Purification method of long-chain diacid monoester

Abstract

The invention discloses a purification method of long-chain dibasic acid monoester, which comprises the following steps: heating and dissolving a long-chain dibasic acid monoester crude product in an ester solvent, and adding organic amine under a stirring condition; after stirring and reacting for a set time, cooling the solution to 15-25 DEG C, and crystallizing and separating out the long-chain dibasic acid monoester; and carrying out solid-liquid separation and drying to obtain the long-chain dibasic acid monoester product. Based on the principle of similar dissolvability, the long-chain dibasic acid diester impurity in the long-chain dibasic acid monoester crude product is extremely easy to dissolve in the ester solvent, and cannot be crystallized and separated out even if the temperature is reduced, so that the long-chain dibasic acid diester impurity can be removed by selecting the ester solvent as a recrystallization solvent. As the PKa of the long-chain dibasic acid is smaller than that of monoester, the long-chain dibasic acid can react preferentially to generate organic ammonium salt when encountering organic amine, and the organic ammonium salt is easily dissolved in an ester solvent and cannot be recrystallized and separated out, so that the impurities of the long-chain dibasic acid can be effectively removed.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemicals, and in particular relates to a method for purifying long-chain dibasic acid monoesters. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Long-chain dibasic acid monoester (carbon chain length is generally 10 to 20 carbon atoms) is an important chemical raw material, which can be used in a variety of application fields, such as musk fragrance, coatings, inks, plastics, polyester resins, etc., and the requirements for its purity are getting higher and higher. The main impurities in the crude long-chain dibasic acid monoester product are the diester of over-esterification and the unreacted diacid. The diester impurity has a very low polarity due to the lack of carboxyl groups, and it is easy to enter the mother liquor during the recrystallization process and then be removed. The diacid and monoester with carboxyl groups are easy to precipitate due to their high polarity, which makes it difficult to separate the diacid and the monoester, and the ordinary recrystallization method cannot remove them.

[0004] At present, the method for purifying long-chain dibasic acid monoesters is generally vacuum distillation, that is, using the difference in boiling points between the product and impurities to achieve the purpose of separation. The purity of the purified product can only reach 92-94%. Even if a second vacuum distillation is performed, the product purity is difficult to exceed 95%, and there are still diesters and diacids remaining. In addition, high-temperature (250-300°C) and high-vacuum equipment are required, which consumes a lot of energy, has a slow distillation speed, and the product is easy to carbonize and deteriorate, and has high requirements for distillation tower equipment. In addition, the yield of purifying long-chain dibasic acid monoesters by vacuum distillation is low. For example, the yield of long-chain dibasic acid monoesters after a vacuum distillation is generally less than 75%; the yield of long-chain dibasic acid monoesters after a second vacuum distillation is generally less than 60%. Summary of the invention

[0005] In view of the shortcomings of the prior art, the object of the present invention is to provide a method for purifying long-chain dibasic acid monoesters.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for purifying long-chain dibasic acid monoesters comprises the following steps:

[0008] The crude product of long-chain dibasic acid monoester is heated and dissolved in an ester solvent, and an organic amine is added under stirring;

[0009] After stirring and reacting for a set time, the solution is cooled to 15-25°C to allow the long-chain dibasic acid monoester to crystallize;

[0010] After solid-liquid separation and drying, the long-chain dibasic acid monoester product is obtained.

[0011] Based on the principle of like dissolves like, the long-chain dibasic acid diester impurities in the crude long-chain dibasic acid monoester product are easily soluble in ester solvents and will not crystallize out even when the temperature is lowered. Therefore, the long-chain dibasic acid diester impurities can be removed by selecting ester solvents as recrystallization solvents.

[0012] Since the PKa of long-chain dibasic acid is lower than that of monoester, it will preferentially react to form organic ammonium salt when encountering organic amine. Organic ammonium salt is easily soluble in ester solvents and will not recrystallize and precipitate, thus effectively removing long-chain dibasic acid impurities. Figure 1 .

[0013] PKa:

[0014] Among them, 8≤n≤18.

[0015] Among them, the organic amine is a fatty tertiary amine, because if a primary amine or a secondary amine is used, an amine ester exchange side reaction will occur with the ester group to form new impurities, thereby affecting the purity and yield of the product.

[0016] In some embodiments, the carbon chain length of the long-chain dibasic acid monoester is 10 to 20 carbon atoms (8≤n≤18).

[0017] In some embodiments, the ester solvent is selected from at least one of methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate or ethyl butyrate.

[0018] Preferably, the mass of the crude long-chain dibasic acid monoester product dissolved in each liter of the ester solvent is 800-1200 g.

[0019] In some embodiments, the organic amine is at least one of trimethylamine, triethylamine, tripropylamine, tributylamine, N,N-diethylmethylamine, N-methylmorpholine, N-methylpiperidine or pyridine.

[0020] Preferably, the organic amine is triethylamine. When the organic amine is triethylamine, the purity of the prepared long-chain dibasic acid monoester can reach 99.8% and the yield can reach 88%.

[0021] In some embodiments, the mass ratio of the crude long-chain dibasic acid monoester product to the organic amine is 100:2-4.

[0022] In some embodiments, the stirring reaction time is 1-3 hours.

[0023] Preferably, the stirring reaction temperature is 40-60°C.

[0024] In some embodiments, the drying temperature is 30-40°C.

[0025] The beneficial effects achieved by one or more embodiments of the present invention are as follows:

[0026] Through simple and gentle operation, the long-chain dibasic acid monoester product is purified to more than 99%. By selecting an ester solvent as a recrystallization solvent and adding an organic amine thereto, two main impurities (long-chain dibasic acid diester and long-chain dibasic acid) can be removed at the same time, thereby reducing energy consumption and costs, simplifying equipment and operating procedures, and reducing material losses. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 : is a schematic diagram of the purification principle of the crude long-chain dibasic acid monoester product of an embodiment of the present invention;

[0029] Figure 2 : is a process flow chart of a crude product of a long-chain dibasic acid monoester according to an embodiment of the present invention;

[0030] Figure 3 This is a liquid phase spectrum of the crude product of monomethyl dodecanedioate of Example 1 of the present invention;

[0031] Figure 4 It is the liquid phase spectrum of the refined monomethyl dodecanedioate of Example 1 of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] The present invention will be further described below in conjunction with the embodiments.

[0034] Example 1

[0035] like Figure 2 As shown, a method for purifying a crude product of monomethyl dodecanedioate comprises the following steps:

[0036] A. Add 50 g of crude monomethyl dodecanedioate to 50 ml of ethyl acetate and heat to 60°C to dissolve;

[0037] B. Add 1.25 g of triethylamine dropwise while stirring; keep at 60°C and stir for 1 hour;

[0038] C. Cool down to 20℃ and keep warm for 2h to precipitate crystals;

[0039] D. Filter and dry at 40°C to obtain 44 g of refined product.

[0040] The purity of monomethyl dodecanedioate prepared by the method is 99.8%, and the yield of monomethyl dodecanedioate is 88%.

[0041] Example 2

[0042] A method for purifying a crude product of monomethyl dodecanedioate, comprising the following steps:

[0043] A. Add 50 g of crude monomethyl dodecanedioate to 50 ml of ethyl acetate and heat to 55°C to dissolve;

[0044] B. Add 1.5 g of tripropylamine dropwise while stirring; keep at 55°C and stir for 1 hour;

[0045] C. Cool down to 20℃ and keep warm for 2h to precipitate crystals;

[0046] D. Filter and dry at 40°C to obtain 43 g of refined product.

[0047] The purity of monomethyl dodecanedioate prepared by the method is 99.6%, and the yield of monomethyl dodecanedioate is 86%.

[0048] Example 3

[0049] A method for purifying a crude product of monomethyl dodecanedioate, comprising the following steps:

[0050] A. Add 50 g of crude monomethyl dodecanedioate to 50 ml of methyl propionate and heat to 50°C to dissolve;

[0051] B. Add 1 g of pyridine dropwise while stirring, and keep stirring at 50°C for 1 hour;

[0052] C. Cool down to 20℃ and keep warm for 2h to precipitate crystals;

[0053] D. Filter and dry at 40°C to obtain 42 g of refined product.

[0054] The purity of monomethyl dodecanedioate prepared by the method is 99.5%, and the yield of monomethyl dodecanedioate is 84%.

[0055] Example 4

[0056] The difference from Example 1 is that triethylamine is replaced by tributylamine, and the rest is the same as Example 1.

[0057] The purity of monomethyl dodecanedioate prepared by the method is 99.7%, and the yield of monomethyl dodecanedioate is 86%.

[0058] Example 5

[0059] The difference from Example 1 is that triethylamine is replaced by N,N-diethylmethylamine, and the rest is the same as Example 1.

[0060] The purity of monomethyl dodecanedioate prepared by the method is 99.6%, and the yield of monomethyl dodecanedioate is 85%.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that triethylamine is replaced by diethylamine, and the rest is the same as Example 1.

[0063] The purity of monomethyl dodecanedioate prepared by the method is 95.2%, and the yield of monomethyl dodecanedioate is 76%.

[0064] Comparative Example 2

[0065] The difference from Example 1 is that triethylamine is replaced by n-propylamine, and the rest is the same as Example 1.

[0066] The purity of monomethyl dodecanedioate prepared by the method is 95.1%, and the yield of monomethyl dodecanedioate is 77%.

[0067] Comparative Example 3

[0068] The difference from Example 1 is that triethylamine is replaced by piperidine, and the rest is the same as Example 1.

[0069] The purity of monomethyl dodecanedioate prepared by the method is 94.8%, and the yield of monomethyl dodecanedioate is 75%.

[0070] Comparative Example 4

[0071] The difference from Example 1 is that triethylamine is omitted, and the rest is the same as Example 1.

[0072] The purity of monomethyl dodecanedioate prepared by the method is 94.5%, and the yield of monomethyl dodecanedioate is 74%.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for purifying long-chain dibasic acid monoesters, characterized in that: The steps include: The crude product of long-chain dibasic acid monoester is heated and dissolved in an ester solvent, and an organic amine is added under stirring; After stirring and reacting for a set time, the solution is cooled to 15-25°C to allow the long-chain dibasic acid monoester to crystallize; After solid-liquid separation and drying, the long-chain dibasic acid monoester product is obtained.

2. The method for purifying long-chain dibasic acid monoesters according to claim 1, characterized in that: The carbon chain length of the long-chain dibasic acid monoester is 10 to 20 carbon atoms.

3. The method for purifying long-chain dibasic acid monoesters according to claim 1, characterized in that: The ester solvent is selected from at least one of methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate or ethyl butyrate.

4. The method for purifying long-chain dibasic acid monoesters according to claim 3, characterized in that: The mass of the crude long-chain dibasic acid monoester product dissolved in each liter of the ester solvent is 800-1200 g.

5. The method for purifying long-chain dibasic acid monoesters according to claim 1, characterized in that: The organic amine is at least one of trimethylamine, triethylamine, tripropylamine, tributylamine, N,N-diethylmethylamine, N-methylmorpholine, N-methylpiperidine or pyridine.

6. The method for purifying long-chain dibasic acid monoesters according to claim 5, characterized in that: The organic amine is triethylamine.

7. The method for purifying long-chain dibasic acid monoesters according to claim 1, characterized in that: The mass ratio of the crude long-chain dibasic acid monoester product to the organic amine is 100:2-4.

8. The method for purifying long-chain dibasic acid monoesters according to claim 1, characterized in that: The stirring reaction time is 1-3h.

9. The method for purifying long-chain dibasic acid monoester according to claim 8, characterized in that: The temperature of the stirring reaction is 40-60°C.

10. The method for purifying long-chain dibasic acid monoester according to claim 1, characterized in that: The drying temperature is 30-40°C.

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