Method for extracting high-purity ditrimethylolpropane from TMP rectification residues

Abstract

The invention discloses a method for extracting high-purity ditrimethylolpropane from TMP rectification residues, and belongs to the technical field of ditrimethylolpropane purification. The extraction process sequentially comprises the following steps: dissolving, centrifuging, heating and decoloring, concentrating, filtering, crystallizing, suction filtering, cleaning and drying. By adopting a synergistic strategy of staged decoloration (dynamic decoloration in batches by medicinal activated carbon), gradient temperature control crystallization (crystal nucleus formation at 0-2 DEG C-crystal growth at 3-5 DEG C) and seed crystal induced crystallization, impurities are effectively separated and the co-crystallization behavior of the impurities is inhibited, so that the product purity stably reaches 98.6% or above; the yield exceeds 75%; deionized water at the temperature of 0-2 DEG C is selected as a cleaning agent, lattice defects are inhibited from being formed under the low-temperature condition, and meanwhile, impurities adsorbed on the surfaces of crystals are effectively removed in combination with a multi-stage cleaning liquid replacement strategy. Through the optimized extraction process, the extraction efficiency and the product purity of the ditrimethylolpropane are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ditrimethylolpropane purification, and particularly relates to a method for extracting high-purity ditrimethylolpropane from TMP distillation residue. Background Art

[0002] In the field of chemical raw material recycling technology, the alcohol-aldehyde condensation product (i.e. trimethylolpropane, TMP) generated by using n-butyraldehyde and formaldehyde aqueous solution as raw materials and calcium hydroxide as a catalyst is used as the starting material. The TMP distillation residue produced after the distillation process still contains high value-added components. The main components of the TMP distillation residue include trimethylolpropane (TMP), ditrimethylolpropane, methylal, calcium formate, 2,2-dimethylolbutyraldehyde and water-insoluble lipid compounds, among which ditrimethylolpropane is a key functional component with excellent molecular structure designability. It can be used as a synthetic raw material for high-performance resins, polyurethane foam stabilizers, and epoxy resin curing agents, and is widely used in the fields of coatings, adhesives and elastomer materials. However, the existing technology for the treatment of TMP distillation residue has the following technical difficulties that need to be solved:

[0003] Traditional separation methods are inefficient: Existing solvent extraction and distillation processes for treating TMP distillation residues containing multiple components (including trimethylolpropane, ditrimethylolpropane, methylal, calcium formate, and lipid compounds) suffer from low separation efficiency and high energy consumption due to factors such as the narrow differences in the physicochemical properties of these components and the complex azeotropic system. This makes it difficult to achieve efficient enrichment of these components. The extraction rate of existing technologies is generally less than 50%, which is not a high yield.

[0004] Technical bottleneck of insufficient crystal purity: When using traditional recrystallization methods to process TMP distillation residues containing various polar / non-polar impurities (such as calcium formate, 2,2-dihydroxymethylbutyraldehyde and alkane compounds), the purity of the product ditrimethylolpropane is difficult to reach above 98% because the crystallization behavior of the impurities is similar to that of the target product and there is co-crystallization. This seriously affects its application value as a high-value-added chemical.

[0005] Low yield defect of low-concentration raw materials: The existing crystallization technology has low efficiency in extracting low-concentration ditrimethylolpropane from TMP distillation residue, which is mainly manifested in: (1) the large amount of mother liquor residue leads to a high loss rate of the target product; (2) the lack of a gradient temperature control strategy results in incomplete crystal growth; (3) the lack of an effective seed induction mechanism causes crystal agglomeration.

[0006] The above technical defects make it difficult for the existing process to meet the extraction requirements of ditrimethylolpropane with high purity (≥98%) and high yield. It is urgent to develop a new separation and purification process to break through the bottleneck of the existing technology. Summary of the Invention

[0007] The purpose of the present invention is to solve the above problems in the existing technology and to propose a method for extracting high-purity ditrimethylolpropane from TMP distillation residue.

[0008] The objectives of the present invention can be achieved by the following technical solutions: a method for extracting high-purity ditrimethylolpropane from TMP distillation residue, wherein the TMP distillation residue is obtained from the bottom of a distillation tower after an aldol condensation reaction between n-butyraldehyde and a formaldehyde solution using calcium hydroxide as a catalyst to obtain a TMP raw material, wherein the TMP raw material is distilled and the distillation residue is obtained; the main components of the distillation residue are trimethylolpropane (TMP), ditrimethylolpropane, methylal, calcium formate, 2,2-dihydroxymethylbutyraldehyde and some water-insoluble lipid compounds, and other trace components include alkane compounds;

[0009] The method for extracting high-purity ditrimethylolpropane from TMP distillation residue specifically comprises the following steps:

[0010] S1 Distillation Residue Testing: Perform quality testing on the TMP distillation residue to ensure that it meets the extraction conditions. Submission conditions: The content of ditrimethylolpropane in the organic matter of the TMP distillation residue is higher than 40%. If it is lower than 40%, it cannot be guaranteed that the final crystallization purity of ditrimethylolpropane is not less than 98%.

[0011] S2 seed crystal preparation: using semi-fine ditrimethylolpropane to prepare ditrimethylolpropane seed crystals with a purity of not less than 98%;

[0012] S3 Extraction: First, extract part of the TMP distillation residue according to the extraction process to obtain the first-grade TMP fine product and the first-grade mother liquor, and then perform subsequent TMP distillation residue extraction according to the extraction rules;

[0013] The extraction rules are as follows: first, take part of the TMP distillation residue and add it to the mother liquor of the previous stage, and then extract according to the extraction process;

[0014] The extraction process includes the following steps in order: dissolution, centrifugation, heating decolorization, concentration, filtration, crystallization, suction filtration, washing and drying; in the dissolution step, deionized water is selected as the solvent, and the dissolution is carried out by heating and stirring; in the heating decolorization step, activated carbon specially used for drug decolorization is selected as the decolorizer; in the washing step, deionized water with a temperature of 0-2 degrees is selected as the washing agent; in the crystallization step, a gradient temperature control crystallization strategy and a seed crystal induced crystallization strategy are adopted.

[0015] Preferably, in step S1, the quality test specifically comprises the following steps: taking several small portions of TMP distillation residue in parallel, and performing the following operations on each portion of the TMP distillation residue: adding each portion of the TMP distillation residue to anhydrous ethanol, and sequentially performing ultrasonic dissolution, centrifugation, and gas chromatography testing. The weight of the anhydrous ethanol is not less than 10 times the weight of each portion of the TMP distillation residue.

[0016] Preferably, in the dissolving step, the dissolving temperature is 95-100°C.

[0017] Preferably, in the heating decolorization step, the CAS number of the activated carbon for drug decolorization is 7440-44-0; the heating temperature is 60° C.; the addition is carried out in batches, and the dosage is dynamically adjusted according to the colorimetric detection results; and after each decolorization treatment, filtration is performed.

[0018] Each time the activated carbon specially used for drug decolorization is added, the decolorization treatment time is 60-90 minutes.

[0019] Preferably, in the crystallization step, the specific crystallization operation process is as follows: the liquid obtained in the filtration step is cooled to 0-1°C, and then ditrimethylolpropane seed crystals are added. After stirring evenly, the crystallization temperature is adjusted to 0-2°C and kept warm until crystals no longer precipitate. The crystallization temperature is adjusted to 3-5°C and kept warm until crystals no longer precipitate.

[0020] Preferably, the seed crystal preparation process is as follows: ditrimethylolpropane semi-fine product with a purity greater than 95% is added to deionized water and stirred at a temperature of 90-95°C until fully dissolved. The product is then cooled to 20°C at a cooling rate of 15-25°C / hour while stirring, and crystallized by heat preservation until no more crystals precipitate. The product is then filtered, washed, and dried to obtain ditrimethylolpropane seed crystals. During the washing operation, deionized water at 0-4°C is used for washing.

[0021] Compared with the existing technology, the present invention achieves a synergistic breakthrough in purity, yield and resource utilization in the purification process of ditrimethylolpropane through multi-technological collaborative innovation and precise control of process parameters. The specific technical advantages are as follows:

[0022] High purity and high yield are achieved in synergy: a synergistic strategy of staged decolorization (dynamic decolorization of pharmaceutical activated carbon in batches), gradient temperature-controlled crystallization (0-2°C nucleation → 3-5°C crystal growth) and seed-induced crystallization is adopted to effectively separate impurities and inhibit the co-crystallization behavior of impurities, so that the product purity can be stably achieved at more than 98.6% and the yield exceeds 75%.

[0023] Deep removal of impurities in low-temperature cleaning process: 0-2℃ deionized water is used as the cleaning agent, and the formation of lattice defects is suppressed under low temperature conditions. At the same time, a multi-stage cleaning liquid replacement strategy is combined to effectively remove impurities adsorbed on the crystal surface.

[0024] Reduce costs: Use deionized water as a solvent instead of traditional organic solvents, achieving significant advantages in terms of cost, safety and environmental protection. DETAILED DESCRIPTION

[0025] 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.

[0026] Example 1: Preparation for Extracting High-Purity Ditrimethylolpropane from TMP Distillation Residue: Three 10-gram portions of TMP distillation residue were prepared in parallel. Each portion was subjected to the following procedures: 100 g of ethanol was added, and the mixture was completely dissolved by ultrasonication for 30 minutes. The resulting solution was centrifuged and filtered. Gas chromatography was performed. Measurements showed that the ditrimethylolpropane content accounted for 42% of the organic matter content, trimethylolpropane accounted for 13%, and methylal accounted for 18%. The ditrimethylolpropane content per 10 g of distillation residue was 0.987 g. This result satisfied the requirement that the ditrimethylolpropane content accounted for more than 40% of the organic matter content.

[0027] Example 2: Preparation of ditrimethylolpropane seed crystals: Ditrimethylolpropane semi-fine product with a purity of 95.5% was added to deionized water in a mass ratio of 95.5% ditrimethylolpropane semi-fine product: deionized water of 100:250; stirred at a temperature of 90-95°C until fully dissolved, and then cooled to 20°C at a cooling rate of 20°C / hour under stirring, and crystallized by insulation until no more crystals precipitated, followed by filtration, washing with deionized water at 2°C, and drying to obtain ditrimethylolpropane seed crystals with a purity of 98.5%.

[0028] Example 3: Extracting high-purity ditrimethylolpropane from TMP distillation residue, using the TMP distillation residue in Example 1 as raw material, the requirements are as follows: After each stage of extraction is completed, the extracted ditrimethylolpropane is subjected to purity detection to ensure that the purity is not less than 98.9%. The specific extraction steps are as follows: S1 first-level extraction: dissolution and centrifugation: 150 grams of TMP distillation residue are added to 210 grams of water, heated to 98 degrees, fully stirred to fully dissolve it, and then centrifuged to obtain 310 grams of solution, heating and decolorization: The solution obtained by the above centrifugation is decolorized. In the decolorization process, activated carbon (CAS No.: 7440-44-0) for drug decolorization is used, and the heating temperature is 60°C; a batch addition method is adopted, and the amount of each addition is dynamically adjusted according to the colorimetric detection results; each addition of the decolorization solution is carried out. After treatment, filtered to obtain 305 grams of light yellow liquid; concentrated and filtered: the light yellow solution (wherein the water content is about 264g) was heated and evaporated, and calcium formate water was precipitated into solid during the process. After filtration, 50g of solution (wherein the water content is 10g) was obtained; crystallization: 50 grams of solution were first rapidly cooled to 0 degrees, 1g of ditrimethylolpropane seed crystals were added, stirred thoroughly, and the crystallization temperature was adjusted to 1 degree. A large amount of crystals were separated out, and the temperature was maintained for 0.5h, then the temperature was raised to 4 degrees, and the temperature was maintained for 6h. The solution after crystallization was filtered with suction, and the filter cake and the residual liquid were washed with 200g of deionized water at 2 degrees for 3-4 times, and then dried to obtain 11.5 grams of primary ditrimethylolpropane and 240 grams of primary mother liquor; 1 gram of seed crystals used was deducted and a total of 10.5 grams of ditrimethylolpropane were extracted.

[0029] S2 secondary extraction: solvent and centrifugation: first take 800 grams of TMP distillation residue and add it to the first mother liquor, then add 1300 grams of water, heat to 100 degrees, stir thoroughly to dissolve it, and then centrifuge to obtain 2100 grams of solution (wherein the water content is about 1820 grams); heating decolorization: the solution obtained by the above centrifugation is decolorized. During the decolorization process, activated carbon for drug decolorization (CAS No.: 7440-44-0) is used at a heating temperature of 60°C; batch addition is adopted, and the amount used each time is dynamically adjusted according to the colorimetric test results; after each addition of decolorization treatment, it is filtered to finally obtain 2090 grams of light yellow liquid; concentration and filtration: the light yellow solution (wherein the water content is about 1 815g) heating evaporation, in the process, calcium formate water is separated out solid, and finally obtains 300g solution (wherein water content is 60g) after filtration; Crystallization: 300 gram solution are first cooled to 0 degree rapidly, add ditrimethylolpropane seed crystal 10g, stir evenly, and adjustment crystallization temperature is 1 degree, carry out crystallization, until crystal no longer obviously separates out, then be warming up to 3 degree, maintain this temperature until crystal no longer obviously separates out, the solution suction filtration after the crystallization, filter cake and residual liquid are divided 3-4 time with 2 degree 1200g deionized water washing, then dry, obtain secondary ditrimethylolpropane 71.24 grams and secondary mother liquor; Secondary mother liquor reclaims; Deduct 10 gram crystal seeds used, extract 61.24 gram ditrimethylolpropane altogether,

[0030] In the three-stage extraction, the purity of the extracted ditrimethylolpropane was found to be 98.8%. In order to meet the above purity parameter requirements, only two-stage extraction was performed.

[0031] Yield calculation: A total of 950 g of TMP distillation residue was used, and 950 g of TMP distillation residue contained approximately 93.74 g of ditrimethylolpropane. A total of 71.74 g of ditrimethylolpropane with a purity of not less than 98.9% was extracted, and the yield was 76.53%.

[0032] Comparative Example 1: Using the TMP distillation residue in Specific Implementation 1 as raw material, ditrimethylolpropane was extracted by a traditional method. After distillation and recrystallization, ditrimethylolpropane with a purity of 85% was obtained, and the yield was 25%; the heating temperature was 200° C. and the time was 4 hours.

[0033] Traditional methods for extracting DTMP from heavy component solutions have the following drawbacks: Low product purity: Even after recrystallization, the purity of DTMP reaches only about 85%, far below actual requirements. High energy consumption: Both the heating distillation and subsequent recrystallization processes consume significant amounts of energy.

[0034] Comparative Example 2: Using the TMP distillation residue from Specific Example 1 as raw material, ditrimethylolpropane was extracted using a conventional solvent extraction method, using toluene as the extractant. After extraction, solvent removal by distillation, and recrystallization, ditrimethylolpropane was obtained with a purity of approximately 85%. The yield was relatively low, at 45%.

[0035] Traditional solvent extraction methods for ditrimethylolpropane have the following drawbacks: High solvent consumption: Large amounts of organic solvent are required for extraction, increasing production costs and the environmental burden. Complex post-processing: The organic phase after extraction requires further processing to obtain a high-purity product, a complex and energy-intensive process.

[0036] In contrast, the method proposed in the present invention significantly improves purity and yield, and the process is more environmentally friendly. It not only reduces production costs but also reduces the impact on the environment, and has broad application prospects.

[0037] Comparative Example 3: Using the TMP distillation residue from Specific Example 1 as raw material, seedless crystallization was used to extract ditrimethylolpropane. The results are as follows: Purity: The ditrimethylolpropane crystals collected after seedless crystallization had a purity of approximately 90%. This was due to the lack of induction from the seed crystals, which prevented the effective separation of some impurities during the crystallization process.

[0038] Yield: The yield was 45%, which was due to the uneven crystal particles, resulting in increased losses during filtration and collection, as well as co-crystallization of impurities.

[0039] Results from seedless crystallization attempts showed that without seed induction, the resulting ditrimethylolpropane crystals were of lower purity and had a reduced yield. This further demonstrates the advantages of the seeded crystallization method proposed in this invention in improving crystallization efficiency and purity. By introducing seed crystals, the crystallization process can be more effectively controlled, promoting uniform crystal growth, and thus improving product purity and yield.

[0040] Comparative Example 4: Simplified Extraction: The heating and decolorization treatment in Specific Example 1 was omitted. The results are as follows: Purity: The purity of the ditrimethylolpropane crystals collected after the simplified crystallization step was approximately 92%. This was due to the omission of the decolorization step, which resulted in some colored impurities not being removed, and the relatively short crystallization time, which resulted in some ditrimethylolpropane not being fully crystallized, thus affecting the purity of the product.

[0041] 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 ditrimethylolpropane from TMP distillation residue, wherein the TMP distillation residue is obtained from the bottom of a distillation tower after an aldol condensation reaction of n-butyraldehyde and a formaldehyde solution using calcium hydroxide as a catalyst to obtain a TMP raw material, and the TMP raw material is distilled; characterized in that: The method for extracting high-purity ditrimethylolpropane from TMP distillation residue specifically comprises the following steps: S1 Distillation Residue Testing: Perform quality testing on the TMP distillation residue to ensure that it meets the extraction conditions. The extraction conditions are: the content of ditrimethylolpropane in the organic matter of the TMP distillation residue is higher than 40%; S2 seed crystal preparation: using semi-fine ditrimethylolpropane to prepare ditrimethylolpropane seed crystals with a purity of not less than 98%; S3 Extraction: First, extract part of the TMP distillation residue according to the extraction process to obtain the first-grade TMP fine product and the first-grade mother liquor, and then perform subsequent TMP distillation residue extraction according to the extraction rules; The extraction rules are as follows: first, take part of the TMP distillation residue and add it to the mother liquor of the previous stage, and then extract according to the extraction process; The extraction process includes the following steps in order: dissolution, centrifugation, heating decolorization, concentration, filtration, crystallization, suction filtration, washing and drying; in the dissolution step, deionized water is selected as the solvent, and the dissolution is carried out by heating and stirring; in the heating decolorization step, activated carbon specially used for drug decolorization is selected as the decolorizer; in the washing step, deionized water with a temperature of 0-2 degrees is selected as the washing agent; in the crystallization step, gradient temperature control and seed induction are used for crystallization.

2. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 1, characterized in that: In step S1, the specific steps of quality inspection are as follows: several small amounts of TMP distillation residues are taken in parallel, and the following operations are performed on each portion of TMP refining residue: each portion of TMP refining residue is added to anhydrous ethanol, and ultrasonic dissolution, centrifugation and gas chromatography are performed in sequence.

3. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 2, characterized in that: The weight of anhydrous ethanol is not less than 10 times the weight of each part of TMP refining residue.

4. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 1, characterized in that: In the dissolving step, the dissolving temperature is 95-100°C.

5. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 1, characterized in that: In the heating decolorization step, the CAS number of the activated carbon for drug decolorization is 7440-44-0; the heating temperature is 60°C; the addition is carried out in batches, and the dosage is dynamically adjusted according to the colorimetric test results; and after each decolorization treatment, filtration is performed.

6. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 5, characterized in that: Each time the activated carbon specially used for drug decolorization is added, the decolorization treatment time is 60-90 minutes.

7. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 1, characterized in that: The specific process of crystallization using gradient temperature control and seed induction is as follows: the liquid obtained after the filtration step is cooled to 0-1°C, and then ditrimethylolpropane seed crystals are added. After stirring evenly, the crystallization temperature is adjusted to 0-2°C and kept warm until crystals no longer precipitate. The crystallization temperature is then adjusted to 3-5°C and kept warm until crystals no longer precipitate.

8. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 1, characterized in that: The specific process of seed crystal preparation is as follows: ditrimethylolpropane semi-fine product with a purity greater than 95% is added to deionized water, stirred at a temperature of 90-95°C until fully dissolved, then cooled to 20°C at a cooling rate of 15-25°C / hour under stirring, and crystallized by heat preservation until no more crystals are precipitated, and then filtered, washed and dried to obtain ditrimethylolpropane seed crystals.

9. The method for extracting high-purity ditrimethylolpropane from TMP distillation residue as claimed in claim 8, characterized in that: During the cleaning operation, deionized water at 0-4°C was used for cleaning.