Method for purifying 1-methoxy-2-propanol through selective covalent reaction

Abstract

The invention relates to the technical field of purification of propylene glycol monomethyl ether crude products, in particular to a method for purifying 1-methoxy-2-propanol through a selective covalent reaction. The method comprises the following steps: mixing a nucleophilic substrate and a propylene glycol monomethyl ether crude product to be purified for the first time to obtain a first solution; carrying out secondary mixing on an alkaline substance and a propylene glycol monomethyl ether mixture to be purified to obtain a second solution; and adding the second solution into the first solution for selective covalent reaction, distilling the reaction system, and collecting the distillate, namely the target product. The crude product of the propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol, and the crude product of the propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol. The pKa of 2-methoxy-1-propanol is smaller than that of 1-methoxy-2-propanol, and meanwhile, the steric hindrance of 2-methoxy-1-propanol is smaller than that of 1-methoxy-2-propanol; in the nucleophilic substitution reaction, the reaction activity of the former is higher than that of the latter, the former and a nucleophilic substrate can easily generate a compound with a higher boiling point, and separation and purification of the 1-methoxy-2-propanol are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of propylene glycol monomethyl ether purification, and in particular to a method for purifying 1-methoxy-2-propanol through a selective covalent reaction. Background Art

[0002] Propylene glycol methyl ether (PGME) is a fine chemical with excellent performance. Electronic grade PGME and its acetate are used as cleaning liquid or stripping liquid in liquid crystal panels and as cleaning liquid in semiconductor manufacturing, and the market demand is gradually increasing. PGME is usually obtained by the ring-opening reaction of methanol and propylene oxide. Due to the limited selectivity in the synthesis, there are unavoidable side reactions in the synthesis of PGME. Therefore, the crude PGME contains two isomers (Formula I and Formula II) of 1-methoxy-2-propanol (denoted as PM) and 2-methoxy-1-propanol (denoted as MP), of which the content of 1-methoxy-2-propanol is usually 85% to 99.9%. However, as an electronic chemical, the purity of the components is more demanding.

[0003]

[0004] Existing methods for removing 2-methoxy-1-propanol from isomers are based on distillation. However, since the boiling point difference between 1-methoxy-2-propanol and 2-methoxy-1-propanol is very small (the boiling point of 1-methoxy-2-propanol is 118° C., and the boiling point of 2-methoxy-1-propanol is about 130° C.), and azeotropes are easily formed, direct purification by distillation has high energy consumption, low efficiency, and large product loss. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for purifying 1-methoxy-2-propanol by selective covalent reaction, which consumes less energy and can obtain 1-methoxy-2-propanol with higher purity.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for purifying 1-methoxy-2-propanol by selective covalent reaction, comprising the following steps:

[0008] The nucleophilic substrate and the crude propylene glycol monomethyl ether to be purified are first mixed to obtain a first solution;

[0009] secondly mixing the alkaline substance and the crude propylene glycol monomethyl ether to be purified to obtain a second solution;

[0010] After adding the second solution into the first solution for selective covalent reaction, distilling the reaction system, and collecting the distillate, which is the target product;

[0011] The crude propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol.

[0012] Preferably, the nucleophilic substrate comprises one or more of maleic anhydride-styrene copolymer, benzoic anhydride, dimethoxytriphenylmethane chloride, triphenylmethane chloride and polymethyl acrylate.

[0013] Preferably, the alkaline substance includes one or more of potassium alkoxide, sodium alkoxide and organic amine.

[0014] Preferably, the organic amine includes diisopropylethylamine or triethylamine.

[0015] Preferably, the molar ratio of the alkaline substance to the nucleophilic substrate is 0.1 to 10:1.

[0016] Preferably, the temperature of the selective covalent reaction is 15 to 80° C., and the time is 0.5 to 48 hours.

[0017] Preferably, the distillation is vacuum distillation; the temperature of the vacuum distillation is 80-120°C.

[0018] Preferably, the mass percentage of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.01-15%.

[0019] Preferably, the mass percentage of 1-methoxy-2-propanol in the target product is ≥98%.

[0020] Preferably, the moisture content in the target product is ≤200 ppm.

[0021] The present invention provides a method for purifying 1-methoxy-2-propanol by selective covalent reaction, comprising the following steps: firstly mixing a nucleophilic substrate and a crude product of propylene glycol monomethyl ether to be purified to obtain a first solution; secondly mixing an alkaline substance and the crude product of propylene glycol monomethyl ether to be purified to obtain a second solution; after adding the second solution to the first solution for selective covalent reaction, distilling the reaction system, collecting the distillate, i.e., the target product; the crude product of propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol. The present invention fully considers that the pKa of 2-methoxy-1-propanol in the crude product of propylene glycol monomethyl ether is less than that of 1-methoxy-2-propanol, and it is easier to form oxygen anions than 1-methoxy-2-propanol under alkaline conditions, and at the same time, the steric hindrance of 2-methoxy-1-propanol is smaller than that of 1-methoxy-2-propanol, so the activity in the nucleophilic substitution reaction is higher than that of 1-methoxy-2-propanol. When 2-methoxy-1-propanol reacts preferentially with a nucleophilic substrate, it is easy to generate a compound with a higher boiling point with the nucleophilic substrate, and its properties are greatly different from those of 1-methoxy-2-propanol, so it is easy to separate, thereby achieving the purification of 1-methoxy-2-propanol.

[0022] The data in the examples show that the purity of the mass fraction of single 1-methoxy-2-propanol in the purified propylene glycol monomethyl ether provided by the present invention can be increased from 85.0% to more than 99.0%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a graph showing the change in the molar ratio of 2-methoxy-1-propanol to polymethyl acrylate in the products of Examples 1 to 5. DETAILED DESCRIPTION

[0024] The present invention provides a method for purifying 1-methoxy-2-propanol by selective covalent reaction, comprising the following steps:

[0025] The nucleophilic substrate and the crude propylene glycol monomethyl ether to be purified are first mixed to obtain a first solution;

[0026] secondly mixing the alkaline substance and the crude propylene glycol monomethyl ether to be purified to obtain a second solution;

[0027] After the second solution is added to the first solution for selective covalent reaction, the reaction system is distilled and the distillate, i.e., the target product, is collected; the crude propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol.

[0028] The present invention first mixes a nucleophilic substrate and a crude product of propylene glycol monomethyl ether to be purified to obtain a first solution.

[0029] As an embodiment, the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.01 to 15%.

[0030] As an embodiment, the nucleophilic substrate includes one or more of maleic anhydride-styrene copolymer, benzoic anhydride, dimethoxytriphenylmethane chloride, triphenylmethane chloride and polymethyl acrylate.

[0031] As one embodiment, the molar ratio of the nucleophilic substrate to the 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is ≥1:1. As another embodiment, the molar ratio of the nucleophilic substrate to the 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 4 to 50:1.

[0032] The present invention secondly mixes the alkaline substance and the propylene glycol methyl ether to be purified to obtain a second solution.

[0033] As an embodiment, the alkaline substance includes potassium alcoholate, sodium alcoholate and / or organic amine. In a specific embodiment, the potassium alcoholate can be potassium tert-butoxide; the sodium alcoholate can be sodium tert-butoxide. As an embodiment, the organic amine includes diisopropylethylamine or triethylamine.

[0034] As an embodiment, the molar ratio of the alkaline substance to the nucleophilic substrate is 0.1 to 10:1. In a specific embodiment, the molar ratio of the alkaline substance to the nucleophilic substrate can be 1:1.

[0035] After obtaining the first solution and the second solution, the present invention adds the second solution into the first solution for selective covalent reaction, distills the reaction system, and collects the distillate, which is the target product.

[0036] As an embodiment, the temperature of the selective covalent reaction is 15 to 80° C., and the time is 0.5 to 48 hours. In a specific embodiment, the temperature can be room temperature, and the time can be 4 hours.

[0037] As an embodiment, the distillation is vacuum distillation, and the temperature of the vacuum distillation is 80-120°C.

[0038] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] (1) adding polymethyl acrylate into a flask, and then adding a crude product of propylene glycol monomethyl ether to be purified (the mass proportion of 2-methoxy-1-propanol in the crude product of propylene glycol monomethyl ether to be purified is 0.56%, and the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is 1:1), stirring to dissolve the polymethyl acrylate, and obtaining a first solution;

[0041] (2) adding potassium tert-butoxide (the molar ratio of potassium tert-butoxide to polymethyl acrylate is 1:1) into a beaker, and then adding propylene glycol methyl ether to be purified, and stirring to form a uniform solution to obtain a second solution;

[0042] (3) Under rapid stirring, the second solution was quickly added to the first solution and stirred at room temperature for 4 h.

[0043] (4) Collect the purified product by vacuum distillation (distillation temperature is 100° C.), analyze the isomers and other impurities of the purified product by gas chromatography, and analyze the water content by Karl Fischer titrator.

[0044] The water content in the target product of Example 1 is 182 ppm.

[0045] Example 2

[0046] The difference from Example 1 is that the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is 2:1, and the water content is 155 ppm.

[0047] Example 3

[0048] The difference from Example 1 is that the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is 4:1, and the water content is 100 ppm.

[0049] Example 4

[0050] The difference from Example 1 is that the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is 6:1, and the water content is 70 ppm.

[0051] Example 5

[0052] The difference from Example 1 is that the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is 8:1, and the water content is 110 ppm.

[0053] Figure 1 The graph of the change of 2-methoxy-1-propanol in the products of Examples 1 to 5 with the molar ratio of polymethyl acrylate to 2-methoxy-1-propanol is shown in FIG. Figure 1 It can be seen that as the reaction proceeds, the content of 2-methoxy-1-propanol continues to decrease, and at the same time, as the reactants increase, the rate of decrease of the 2-methoxy-1-propanol content is also accelerated accordingly.

[0054] Example 6

[0055] (1) adding 6.4 g of triphenylmethane into a flask, and then adding crude propylene glycol monomethyl ether to be purified (the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.5%, and the molar ratio of triphenylmethane to 2-methoxy-1-propanol is 4:1), stirring to dissolve the triphenylmethane to obtain a first solution;

[0056] (2) adding 1.42 g of diisopropylethylamine into a beaker, and then adding propylene glycol methyl ether to be purified, and stirring to form a uniform solution to obtain a second solution;

[0057] (3) Under rapid stirring, the second solution was quickly added to the first solution and stirred at room temperature for 4 h.

[0058] (4) The purified product was collected by vacuum distillation (distillation temperature was 120° C.), and the isomers and other impurities of the purified product were analyzed by gas chromatography, and the water content was analyzed by Karl Fischer titrator.

[0059] After testing, the mass percentage of 2-methoxy-1-propanol in the purified product was 0.3%, and the water content was 180 ppm.

[0060] Example 7

[0061] (1) adding 7.78 g of dimethoxytriphenylmethane into a flask, and then adding crude propylene glycol monomethyl ether to be purified (the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.36%, and the molar ratio of dimethoxytriphenylmethane to 2-methoxy-1-propanol is 6:1), stirring to dissolve the dimethoxytriphenylmethane to obtain a first solution;

[0062] (2) adding 1.42 g of diisopropylethylamine into a beaker, and then adding propylene glycol methyl ether to be purified, and stirring to form a uniform solution to obtain a second solution;

[0063] (3) Under rapid stirring, the second solution was quickly added to the first solution and stirred at room temperature for 4 h.

[0064] (4) The purified product was collected by vacuum distillation (distillation temperature was 90° C.), and the isomers and other impurities of the purified product were analyzed by gas chromatography, and the water content was analyzed by Karl Fischer titrator.

[0065] After testing, the mass percentage of 2-methoxy-1-propanol in the purified product was 0.22%, and the water content was 100 ppm.

[0066] Example 8

[0067] (1) adding 2.18 g of benzoic anhydride into a flask, and then adding crude propylene glycol monomethyl ether to be purified (the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.55%, and the molar ratio of benzoic anhydride to 2-methoxy-1-propanol is 6:1), stirring to dissolve the benzoic anhydride, and obtaining a first solution;

[0068] (2) adding 1.12 g of triethylamine into a beaker, then adding propylene glycol methyl ether to be purified, and stirring to form a uniform solution to obtain a second solution;

[0069] (3) Under rapid stirring, the second solution was quickly added to the first solution and stirred at room temperature for 4 h.

[0070] (4) The purified product was collected by vacuum distillation (distillation temperature was 80° C.), and the isomers and other impurities of the purified product were analyzed by gas chromatography, and the water content was analyzed by Karl Fischer titrator.

[0071] After testing, the mass percentage of 2-methoxy-1-propanol in the purified product was 0.37%, and the water content was 80 ppm.

[0072] Example 9

[0073] (1) adding 3.66 g of maleic anhydride-styrene copolymer into a flask, and then adding crude propylene glycol monomethyl ether to be purified (the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.55%, and the molar ratio of maleic anhydride-styrene copolymer to 2-methoxy-1-propanol is 5:1), stirring to dissolve the maleic anhydride-styrene copolymer, to obtain a first solution;

[0074] (2) adding 1.42 g of diisopropylethylamine into a beaker, and then adding propylene glycol methyl ether to be purified, and stirring to form a uniform solution to obtain a second solution;

[0075] (3) Under rapid stirring, the second solution was quickly added to the first solution and stirred at room temperature for 4 h.

[0076] (4) collecting the purified product by vacuum distillation, analyzing the isomers and other impurities of the purified product by gas chromatography, and analyzing the water content by Karl Fischer titrator.

[0077] After testing, the mass percentage of 2-methoxy-1-propanol in the purified product was 0.35%, and the water content was 100 ppm.

[0078] Example 10

[0079] The only difference from Example 9 is that the mass proportion of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 15%.

[0080] After testing, the mass percentage of 2-methoxy-1-propanol in the purified product was 0.27%, and the water content was 200 ppm.

[0081] It should be noted that the purity of the product in this example was detected by GC-MS method.

[0082] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for purifying 1-methoxy-2-propanol by selective covalent reaction, comprising the following steps: The nucleophilic substrate and the crude propylene glycol monomethyl ether to be purified are first mixed to obtain a first solution; secondly mixing the alkaline substance and the crude propylene glycol monomethyl ether to be purified to obtain a second solution; After adding the second solution into the first solution for selective covalent reaction, distilling the reaction system, and collecting the distillate, which is the target product; The crude propylene glycol monomethyl ether to be purified contains 1-methoxy-2-propanol and 2-methoxy-1-propanol.

2. The method according to claim 1, characterized in that The nucleophilic substrate includes one or more of maleic anhydride-styrene copolymer, benzoic anhydride, dimethoxytriphenylmethane chloride, triphenylmethane chloride and polymethyl acrylate.

3. The method according to claim 1, characterized in that The alkaline substance includes one or more of potassium alcoholate, sodium alcoholate and organic amine.

4. The method according to claim 3, characterized in that The organic amine includes diisopropylethylamine or triethylamine.

5. The method according to any one of claims 2 to 4, characterized in that: The molar ratio of the alkaline substance to the nucleophilic substrate is 0.1 to 10:

1.

6. The method according to claim 1, characterized in that The temperature of the selective covalent reaction is 15 to 80° C., and the time is 0.5 to 48 hours.

7. The method according to claim 1, characterized in that The distillation is vacuum distillation; the temperature of the vacuum distillation is 80-120°C.

8. The method according to claim 1, characterized in that The mass percentage of 2-methoxy-1-propanol in the crude propylene glycol monomethyl ether to be purified is 0.01-15%.

9. The method according to claim 1, characterized in that The mass percentage content of 1-methoxy-2-propanol in the target product is ≥98%.

10. The method according to claim 1, characterized in that The moisture content in the target product is ≤200ppm.

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