Water-phase melt crystallization purification method of long-chain dicarboxylic acid

Abstract

The invention discloses a water-phase melt crystallization purification method of long-chain dicarboxylic acid, and relates to the technical field of refining and purification of long-chain dicarboxylic acid. The method comprises the following steps: mixing a long-chain dicarboxylic acid crude product with water, and heating to a preheating temperature to completely melt a solid material; reducing the preheating temperature to a first preset temperature to convert the melt into crystals, and keeping the temperature to grow the crystals; cooling from the first preset temperature to a second preset temperature, and preserving heat and growing crystal; cooling from the second preset temperature to the final temperature, and preserving heat and growing crystals; and finally, filtering and drying to obtain a long-chain dicarboxylic acid product. According to the method, key parameters such as the mixing ratio, the melting temperature and the cooling rate are accurately controlled, so that the impurity content is effectively reduced, and the purity of the long-chain dicarboxylic acid product can stably reach 99.3 wt% or above. In addition, operation steps are simplified, production efficiency is improved, and unnecessary energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refining and purifying long-chain dibasic acid, and particularly relates to a water-phase melt crystallization purification method of long-chain dibasic acid. BACKGROUND

[0002] Long-chain dibasic acid is an important fine chemical raw material, which has wide industrial applications, including synthesis of high-grade perfumes, high-performance nylon engineering plastics, high-grade hot melt adhesives, cold-resistant plasticizers, high-grade lubricating oils, high-grade paints and coatings, etc. Due to its key role in multiple fields, the production method and purification technology of long-chain dibasic acid have always been a research hotspot.

[0003] At present, there are mainly three methods for producing long-chain dibasic acid: catalytic oil method, chemical synthesis method and biological fermentation method. The catalytic oil method prepares long-chain dibasic acid by cracking plant oil and other raw materials at high temperature, but this method has problems such as low product purity, great influence of raw materials, etc., and it is difficult to realize large-scale production. The chemical synthesis method can synthesize various long-chain dibasic acids, but its process is complex, the reaction conditions are harsh, there are many by-products, and the longest chain dibasic acid that can be synthesized is only 12 carbon atoms. In comparison, the biological fermentation method has attracted attention due to its advantages such as wide source of raw materials and simple production process, but it has problems such as complex process, high energy consumption, poor product quality, etc. in the process of extracting and refining long-chain dibasic acid.

[0004] In the biological fermentation method, microbial fermentation is the main way to produce long-chain dibasic acid. This method collects and identifies microbial strains that can ferment alkanes, selects high-quality strains, and uses mutagenic strain technology to create a new process for producing long-chain dibasic acid by fermenting alkanes. However, the biological fermentation method faces many challenges in the purification process. The current purification method still has problems such as complex purification process, high energy consumption, low product purity, and serious impurity color. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a water-phase melt crystallization purification method of long-chain dibasic acid, which at least achieves the purpose of further improving the purity of long-chain dibasic acid products.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a water-phase melt crystallization purification method of long-chain dibasic acid, comprising: Step one, mix long-chain dibasic acid crude product with water, and heat to a preheating temperature to melt all solid materials; Step two, primary cooling and crystal growing, cool from the preheating temperature to a first preset temperature to convert the molten material into crystals, and incubate at the first preset temperature for crystal growing; Step three, secondary cooling and crystal growing, cool from the first preset temperature to a second preset temperature, and incubate at the second preset temperature for crystal growing; Step four, three times of cooling and crystal growing, cooling from the second preset temperature to the end temperature, and keeping the end temperature for crystal growing; Step five, filtering and drying to obtain long-chain dibasic acid product.

[0007] Further, the long-chain dibasic acid crude product is obtained by directly acidifying and precipitating the fermentation liquor of the long-chain dibasic acid prepared by the biological method, or is obtained from the waste liquid containing long-chain dibasic acid discharged in the fermentation and refining process of the long-chain dibasic acid.

[0008] Further, the long-chain dibasic acid is one or a mixture of more than one of azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid and 9-ene-octadecanedioic acid.

[0009] Further, in step one, the long-chain dibasic acid crude product and water are mixed at a mass ratio of 1:5-10.

[0010] Further, in step one, the preheating temperature is 120℃, and the temperature is kept at the preheating temperature for 1-2h.

[0011] Further, in step two, the first preset temperature is 110℃.

[0012] Further, in step two, the first preset temperature is 110℃.

[0013] Further, in step three, the second preset temperature is 55℃, and the cooling rate is 12-25℃ / h.

[0014] Further, in step four, the end temperature is 40±3℃, and the cooling rate is 1℃ / min.

[0015] Further, in steps two, three and four, the time for keeping the temperature for crystal growing is 0.1-2.5h.

[0016] The long-chain dibasic acid water-phase melt crystallization purification system and method provided by the application can effectively reduce the impurity content by accurately controlling the mixing ratio, melting temperature, cooling rate and other key parameters, so that the purity of the long-chain dibasic acid product can be stably increased to more than 99.3wt%. In addition, the operation steps are simplified, the production efficiency is improved, and unnecessary energy consumption is reduced.

[0017] The application can be applied to the industrial fields of synthetic high-grade fragrances, high-performance engineering plastics, high-temperature dielectrics and the like. DETAILED DESCRIPTION

[0018] The long-chain dibasic acid water-phase melt crystallization purification method according to an embodiment of the present application comprises the following steps one to five.

[0019] Step one, mixing and preheating.

[0020] The long-chain dibasic acid crude product is mixed with water, and heated to a preheating temperature to melt the solid materials.

[0021] In this step, the long-chain dibasic acid crude product is obtained by directly acidifying and precipitating a fermentation liquor of a long-chain dibasic acid prepared by a biological method, or is obtained from a waste liquid containing long-chain dibasic acid discharged in a long-chain dibasic acid fermentation and refining process. The long-chain dibasic acid is one or a mixture of more than one of azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, and 9-ene-octadecanedioic acid.

[0022] This step is implemented in a mixing unit. The mixing unit comprises a stirring device and can uniformly mix the long-chain dibasic acid crude product and water in a predetermined ratio.

[0023] The long-chain dibasic acid crude product is uniformly dispersed in water by fully mixing the long-chain dibasic acid crude product and water, which creates good conditions for subsequent heating and melting and is conducive to improving the purity and yield of the product. The long-chain dibasic acid crude product and water are mixed in a mass ratio of 1:5-10.

[0024] The melting unit is connected to the mixing unit. In the melting unit, the mixed materials are heated to a temperature at which the solid is completely melted and are kept at the temperature. The melting unit comprises a heating device and a temperature control system for accurately controlling the preheating temperature and the holding time.

[0025] The melting point of the long-chain dibasic acid is mainly between 110-130°C, and the preheating temperature is set to be 10-30°C lower than the melting point of the long-chain dibasic acid. Preferably, the preheating temperature is set to be 120°C, and the holding time is 1-2h at the preheating temperature. In the melting process, part of the insoluble impurities are precipitated or separated, which helps to preliminarily remove the impurities and improve the purity of the product.

[0026] The temperature is lowered and the crystal is grown according to the procedures of steps two to four, which are implemented in a temperature lowering unit. The temperature lowering unit is connected to the melting unit, and is used to lower the temperature to the terminal temperature according to the predetermined procedure. The temperature lowering unit comprises a cooling device and a temperature control system for accurately controlling the temperature lowering rate and the temperature.

[0027] Step two, first temperature lowering and crystal growing.

[0028] The temperature is lowered from the preheating temperature to a first preset temperature to convert the melt into crystals, and the crystals are grown at the first preset temperature.

[0029] In this step, the first preset temperature is preferably set to 110°C, and the first temperature reduction is performed in two stages.

[0030] First, before the precipitation point, i.e. in the temperature reduction stage of 120°C-115°C, the temperature reduction rate is 10-25°C / h, so that the solution gradually approaches the precipitation temperature of long-chain dibasic acid, creating conditions for the formation of crystals, while avoiding too fast temperature reduction leading to too small crystals or impurities being wrapped, allowing the formed crystal nucleus to have sufficient time to grow, forming larger crystals, which is beneficial to subsequent filtration and washing, and improves the purity and yield of the product. Then, in the temperature reduction stage of 115°C-110°C, the temperature is reduced to the melting substance to crystals at a rate of 6-15°C / h. The slow temperature reduction rate helps the uniform growth and full ripening of the crystals, making the crystal structure more complete and reducing the mixing of impurities.

[0031] When the temperature is reduced to 110°C, the crystal growth step is performed, and the temperature is kept for 0.1-2.5h to allow the crystals to fully convert and fully ripen; allowing the crystals to further stabilize and purify at a lower temperature, allowing more impurities in the crystal lattice to precipitate, improving the purity of the product.

[0032] Step three, secondary temperature reduction and crystal growth.

[0033] From the first preset temperature to the second preset temperature, the temperature is kept at the second preset temperature for crystal growth.

[0034] The second preset temperature is preferably set to 55°C, and the temperature is reduced at a rate of 12-25°C / h. When the temperature is reduced to 55°C, the crystal growth step is repeated again, and the temperature is kept for 0.1-2.5h to allow the crystals to fully convert and fully ripen; allowing the crystals to further stabilize and purify at a lower temperature, allowing more impurities in the crystal lattice to precipitate, improving the purity of the product.

[0035] Step four, third temperature reduction and crystal growth.

[0036] From the second preset temperature to the final temperature, the temperature is kept at the final temperature for crystal growth.

[0037] The final temperature is 40±3°C, and the temperature reduction rate is controlled at 1°C / min. The slow temperature reduction process helps the final stabilization and purification of the crystals, while avoiding the breakage of the crystals or the re-mixing of impurities due to a large temperature difference.

[0038] After temperature reduction, the crystal growth step is repeated for the third time, and the temperature is kept for 0.1-2.5h to allow the crystals to fully convert and fully ripen; allowing the crystals to further stabilize and purify at a lower temperature, allowing more impurities in the crystal lattice to precipitate, improving the purity of the product.

[0039] Step five, filtration and drying.

[0040] In this step, the filter cake is washed with pure water, and the high-purity long-chain dibasic acid product is obtained after drying. The crystallized long-chain dibasic acid solid is separated from the mother liquor by filtration to obtain relatively pure crystals. The filter cake is washed with pure water to further remove soluble impurities attached to the surface of the crystals, thereby improving the purity of the product.

[0041] This step is realized in a filtering unit and a washing and drying unit. The filtering unit is connected to the cooling unit and is used to filter and separate the cooled material. The washing and drying unit is connected to the filtering unit and is used to wash the filter cake with pure water and dry it to obtain a high-purity long-chain dibasic acid product.

[0042] The technical solutions claimed in the present application are further described below through some embodiments. However, the embodiments are used to explain the embodiments of the present application and do not exceed the scope of the subject matter of the present application, and the protection scope of the present application is not limited by the described embodiments. Unless otherwise specified, the materials and reagents used in the present application can be obtained from commercial products in the art. Example 1

[0043] Take 100 g (dry weight) of dodecanedioic acid crude product obtained by biological fermentation, add 900 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit and heated to 120°C for 1 h. Then, the material enters the cooling unit and is cooled according to the following program: in the 120°C-115°C cooling stage, the cooling rate is 15°C / h; in the 115°C-110°C cooling stage, the cooling rate is 8°C / h; the nucleation temperature is controlled at 110°C for 2 h. In the 110°C-55°C cooling stage, the cooling rate is 18°C / h; the nucleation temperature is controlled at 55°C for 2 h. When the temperature decreases from 55°C to 37°C, the cooling rate is controlled at 1°C / min; the nucleation temperature is controlled at 37°C for 2 h. After cooling to 37°C, the material enters the filtering unit for filtering and separation, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.8 wt%, a platinum-cobalt color number of 3, a total nitrogen index of 23, a 440 nm transmittance of 98.6%, and a 550 nm transmittance of 99.8%. Example 2

[0044] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 850 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit and heated to 120°C for 1 h. Subsequently, the material enters the cooling unit and is cooled according to the following program: in the 120°C-115°C cooling stage, the cooling rate is 12°C / h; in the 115°C-110°C cooling stage, the cooling rate is 7°C / h; and the crystal growth temperature is controlled at 110°C for 1.2 h. In the 110°C-55°C cooling stage, the cooling rate is 20°C / h; and the crystal growth temperature is controlled at 55°C for 1.2 h. When the temperature decreases from 55°C to 43°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 43°C for 1.2 h. After cooling to 43°C, the material is filtered in the filtration unit, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.8 wt%, a platinum-cobalt color number of 5, a total nitrogen index of 25, a 440 nm transmittance of 98.9%, and a 550 nm transmittance of 99.6%. Example 3

[0045] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 850 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit and heated to 120°C for 1 h. Subsequently, the material enters the cooling unit and is cooled according to the following program: in the 120°C-115°C cooling stage, the cooling rate is 12°C / h; in the 115°C-110°C cooling stage, the cooling rate is 7°C / h; and the crystal growth temperature is controlled at 110°C for 1.2 h. In the 110°C-55°C cooling stage, the cooling rate is 20°C / h; and the crystal growth temperature is controlled at 55°C for 1.2 h. When the temperature decreases from 55°C to 43°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 43°C for 1.2 h. After cooling to 43°C, the material is filtered in the filtration unit, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.8 wt%, a platinum-cobalt color number of 5, a total nitrogen index of 25, a 440 nm transmittance of 98.9%, and a 550 nm transmittance of 99.6%. Example 4

[0046] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 1000 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit, heated to 120°C, and kept for 2 h. Then, the material enters the cooling unit, and the cooling program is as follows: in the 120°C-115°C cooling stage, the cooling rate is 13°C / h; in the 115°C-110°C cooling stage, the cooling rate is 9°C / h; and the crystal growth temperature is controlled at 110°C for 1 h. In the 110°C-55°C cooling stage, the cooling rate is 12°C / h; and the crystal growth temperature is controlled at 55°C for 1 h. When the temperature decreases from 55°C to 43°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 43°C for 1 h. After cooling to 43°C, the material is sent to the filtration unit for filtration separation, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.7 wt%, a platinum-cobalt color number of 4, a total nitrogen index of 22, a 440 nm light transmittance of 98.8%, and a 550 nm light transmittance of 99.3%. Example 5

[0047] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 800 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit, heated to 120°C, and kept for 1 h. Then, the material enters the cooling unit, and the cooling program is as follows: in the 120°C-115°C cooling stage, the cooling rate is 25°C / h; in the 115°C-110°C cooling stage, the cooling rate is 10°C / h; and the crystal growth temperature is controlled at 110°C for 1.8 h. In the 110°C-55°C cooling stage, the cooling rate is 16°C / h; and the crystal growth temperature is controlled at 55°C for 1.8 h. When the temperature decreases from 55°C to 42°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 42°C for 1.8 h. After cooling to 42°C, the material is sent to the filtration unit for filtration separation, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.5 wt%, a platinum-cobalt color number of 5, a total nitrogen index of 25, a 440 nm light transmittance of 98.5%, and a 550 nm light transmittance of 99.1%. Example 6

[0048] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 650 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit and heated to 120°C for 1 h. Subsequently, the material enters the cooling unit and is cooled according to the following program: in the 120°C-115°C cooling stage, the cooling rate is 10°C / h; in the 115°C-110°C cooling stage, the cooling rate is 15°C / h; and the crystal growth temperature is controlled at 110°C for 0.1 h. In the 110°C-55°C cooling stage, the cooling rate is 13°C / h; and the crystal growth temperature is controlled at 55°C for 0.1 h. When the temperature decreases from 55°C to 38°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 38°C for 0.1 h. After cooling to 38°C, the material is filtered in the filtration unit, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.3 wt%, a platinum-cobalt color number of 6, a total nitrogen index of 28, a 440 nm light transmittance of 98.3%, and a 550 nm light transmittance of 99.0%. Example 7

[0049] Take the dodecanedioic acid crude product 100 g (dry weight) obtained by biological fermentation, add 650 g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit and heated to 120°C for 1 h. Subsequently, the material enters the cooling unit and is cooled according to the following program: in the 120°C-115°C cooling stage, the cooling rate is 10°C / h; in the 115°C-110°C cooling stage, the cooling rate is 15°C / h; and the crystal growth temperature is controlled at 110°C for 0.1 h. In the 110°C-55°C cooling stage, the cooling rate is 13°C / h; and the crystal growth temperature is controlled at 55°C for 0.1 h. When the temperature decreases from 55°C to 38°C, the cooling rate is controlled at 1°C / min; and the crystal growth temperature is controlled at 38°C for 0.1 h. After cooling to 38°C, the material is filtered in the filtration unit, the filter cake is washed with 200 g of deionized water, and finally dried at 105°C for 4 h in the washing and drying unit to obtain a high-purity dodecanedioic acid product with a purity of 99.3 wt%, a platinum-cobalt color number of 6, a total nitrogen index of 28, a 440 nm light transmittance of 98.3%, and a 550 nm light transmittance of 99.0%. Example 8

[0050] Take dodecanedioic acid crude product 100g (dry weight) obtained by biological fermentation, add 900g of deionized water, and mix uniformly using the stirring device in the mixing unit. The mixed material is sent to the melting unit, heated to 120℃, and kept for 1h. Subsequently, the material enters the cooling unit, and is cooled according to the following program: in the 120℃-115℃ cooling stage, the cooling rate is 15℃ / h; in the 115℃-110℃ cooling stage, the cooling rate is 6℃ / h; the crystal growth temperature is controlled at 110℃, and the crystal growth time is 2.2h. In the 110℃-55℃ cooling stage, the cooling rate is 15℃ / h; the crystal growth temperature is controlled at 55℃, and the crystal growth time is 2.2h. When the temperature decreases from 55℃ to 40℃, the cooling rate is controlled at 1℃ / min; the crystal growth temperature is controlled at 40℃, and the crystal growth time is 2.2h. After cooling to 40℃, the material enters the filtration unit for filtration separation, the filter cake is washed with 200g of deionized water, and finally dried at 110℃ in the washing and drying unit for 8h, to obtain high-purity dodecanedioic acid product, with a purity of 99.8wt%, platinum-cobalt color number of 3, total nitrogen index of 23, 440nm light transmittance of 98.9%, and 550nm light transmittance of 99.7%.

[0051] The scope of protection of the present application is not limited to the above specific embodiments, and the present application can have various modifications and alterations for those skilled in the art, and any modifications, improvements and equivalent replacements made within the concept and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for purification of long-chain dibasic acids by aqueous melt crystallization, characterized in that, The application relates to a long-chain dibasic acid production method. Step one, long-chain dibasic acid crude product is mixed with water, and heated to a preheating temperature to melt the solid materials; Step two, primary temperature reduction and crystal growth, the molten material is converted into crystals by reducing the temperature from the preheating temperature to a first preset temperature, and the crystal growth is maintained at the first preset temperature; Step three, secondary temperature reduction and crystal growth, the crystal growth is maintained at a second preset temperature by reducing the temperature from the first preset temperature to the second preset temperature; Step four, tertiary temperature reduction and crystal growth, the crystal growth is maintained at an endpoint temperature by reducing the temperature from the second preset temperature to the endpoint temperature; Step five, filtration and drying to obtain long-chain dibasic acid product.

2. The process for purification of long chain diacids by aqueous melt crystallization according to claim 1, characterized in that: The long-chain dibasic acid crude product is obtained by directly acidizing and precipitating a fermentation liquor of long-chain dibasic acid prepared by a biological method, or is obtained from waste liquid containing long-chain dibasic acid discharged in a long-chain dibasic acid fermentation and refining process.

3. The process for purification of long chain diacids by aqueous melt crystallization according to claim 2, characterized in that: The long-chain dibasic acid is one or a mixture of more than one of azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid and 9-ene-octadecanedioic acid.

4. The process for purification of long chain diacids by aqueous melt crystallization according to claim 1, 2 or 3, characterized in that: In step one, the long-chain dibasic acid crude product and water are mixed according to a mass ratio of 1:5-10.

5. The process for purification of long chain diacids by aqueous melt crystallization according to claim 4, characterized in that: In step one, the preheating temperature is 120 DEG C, and the temperature is maintained at the preheating temperature for 1-2 h.

6. The process for purification of long chain diacids by aqueous melt crystallization according to claim 1 or 5, characterized in that: In step two, the first preset temperature is 110 DEG C.

7. The process for purification of long chain diacids by aqueous melt crystallization according to claim 6, characterized in that: In step two, the primary temperature reduction is performed in two stages, the temperature is first reduced from the preheating temperature to 115 DEG C at a reduction rate of 10-25 DEG C / h, and then is reduced from 115 DEG C to 110 DEG C at a reduction rate of 6-15 DEG C / h.

8. The process for purification of long chain diacids by aqueous melt crystallization according to claim 7, characterized in that: In step three, the second preset temperature is 55 DEG C, and the temperature is reduced at a rate of 12-25 DEG C / h.

9. The process for purification of long chain diacids by aqueous melt crystallization according to claim 8, characterized in that: In step four, the endpoint temperature is 40+ / -3 DEG C, and the temperature is reduced at a rate of 1 DEG C / min.

10. The process for purification of long chain diacids by aqueous melt crystallization according to claim 1 or 9, characterized in that: In steps two, three and four, the time for maintaining the crystal growth is 0.1-2.5 h.