Process and apparatus for the synthesis of isosorbide
By using a membrane reactor and a fluorine-modified solid catalyst in the preparation of isosorbide, the problems of excessive by-product formation and easy catalyst clogging were solved, the yield was improved and the catalyst life was extended, and the catalyst was recycled.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-11-28
- Publication Date
- 2026-05-29
AI Technical Summary
In the existing technology for the preparation of isosorbide, many by-products are generated, the catalyst is easily blocked, the yield is low, the catalyst is difficult to recover and reuse, the reaction time is long, and the equipment is severely damaged.
A membrane reactor combined with a fluorine-modified solid catalyst was used. The nano-sized fluorine-modified solid catalyst and a small amount of sulfonic acid resin catalyst were used to carry out the dehydration reaction of sorbitol through the membrane reactor, which rapidly removed water and separated the catalyst. Isosorbitol was purified by programmed cooling crystallization.
This improved the yield of isosorbide, reduced the formation of byproducts, extended the service life of the catalyst, enabled the recycling of the catalyst, and simplified the post-processing.
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Figure BDA0005158824510000101
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical preparation technology, specifically relating to a method and apparatus for synthesizing isosorbide. Background Technology
[0002] Isosorbide, as an important material and chemical intermediate for future bioenergy, has been widely used in the pharmaceutical, food, and chemical materials industries, and is hailed as the second largest bio-based material after polylactic acid. Due to its rigid and chiral molecular structure, modified PC and PET polymers exhibit excellent mechanical and heat resistance properties, making it a research hotspot both domestically and internationally.
[0003] Isosorbide is mainly prepared from sorbitol through two acid-catalyzed dehydration processes. The first dehydration yields 1,4-dehydrated sorbitol, which is then further dehydrated in a second step to obtain isosorbide. However, the first dehydration of sorbitol yields many intermediates; only 1,4-dehydrated sorbitol and 3,6-dehydrated sorbitol can be dehydrated in the second step to obtain isosorbide. The others cannot be dehydrated in the second step to obtain isosorbide. The second dehydration of the intermediates is a deep dehydration, which is difficult and requires a strong acid. Furthermore, the reaction system has a high viscosity, making it prone to water molecule encapsulation. If water is not removed from the reaction system in a timely manner, it will directly affect the chemical equilibrium and reduce the yield of the final product, isosorbide. To improve the yield, the stronger the acidity of the catalyst, the easier it is to over-condense and generate more byproducts, contaminating the entire reaction system.
[0004] Traditionally, isosorbide is prepared in industrial processes using sulfuric acid as a catalyst via a one-pot high-vacuum dehydration reaction in a molten state. This method suffers from significant equipment damage from the liquid acid, produces numerous byproducts, and involves complex and lengthy post-processing steps, requiring the addition of alkali to neutralize the acid and separate the solid salt, resulting in high production costs. Furthermore, the molten state of sorbitol has a certain viscosity, hindering the rapid removal of water from the reaction system, leading to a prolonged overall reaction time and preventing the separation of the solid catalyst from the materials and the continuation of the reaction.
[0005] Therefore, researchers are currently focusing on the development of solid acid catalysts. Although the catalyst and the reaction system can be separated, it is still impossible to avoid the byproducts generated by the two-step dehydration process from further condensing into high-polymer byproducts. After a long period of reaction, these substances will block the internal pores of the solid acid catalyst, leading to catalyst deactivation and reducing its service life.
[0006] CN201611181594.6 discloses a method for preparing isosorbide. Using solid sorbitol as a raw material and solid acidic molecular sieve as a catalyst, the mass ratio of solid sorbitol to molecular sieve is 100:1.0–5.0. The reaction is carried out under catalytic conditions in the molten state at a pressure of -0.02–-0.06 MPa and a temperature of 120–200 °C for 2–6 hours to obtain isosorbide. After the reaction, the isosorbide content in the product is above 80%. This method uses β-molecular sieve as a solid acid catalyst. The two-step dehydration reaction accumulates byproducts, and prolonged reaction time can clog the catalyst's pore structure, leading to catalyst deactivation. Furthermore, because the reaction is carried out in the molten state, the generated water cannot quickly leave the reaction system, and the separation of the solid catalyst from the material is also impossible.
[0007] CN201510068551.6 discloses a continuous preparation method for isosorbide. The preparation apparatus used in this method includes: a raw material premixing device (1), a primary dehydration reactor (2), an intermediate dehydration device (3), a secondary dehydration reactor (4), a neutralization and deacidification reactor (5), a distillation column (6), an isosorbide condenser (7), a desalting and impurity removal device (8), connecting pipelines between equipment, control instruments, and various accessories. The preparation process involves sorbitol and a dehydration catalyst being premixed in the raw material premixing device (1) in a certain proportion, then reacted in the primary dehydration reactor (2), dehydrated in the intermediate dehydration device (3), and then further dehydrated in the secondary dehydration reactor (4). This patent uses an acid catalyst and connects several batch reactors in series to achieve continuous processing. However, it cannot achieve rapid dehydration, nor can it avoid the generation of reaction byproducts. Furthermore, after secondary dehydration, the catalyst needs to be neutralized and deacidified before further distillation separation.
[0008] CN202410337723.4 discloses a method and apparatus for synthesizing isosorbide. The method includes: adding p-toluenesulfonic acid to molten sorbitol, wherein the amount of p-toluenesulfonic acid added is 0.03%–0.08% based on the molar amount of sorbitol; dehydrating sorbitol through a first-stage reaction at a preset temperature and a first pressure to obtain a first-stage product, which includes 1,4-dehydrated sorbitol and isosorbide; maintaining the preset temperature constant, dehydrating 1,4-dehydrated sorbitol through a second-stage reaction to generate isosorbide under a second pressure, and simultaneously distilling off a gaseous mixture of isosorbide and water; the first pressure is higher than the second pressure; and isosorbide is separated from the gaseous mixture. Compared to the traditional isosorbide preparation process which uses a large dose of acidic catalyst and requires neutralization after the catalytic reaction, using p-toluenesulfonic acid as an acidic catalyst, replacing strong acid catalysts such as sulfuric acid, results in a lower acidity in the reaction system and a higher product yield, reaching over 75%. However, the catalyst in this synthesis method is not easily recovered and reused. Summary of the Invention
[0009] To address the shortcomings of existing technologies, this invention provides a method and apparatus for synthesizing isosorbide. This invention utilizes a membrane reactor combined with a fluorine-modified solid catalyst for the synthesis reaction, ensuring high yield while allowing the released water to rapidly exit the reaction system, reducing byproduct formation, preventing catalyst blockage, and extending catalyst lifespan.
[0010] This invention provides a method for synthesizing isosorbide, comprising the following:
[0011] (1) Mix the sorbitol aqueous solution and solid catalyst in a preheater, feed them from the top of the membrane reactor, react under vacuum conditions, and the product flows out from the bottom of the reactor.
[0012] (2) The product was dissolved in an organic solvent and the solid catalyst was separated. The filtrate was cooled and crystallized to obtain isosorbide.
[0013] Furthermore, the mass concentration of the sorbitol aqueous solution in step (1) is 60%-80%.
[0014] Further, the amount of the solid catalyst used in step (1) is 1%-3% of the mass of sorbitol.
[0015] Further, the solid catalyst in step (1) is a nano-sized fluorine-modified solid catalyst. The preparation of the fluorine-modified solid catalyst includes the following steps: (a) mixing beta molecular sieve with a fluorine-containing ion solution, heating to 60-100℃ for reaction, separating the solid after reaction, washing and drying to obtain the solid product; (b) mixing the solid product with SnF4 in a certain proportion, ball milling reaction under an inert atmosphere, and then calcining to obtain the catalyst.
[0016] In the above catalyst preparation method, the beta molecular sieve mentioned in step (a) is preferably an H-beta molecular sieve, and the silicon-to-aluminum ratio of the molecular sieve, calculated as SiO2 / Al2O3, is 20-80, preferably 20-40. The solute in the fluoride-containing solution is at least one of hydrofluoric acid, ammonium fluoride, etc., and the mass fraction of the solute in the solution is 5%-30%. The solid-liquid ratio of the beta molecular sieve to the fluoride-containing solution is 1g:15-30mL.
[0017] In the above catalyst preparation method, step (a) involves heating to 60-100℃, preferably 70-90℃, for a reaction time of 4-8 hours. Solid-liquid separation is performed by filtration, centrifugation, etc. The solid is washed with water until neutral and then dried at 100-120℃ for 10-24 hours.
[0018] In the above catalyst preparation method, SnF4 in step (b) is mixed with the solid from step (1) at a mass ratio of 1:8-15. The inert atmosphere is any one of nitrogen, helium, or argon. The ball milling speed is 35-45 r / min, and the milling time is 6-10 h. The calcination temperature is 500-600℃, and the calcination time is 6-12 h.
[0019] Furthermore, the solid catalyst also includes a small amount of sulfonic acid resin catalyst, more preferably sulfonic acid ion exchange resin Amberlyst 15. The amount of sulfonic acid resin catalyst accounts for 0.01%-1.0% of the total solid catalyst, preferably 0.1%-0.5%.
[0020] Furthermore, the preheating temperature in the preheater described in step (1) is 80-100℃.
[0021] Furthermore, the membrane reactor described in step (1) can be any one of a falling film reactor, a scraped film reactor, etc.
[0022] Furthermore, the vacuum degree in step (1) is 5-30 kPa, and the reaction temperature is 110-150 °C.
[0023] Further, the organic solvent in step (2) is at least one of ester organic solvents, polyol organic solvents, etc., preferably at least one of ethyl acetate and ethylene glycol.
[0024] Furthermore, the liquid-to-solid ratio of the organic solvent to sorbitol in step (2) is 5-15 mL: 1 g.
[0025] In this invention, the product effluent described in step (2) is dissolved in an organic solvent at a temperature of 60-80°C.
[0026] Furthermore, in step (2), a programmed cooling method is used during the crystallization process, with a cooling rate of 5-15℃ / h, the intermediate temperature is maintained at 30-40℃ for 2-4 hours, and the final temperature of the crystallization process is -5-5℃, which is maintained for 1-2 hours. This crystallization process is repeated 2-4 times.
[0027] A second aspect of the present invention provides a synthesis apparatus for the isosorbide synthesis method described herein, mainly comprising a preheater, a membrane reactor, a separator, and a crystallizer. The preheater is used to preheat the sorbitol aqueous solution and the solid catalyst to the required temperature and mix them. The membrane reactor is used to react the sorbitol aqueous solution and the solid acid catalyst under vacuum conditions. The product flows out from the bottom of the reactor. After the product is dissolved in an organic solvent, it enters the separator to separate the solid catalyst. The filtrate enters the crystallizer for cooling and crystallization to obtain the product isosorbide.
[0028] Compared with the prior art, the present invention has the following beneficial effects:
[0029] (1) The present invention uses a membrane reactor and combines it with a fluorine-modified solid catalyst for the synthesis reaction. While ensuring the yield, the water that is removed can be quickly removed from the reaction system, reducing the substrate residence time, avoiding the generation of by-products, and improving the yield of isosorbide.
[0030] (2) The fluorine-modified solid catalyst used in this invention is nanoscale, which makes it easy to separate from the product components and realize the recycling of the catalyst. On the other hand, it has good mixing effect with raw materials under the set reaction conditions and good mass and heat transfer effect, which not only makes the dehydration process efficient, but also reduces the generation of by-products by excessive dehydration condensation, avoids catalyst blockage, and extends the service life of the catalyst.
[0031] (3) The solid catalyst of the present invention may also include a small amount of sulfonic acid resin catalyst. Through the combined action of the two, the yield is higher. Detailed Implementation
[0032] The technical solution and its effects of the present invention will be described in detail below with reference to the embodiments. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.
[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.
[0034] This invention uses an Agilent 1260 liquid chromatograph with a BIO-RAD HPX-87H column for quantitative analysis of sorbitol and isosorbide.
[0035] Sorbitol conversion rate = mass of sorbitol after reaction / mass of initial sorbitol × 100%.
[0036] Isosorbide yield = (Isosorbide mass / Initial sorbitol mass) × 100%.
[0037] By-product yield = by-product mass / initial sorbitol mass × 100%.
[0038] Example 1
[0039] (1) Preparation of fluorine-modified solid catalyst: (a) 6g of microporous H-Beta molecular sieve (SiO2 / Al2O3 ratio of 40) was added to the reaction vessel, and 120mL of hydrofluoric acid solution (hydrofluoric acid mass content of 15%) was added. The reaction was carried out at 80℃ for 6h. The solid was obtained by centrifugation, washed multiple times until neutral, and dried at 100℃ for 12h to obtain the solid product; (b) SnF4 powder and solid product were mixed at a mass ratio of 1:10 and ball milled in a ball mill reactor under a nitrogen atmosphere at a speed of 40r / min for 6h. Then, the mixture was calcined at 550℃ for 8h to finally obtain the solid catalyst.
[0040] (2) Mix 100g of sorbitol aqueous solution (mass concentration of 70%) and 1.4g of fluorine-modified catalyst in a 90℃ preheater, and feed them from the top of the falling film reactor. The reaction is carried out at a temperature of 130℃ and a vacuum of 15kPa. The water generated by the reaction is recovered and condensed from the top of the reactor, and the product flows out from the bottom of the reactor.
[0041] (3) The product was dissolved in 700 mL of ethyl acetate at 70 °C. After filtering out the solid catalyst, the filtrate was cooled and crystallized at a rate of 10 °C / h. The temperature was lowered to 35 °C and maintained for 2 h. The temperature was then lowered to 0 °C and maintained for 1.5 h. This crystallization process was repeated 3 times to obtain the product isosorbide.
[0042] Example 2
[0043] (1) Preparation of fluorine-modified solid catalyst: (a) 6g of hierarchical H-Beta molecular sieve, of which the mesoporous content is 30% (SiO2 / Al2O3 is 40), was added to a reaction vessel, and 120mL of ammonium fluoride solution (ammonium fluoride mass content is 15%) was added. The reaction was carried out at 80℃ for 6h. The solid was obtained by centrifugation, washed multiple times until neutral, and dried at 100℃ for 12h to obtain the solid product; (b) SnF4 powder and solid product were mixed at a mass ratio of 1:10 and ball milled in a ball mill reactor under a nitrogen atmosphere at a speed of 40r / min for 6h. Then, the mixture was calcined at 550℃ for 8h to finally obtain the solid catalyst.
[0044] (2) Mix 100g of sorbitol aqueous solution (mass concentration of 60%) and 0.6g of fluorine-modified catalyst in an 80℃ preheater, and feed them from the top of the falling film reactor. The reaction is carried out at a temperature of 110℃ and a vacuum of 5kPa. The water generated by the reaction is recovered and condensed from the top of the reactor, and the product flows out from the bottom of the reactor.
[0045] (3) The product was dissolved in 300 mL of ethyl acetate at 60 °C. After filtering out the solid catalyst, the filtrate was cooled and crystallized at a rate of 5 °C / h. The temperature was lowered to 30 °C and maintained for 2 h. The temperature was then lowered to -5 °C and maintained for 1 h. This crystallization process was repeated twice to obtain the product isosorbide.
[0046] Example 3
[0047] (1) The preparation of the fluorine-modified solid catalyst is the same as in Example 1.
[0048] (2) Mix 100g of sorbitol aqueous solution (mass concentration of 80%) and 1.4g of fluorine-modified catalyst in a 100℃ preheater, and feed them from the top of the scraped film reactor. The reaction is carried out at a temperature of 150℃ and a vacuum of 30kPa. The water generated by the reaction is recovered and condensed from the top of the reactor, and the product flows out from the bottom of the reactor.
[0049] (3) The product was dissolved in 1200 mL of ethyl acetate at 80 °C. After filtering out the solid catalyst, the filtrate was cooled and crystallized at a rate of 15 °C / h. The temperature was lowered to 40 °C and maintained for 2 h. The temperature was then lowered to 5 °C and maintained for 2 h. This crystallization process was repeated twice to obtain the product isosorbide.
[0050] Example 4
[0051] Same as Example 1, except that ethylene glycol was used as the organic solvent in step (2). The final product isosorbide was obtained.
[0052] Example 5
[0053] Similar to Example 1, except that in step (1), the solid catalyst also includes Amberlyst 15 sulfonic acid resin catalyst (commercially available), which accounts for 0.2% of the total amount of solid acid catalyst. The final product is isosorbide is obtained.
[0054] Example 6
[0055] Similar to Example 3, except that in step (1), the solid catalyst also includes Amberlyst 15 sulfonic acid resin catalyst (commercially available), which accounts for 0.5% of the total amount of solid acid catalyst. The final product is isosorbide is obtained.
[0056] Comparative Example 1
[0057] Same as Example 1, except that: the solid catalyst used was the sulfonic acid resin catalyst Amberlyst 15. The final product obtained was isosorbide.
[0058] Comparative Example 2
[0059] Same as Example 1, except that the solid catalyst used is the solid prepared in step (1) and is not mixed with SnF4.
[0060] Comparative Example 3
[0061] Same as Example 1, except that a conventional batch reactor was used. The final product obtained was isosorbide.
[0062] Comparative Example 4
[0063] Same as Example 1, except that N,N-dimethylformamide was used as the organic solvent. The final product obtained was isosorbide.
[0064] Table 1. Test results of each embodiment and comparative example.
[0065]
Claims
1. A method for synthesizing isosorbide, characterized in that... The process includes the following: (1) Sorbitol aqueous solution and solid catalyst are mixed in a preheater and fed from the top of the membrane reactor. The reaction is carried out under vacuum and the product flows out from the bottom of the reactor; (2) The product is dissolved in an organic solvent and the solid catalyst is separated. The filtrate is cooled and crystallized to obtain the product isosorbide.
2. The method according to claim 1, characterized in that: The mass concentration of the sorbitol aqueous solution in step (1) is 60%-80%.
3. The method according to claim 1, characterized in that: The amount of solid catalyst used in step (1) is 1%-3% of the mass of sorbitol.
4. The method according to claim 1, characterized in that: The solid catalyst in step (1) is a nano-sized fluorine-modified solid catalyst, and the preparation of the fluorine-modified solid catalyst includes the following steps: (a) Mix beta molecular sieve with a fluoride ion solution, heat to 60-100℃ to react, separate the solid after reaction, wash and dry to obtain solid product; (b) Mix the solid product with SnF4 in proportion, ball mill under an inert atmosphere, and then calcine to obtain the catalyst.
5. The method according to claim 4, characterized in that: The beta molecular sieve mentioned in step (a) is an H-beta molecular sieve, and the silicon-to-aluminum ratio of the molecular sieve, calculated as SiO2 / Al2O3, is 20-80, preferably 20-40.
6. The method according to claim 4, characterized in that: The solute in the fluoride-containing solution mentioned in step (a) is at least one of hydrofluoric acid and ammonium fluoride, and the mass fraction of the solute in the solution is 5%-30%.
7. The method according to claim 4, 5 or 6, characterized in that: The solid-liquid ratio of the beta molecular sieve to the fluoride ion solution in step (a) is 1g:15-30mL.
8. The method according to claim 4, characterized in that: Step (a) Heat to 60-100℃, preferably 70-90℃, for reaction time of 4-8h.
9. The method according to claim 4, characterized in that: In step (b), SnF4 is mixed with the solid from step (1) at a mass ratio of 1:8-15; the inert atmosphere is any one of nitrogen, helium, or argon; the ball milling speed is 35-45 r / min, and the ball milling time is 6-10 h; the calcination temperature is 500-600℃, and the calcination time is 6-12 h.
10. The method according to claim 1, characterized in that: The solid catalyst also includes a sulfonic acid resin catalyst, more preferably a sulfonic acid ion exchange resin Amberlyst 15.
11. The method according to claim 10, characterized in that: The amount of sulfonic acid resin catalyst is 0.01%-1.0% of the total amount of solid catalyst, preferably 0.1%-0.5%.
12. The method according to claim 1, characterized in that: The preheating temperature in the preheater in step (1) is 80-100℃.
13. The method according to claim 1, characterized in that: The membrane reactor mentioned in step (1) is either a falling film reactor or a scraped film reactor.
14. The method according to claim 1, characterized in that: The vacuum degree in step (1) is 5-30 kPa, and the reaction temperature is 110-150 °C.
15. The method according to claim 1, characterized in that: The organic solvent mentioned in step (2) is at least one of ester organic solvents and polyol organic solvents, preferably at least one of ethyl acetate and ethylene glycol.
16. The method according to claim 1, characterized in that: The liquid-to-solid ratio of the organic solvent to sorbitol in step (2) is 5-15 mL: 1 g; the effluent product is dissolved in the organic solvent at a temperature of 60-80 °C.
17. The method according to claim 1, characterized in that: In step (2), a programmed cooling method is used during the crystallization process. The cooling rate is 5-15℃ / h, the intermediate temperature is maintained at 30-40℃ for 2-4h, and the final temperature of the crystallization process is -5-5℃ for 1-2h. This crystallization process is repeated 2-4 times.
18. A synthetic apparatus for the isosorbide synthesis method according to any one of claims 1-17, characterized in that: The main components include a preheater, a membrane reactor, a separator, and a crystallizer. The preheater is used to preheat the sorbitol aqueous solution and the solid catalyst to the required temperature and mix them. The membrane reactor is used to react the sorbitol aqueous solution and the solid acid catalyst under vacuum conditions. The product flows out from the bottom of the reactor. After the product is dissolved in an organic solvent, it enters the separator to separate the solid catalyst. The filtrate enters the crystallizer for cooling and crystallization to obtain the product isosorbitol.