A method for preparing an organic acid seed crystal
By adding a cooling solvent to a long-chain dicarboxylic acid solution and combining it with a heating and cooling process to prepare seed crystals, the problems of low heat transfer efficiency and uneven seed crystals during crystallization were solved, achieving high yield and uniform crystallization of long-chain dicarboxylic acids, and improving production stability and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-09
Smart Images
Figure BDA0005174786990000061 
Figure BDA0005174786990000071
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing organic acid seed crystals, and more particularly to a method for preparing long-chain dicarboxylic acids seed crystals. Background Technology
[0002] Long-chain dicarboxylic acids are metabolic products produced by microorganisms through fermentation using long-chain alkanes or fatty acids as raw materials. Their general molecular formula is C1. n H 2n-2 O4, where n is 8-18, contains two terminal carboxyl groups, and is a monomer for synthesizing nylon engineering plastics and hot melt adhesives.
[0003] Recrystallization is a common technique for refining high-quality chemicals, producing products with high purity, good quality, and the ability to meet polymerization-grade requirements. Industry professionals understand the characteristic of long-chain dicarboxylic acids (DCAs) crystallizing in organic solvents upon cooling; that is, DCAs spontaneously generate crystal nuclei as the temperature decreases. However, during cooling crystallization, without crystal nuclei as a substrate, growth preferentially occurs at the cooling interface, eventually forming scale on the inner wall of the crystallizer. This results in low cooling heat transfer efficiency, and the crystals obtained without seed crystals are of inconsistent size. Large scale fragments can detach under stirring, causing pipe blockage and affecting subsequent solid-liquid separation and production stability. Therefore, inducing crystallization with suitable seed crystals can effectively control the crystallization process and obtain uniform crystal particles.
[0004] Patent CN202210063486.8 proposes a method for preparing seed crystals, which involves mechanically ball milling dodecanoic acid crystals for 20–60 minutes and then passing them through a 100–300 mesh sieve to obtain seed crystals with a particle size of 48–150 μm. This method has several problems: First, even with ball milling equipment made of stainless steel, continuous contact and abrasion with the crystals inevitably introduces mechanical impurities that mix with the seed crystals, affecting the product quality of long-chain dicarboxylic acids, and resulting in low powder recovery. Second, the sieving process for seed crystals produces significant dust, posing a safety hazard, and the sieving yield is low. Third, because the seed crystals are micron-sized powders, when added to a crystallization tank containing a high-temperature solvent under slight positive pressure, the powdered seed crystals are easily blown out by the positive pressure solvent vapor, and the powdered seed crystals are easily wetted and agglomerated by the solvent, clogging the feed port, introducing uncertainty and operational hazards to crystallization control. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing organic acid seed crystals, which solves the problems existing in current seed crystal preparation technologies, is easier to implement, and produces more uniform long-chain dicarboxylic acid crystals.
[0006] The inventors unexpectedly discovered during their research that adding a cooling solvent to a mixed solution of long-chain dicarboxylic acids and an organic solvent can rapidly and easily obtain microcrystals of 40–100 μm. Adding these microcrystals as seed crystals to the long-chain dicarboxylic acid solvent solution yields uniformly sized crystals. Further research revealed that appropriately heating the micron-sized crystallization solution can eliminate even smaller microcrystals, resulting in a narrower distribution of microcrystal seed sizes. Furthermore, it was found that synergistic heating and cooling can further obtain seed crystals of 100–150 μm. With the addition of stirring, and based on the correlation between seed size and sedimentation rate, seeds within a specific size range can be enriched online in a seed preparation tank. Moreover, the method of this invention achieves a high seed yield.
[0007] Based on the above findings, the present invention provides a method for preparing organic acid seed crystals, comprising the following steps:
[0008] I. Mix the organic acid with the organic solvent and heat to dissolve it;
[0009] II. Add cooling solvent to the solution to lower the system temperature by 1-60℃;
[0010] III. Then, control the system to heat up by 1-40℃ for 10-600 min; then control the system to cool down at a rate of 0.05-0.5℃ / min to 0℃-60℃ to obtain a seed solution.
[0011] Furthermore, in the above method, the organic acid mentioned in step I includes, but is not limited to, organic acids such as long-chain dicarboxylic acids, preferably long-chain dicarboxylic acids of C10-C18.
[0012] Furthermore, in the above method, the organic solvent mentioned in step I is at least one of hydrocarbons, alcohols, acids, esters and ethers, preferably at least one of ethers and organic acids, specifically, preferably at least one of butyl ether, pentyl ether and acetic acid.
[0013] Furthermore, in the above method, the weight ratio of organic acid to organic solvent in step I is 1:1-1:10, preferably 1:2-1:8, and more preferably 1:3-1:6.
[0014] Furthermore, in the above method, adding a cooling solvent to the solution in step II preferably lowers the system temperature by 25-60°C, more preferably by 35-60°C.
[0015] Furthermore, in the above method, the cooling solvent mentioned in step II is the same solvent as the organic solvent used in step I, or water.
[0016] Furthermore, in the above method, when adding the cooling solvent in step II, the stirring speed is 50-500 rpm, preferably 100-350 rpm, and more preferably 150-300 rpm.
[0017] Furthermore, in the above method, the temperature of the cooling solvent in step II is 0-60°C, preferably 0-40°C, and more preferably 5-20°C.
[0018] Furthermore, in the above method, the weight of the added cooling solvent is 5%-2000% of the organic acid, preferably 100%-1500%, more preferably 200%-1000%.
[0019] Furthermore, in the above method, the temperature rise in step III is preferably 5°C-30°C, more preferably 5-25°C; the temperature holding time is preferably 30-240 min, more preferably 60-120 min.
[0020] Furthermore, in the above method, the cooling temperature endpoint in step III is preferably 7℃-50℃, more preferably 10-25℃, and most preferably 15-20℃.
[0021] Furthermore, in the above method, after the cooling is completed, the stirring speed is adjusted to 5-500 rpm, preferably 20-350 rpm, and more preferably 50-100 rpm.
[0022] Furthermore, in the above method, 100% of the seed solution is extracted as seed crystals, or 98% of the solution can be selectively extracted, or even more selectively, 95% of the solution can be extracted. The remaining solution not used as seed crystals is mixed with the next batch of material for seed crystal preparation.
[0023] The technical solution of the present invention has the following advantages:
[0024] In the above-described seed crystal preparation method, a cooling solvent is added to a mixed solution of organic acid, especially long-chain dicarboxylic acid, to rapidly cool the solution and stimulate the formation of micron-sized crystals of the organic acid. This eliminates the need for complex seed crystal preparation processes such as ball milling, making it easier to obtain micron-sized seed crystals. Furthermore, by employing heating and cooling procedures, coupled with the synergistic effect of stirring, ideal seed crystals with a narrow particle size distribution can be obtained. Compared to adding powdered seed crystals to a crystallization tank, the seed crystals, carried by the solvent, are more easily transported to the crystallization tank, facilitating back-mixing and dispersion of the seed crystals with the solution to be crystallized and reducing the likelihood of agglomeration. The seed crystal preparation method of this invention offers simpler process control and has practical application value. Detailed Implementation
[0025] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.
[0026] Example 1
[0027] I. Dissolve 1 kg of decacarbon dicarboxylic acid and 3 kg of butyl ether by heating, and the solution temperature is 115℃;
[0028] II. Add 6 kg of 7℃ butyl ether to the solution, and lower the temperature of the mixed solution to 58℃. Stir at 200 rpm during mixing.
[0029] III. Heat the solution to 80°C for 120 minutes.
[0030] IV. The solution from step III was cooled to 15°C within 240 min under stirring at 100 rpm to obtain a decacarbon dicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0031] Example 2
[0032] I. Dissolve 1 kg of decacarbon dicarboxylic acid and 2.5 kg of acetic acid by heating, and the solution temperature is 80℃;
[0033] II. Add 5 kg of acetic acid at 10℃ to the solution, and lower the temperature of the mixed solution to 43℃. Stir at 200 rpm during mixing.
[0034] III. Heat the solution to 50°C for 120 minutes.
[0035] IV. The solution from step III was cooled to 18°C within 240 min under stirring at 80 rpm to obtain a decacarbon dicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0036] Example 3
[0037] I. Dissolve 1 kg of dodecanoic acid and 3 kg of acetic acid by heating, and the solution temperature is 85℃;
[0038] II. Add 6 kg of acetic acid at 15℃ to the solution, and lower the temperature of the mixed solution to 45℃. Stir at 200 rpm during mixing.
[0039] III. Heat the solution to 55°C for 60 minutes.
[0040] IV. The solution from step III was cooled to 18°C within 240 min under stirring at 80 rpm to obtain a dodecanoic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0041] Example 4
[0042] I. Dissolve 1 kg of dodecanoic acid dicarboxylic acid and 4 kg of butyl ether by heating, and the solution temperature is 105℃;
[0043] II. Add 6 kg of 20℃ butyl ether to the solution, and the temperature of the mixed solution drops to 61℃. Stir at 200 rpm during mixing.
[0044] III. Heat the solution to 75°C for 120 minutes.
[0045] IV. The solution from step III was cooled to 15°C within 180 min under stirring at 100 rpm to obtain a dodecanoic acid dicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0046] Example 5
[0047] I. Dissolve 1 kg of tetradecanoic acid and 4 kg of acetic acid by heating until the solution temperature is 85°C;
[0048] II. Add 6 kg of acetic acid at 7℃ to the solution, and lower the temperature of the mixed solution to 44℃. Stir at 200 rpm during mixing.
[0049] III. Heat the solution to 50°C for 60 minutes.
[0050] IV. The solution from step III was cooled to 18°C within 180 min under stirring at 80 rpm to obtain a tetradecanoic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0051] Example 6
[0052] I. Dissolve 1 kg of tetradecanedicarboxylic acid and 5 kg of butyl ether by heating, and the solution temperature is 103℃;
[0053] II. Add 8 kg of 10℃ butyl ether to the solution, and lower the temperature of the mixed solution to 58℃. Stir at 200 rpm during mixing.
[0054] III. Heat the solution to 85°C for 100 minutes.
[0055] IV. The solution from step III was cooled to 15°C within 180 min under stirring at 100 rpm to obtain a hexadecanedicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0056] Example 7
[0057] I. Dissolve 1 kg of hexadecanedicarboxylic acid and 4 kg of acetic acid by heating, and the solution temperature is 80℃;
[0058] II. Add 5 kg of acetic acid at 7℃ to the solution, and lower the temperature of the mixed solution to 44℃. Stir at 200 rpm during mixing.
[0059] III. Heat the solution to 50°C for 60 minutes.
[0060] IV. The solution from step III was cooled to 18°C within 180 min under stirring at 80 rpm to obtain a hexadecanedicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0061] Example 8
[0062] I. Dissolve 1 kg of hexadecanedicarboxylic acid and 4 kg of butyl ether by heating, and the solution temperature is 105℃;
[0063] II. Add 6 kg of 15℃ butyl ether to the solution, and lower the temperature of the mixed solution to 58℃. Stir at 200 rpm during mixing.
[0064] III. Heat the solution to 80°C for 120 minutes.
[0065] IV. The solution from step III was cooled to 15°C within 180 min under stirring at 100 rpm to obtain a hexadecanedicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0066] Comparative Example 1
[0067] 4g of dodecanoic acid and grinding balls were directly mechanically ball-milled using a ball mill. The ball-to-material ratio was 3:1, the ball mill speed was 250 r / min, and the ball milling time was 60 min. The dodecanoic acid seed crystals were taken out after ball milling, and 3.5g of powder was recovered, with a powder recovery rate of 87.5%. Seed crystals with a particle size of 120-150 μm were obtained by passing them through a 100-120 mesh standard sieve.
[0068] Comparative Example 2
[0069] I. Dissolve 1 kg of dodecanoic acid and 3 kg of acetic acid by heating, and the solution temperature is 85℃;
[0070] II. Add 6 kg of acetic acid at 15°C to the solution. The temperature of the mixed solution is reduced to 45°C. Under the condition of stirring at 200 rpm, the temperature is reduced to 18°C within 240 min to obtain a dodecanoic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0071] Comparative Example 3
[0072] I. Dissolve 1 kg of dodecanoic acid and 3 kg of acetic acid by heating, and the solution temperature is 85℃;
[0073] II. Within 240 minutes, under the condition of stirring at 200 rpm, the temperature was lowered to 18℃ to obtain a dodecanoic acid dicarboxylic acid seed solution. The particle size and other data of the seed crystals are shown in Table 1.
[0074] Table 1.
[0075]
[0076]
[0077] The seed crystal size was determined using a laser particle size analyzer.
Claims
1. A method for preparing organic acid seed crystals, comprising the following steps: I. Mix the organic acid with the organic solvent and heat to dissolve it; II. Add cooling solvent to the solution to lower the system temperature by 1-60℃; III. Then, control the system to heat up by 1-40℃ for 10-600 min; then control the system to cool down at a rate of 0.05-0.5℃ / min to 0℃-60℃ to obtain a seed solution.
2. The preparation method according to claim 1, characterized in that, The organic acid mentioned in step I is a long-chain dicarboxylic acid of C10-C18.
3. The preparation method according to claim 1, characterized in that, The organic solvent mentioned in step I is at least one of hydrocarbons, alcohols, acids, esters and ethers; the weight ratio of organic acid to organic solvent is 1:1 to 1:
10.
4. The preparation method according to claim 3, characterized in that, The organic solvent mentioned in step I is selected from at least one of butyl ether, pentyl ether, and acetic acid.
5. The preparation method according to claim 1, characterized in that, In step II, adding a cooling solvent to the solution preferably lowers the system temperature by 25-60°C.
6. The preparation method according to claim 1, characterized in that, The cooling solvent mentioned in step II is the same solvent as the organic solvent used in step I, or water.
7. The preparation method according to claim 1, characterized in that, When adding the cooling solvent in step II, stir at 50-500 rpm.
8. The preparation method according to claim 1, characterized in that, The temperature of the cooling solvent mentioned in step II is 0-60℃.
9. The preparation method according to claim 8, characterized in that, The temperature of the cooling solvent mentioned in step II is 0-40℃.
10. The preparation method according to claim 1, characterized in that, The added cooling solvent is 5%-2000% of the weight of the organic acid.
11. The preparation method according to claim 1, characterized in that, The temperature increase in step III is 5℃-30℃, and the temperature holding time is 30-240min.
12. The preparation method according to claim 1, characterized in that, The final temperature for cooling in step III is 7℃-50℃.
13. The preparation method according to claim 1, characterized in that, The final temperature for cooling in step III is 10-25℃.
14. The preparation method according to claim 1, characterized in that, After cooling is complete, adjust the stirring speed to 5-500 rpm.