Method for preparing isosorbide dimethyl ether based on continuous flow micro-reaction technical effect

Abstract

The invention relates to a method for preparing isosorbide dimethyl ether based on a continuous flow micro-reaction technical effect, and belongs to the technical field of organic synthesis. The method comprises the following steps: uniformly stirring and mixing isosorbide and methanol, feeding the mixture into a microreactor, filling sulfonic acid type ion exchange resin into the microreactor in the form of a fixed bed, and carrying out etherification reaction on isosorbide and methanol under the action of the sulfonic acid type ion exchange resin to generate isosorbide dimethyl ether; and refining the reacted mixed solution through a gas-liquid separator, reduced pressure distillation and silica gel column chromatography to obtain a high-purity isosorbide dimethyl ether product. The isosorbide sulfonic acid type ion exchange resin is prepared from styrene, divinyl benzene, isosorbide, 1-vinyl-1, 2, 4-triazole, water, benzoyl peroxide, polyvinyl alcohol and sulfuric acid; the method can be used for efficiently preparing a high-purity isosorbide dimethyl ether product, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis, and in particular to a method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology. Background Art

[0002] Isosorbide dimethyl ether, as an important organic compound, shows broad application prospects in multiple fields. In the cosmetics industry, due to its unique penetration performance, it can effectively promote the penetration of active ingredients through cell membranes and enhance the efficacy of products; in the chemical industry, it can be used as a green solvent to improve the performance of reaction systems.

[0003] Traditional methods for preparing isosorbide dimethyl ether have many drawbacks. For example, the patent with the authorization announcement number CN105646514B discloses a method for synthesizing 1,4:3,6-dianhydrohexitol methyl ether, using dimethoxymethane, 1,2-dimethoxyethane, etc. as methylation reagents, and synthesizing in a reaction kettle at a high temperature of 130 - 180°C. Not only are the reaction conditions harsh, but the cost of methylation reagents is relatively high.

[0004] The patent with the authorization announcement number CN101445508B discloses a method for synthesizing isosorbide dimethyl ether, using chloromethane and alkali, and adding a phase transfer catalyst to synthesize isosorbide dimethyl ether. This process requires subsequent acid neutralization and desalting treatment, with complex operations. At the same time, the use of chloromethane and alkali is neither environmentally friendly nor without certain safety risks.

[0005] As a key technology in the field of chemical process intensification, continuous flow microreaction technology has unique advantages. Compared with traditional reaction kettles, the microreactor has a tiny channel structure inside, where reactants can achieve rapid mixing and efficient heat and mass transfer. This enables the reaction to proceed under milder conditions, significantly improving the reaction efficiency, reducing the occurrence of side reactions, while reducing energy consumption and raw material waste, which is in line with the current development trend of green chemistry. Therefore, applying continuous flow microreaction technology to the preparation of isosorbide dimethyl ether is expected to overcome the deficiencies of traditional methods and open up an efficient and green synthesis route. Summary of the Invention

[0006] To solve the above problems, the present invention provides a method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, including the following steps: S1 Reaction process: Mix 10 - 20 parts of isosorbide and 16 - 32 parts of methanol evenly to form a mixed raw material liquid, and send it to a microreactor. At the same time, pack 5 - 10 parts of isosorbide sulfonic acid type ion exchange resin in the form of a fixed bed inside the microreactor; isosorbide and methanol undergo an etherification reaction under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction ends, filter out the isosorbide sulfonic acid type ion exchange resin to produce isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters a gas - liquid separator for preliminary separation at normal temperature and pressure, separating unreacted methanol vapor and a small amount of by - product gas; Transfer the liquid product obtained at the bottom of the gas - liquid separator to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high - boiling impurities, and collect the fraction at 92 - 95 °C to obtain crude isosorbide dimethyl ether; S3 Product purification: Purify the crude isosorbide dimethyl ether by silica gel column chromatography using n - hexane and ethyl acetate as eluents to remove residual impurities and obtain a high - purity isosorbide dimethyl ether product.

[0007] The described microreactor uses a continuous - flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 - 2 mm, and the length is 10 - 50 cm; this kind of microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0008] The reaction temperature in S1 is 80 - 120 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 - 2 MPa, which is controlled by a back - pressure valve to ensure that the reaction proceeds smoothly under liquid - phase conditions.

[0009] The vacuum degree of the described vacuum distillation is - 0.09~ - 0.095 Mpa, and the distillation temperature is 90 - 110 °C.

[0010] The volume ratio of n - hexane to ethyl acetate in the described eluent is (5:1) - (10:1).

[0011] The preparation method of the described isosorbide sulfonic acid type ion exchange resin is as follows: By mass parts, 100 - 120 parts of styrene, 10 - 20 parts of divinylbenzene, 1 - 4 parts of isosorbide, 0.05 - 0.2 parts of 1 - vinyl - 1,2,4 - triazole, 1000 - 1500 parts of water, 2 - 4 parts of benzoyl peroxide, and 1 - 3 parts of polyvinyl alcohol are added to a polymerization kettle. The reaction temperature is controlled at 80 - 90 °C, and the reaction is carried out in the dark for 120 - 200 min. After filtration and drying, it is added to 1000 - 1500 parts of sulfuric acid with a mass percentage concentration of 95 - 98%, and the reaction is carried out at 80 - 90 °C for 10 - 20 h. After filtration, washing with water, and drying, isosorbide sulfonic acid - type ion - exchange resin is obtained.

[0012] Reaction mechanism: Acid - catalyzed nucleophilic substitution: The sulfonic acid group of isosorbide sulfonic acid - type ion - exchange resin releases a proton, protonating the hydroxyl group of isosorbide to form a hydronium ion. Methanol, as a nucleophile, attacks the protonated carbon atom, and after dehydration, an ether bond is formed to complete the nucleophilic substitution reaction. Step - by - step reaction and catalytic cycle: The reaction is carried out in two steps. First, an isosorbide monomethyl ether intermediate is formed, and then isosorbide dimethyl ether is obtained by secondary etherification. The catalyst hydrogen ion participates in the reaction and is released cyclically to maintain catalytic activity.

[0013] The role of triazole and isosorbide: 1 - vinyl - 1,2,4 - triazole participates in the resin polymerization, enhancing stability and optimizing the electron cloud distribution, and improving the catalytic activity of the sulfonic acid group; isosorbide introduces a similar structure, enhancing the adsorption force of the resin for reactants and improving the reaction selectivity. The method for preparing isosorbide dimethyl ether based on continuous - flow micro - reaction technology of the present invention has the following remarkable effects: 1. Micro - reaction high efficiency: The micro - channel structure of the micro - reactor increases the specific surface area, strengthens mass and heat transfer; the continuous - flow mode precisely controls the materials, reduces side reactions, and significantly improves the reaction rate and product yield. 2. Green and safe process: The fixed - bed resin can be filtered and recycled, reducing costs and pollution; the micro - reaction system is small, heat is easily dissipated, the pressure is controllable, avoiding thermal runaway; methanol can be recycled, meeting the concept of green chemistry. Specific embodiments

[0014] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following is a detailed description in combination with examples and comparative examples: Example 1: The method for preparing isosorbide dimethyl ether based on continuous - flow micro - reaction technology includes the following steps: S1 Reaction process: 10 g of isosorbide and 16 g of methanol were stirred and mixed evenly to form a mixed raw material liquid, which was sent to a microreactor. At the same time, 5 g of isosorbide sulfonic acid type ion exchange resin was loaded inside the microreactor in the form of a fixed bed to ensure sufficient contact between the raw materials and the catalyst. The etherification reaction occurred between isosorbide and methanol under the action of isosorbide sulfonic acid type ion exchange resin. After the reaction ended, the isosorbide sulfonic acid type ion exchange resin was removed by filtration to produce isosorbide dimethyl ether. S2 Product separation: After the reaction mixture flowed out of the microreactor, it first entered a gas-liquid separator for preliminary separation under normal temperature and pressure, separating unreacted methanol vapor and a small amount of by-product gas. The liquid product obtained at the bottom of the gas-liquid separator was transferred to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities. The fraction at 92 °C was collected to obtain crude isosorbide dimethyl ether. S3 Product purification: The crude isosorbide dimethyl ether was refined by silica gel column chromatography using n-hexane and ethyl acetate as eluents to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0015] The microreactor used is a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 mm and the length is 10 cm. This microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0016] The reaction temperature in S1 is 80 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0017] The vacuum degree of the vacuum distillation is -0.09 Mpa, and the distillation temperature is 90 °C.

[0018] The volume ratio of n-hexane to ethyl acetate in the eluent is 5:1.

[0019] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: 100 g of styrene, 10 g of divinylbenzene, 1 g of isosorbide, 0.05 g of 1-vinyl-1,2,4-triazole, 1000 g of water, 2 g of benzoyl peroxide, and 1 g of polyvinyl alcohol were added to a polymerization kettle. The reaction temperature was controlled at 80 °C, and the reaction was carried out for 120 min in the dark. After filtration and drying, it was added to 1000 g of sulfuric acid with a mass percentage concentration of 95%. The reaction was carried out at 80 °C for 10 h, followed by filtration, washing with water, and drying to obtain isosorbide sulfonic acid type ion exchange resin.

[0020] Example 2: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, comprising the following steps: S1 Reaction process: 13 g of isosorbide and 20 g of methanol are stirred and mixed evenly to form a mixed raw material liquid, which is sent to a microreactor. At the same time, 6 g of isosorbide sulfonic acid type ion exchange resin is packed inside the microreactor in the form of a fixed bed to ensure sufficient contact between the raw materials and the catalyst; isosorbide and methanol undergo an etherification reaction under the action of isosorbide sulfonic acid type ion exchange resin. After the reaction, the isosorbide sulfonic acid type ion exchange resin is removed by filtration to produce isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters a gas-liquid separator for preliminary separation under normal temperature and pressure to separate unreacted methanol vapor and a small amount of by-product gas; The liquid product obtained at the bottom of the gas-liquid separator is transferred to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities, and the fraction at 93 °C is collected to obtain crude isosorbide dimethyl ether; S3 Product purification: The crude isosorbide dimethyl ether is refined by silica gel column chromatography using n-hexane and ethyl acetate as eluents to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0021] The microreactor used is a continuous flow microreactor with a regular microchannel structure, the inner diameter of the microchannel is 1 mm, and the length is 20 cm; this microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0022] The reaction temperature of S1 is 90 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 1 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0023] The vacuum degree of the vacuum distillation is -0.09 Mpa, and the distillation temperature is 95 °C.

[0024] The volume ratio of n-hexane to ethyl acetate in the eluent is 6:1.

[0025] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: 105 g of styrene, 13 g of divinylbenzene, 2 g of isosorbide, 0.1 g of 1-vinyl-1,2,4-triazole, 1100 g of water, 3 g of benzoyl peroxide, and 2 g of polyvinyl alcohol were added to a polymerization kettle. The reaction temperature was controlled at 85 °C, and the reaction was carried out in the dark for 140 min. After filtration and drying, the product was added to 1100 g of sulfuric acid with a mass percentage concentration of 96%. The reaction was carried out at 85 °C for 14 h, followed by filtration, washing with water, and drying to obtain isosorbide sulfonic acid type ion exchange resin.

[0026] Example 3: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, comprising the following steps: S1 Reaction process: 18 g of isosorbide and 28 g of methanol were stirred and mixed evenly to form a mixed raw material liquid, which was sent to a microreactor. At the same time, 8 g of isosorbide sulfonic acid type ion exchange resin was packed in the microreactor in the form of a fixed bed to ensure sufficient contact between the raw materials and the catalyst. The etherification reaction occurred between isosorbide and methanol under the action of isosorbide sulfonic acid type ion exchange resin. After the reaction ended, the isosorbide sulfonic acid type ion exchange resin was removed by filtration to generate isosorbide dimethyl ether. S2 Product separation: After the reaction mixture flowed out of the microreactor, it first entered a gas-liquid separator for preliminary separation under normal temperature and pressure to separate unreacted methanol vapor and a small amount of by-product gas. The liquid product obtained at the bottom of the gas-liquid separator was transferred to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities. The fraction at 94 °C was collected to obtain crude isosorbide dimethyl ether. S3 Product purification: The crude isosorbide dimethyl ether was refined by silica gel column chromatography using n-hexane and ethyl acetate as eluents to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0027] The microreactor used was a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel was 1.5 mm and the length was 40 cm. This microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0028] The reaction temperature in S1 was 110 °C, and the temperature of the microreactor was precisely controlled by an external circulation heating system. The reaction pressure was 1.5 MPa, which was controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0029] The vacuum degree of the vacuum distillation was -0.095 Mpa, and the distillation temperature was 105 °C.

[0030] The volume ratio of n-hexane to ethyl acetate in the eluent was 8:1.

[0031] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: Add 115 g of styrene, 18 g of divinylbenzene, 3 g of isosorbide, 0.15 g of 1-vinyl-1,2,4-triazole, 1400 g of water, 3 g of benzoyl peroxide, and 2 g of polyvinyl alcohol into a polymerization kettle. Control the reaction temperature at 85 °C, and react for 180 min in the dark. After filtration and drying, add it to 1400 g of sulfuric acid with a mass percentage concentration of 97%. React at 85 °C for 18 h, filter, wash with water, and dry to obtain the isosorbide sulfonic acid type ion exchange resin.

[0032] Example 4: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, comprising the following steps: S1 Reaction process: Stir and mix 20 g of isosorbide and 32 g of methanol evenly to form a mixed raw material liquid, and send it to a microreactor. At the same time, pack 10 g of isosorbide sulfonic acid type ion exchange resin in the form of a fixed bed inside the microreactor to ensure full contact between the raw materials and the catalyst; isosorbide and methanol undergo an etherification reaction under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction ends, filter out the isosorbide sulfonic acid type ion exchange resin to generate isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters a gas-liquid separator for preliminary separation at normal temperature and pressure to separate unreacted methanol vapor and a small amount of by-product gas; Transfer the liquid product obtained at the bottom of the gas-liquid separator to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities, and collect the fraction at 95 °C to obtain crude isosorbide dimethyl ether; S3 Product purification: Purify the crude isosorbide dimethyl ether by silica gel column chromatography using n-hexane and ethyl acetate as eluents to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0033] The microreactor used is a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 2 mm and the length is 50 cm; this microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0034] The reaction temperature of S1 is 120 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 2 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0035] The vacuum degree of the vacuum distillation is -0.095 Mpa, and the distillation temperature is 110 °C.

[0036] The volume ratio of n-hexane to ethyl acetate in the eluent is 10:1.

[0037] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: 120 g of styrene, 20 g of divinylbenzene, 4 g of isosorbide, 0.2 g of 1-vinyl-1,2,4-triazole, 1500 g of water, 4 g of benzoyl peroxide, and 3 g of polyvinyl alcohol are added to a polymerization kettle. The reaction temperature is controlled at 90 °C, and the reaction is carried out in the dark for 200 min. After filtration and drying, it is added to 1500 g of sulfuric acid with a mass percentage concentration of 98%. The reaction is carried out at 90 °C for 20 h, followed by filtration, washing with water, and drying to obtain the isosorbide sulfonic acid type ion exchange resin.

[0038] Comparative Example 1: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, comprising the following steps: S1 Reaction process: 10 g of isosorbide and 16 g of methanol are stirred and mixed evenly to form a mixed raw material liquid, which is sent to a microreactor. At the same time, 5 g of isosorbide sulfonic acid type ion exchange resin is loaded inside the microreactor in the form of a fixed bed to ensure sufficient contact between the raw materials and the catalyst; the etherification reaction occurs between isosorbide and methanol under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction is completed, the isosorbide sulfonic acid type ion exchange resin is removed by filtration to produce isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters a gas-liquid separator for preliminary separation under normal temperature and pressure, separating unreacted methanol vapor and a small amount of by-product gas; The liquid product obtained at the bottom of the gas-liquid separator is transferred to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities. The fraction at 92 °C is collected to obtain crude isosorbide dimethyl ether; S3 Product purification: The crude isosorbide dimethyl ether is refined by silica gel column chromatography using n-hexane and ethyl acetate as the eluent to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0039] The microreactor used is a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 mm and the length is 10 cm; this microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0040] The reaction temperature in S1 is 80 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0041] The vacuum degree of the reduced-pressure distillation is -0.09 Mpa, and the distillation temperature is 90 °C.

[0042] The volume ratio of n-hexane to ethyl acetate in the eluent is 5:1.

[0043] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: Add 100 g of styrene, 1 g of isosorbide, 1000 g of water, 2 g of benzoyl peroxide, and 1 g of polyvinyl alcohol into the polymerization kettle. Control the reaction temperature at 80 °C and react under light protection for 120 min. After filtration and drying, add it to 1000 g of sulfuric acid with a mass percentage concentration of 95%. React at 80 °C for 10 h, filter, wash with water, and dry to obtain the isosorbide sulfonic acid type ion exchange resin.

[0044] Comparative Example 2: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, including the following steps: S1 Reaction process: Stir and mix 10 g of isosorbide and 16 g of methanol evenly to form a mixed raw material liquid, and send it to the microreactor. At the same time, load 5 g of isosorbide sulfonic acid type ion exchange resin in the form of a fixed bed inside the microreactor to ensure full contact between the raw materials and the catalyst; isosorbide and methanol undergo an etherification reaction under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction ends, filter out the isosorbide sulfonic acid type ion exchange resin to generate isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters the gas-liquid separator for preliminary separation under normal temperature and pressure, separating unreacted methanol vapor and a small amount of by-product gas; Transfer the liquid product obtained at the bottom of the gas-liquid separator to a reduced-pressure distillation device for reduced-pressure distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities, and collect the fraction at 92 °C to obtain crude isosorbide dimethyl ether; S3 Product purification: Purify the crude isosorbide dimethyl ether by silica gel column chromatography, using n-hexane and ethyl acetate as the eluent to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0045] The microreactor used is a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 mm and the length is 10 cm; this kind of microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0046] The reaction temperature of S1 is 80°C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0047] The vacuum degree of the reduced pressure distillation is -0.09 Mpa, and the distillation temperature is 90°C.

[0048] The volume ratio of n-hexane to ethyl acetate in the eluent is 5:1.

[0049] The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: 100 g of styrene, 1 g of isosorbide, 0.05 g of 1-vinyl-1,2,4-triazole, 1000 g of water, 2 g of benzoyl peroxide, and 1 g of polyvinyl alcohol are added to a polymerization kettle. The reaction temperature is controlled at 80°C, and the reaction is carried out under light avoidance for 120 min. After filtration and drying, it is added to 1000 g of sulfuric acid with a mass percentage concentration of 95%. The reaction is carried out at 80°C for 10 h, followed by filtration, washing with water, and drying to obtain the isosorbide sulfonic acid type ion exchange resin.

[0050] Comparative Example 3: A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, comprising the following steps: S1 reaction process: 10 g of isosorbide and 16 g of methanol are stirred and mixed evenly to form a mixed raw material liquid, which is sent to a microreactor. At the same time, 5 g of isosorbide sulfonic acid type ion exchange resin is loaded into the microreactor in the form of a fixed bed to ensure full contact between the raw materials and the catalyst; the etherification reaction occurs between isosorbide and methanol under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction, the isosorbide sulfonic acid type ion exchange resin is filtered off to produce isosorbide dimethyl ether. S2 product separation: After the reaction mixture flows out of the microreactor, it first enters a gas-liquid separator for preliminary separation at normal temperature and pressure, separating unreacted methanol vapor and a small amount of by-product gas. The liquid product obtained at the bottom of the gas-liquid separator is transferred to a reduced pressure distillation device for reduced pressure distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high-boiling impurities. The fraction at 92°C is collected to obtain crude isosorbide dimethyl ether. S3 product purification: The crude isosorbide dimethyl ether is refined by silica gel column chromatography using n-hexane and ethyl acetate as eluents to remove residual impurities and obtain a high-purity isosorbide dimethyl ether product.

[0051] The described microreactor uses a continuous flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 mm and the length is 10 cm. Such a microreactor can provide a large specific surface area and strengthen the mass transfer and heat transfer processes between reactants.

[0052] The reaction temperature of S1 is 80 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 MPa, which is controlled by a back pressure valve to ensure the smooth progress of the reaction under liquid phase conditions.

[0053] The vacuum degree of the described vacuum distillation is -0.09 Mpa, and the distillation temperature is 90 °C.

[0054] The volume ratio of n-hexane to ethyl acetate in the described eluent is 5:1.

[0055] The preparation method of the described isosorbitol sulfonic acid type ion exchange resin is as follows: 100 g of styrene, 10 g of divinylbenzene, 1 g of isosorbitol, 1000 g of water, 2 g of benzoyl peroxide, and 1 g of polyvinyl alcohol are added to a polymerization kettle. The reaction temperature is controlled at 80 °C, and the reaction is carried out in the dark for 120 min. After filtration and drying, it is added to 1000 g of sulfuric acid with a mass percentage concentration of 95%. The reaction is carried out at 80 °C for 10 h, followed by filtration, washing with water, and drying to obtain the isosorbitol sulfonic acid type ion exchange resin.

[0056] Purity test of isosorbitol dimethyl ether: It is determined by gas chromatography. The test results are shown in Table 1: Table 1: Detection results of each example and comparative example

[0057] Through the data analysis of the above examples and comparative examples, the present invention can efficiently prepare high-purity isosorbitol dimethyl ether products, having good application prospects.

[0058] The above is only a preferred embodiment of the present invention, and it does not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology, characterized in that: It includes the following steps: S1 Reaction process: Mix 10 - 20 parts of isosorbide and 16 - 32 parts of methanol evenly to form a mixed raw material liquid, and send it to a microreactor. At the same time, pack 5 - 10 parts of isosorbide sulfonic acid type ion exchange resin in the form of a fixed bed inside the microreactor; isosorbide and methanol undergo an etherification reaction under the action of the isosorbide sulfonic acid type ion exchange resin. After the reaction ends, filter out the isosorbide sulfonic acid type ion exchange resin to produce isosorbide dimethyl ether; S2 Product separation: After the reaction mixture flows out of the microreactor, it first enters a gas - liquid separator for preliminary separation under normal temperature and pressure, separating unreacted methanol vapor and a small amount of by - product gas; Transfer the liquid product obtained at the bottom of the gas - liquid separator to a vacuum distillation device for vacuum distillation to separate isosorbide dimethyl ether from unreacted isosorbide and other high - boiling impurities, and collect the fraction at 92 - 95 °C to obtain crude isosorbide dimethyl ether; S3 Product purification: Refine the crude isosorbide dimethyl ether by silica gel column chromatography using n - hexane and ethyl acetate as eluents to remove residual impurities and obtain isosorbide dimethyl ether product; The isosorbide sulfonic acid type ion exchange resin is prepared by reacting styrene, divinylbenzene, isosorbide, 1 - vinyl - 1,2,4 - triazole, water, benzoyl peroxide, and polyvinyl alcohol.

2. The method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology according to claim 1, wherein: The microreactor uses a continuous - flow microreactor with a regular microchannel structure. The inner diameter of the microchannel is 0.5 - 2 mm and the length is 10 - 50 cm.

3. The method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology according to claim 1, characterized in that: The reaction temperature of S1 is 80 - 120 °C, and the temperature of the microreactor is precisely controlled by an external circulation heating system; the reaction pressure is 0.5 - 2 MPa, which is controlled by a back - pressure valve to ensure the smooth progress of the reaction under liquid - phase conditions.

4. The method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology according to claim 1, wherein: The vacuum degree of the vacuum distillation is - 0.09~ - 0.095 Mpa, and the distillation temperature is 90 - 110 °C.

5. The method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology according to claim 1, characterized in that: The volume ratio of n - hexane to ethyl acetate in the eluent is (5:1) - (10:1).

6. The method for preparing isosorbide dimethyl ether based on continuous flow microreaction technology according to claim 1, characterized in that: The preparation method of the isosorbide sulfonic acid type ion exchange resin is as follows: By mass, add 100 - 120 parts of styrene, 10 - 20 parts of divinylbenzene, 1 - 4 parts of isosorbide, 0.05 - 0.2 parts of 1 - vinyl - 1,2,4 - triazole, 1000 - 1500 parts of water, 2 - 4 parts of benzoyl peroxide, and 1 - 3 parts of polyvinyl alcohol into a polymerization kettle. Control the reaction temperature at 80 - 90 °C, react under light - proof conditions for 120 - 200 min, filter, dry, and then add it to 1000 - 1500 parts of sulfuric acid with a mass percentage concentration of 95 - 98%. React at 80 - 90 °C for 10 - 20 h, filter, wash with water, and dry to obtain the isosorbide sulfonic acid type ion exchange resin.

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