity of the 1,2 - propanediol ≥ 99.99%, and the light transmittance at 220 nm > 55.

[0031] The reasons for the poor quality of 1,2 - propanediol products prepared by the transesterification method are that the products contain trace impurities such as 1 - methoxy - 2 - propanol, 2 - methoxy - 1 - propanol, 1 - hydroxy - 2 - acetone, 1 - (2 - propenyloxy) - 2 - propanol, 3 - (1,3 - dimethylbutoxy) - 2 - butanol, 1,2 - dimethoxypropane, methyl - acetate - ethyl ester, 1,1 - dihydroxy - 2 - propanol, etc. The total impurity content is about 0.10% - 0.30%, and the content of some impurities is only about 0.005%. Therefore, by using the conventional rectification method, 1,2 - propanediol products with qualified chromaticity and odor cannot be obtained.

[0032] The purification method provided by this application adopts a two-stage molecular distillation technology to sequentially remove the light components and heavy components in the crude 1,2-propanediol, and then uses an activated carbon fiber membrane for filtration to further remove trace impurities and odors in the product, obtaining high-purity 1,2-propanediol. The method provided by this application does not introduce new substances additionally, has a high product purity, mild reaction conditions, a simple process, and generates less three wastes, is suitable for industrial production, and the product can be used in high-end fields such as daily chemical fragrances and unsaturated resins.

[0033] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0034] Example 1

[0035] In the 1,2-propanediol used in this example in the industry, by weight percentage, the content of 1,2-propanediol is 99%, the light transmittance at 220 nm is 5.4, and there is an irritating odor after adding hot water.

[0036] Take the industrial 1,2-propanediol for molecular distillation. The first-stage molecular distillation is carried out under the conditions of 65 °C, a vacuum degree of 1 Pa, and a feeding rate of 4 kg / h to remove the light component impurities in the product, obtaining the light-removed 1,2-propanediol. After preheating the obtained light-removed 1,2-propanediol to 80 °C, it is transferred to the second-stage molecular distillation equipment. The temperature of the second-stage molecular distillation is 90 °C, the vacuum pressure is 1 Pa, and the feeding rate is controlled at 3 kg / h. The second-stage molecular distillation removes the heavy component impurities to obtain the heavy-removed 1,2-propanediol.

[0037] Take the heavy-removed 1,2-propanediol obtained after the second-stage distillation, add it to the activated carbon fiber membrane equipment (the thickness of the activated carbon fiber membrane is 20 cm, and the pore diameters of the front and rear filter membranes are 0.45 μm), introduce nitrogen gas at the top of the activated carbon fiber membrane equipment, keep the equipment pressure at 0.05 MPa, and keep the material flow rate at 3 kg / h for filtration to obtain high-purity 1,2-propanediol.

[0038] Example 2

[0039] In the industrial 1,2-propanediol used in this example, by weight percentage, the content of 1,2-propanediol is 95%, the light transmittance at 220 nm is 0.2, and there is an irritating odor after adding hot water.

[0040] Take industrial-grade 1,2-propanediol for molecular distillation. In the first-stage molecular distillation, under the conditions of 55°C, a vacuum degree of 0.1 Pa, and a feeding rate of 2 kg / h, the light-component impurities in the product are removed to obtain light-component-removed 1,2-propanediol. The obtained light-component-removed 1,2-propanediol is preheated to 70°C and then transferred to a second-stage molecular distillation device. The temperature of the second-stage molecular distillation is 75°C, the vacuum pressure is 0.1 Pa, and the feeding rate is controlled at 2 kg / h. The second-stage molecular distillation removes the heavy-component impurities to obtain heavy-component-removed 1,2-propanediol.

[0041] Take the heavy-component-removed 1,2-propanediol obtained after the second-stage distillation and add it to an activated carbon fiber membrane device (the thickness of the activated carbon fiber membrane is 40 cm, and the pore diameters of the front and rear filter membranes are 0.22 μm). Nitrogen is introduced at the top of the activated carbon fiber membrane device, the pressure of the device is maintained at 0.02 MPa, and the material flow rate is maintained at 1.5 kg / h for filtration to obtain high-purity 1,2-propanediol. The gas chromatograph-mass spectrometer analysis comparison chart of the 1,2-propanediol before and after purification is as Figure 1 shown.

[0042] Example 3

[0043] In the industrial-grade 1,2-propanediol used in this example, by weight percentage, the content of 1,2-propanediol is 99.5%, the transmittance at 220 nm is 7.2, and it has an irritating odor after adding hot water.

[0044] Take industrial-grade 1,2-propanediol for molecular distillation. In the first-stage molecular distillation, under the conditions of 75°C, a vacuum degree of 10 Pa, and a feeding rate of 5 kg / h, the light-component impurities in the product are removed to obtain light-component-removed 1,2-propanediol. The obtained light-component-removed 1,2-propanediol is preheated to 90°C and then transferred to a second-stage molecular distillation device. The temperature of the second-stage molecular distillation is 100°C, the vacuum pressure is 10 Pa, and the feeding rate is controlled at 5 kg / h. The second-stage molecular distillation removes the heavy-component impurities to obtain heavy-component-removed 1,2-propanediol.

[0045] Take the heavy-component-removed 1,2-propanediol obtained after the second-stage distillation and add it to an activated carbon fiber membrane device (the thickness of the activated carbon fiber membrane is 15 cm, and the pore diameters of the front and rear filter membranes are 1 μm). Nitrogen is introduced at the top of the activated carbon fiber membrane device, the pressure of the device is maintained at 0.1 MPa, and the material flow rate is maintained at 4 kg / h for filtration to obtain high-purity 1,2-propanediol.

[0046] Comparative Example 1

[0047] In the industrial-grade 1,2-propanediol used in this comparative example, by weight percentage, the content of 1,2-propanediol is 99.5%, the transmittance at 220 nm is 7.2, and it has an irritating odor after adding hot water.

[0048] Take industrial-grade 1,2-propanediol for molecular distillation. In the first-stage molecular distillation, under the conditions of 48 °C, a vacuum degree of 10 Pa, and a feeding rate of 5 kg / h, the light-component impurities in the product are removed to obtain light-component-removed 1,2-propanediol. The obtained light-component-removed 1,2-propanediol is preheated to 95 °C and then transferred to a second-stage molecular distillation device. The temperature of the second-stage molecular distillation is 105 °C, the vacuum pressure is 10 Pa, and the feeding rate is controlled at 5 kg / h. The second-stage molecular distillation removes the heavy-component impurities to obtain purified 1,2-propanediol.

[0049] Comparative Example 2

[0050] In the industrial-grade 1,2-propanediol used in this comparative example, by weight percentage, the content of 1,2-propanediol is 99.5%, the transmittance at 220 nm is 7.2, and there is an irritating odor after adding hot water.

[0051] Take industrial-grade 1,2-propanediol and add it to an activated carbon fiber membrane device (the thickness of the activated carbon fiber membrane is 15 cm, and the pore size of the front and rear filter membranes is 1 μm). Nitrogen is introduced at the top of the activated carbon fiber membrane device, the pressure of the device is maintained at 0.1 MPa, and the material flow rate is maintained at 4 kg / h for filtration to obtain purified 1,2-propanediol.

[0052] Comparative Example 3

[0053] In the industrial-grade 1,2-propanediol used in this example, by weight percentage, the content of 1,2-propanediol is 99.5%, the transmittance at 220 nm is 7.2, and there is an irritating odor after adding hot water.

[0054] Take industrial-grade 1,2-propanediol for molecular distillation. In the first-stage molecular distillation, under the conditions of 45 °C, a vacuum degree of 20 Pa, and a feeding rate of 5 kg / h, the light-component impurities in the product are removed to obtain light-component-removed 1,2-propanediol. The obtained light-component-removed 1,2-propanediol is preheated to 100 °C and then transferred to a second-stage molecular distillation device. The temperature of the second-stage molecular distillation is 110 °C, the vacuum pressure is 10 Pa, and the feeding rate is controlled at 5 kg / h. The second-stage molecular distillation removes the heavy-component impurities to obtain heavy-component-removed 1,2-propanediol.

[0055] Take the heavy-component-removed 1,2-propanediol obtained after the second-stage distillation and add it to an activated carbon fiber membrane device (the thickness of the activated carbon fiber membrane is 15 cm, and the pore size of the front and rear filter membranes is 1 μm). Nitrogen is introduced at the top of the activated carbon fiber membrane device, the pressure of the device is maintained at 0.1 MPa, and the material flow rate is maintained at 4 kg / h for filtration to obtain high-purity 1,2-propanediol.

[0056] Comparative Example 4

[0057] In the industrial-grade 1,2-propanediol used in this example, by weight percentage, the content of 1,2-propanediol is 99.5%, the transmittance at 220 nm is 7.2, and there is an irritating odor after adding hot water.

[0058] Molecular distillation was carried out on the industrial-grade 1,2-propanediol. In the first-stage molecular distillation, under the conditions of 75 °C, a vacuum degree of 10 Pa, and a feeding rate of 5 kg / h, the light-component impurities in the product were removed to obtain light-component-removed 1,2-propanediol. The obtained light-component-removed 1,2-propanediol was preheated to 90 °C and then transferred to a second-stage molecular distillation device. The temperature of the second-stage molecular distillation was 100 °C, the vacuum pressure was 10 Pa, and the feeding rate was controlled at 5 kg / h. The second-stage molecular distillation removed the heavy-component impurities to obtain 1,2-propanediol after removing the heavy components.

[0059] The 1,2-propanediol after removing the heavy components obtained after the second-stage distillation was subjected to atmospheric pressure filtration using an ion exchange membrane with a pore size of 0.22 μm, and the material flow rate was maintained at 4 kg / h for filtration to obtain high-purity 1,2-propanediol.

[0060] Performance test

[0061] The products prepared in each example and comparative example were tested by gas chromatography according to HG / T 5392-2018, and the specific results are shown in Table 1.

[0062] Table 1

[0063]

[0064] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for purifying 1,2-propylene glycol prepared by an ester exchange method, characterized in that: The steps include: 1) subjecting the crude 1,2-propylene glycol to a first-stage molecular distillation to obtain light-removed 1,2-propylene glycol; 2) subjecting the 1,2-propylene glycol to secondary molecular distillation to obtain deweighted 1,2-propylene glycol; 3) filtering the deweighted 1,2-propylene glycol using an activated carbon fiber membrane to obtain purified 1,2-propylene glycol.

2. The purification method according to claim 1, characterized in that The temperature of the first-stage molecular distillation in step 1) is 55-75° C., and the vacuum degree is 0.1-10 Pa.

3. The purification method according to claim 1, characterized in that The temperature of the secondary molecular distillation in step 2) is 75-100° C. and the vacuum degree is 0.1-10 Pa.

4. The purification method according to claim 1, characterized in that In step 3), nitrogen is introduced into the filtering device and filtering is performed using a slight positive pressure.

5. The purification method according to claim 4, characterized in that The pressure during filtration is between 0.01 and 0.1 MPa.

6. The purification method according to claim 1, characterized in that The thickness of the activated carbon fiber membrane used for filtration in step 3) is 4 to 40 cm, and the pore size of the filter membranes before and after the activated carbon fiber membrane is 0.22 to 1 μm.

7. The purification method according to claim 1, characterized in that The flow rate of the material during filtration in step 3) is 1-5 Kg / h.

8. The purification method according to claim 1, characterized in that Calculated by weight percentage, the purity of the crude 1,2-propylene glycol in step 1) is ≥ 95%.

9. 1,2-propylene glycol obtained by the purification method according to any one of claims 1 to 8, characterized in that The purity of the 1,2-propylene glycol is ≥99.99%, and the transmittance at 220 nm is >55.

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