Method for extracting high-purity trimethylolethane from reaction liquid after synthesis of trimethylolethane

Abstract

The invention relates to a method for extracting high-purity trimethylolethane from reaction liquid after synthesis of trimethylolethane, belonging to the technical field of purification of trimethylolethane. The method comprises the following steps: S1, quality detection and seed crystal preparation; S2, crude product extraction; and S3, fine product extraction. According to the method, the reaction liquid in which the calcium formate content is lower than 5% and the mass ratio of the target product trimethylolethane in the organic matter is higher than 95.5% is extracted, so that the trimethylolethane finished product of which the calcium formate content is not higher than 0.1% and the purity is not lower than 99.3% can be prepared. According to the method disclosed by the invention, the impurities of the crystal substance are effectively removed by using a specific algal soil melting agent sintered product filter aid, a gradient crystallization strategy and seed crystal directional induction and combining low-temperature crystallization dynamic control, such as maintenance of fluidity crystallization conditions in a crystallization stage and setting and using of different cleaning agents and corresponding cleaning temperatures; the purity and the yield are further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of trimethylolethane purification, and particularly relates to a method for extracting high-purity trimethylolethane from a reaction liquid after trimethylolethane synthesis. Background Art

[0002] Trimethylolethane (TME), as an important organic chemical intermediate, is widely used in resin synthesis, pharmaceutical intermediates, flame retardant materials, and polymer material modification. With the rapid development of high-end application fields, the industry has increasingly stringent requirements for the purity of TME products, especially in the field of electronic-grade or special engineering plastics, which have put forward higher standards for indicators such as impurity content, crystal morphology, and color. However, the current industrial process for extracting TME still faces many technical bottlenecks, which seriously restrict the improvement of product quality and production efficiency. First, the existing technology has deficiencies in the purity of TME finished products, making it difficult to meet the strict requirements of certain high-end application fields for high-purity TME. Second, the yield of some processes is low, resulting in low raw material utilization. In addition, in some existing technologies, when specific solvents (such as anhydrous ethanol) are used for purification, the high cost and strict requirements on the dryness of the raw materials further increase the overall production cost. These problems jointly limit the efficient and economical production of TME. There is an urgent need for a more efficient, low-cost and easy-to-operate extraction and purification method to meet the needs of industrial production. Summary of the Invention

[0003] The present invention aims to solve the above problems in the existing technology and proposes a method for extracting high-purity trimethylolethane from the reaction liquid after trimethylolethane synthesis.

[0004] The purpose of the present invention can be achieved by the following technical scheme: a method for extracting high-purity trimethylolethane from the reaction liquid after trimethylolethane synthesis, the trimethylolethane synthesis process is as follows: calcium hydroxide is used as a catalyst, formaldehyde and propionaldehyde are used as raw materials for preparation, and finally formic acid is added dropwise to neutralize the obtained product; the specific steps are as follows: S1 preparation: S1.1 reaction liquid quality detection: the reaction liquid is subjected to a quality detection to ensure that the reaction liquid meets the extraction conditions, and the extraction conditions are as follows: in the reaction liquid, the calcium formate content is less than 5%; in the organic components of the reaction liquid, the mass proportion of the target product trimethylolethane is greater than 95.5%;

[0005] S1.2 Seed crystal preparation: Prepare TME seed crystals with a purity of not less than 99% using dried TME semi-fine product; the calcium formate content in the TME semi-fine product is less than 0.1%;

[0006] S2 Crude Product Extraction: S2.1 Set Crude Product Extraction Rules: The crude product extraction operations at all levels are as follows: Cleaning: Use deionized water at a temperature of 0-4 degrees Celsius as the cleaning agent; The crystallization process is as follows: Cool down → Keep warm → Add TME seeds → Keep warm → Heat up to maintain fluidity and crystallize. The amount of TME seeds added is 0.5-1% of the weight of the reaction solution added in the corresponding level of crude product extraction operation;

[0007] The first-level crude product extraction process includes dissolution, centrifugation, crystallization, filtration, washing, and drying. The crude product extraction process at any level from the second to the N-level crude product extraction process is as follows: first, a portion of the reaction solution is added to the crude TME mother liquor of the previous level, and then the crude product extraction process of the corresponding level is started. The extraction process includes dissolution, centrifugation, water evaporation, crystallization, filtration, washing, and drying.

[0008] S2.2 Crude Product Extraction: First-stage crude product extraction: Take part of the reaction solution for first-stage crude product extraction to obtain first-stage crude product and first-stage TME crude product mother liquor; S2.3 Step-by-step crude product extraction: Perform subsequent crude product extractions according to the crude product extraction rules to obtain second-stage TEM crude product and second-stage TME crude product mother liquor, third-stage TME crude product and third-stage TME crude mother liquor, and N-stage TME crude product and N-stage TME crude mother liquor respectively;

[0009] S2.3 Collection: After collecting all levels of TME crude products, obtain TEM crude raw materials;

[0010] S3 Fine Extraction: S3.1 Set the fine extraction rules: Purification liquid: ethanol-water or methanol, in the ethanol-water solution, the ethanol concentration is 95%; Adsorbent: 40μm diatomaceous earth melt sintered product filter aid, the operating environment temperature is 55-70 degrees; the addition amount is not less than 1% of the TEM crude material added to the corresponding level of fine extraction; Cleaning: When using ethanol-water as the purification liquid, the filter cake obtained after filtration is washed with -8 degree anhydrous ethanol when the filter cake color is yellow. When the filter cake color is normal, it is washed with -8 degree ethanol-water; when using methanol as the purification liquid, use -15 degree methanol for cleaning;

[0011] In all levels of TME fine extraction operations, the extraction process includes dissolution, cooling and filtration, adsorption, refiltration, evaporation, crystallization, filtration, washing and drying. The crystallization process is set as follows: cooling → insulation. During the insulation stage, the fluidity of the crystallization process is maintained by adding cold purification liquid;

[0012] The following provisions apply to any level of TME fine extraction operation from Level 2 to Level N: first, a portion of the crude TME raw material is added to the mother liquor after TME purification in the previous level, and then a corresponding amount of purified liquid is added before starting the fine extraction operation of the corresponding level;

[0013] S3.2 Extraction of fine products: First-level extraction of fine products: Take part of the crude TME raw material and add it to the purified liquid to perform the first-level TME fine product extraction operation to obtain the first-level TME fine product and the first-level purified mother liquor; S3.2 Step-by-step extraction of fine products: Perform subsequent extractions of fine products according to the set extraction rules to obtain the second-level TME fine product and the second-level purified mother liquor, the third-level TME fine product and the third-level purified mother liquor, and the N-level TME fine product and the N-level purified mother liquor respectively;

[0014] S3.3 Collection: Collect all levels of TME products to obtain high-purity trimethylolethane.

[0015] The specific steps of the quality inspection in step S1.1 are as follows: take several small amounts of reaction liquid in parallel, and perform the following operations on each reaction liquid: add the small amount of reaction liquid into anhydrous ethanol, and then perform ultrasonic dissolution, centrifugation and gas chromatography detection in sequence, and the weight of anhydrous ethanol is not less than 10 times the weight of the small amount of reaction liquid.

[0016] In step S1.2, the specific preparation process of TME seed crystals is as follows: adding the dried TME semi-fine product to an ethanol aqueous solution, and performing dissolution, centrifugation, crystallization, filtration, washing and drying operations in sequence;

[0017] The purity of the dried TME semi-fine product is not less than 97%; the mass ratio of the dried TME semi-fine product to the ethanol aqueous solution is 100:70;

[0018] Dissolution parameters are as follows: Dissolution temperature: 80-90 degrees; Filtration requirements: Filtration until the last drop of liquid drops and maintain for 10-15 minutes; Cleaning: -8 to -10 degrees ethanol water solution is used as the cleaning agent;

[0019] The specific process of crystallization operation is as follows: cool down to 20-22 degrees at a cooling rate of 38-42 degrees / hour → keep warm for 1-1.2 hours → cool down to 5 degrees at a cooling rate of 10-11 degrees / hour → keep warm for 1-1.2 hours, and use 0-5 degrees anhydrous ethanol to adjust the fluidity of the liquid during the crystallization process.

[0020] The crude product extraction process at each level in step S2 is set as follows: in the dissolution step, the dissolution method is heating and stirring, and the heating temperature is 94-96 degrees Celsius; the operation cutoff condition of the water evaporation step is: a layer of crystal shell covering the liquid surface; in the cooling stage of the crystallization step, the cooling rate is 38-42 degrees Celsius / hour;

[0021] In the first-level crude product extraction operation, the cooling target temperature of the cooling stage is 14-16 degrees. In the second-level crude product extraction operation, the cooling target temperature of the cooling stage is 4-5 degrees. In the third to N-level crude product extraction operations, the cooling target temperature of the cooling stage is 1-3 degrees.

[0022] In step S3, the following settings are made for each level of fine product extraction: in the dissolution step, the dissolution method is heating and stirring, and the heating temperature is 70-80 degrees; in the cooling filtration and re-filtration operations, the parameters are as follows: filtration temperature: 60-65 degrees; filtration parameters: 3-5um;

[0023] When using ethanol-water as the purification liquid, the following settings are set in each level of fine extraction operation: in the evaporation step, the evaporation temperature is 85-90 degrees; in the crystallization step, the parameters are as follows: the cooling rate in the cooling stage is 28-32 degrees / hour, the cooling target temperature is 5 degrees, and cold ethanol-water at -8 degrees is added to maintain the fluidity of the liquid;

[0024] When methanol is used as the purification liquid, the settings in each level of fine extraction operation are as follows: in the evaporation step, the evaporation temperature is 75-80 degrees; in the crystallization step, the parameters are as follows: the cooling rate in the cooling stage is 28-32 degrees / hour, and the cooling target temperature is 2 degrees; use methanol at -15 degrees to keep the liquid fluid.

[0025] When methanol is used as the purification liquid, in the drying step of each level of fine extraction operation, the cleaned crystals are first pre-dried at 50 degrees, and then continued to be dried at 60-70 degrees.

[0026] In step S2, the washed crystals are dried at a temperature of 60-70 degrees. In step S3, when an ethanol aqueous solution is used as the purification liquid, the washed crystals are dried at a temperature of 60-70 degrees.

[0027] Compared with the existing technology, the present invention achieves efficient purification and low-cost production of trimethylolethane (TME) through multi-stage gradient crystallization, selective adsorption and coordinated optimization of process parameters, which is specifically manifested in the following aspects:

[0028] Selection of adsorbent type: By using algae earth melt with specific parameters and models to burn into filter aids, as well as the temperature and time of adsorbent use, calcium formate can be more effectively adsorbed.

[0029] Optimized crystallization process: Through gradient crystallization strategy, seed crystal orientation induction and combined with low-temperature crystallization kinetic control (such as maintaining fluid crystallization conditions during the crystallization stage), the yield of TME is higher.

[0030] Optimized cleaning conditions: Different cleaning agents and corresponding cleaning temperatures are set to effectively remove impurities on the surface of the crystals, further improving the purity.

[0031] Optimized temperature conditions: According to the extraction requirements at different stages, the dissolution temperature, filtration temperature, crystallization cooling rate and other operating conditions are precisely controlled to effectively improve the extraction efficiency and purity.

[0032] Optimized extraction solvent: Compared with the high cost and stringent operating conditions of anhydrous ethanol, the use of ethanol-water solution or methanol can achieve high-purity TME extraction under more relaxed conditions by optimizing the extraction conditions. DETAILED DESCRIPTION

[0033] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0034] Example 1: Preparation for extracting high-purity trimethylolethane from the reaction liquid after trimethylolethane synthesis: The trimethylolethane synthesis process is as follows: calcium hydroxide is used as a catalyst, formaldehyde and propionaldehyde are used as raw materials, and formic acid is added dropwise for neutralization; in the reaction liquid, the main components are trimethylolethane, calcium formate and water, and the other components are: formaldehyde, propionaldehyde, 2,2-dimethylolpropionaldehyde,

[0035] Three 10g portions of TME were taken in parallel, and 100g of ethanol was added. The mixture was sonicated for 30 minutes to completely dissolve the mixture. The resulting solution was centrifuged and filtered, and then analyzed by gas chromatography. The results showed that trimethylolpropane accounted for 95.8% of the organic matter content, and calcium formate content was 4.8%. Theoretically, 45g of TME could be obtained per 100g of reaction solution.

[0036] The results met the extraction conditions of TME content above 95.5% and calcium formate content below 5%; extraction target parameters: TME crude parameters: calcium formate content not higher than 0.2%, purity not lower than 98.5%; fine TME parameters: calcium formate content not higher than 0.1%, purity not lower than 99.3%; color: white.

[0037] Seed preparation: Take dried semi-fine product (TME content is 97.5%, calcium formate content is 0.09%); the specific preparation process of TME seed crystals is as follows: add the dried TME semi-fine product to a 95% ethanol aqueous solution, stir at 85 degrees for 2 hours to obtain a clear transparent liquid, and crystallize the clear transparent liquid. The crystallization process is as follows: cool to 20 degrees at a cooling rate of 40 degrees / hour → keep warm for 1 hour → cool to 5 degrees at a cooling rate of 10 degrees / hour → keep warm for 1.2 hours. During the crystallization process, 2 degrees of anhydrous ethanol is used to adjust the fluidity of the liquid during the crystallization process; after the crystallization is completed, suction filtration is carried out, and suction filtration is carried out until the last drop of liquid drips and maintained for 10 minutes; after the suction filtration is completed, a filter cake is obtained, and the filter cake is washed with a 95% ethanol aqueous solution at a temperature of -8 degrees, and then placed in an oven and dried at 65 degrees for 2.5 hours to obtain TME seed crystals. After gas chromatography detection, the purity of the TME seed crystals is 99.5%;

[0038] Example 2: According to the purity requirements of the reaction solution, TME seed crystals, and TME crude product provided in Specific Example 1, the crude TME product extraction operation was carried out, with the following requirements: After each level of crude product extraction operation, quality testing was performed to ensure that the purity requirements of the crude TME product were met: the calcium formate content was not higher than 0.2%, and the purity was not lower than 98.5%. The crude TME product extraction specifically included the following steps:

[0039] S1 first-level crude product extraction operation: 100g of the reaction solution was stirred at a temperature of 95 degrees to fully dissolve it, and then centrifuged. The liquid after centrifugation was cooled to 15 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining 15 degrees for one hour, 0.8 grams of TME seed crystals were added, and the temperature was continued to be maintained at 15 degrees. After a large amount of crystals were precipitated, the solution showed poor fluidity, and then the temperature was slowly increased to make it fluid. When the solution regained fluidity, crystallization was continued for a period of time until no obvious crystals were precipitated; then suction filtration was performed to obtain a filter cake. In the suction filtration operation, suction filtration was performed until the last drop of liquid dripped and maintained for 10 minutes; the filter cake was washed, and during the washing, it was washed with 2-degree deionized water. After the washing was completed, it was dried in an oven at 65 degrees to obtain a first-level TME crude product and a first-level TME crude product mother liquor; the TME crude product mother liquor was a mixture of the liquids obtained after suction filtration and re-filtration;

[0040] S2 secondary crude product extraction operation: 100g of the reaction solution was added to the primary TME crude product mother liquor, stirred at a temperature of 95 degrees for 2 hours to fully dissolve it, and then centrifuged. The centrifuged liquid was evaporated. After a layer of crystal shell appeared on the surface of the liquid, the evaporation was stopped. Then, the temperature was cooled to 5 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 5 degrees for one hour, 1 gram of TME seed crystals was added. After a large amount of crystals were precipitated, the solution showed poor fluidity. Then, the temperature was slowly increased to make it just fluid. When the solution regained fluidity, crystallization was continued for a period of time until no obvious crystals were precipitated. Then, a suction filtration operation was performed to obtain a filter cake. In the suction filtration operation, suction filtration was performed until the last drop of liquid dripped and kept for 10 minutes. The filter cake was washed. During the washing, it was washed with 2-degree deionized water. After the washing was completed, it was dried in an oven at 65 degrees for 3 hours to obtain a secondary TME crude product and a secondary TME crude product mother liquor.

[0041] S3 three-level crude product extraction operation: add 100g of reaction solution to the secondary TME crude product mother liquor, stir at a temperature of 95 degrees for 2 hours to fully dissolve it, and then perform a centrifugal operation. The centrifuged liquid is subjected to a water evaporation operation. After a layer of crystal shell appears on the surface of the liquid, the evaporation is stopped. Then, the temperature is cooled to 5 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 5 degrees for one hour, 1 gram of TME seed crystals is added. After a large amount of crystals are precipitated, the solution has poor fluidity. Then, a slow heating operation is performed to make it just fluid. When the solution regains fluidity, crystallization is continued for a period of time until no obvious crystals are precipitated; then, a suction filtration operation is performed to obtain a filter cake. In the suction filtration operation, suction filtration is performed until the last drop of liquid drips and maintained for 10 minutes; the filter cake is washed. During the washing, it is washed with 1-degree deionized water. After the washing is completed, it is dried in an oven at 65 degrees for 3 hours to obtain a three-level TME crude product and a three-level TME crude product mother liquor;

[0042] S4 fourth-level crude product extraction operation: 100g of the reaction solution was added to the third-level TME crude product mother liquor, stirred at a temperature of 95 degrees for 2 hours to fully dissolve it, and then centrifuged. The centrifuged liquid was evaporated. After a layer of crystal shell appeared on the surface of the liquid, the evaporation was stopped. Then, the temperature was cooled to 2 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 2 degrees for one hour, 1 gram of TME seed crystals was added. After a large amount of crystals were precipitated, the solution showed poor fluidity. Then, the temperature was slowly increased to make it just fluid. When the solution regained fluidity, crystallization was continued for a period of time until no obvious crystals were precipitated. Then, a suction filtration operation was performed to obtain a filter cake. In the suction filtration operation, suction filtration was performed until the last drop of liquid dripped and kept for 10 minutes. The filter cake was washed. During the washing, it was washed with 1-degree deionized water. After the washing was completed, it was dried in an oven at 65 degrees for 3 hours to obtain a fourth-level TME crude product and a fourth-level TME crude product mother liquor.

[0043] S5 five-level crude product extraction operation: add 100g of reaction solution to the four-level TME crude product mother liquor, stir at a temperature of 95 degrees for 2 hours to fully dissolve it, and then perform a centrifugal operation. The centrifuged liquid is subjected to a water evaporation operation. After a layer of crystal shell appears on the surface of the liquid, the evaporation is stopped. Then, the temperature is cooled to 2 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 2 degrees for one hour, 1 gram of TME seed crystals is added. After a large amount of crystals are precipitated, the solution has poor fluidity. Then, a slow heating operation is performed to make it just fluid. When the solution regains fluidity, crystallization is continued for a period of time until no obvious crystals are precipitated; then, a suction filtration operation is performed to obtain a filter cake. In the suction filtration operation, suction filtration is performed until the last drop of liquid drips and maintained for 10 minutes; the filter cake is washed. During the washing, it is washed with 1-degree deionized water. After the washing is completed, it is dried in an oven at 65 degrees for 3 hours to obtain a five-level TME crude product and a five-level TME crude product mother liquor;

[0044] S6 Six-level crude product extraction operation: add 100g of reaction solution to the five-level TME crude product mother liquor, stir at a temperature of 95 degrees for 2 hours to fully dissolve it, and then perform a centrifugal operation. The centrifuged liquid is subjected to a water evaporation operation. After a layer of crystal shell appears on the surface of the liquid, the evaporation is stopped. Then, the temperature is cooled to 2 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 2 degrees for one hour, 1 gram of TME seed crystals is added. After a large amount of crystals are precipitated, the solution has poor fluidity. Then, a slow heating operation is performed to make it just fluid. When the solution regains fluidity, crystallization is continued for a period of time until no obvious crystals are precipitated; then a suction filtration operation is performed to obtain a filter cake. In the suction filtration operation, suction filtration is performed until the last drop of liquid drips and maintained for 10 minutes; the filter cake is washed. During the washing, it is washed with 1-degree deionized water. After the washing is completed, it is dried in an oven at 65 degrees for 3 hours to obtain a six-level TME crude product and a six-level TME crude product mother liquor;

[0045] S7 seventh-level crude product extraction operation: add 100g of reaction solution to the sixth-level TME crude product mother liquor, stir at a temperature of 95 degrees for 2 hours to fully dissolve it, and then perform a centrifugal operation. The centrifuged liquid is subjected to a water evaporation operation. After a layer of crystal shell appears on the surface of the liquid, the evaporation is stopped. Then, the temperature is cooled to 2 degrees at a cooling rate of 40 degrees / hour under stirring. After maintaining at 2 degrees for one hour, 1 gram of TME seed crystal is added. After a large amount of crystals are precipitated, the solution has poor fluidity. Then, a slow heating operation is performed to make it just fluid. When the solution regains fluidity, crystallization is continued for a period of time until no obvious crystals are precipitated; then a suction filtration operation is performed to obtain a filter cake. In the suction filtration operation, suction filtration is performed until the last drop of liquid drips and maintained for 10 minutes; the filter cake is washed. During the washing, it is washed with 1-degree deionized water. After the washing is completed, it is dried in an oven at 65 degrees for 3 hours to obtain a seventh-level TME crude product and a seventh-level TME crude product mother liquor; the seventh-level TME crude product mother liquor is recovered.

[0046] All grades of crude TME were weighed, yielding a total of 261.4 g of crude product. After deducting 7 g of seed crystals, a total of 254.4 g of crude TME was extracted from the reaction solution, with a yield of 80.76%. Using 700 g of reaction solution, theoretically 315 g of TME should be obtained. If 252 g or more of crude product is actually obtained, it is qualified.

[0047] Example 3: An ethanol aqueous solution was used as a purification solution, wherein the ethanol concentration in the ethanol aqueous solution was 95%. The crude TME product in Example 2 was used as a raw material to extract the TME fine product. After each level of fine product extraction operation, quality testing was performed to ensure that the purity requirements of the TME fine product were met: the calcium formate content was not higher than 0.1%, and the purity was not lower than 99.3%. The specific steps for extracting the fine product are as follows:

[0048] S1 first-level fine extraction: take 50 grams of TME crude product and add it to ethanol aqueous solution (the mass ratio of TME crude product to ethanol is 1:1.5), stir it at a temperature of 75 degrees until it is fully dissolved, and filter it with 3um filter paper at a temperature of 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb it at 70 degrees for 50 minutes, and then filter it with 3um filter paper at a temperature of 63 degrees to obtain a clear TME ethanol aqueous solution; stir the TME ethanol aqueous solution at a temperature of 90 degrees to evaporate ethanol. When small crystals or crystal films are observed in the solution during the evaporation process, the evaporation should be stopped immediately, and then Under stirring, the temperature was lowered to 5 degrees at a cooling rate of 30 degrees / hour, and the mixture was kept warm for crystallization until no obvious crystals were precipitated. During the heat preservation crystallization, the solution state was observed. If the solution condensed into a block, a cold ethanol solution of -8 degrees was added dropwise to make it just fluid. After the crystallization was completed, suction filtration was performed to obtain a filter cake, which was then washed with a cold ethanol solution of -8 degrees (the color of the filter cake was normal in this embodiment. If the filter cake was yellow, anhydrous ethanol of -8 degrees was used for washing). After the washing was completed, the mixture was dried at a drying temperature of 63 degrees for 3 hours. A first-level fine product and a first-level purified mother liquor were obtained, and the purified mother liquor was a mixed solution of the liquid after suction filtration and re-filtration.

[0049] S2 secondary fine extraction: add 50g of TME crude product to the mother liquor after primary purification, add a certain amount of ethanol aqueous solution, and then stir at 75 degrees until fully dissolved, and filter with 3um filter paper at 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3um filter paper at 63 degrees to obtain clear TME ethanol aqueous solution; stir the TME ethanol aqueous solution at 90 degrees to evaporate ethanol. When small crystals or crystal films are observed in the solution during the evaporation process, the solution should be immediately That is, stop evaporation, then cool to 5 degrees at a cooling rate of 30 degrees / hour under stirring, and carry out heat preservation and crystallization until no obvious crystals are precipitated; during the heat preservation and crystallization, observe the state of the solution. If the solution has poor fluidity, add -8 degrees cold ethanol aqueous solution to make it just fluid. After the crystallization is completed, filter to obtain a filter cake, which is then washed with -8 degrees cold ethanol aqueous solution (this specific embodiment is normal color. If the filter cake is yellow, use -8 degrees anhydrous ethanol for washing). After washing, dry it at a drying temperature of 63 degrees for 3 hours to obtain secondary fine products and secondary purified mother liquor.

[0050] S3 three-level fine extraction: add 50 grams of TME crude product to the mother liquor after secondary purification, and then add a certain amount of ethanol aqueous solution to ensure that the TME crude product can be fully dissolved; then stir at a temperature of 75 degrees until it is fully dissolved, and filter with 3-5um filter paper at a temperature of 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3-5um filter paper at a temperature of 63 degrees to obtain a clear TME ethanol aqueous solution; stir the TME ethanol aqueous solution at a temperature of 90 degrees to evaporate the ethanol, and when the evaporation process is observed, fine particles begin to appear in the solution. When crystals or crystal films appear, evaporation should be stopped immediately, and then the temperature should be lowered to 5 degrees at a cooling rate of 30 degrees / hour under stirring, and heat-insulated crystallization should be carried out until no obvious crystals are precipitated; during the heat-insulating crystallization, the solution state should be observed. If the solution has poor fluidity, a cold ethanol aqueous solution at -8 degrees should be added dropwise to make it just fluid. After the crystallization is completed, suction filtration is performed to obtain a filter cake, which is then washed with a cold ethanol aqueous solution at -8 degrees (this specific embodiment is normal color. If the filter cake is yellow, anhydrous ethanol at -8 degrees is used for washing). After washing, drying is performed at a drying temperature of 70 degrees for 2.5 hours; a three-level fine product and a mother liquor after three-level purification are obtained.

[0051] S4 four-level fine extraction: add 50 grams of TME crude product to the mother liquor after three-level purification, and then add a certain amount of ethanol aqueous solution to ensure that the TME crude product can be fully dissolved; then stir at a temperature of 75 degrees until it is fully dissolved, and filter with 3um filter paper at a temperature of 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3um filter paper at a temperature of 63 degrees to obtain a clear TME ethanol aqueous solution; stir the TME ethanol aqueous solution at a temperature of 90 degrees to evaporate the ethanol, and when small crystals or crystal films are observed in the solution during the evaporation process , the evaporation should be stopped immediately, and then the temperature should be lowered to 5 degrees at a cooling rate of 30 degrees / hour under stirring, and heat preservation and crystallization should be carried out until no obvious crystals are precipitated; during the heat preservation and crystallization, the solution state is observed. If the solution has poor fluidity, a cold ethanol aqueous solution of -8 degrees is added dropwise to make it just fluid. After the crystallization is completed, suction filtration is performed to obtain a filter cake, which is then washed with a cold ethanol aqueous solution of -8 degrees (this specific embodiment is normal color. If the filter cake is yellow, anhydrous ethanol of -8 degrees is used for washing). After the washing is completed, drying is performed at a drying temperature of 70 degrees for 3 hours; a fourth-level fine product and a mother liquor after fourth-level purification are obtained, and the mother liquor after fourth-level purification is recovered;

[0052] All levels of TME products were weighed, and a total of 178.3g of products were obtained.

[0053] Example 4: Methanol was used as the purification liquid, and the crude TME product in Example 2 was used as the raw material to extract the TME fine product. After each level of fine product extraction operation, quality testing was performed to ensure that the purity requirements of the TME fine product were met: the calcium formate content was not higher than 0.1%, and the purity was not lower than 99.3%. The specific steps for extracting the fine product were as follows: Methanol was used as the purification liquid, and the specific steps were as follows:

[0054] S1 first-level fine extraction: Take 50 grams of TME crude product and add it to methanol (the mass ratio of TME crude product to methanol is 1:1.2) and stir it at 72 degrees until it is fully dissolved, and then filter it with 3um filter paper at 60 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb it at 70 degrees for 50 minutes, and then filter it with 3um filter paper at 60 degrees to obtain a clear TME methanol aqueous solution; stir the TME methanol aqueous solution at 80 degrees to evaporate methanol. When fine crystals or crystal films are observed in the solution during the evaporation process, Stop evaporation immediately, then cool to 2 degrees at a cooling rate of 30 degrees per hour under stirring, and carry out heat preservation and crystallization until no obvious crystals are precipitated; during the heat preservation and crystallization, observe the state of the solution. If the solution condenses into lumps, add -15 degrees cold methanol to make it just fluid. After the crystallization is completed, filter to obtain a filter cake, which is then washed with -15 degrees cold methanol. After washing, dry the filter cake. First, dry it in a 50-degree oven for 30 minutes, then heat it to 65 degrees and dry it for two hours to obtain a first-level fine product and a first-level purified mother liquor. The purified mother liquor is a mixture of the filtered and re-filtered liquids.

[0055] S2 secondary fine extraction: take 50g of TME crude product and add it to the mother liquor after primary purification, then add a certain amount of methanol, stir at 70 degrees until fully dissolved, and filter with 3um filter paper at 60 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3um filter paper at 60 degrees to obtain a clear TME methanol aqueous solution; stir the TME methanol aqueous solution at 80 degrees to evaporate methanol, and when the evaporation process is observed, fine particles begin to appear in the solution. When crystals or crystal films appear, evaporation should be stopped immediately, and then the temperature should be lowered to 2 degrees at a cooling rate of 30 degrees / hour under stirring, and heat preservation and crystallization should be carried out until no obvious crystals are precipitated; during the heat preservation and crystallization, the state of the solution should be observed. If the solution condenses into lumps, add -15 degrees cold methanol to make it just fluid. After the crystallization is completed, filter to obtain a filter cake, and then use -15 degrees cold methanol for washing. After washing, dry it. First, dry the filter cake in a 50-degree oven for 30 minutes, then heat it to 65 degrees and dry it for two hours to obtain the secondary fine product and the secondary purified mother liquor.

[0056] S3 three-level fine extraction: take 50 grams of TME crude product and add it to the mother liquor after secondary purification, then add a certain amount of methanol, stir at 72 degrees until fully dissolved, and filter with 3um filter paper at 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3um filter paper at 63 degrees to obtain a clear TME methanol aqueous solution; stir the TME methanol aqueous solution at 80 degrees to evaporate methanol, and when the evaporation process is observed, fine particles begin to appear in the solution. When crystals or crystal films appear, evaporation should be stopped immediately, and then the temperature should be lowered to 2 degrees at a cooling rate of 30 degrees / hour under stirring, and heat preservation and crystallization should be carried out until no obvious crystals are precipitated; during the heat preservation and crystallization, the state of the solution should be observed. If the solution condenses into lumps, add -15 degrees cold methanol to make it just fluid. After the crystallization is completed, filter to obtain a filter cake, and then use -15 degrees cold methanol for washing. After washing, dry it. First, dry the filter cake in a 50-degree oven for 30 minutes, then heat it to 65 degrees and dry it for two hours to obtain the third-level fine product and the mother liquor after the third-level purification.

[0057] S4 Four-level fine extraction: Take 50 grams of TME crude product and add it to the mother liquor after three-level purification, then add a certain amount of methanol, stir at 73 degrees until fully dissolved, and filter with 3um filter paper at 63 degrees; add 0.5g of 40μm diatomaceous earth melt calcined product filter aid to the filtrate, fully adsorb at 70 degrees for 50 minutes, and then filter with 3um filter paper at 63 degrees to obtain a clear TME methanol aqueous solution; stir the TME methanol aqueous solution at 80 degrees to evaporate methanol, and when the evaporation process is observed, fine particles begin to appear in the solution. When crystals or crystal films form, evaporation should be stopped immediately, and then the temperature should be lowered to 2 degrees at a cooling rate of 30 degrees / hour under stirring, and crystallization should be carried out by heat preservation until no obvious crystals are precipitated. During the heat preservation crystallization, the state of the solution should be observed. If the solution condenses into lumps, add -15 degree cold methanol to make it just fluid. After the crystallization is completed, filter to obtain a filter cake, and then use -15 degree cold methanol for washing. After washing, dry the filter cake. First, dry it in a 50 degree oven for 30 minutes, then heat it to 65 degrees and dry it for two hours to obtain the fourth-level fine product and the mother liquor after fourth-level purification.

[0058] All levels of TME fine products were weighed, and a total of 185.6 g of fine products were obtained.

[0059] Example 5: Adsorbent Parameter Verification: Effects of Different Adsorbent Conditions on Calcium Formate Adsorption Rate: Common flocculants that adsorb organic salts, including polyaluminum chloride, polyaluminum ferric silicate, ferric chloride, polyacrylamide, ordinary diatomaceous earth, diatomaceous earth melt sintered filter aid, activated clay, and activated carbon, were tested. Experiments revealed that diatomaceous earth melt sintered filter aid (CAS No. 68855-54-9) exhibited the best calcium formate adsorption performance. Its advantages include low cost, relatively low addition dosage, and minimal adsorption of target substances in solution. The adsorption rates of diatomaceous earth melt sintered filter aids of varying specifications and reaction conditions were investigated.

[0060] 1. The effect of different particle sizes of diatomite melts on the adsorption rate of calcium formate filter aids is shown in the following table:

[0061]

[0062]

[0063] Considering economic factors and filtration speed, the best filter aid is diatomite melt sintered product with a median particle size of 40μm.

[0064] 2. Effect of the amount of diatomite melt calcined filter aid (40 μm) added on the adsorption rate of calcium formate: 100 g of dried TME crude product (calcium formate content in TME crude product is less than 3%) was used for the experiment. The results are shown in the following table.

[0065]

[0066] Taking economic factors and adsorption effect into consideration, the optimal addition amount is not less than 1 g (1% of the amount of crude TME added).

[0067] 3. Effect of adsorption temperature of filter aid (40μm) of different diatomite melt products on the adsorption rate of calcium formate. The results are shown in the following table:

[0068]

[0069] Considering economic factors and adsorption effect, the adsorption temperature is best at 55-70 degrees.

[0070] 4. Effect of adsorption time of filter aids (40 μm) of different diatomite melts on the adsorption rate of calcium formate

[0071]

[0072] Taking economic factors and adsorption effect into consideration, the best effect is achieved when the adsorption time is not less than 50 minutes.

[0073] The conclusion of the above research is: it is best to use diatomite melt with a median particle size of 40μm as the filter aid, the addition amount should be more than 1% of the addition amount of TME crude product, the operating temperature should be above 55-70 degrees, and the adsorption time should be no less than 50 minutes.

[0074] Crystallization temperature parameter verification:

[0075] In the fine product extraction, 95% ethanol aqueous solution is used as the purification liquid for crystallization. The results are shown in the following table:

[0076] Crystallization temperature 10 degrees 8 degrees 5 degrees 2 degrees 0 degrees purity 98.7％ 98.9％ 99.3％ 99.2％ 99.2％

[0077] In the fine product extraction, methanol is used as the purification liquid for crystallization. The crystallization temperature is shown in the following table:

[0078] Crystallization temperature 10 degrees 5 degrees 2 degrees 0 degrees -5 degrees purity 98.7％ 99.1％ 99.3％ 99.2％ 99.2％

[0079] In summary, when 95% ethanol aqueous solution is used as the purification liquid, the optimal crystallization temperature is 5 degrees, and when methanol is used as the purification liquid, the optimal crystallization temperature is 2 degrees.

[0080] Cleaning Temperature Verification:

[0081] When 95% ethanol aqueous solution is used as the cleaning agent, the results are shown in the following table:

[0082]

[0083] When methanol is used for cleaning, the results are shown in the following table:

[0084]

[0085] In summary, the best cleaning temperature for filter cakes with 95% ethanol aqueous solution is -8 degrees, and the best cleaning temperature for filter cakes with methanol is -15 degrees.

[0086] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the invention.

Claims

1. A method for extracting high-purity trimethylolethane from a reaction solution after trimethylolethane synthesis. The trimethylolethane synthesis process is as follows: calcium hydroxide is used as a catalyst, formaldehyde and propionaldehyde are used as raw materials, and formic acid is added dropwise to neutralize the obtained product; the method is characterized in that: The specific steps include: S1 Preparation: S1.1 Reaction liquid quality test: The reaction liquid is tested to ensure that it meets the extraction conditions. The extraction conditions are as follows: the calcium formate content in the reaction liquid is less than 5%; the target product trimethylolethane accounts for more than 95.5% of the organic components in the reaction liquid; S1.2 Seed crystal preparation: Prepare TME seed crystals with a purity of not less than 99% using dried TME semi-fine product; the calcium formate content in the TME semi-fine product is less than 0.1%; S2 Crude Product Extraction: S2.1 First-stage Crude Product Extraction: Take a portion of the reaction solution and perform dissolution, centrifugation, crystallization, filtration, washing, and drying operations in sequence to obtain a first-stage crude product and a first-stage TME crude product mother liquor; S2.2 Step-by-step crude product extraction: In the crude product extraction operations from level 2 to level N, the crude product extraction process at any level is as follows: first, a portion of the reaction solution is added to the crude TME mother liquor of the previous level, and then dissolution, centrifugation, water evaporation, crystallization, filtration, washing and drying operations are carried out in sequence; The second-grade TEM crude product and the second-grade TME crude product mother liquor, the third-grade TME crude product and the third-grade TME crude product mother liquor, the N-grade TME crude product and the N-grade TME crude product mother liquor were obtained respectively; Crude product extraction operation regulations: The crystallization operation steps are as follows: cooling → holding → heating to maintain fluidity and crystallization. During the holding stage, TME seed crystals are added. The amount of TME seed crystals added is 0.5-1% of the reaction solution used in the crude product extraction operation of the corresponding grade. Deionized water with a temperature of 0-4 is used as the cleaning agent. S2.3 Crude product collection: After collecting all levels of TME crude products, obtain TEM crude raw materials; S3 Fine Product Extraction: S3.1 First-level Fine Product Extraction: Take a portion of the crude TME raw material and add it to the corresponding amount of purified liquid. Then perform dissolution, cooling and filtration, adsorption, refiltration, evaporation, crystallization, suction filtration, washing and drying in sequence to obtain the first-level TME fine product and the first-level purified mother liquor; S3.2 Step-by-step extraction: In the second to N-level extraction operations, the extraction process of any level is as follows: first, take a portion of the crude TME raw material and add it to the mother liquor after TME purification in the previous level, then add the corresponding amount of purified liquid, and then carry out dissolution, cooling and filtration, adsorption, refiltration, evaporation, crystallization, suction filtration, washing and drying operations in sequence; Were obtained the secondary TME fine product and the secondary purified mother liquor, the tertiary TME fine product and the tertiary purified mother liquor, the N-grade TME fine product and the N-grade purified mother liquor respectively; S3.3 Collection of fine products: Collect all levels of TME fine products to obtain high-purity trimethylolethane; The crude product extraction regulations are as follows: purification liquid: ethanol-water solution or methanol, in the ethanol-water solution, the ethanol concentration is 95%; adsorbent: 40μm diatomaceous earth melt sintered product filter aid, CAS number: 68855-54-9, the operating environment temperature is 55-70 degrees, and the addition amount is not less than 1% of the TEM crude product raw material used in the corresponding level of fine extraction operation; the crystallization operation steps are as follows: cooling → insulation, during the insulation stage, the fluidity of the crystallization process is maintained by adding the corresponding cold purification liquid; cleaning: when using ethanol-water solution as the purification liquid, the filter cake obtained after filtration, when the filter cake color is yellow, use cold anhydrous ethanol for cleaning, when the filter cake color appears normal, use cold ethanol-water solution for cleaning; when using methanol as the purification liquid, use cold methanol for cleaning.

2. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis according to claim 1, characterized in that: The specific steps of the quality inspection in step S1.1 are as follows: take several small amounts of reaction liquid in parallel, and perform the following operations on each small amount of reaction liquid: add the small amount of reaction liquid into anhydrous ethanol, and then perform ultrasonic dissolution, centrifugation and gas chromatography detection in sequence, and the weight of anhydrous ethanol is not less than 10 times the weight of the small amount of reaction liquid.

3. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis as claimed in claim 1, characterized in that: In step S1.2, the TME seed crystals are prepared as follows: dried TME semi-fine product is added to an ethanol-water solution, and the process is sequentially performed: dissolution, centrifugation, crystallization, filtration, washing, and drying; the purity of the dried TME semi-fine product is not less than 97%; the mass ratio of dried TME semi-fine product to ethanol-water solution is 100:70; Dissolution parameters are as follows: Dissolution temperature: 80-90 degrees; Filtration requirements: Filter until the last drop of liquid drops and keep it for 10-15 minutes; Cleaning: -8 to -10 degrees ethanol water solution is used as cleaning agent; The specific process of crystallization operation is as follows: cool down to 20-22 degrees at a cooling rate of 38-42 degrees / hour → keep warm for 1-1.2 hours → cool down to 5 degrees at a cooling rate of 10-11 degrees / hour → keep warm for 1-1.2 hours, and use 0-5 degrees anhydrous ethanol to adjust the fluidity of the liquid during the crystallization process.

4. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis according to claim 1, characterized in that: The settings for each level of crude product extraction in step S2 are as follows: in the dissolution operation, the dissolution method is heating and stirring, and the heating temperature is 94-96 degrees; in the cooling stage of the crystallization operation, the cooling rate is 38-42 degrees / hour; In the crystallization operation of the first-level crude product extraction operation, the cooling target temperature is 14-16 degrees. In the crystallization operation of the second-level crude product extraction operation, the cooling target temperature is 4-5 degrees. In the crystallization operation of the third to N-level crude product extraction operations, the cooling target temperature is 1-3 degrees.

5. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis as claimed in claim 1, characterized in that: The temperature of cold anhydrous ethanol is -8 degrees; the temperature of cold ethanol aqueous solution is -8 degrees, and the temperature of cold methanol is -15 degrees.

6. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis according to claim 1, characterized in that: In step S3, the following settings are made for each level of fine product extraction: in the dissolution operation, the dissolution method is heating and stirring, and the heating temperature is 70-80 degrees; in the cooling filtration and re-filtration operations, the parameters are as follows: filtration temperature: 60-65 degrees; filtration parameters: 3-5um; When using ethanol-water as the purification liquid, the following settings are set in each level of fine extraction operation: in the evaporation operation, the evaporation temperature is 85-90 degrees; in the crystallization operation, the parameters are as follows: the cooling rate in the cooling stage is 28-32 degrees / hour, the cooling target temperature is 5 degrees, and cold ethanol-water at -8 degrees is added to maintain the fluidity of the liquid; When methanol is used as the purification liquid, the settings for each level of fine extraction operation are as follows: in the evaporation operation, the evaporation temperature is 75-80 degrees; in the crystallization operation, the parameters are as follows: the cooling rate in the cooling stage is 28-32 degrees / hour, and the cooling target temperature is 2 degrees; use methanol at -15 degrees to keep the liquid fluid.

7. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis according to claim 1, characterized in that: When methanol is used as the purification liquid, in the drying operation of each level of fine extraction operation, the cleaned crystals are first pre-dried at 50 degrees, and then continued to be dried at 60-70 degrees.

8. The method for extracting high-purity trimethylolethane from the reaction solution after trimethylolethane synthesis according to claim 1, characterized in that: In step S2, the washed crystals are dried at a temperature of 60-70 degrees. In step S3, when an ethanol aqueous solution is used as the purification liquid, the washed crystals are dried at a temperature of 60-70 degrees.

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