A solid acid resin catalyst, its preparation method and application

Abstract

This application relates to the field of diisopropyl maleate synthesis technology and discloses a solid acid resin catalyst. The raw materials include styrene, divinylbenzene, and a fluorinated acrylate monomer. The mass fraction of the fluorinated acrylate monomer is 0.5 wt%–5 wt% based on the mass of styrene. This application, by introducing the fluorinated acrylate monomer, utilizes the strong electronegativity of the fluorine atoms and the high bond energy of the C-F bonds in the fluorinated acrylate monomer to enhance the hydrophobicity and stability of the polymer backbone, and protects the stability of the subsequently introduced sulfonic acid groups in high-temperature environments.

Description

Technical Field

[0001] This application relates to the field of diisopropyl maleate synthesis technology, specifically to a solid acid resin catalyst, its preparation method, and its application. Background Technology

[0002] Diisopropyl maleate, as an important organic intermediate and chemical product, is widely used in plasticizers, lubricant additives, polycarboxylate superplasticizer monomers, and as an internal electron donor in olefin polymerization catalysts. The traditional industrial production of dimaleate typically uses concentrated sulfuric acid as a homogeneous catalyst. While this method offers high catalytic activity and low cost, it suffers from several insurmountable drawbacks. For example, the strong acid severely corrodes reaction equipment; side reactions such as dehydration and isomerization easily occur during the reaction, leading to decreased selectivity; and the reaction requires cumbersome neutralization and washing steps to remove the catalyst, generating large amounts of acidic wastewater and putting pressure on the environment.

[0003] To overcome the shortcomings of homogeneous acid catalysts, various heterogeneous catalytic pathways have been developed. Among them, ionic liquid catalysts (such as binuclear functionalized ionic liquids) have attracted attention due to their strong designability and high catalytic activity. However, ionic liquids have problems such as complex synthesis steps, high cost, potential decomposition and deactivation at high temperatures, and the need for specific steps (such as static separation) to separate them from products, which limit their large-scale industrial application.

[0004] Solid acid resin catalysts, especially sulfonic acid cation exchange resins, are considered promising alternatives to liquid acids due to their ease of separation from the reaction system, recyclability, and environmental friendliness. However, the esterification of maleic anhydride typically requires high temperatures (e.g., above 100°C) to achieve satisfactory reaction rates. When conventional styrene-divinylbenzene sulfonic acid resins are used for maleic anhydride esterification, the sulfonic acid groups in the resin backbone are prone to detachment at sustained high temperatures (especially in polar alcohol solvent environments), leading to the loss of catalyst active sites, shortened lifespan, and potential discoloration of the product due to sulfur impurities. Summary of the Invention

[0005] This application provides a solid acid resin catalyst, its preparation method, and its application, to solve the problem that the sulfonic acid groups in the solid acid resin catalysts provided by the prior art are easily detached at continuous high temperatures, resulting in easy deactivation of the catalyst and short service life.

[0006] In one aspect, this application provides a solid acid resin catalyst, the raw materials of which include styrene, divinylbenzene, and fluorinated acrylate monomer.

[0007] In one alternative embodiment, the fluorinated acrylate monomer has a mass fraction of 0.5wt%-5wt% and the divinylbenzene has a mass fraction of 5wt%-30wt% based on the mass of styrene.

[0008] In one optional embodiment, the fluorinated acrylate monomer includes at least one of hexafluorobutyl acrylate, trifluoroethyl methacrylate, and dodecafluoroheptyl methacrylate.

[0009] In one alternative embodiment, the mass fraction of the fluorinated acrylate monomer is 1wt%-3wt% based on the mass of styrene.

[0010] Secondly, this application also provides a method for preparing a solid acid resin catalyst, comprising the following steps: sequentially polymerizing and sulfonating styrene, divinylbenzene and fluorinated acrylate monomers.

[0011] In one optional embodiment, a chlorination reaction is included after the polymerization reaction and before the sulfonation reaction. The chlorination reaction is carried out at a temperature of 10°C-25°C, and the chlorine content of the chlorinated product after the chlorination reaction is 15wt%-25wt%.

[0012] In one optional embodiment, the specific steps of the polymerization reaction include: in an inert atmosphere and in the presence of an initiator, initiating a reaction of styrene, divinylbenzene, and fluorinated acrylate monomers at a first temperature, reacting at a second temperature for a second time, and then performing a curing reaction. The first temperature is 75°C-85°C, and the initiation reaction time is 6-10 hours; the second temperature is 85°C-100°C, and the second time is 2-4 hours; the curing reaction temperature is 90°C-100°C, and the curing reaction time is 2-6 hours.

[0013] In one optional embodiment, the specific steps of the sulfonation reaction include reacting the product after polymerization or chlorination with 85wt%-98wt% concentrated sulfuric acid at 30℃-60℃ for 6h-10h.

[0014] In order to facilitate the control of sulfur content in resin catalysts, the determination of sulfonation temperature and sulfuric acid concentration is very important, especially the use of 98% concentrated sulfuric acid, which has carbonization ability and provides better control.

[0015] In one alternative embodiment, the sulfur content of the resin catalyst after sulfonation is controlled at 5wt%-12wt%.

[0016] In one alternative embodiment, the specific steps for determining the sulfur content of the resin catalyst during the sulfonation reaction include: fixing the sulfuric acid concentration (e.g., 98%), the amount (acid to resin ratio), and a relatively low temperature (typically, low temperature reduces side reactions) according to the target sulfur content; taking samples at regular intervals during the reaction to rapidly determine the degree of sulfonation (e.g., titrating the acid amount); and plotting a "reaction time-sulfur content" curve. The reaction is immediately terminated when the sulfur content reaches the target value; in this application, the reaction is terminated by cooling or rapid dilution with water.

[0017] In one alternative embodiment, the initiator includes at least one of benzoyl peroxide or azobisisobutyronitrile.

[0018] In an optional embodiment, the polymerization reaction further includes a porogen. The porogen includes at least one of liquid paraffin, dextrin powder, and dioctyl phthalate.

[0019] In one alternative embodiment, after the polymerization reaction, the degree of crosslinking of the polymer product is 15%-30%, preferably 18%-25%. The degree of crosslinking of the polymer product is controlled by the amount of divinylbenzene used.

[0020] In one alternative embodiment, the porogen has a mass fraction of 15wt%-25wt% based on the mass of styrene, and the initiator has a mass fraction of 0.2wt%-1wt%.

[0021] In one optional embodiment, the concentration of concentrated sulfuric acid in the sulfonation reaction is 90wt%-95wt%. In one alternative embodiment, the sulfonation reaction is carried out at a temperature of 40°C-50°C.

[0022] Thirdly, the above-mentioned solid acid resin catalyst or a method for preparing a solid acid resin catalyst can synthesize diisopropyl maleate. The method for synthesizing diisopropyl maleate includes the following steps: esterifying maleic anhydride and isopropanol in the presence of the solid acid resin catalyst.

[0023] In one optional embodiment, the solid acid resin catalyst has a mass fraction of 5wt%-15wt% based on the mass of maleic anhydride, preferably 8wt%-12wt%.

[0024] In one optional embodiment, the molar ratio of maleic anhydride to isopropanol is 1:3-8, preferably 1:4-6.

[0025] In one optional embodiment, the specific steps of the esterification reaction include refluxing the solid acid resin catalyst, maleic anhydride, and isopropanol at 80°C-130°C for 4-10 hours under stirring conditions.

[0026] In one optional embodiment, after the esterification reaction is completed, solid-liquid separation is performed to obtain a solid acid resin catalyst and a reaction solution. The separated solid acid resin catalyst is reused, and the reaction solution is distilled under normal pressure to recover isopropanol, and then distilled under reduced pressure to obtain diisopropyl maleate.

[0027] In one alternative embodiment, the esterification reaction is carried out in a solvent environment, the solvent including at least one of cyclohexane, methyl isobutyl ketone, or benzene.

[0028] In one optional embodiment, the esterification reaction temperature is 100°C-120°C.

[0029] In one alternative implementation, the condensation reflux time is 5-7 hours.

[0030] In one alternative implementation, the solid-liquid separation step includes at least one of filtration or sedimentation.

[0031] In one optional embodiment, after the synthesis reaction, the solid acid resin catalyst obtained after solid-liquid separation is washed and dried with a solvent, the solvent including isopropanol, and then reused.

[0032] The technical solution of this application has the following advantages: 1. This application provides a solid acid resin catalyst, the raw materials of which include styrene, divinylbenzene, and fluorinated acrylate monomers. This application introduces fluorinated acrylate monomers, utilizing the strong electronegativity of fluorine atoms and the high bond energy of CF bonds in the fluorinated acrylate monomers to enhance the hydrophobicity and stability of the polymer skeleton, protect the stability of subsequently introduced sulfonic acid groups in high-temperature environments, and improve the catalyst's lifespan.

[0033] 2. This application provides a solid acid resin catalyst in which the mass fraction of divinylbenzene, based on the mass of styrene, is 5wt%-30wt%. This application controls the degree of crosslinking by controlling the amount of divinylbenzene, thereby ensuring the mechanical strength of the final solid acid resin catalyst.

[0034] 3. This application provides a method for preparing a solid acid resin catalyst, comprising the following steps: sequentially polymerizing styrene, divinylbenzene, and fluorinated acrylate monomers, followed by sulfonation. This application introduces fluorine atoms into the polymer formed from styrene and divinylbenzene through polymerization. Utilizing the strong electronegativity and high CF bond energy of fluorine atoms, the stability of the polymer structure is enhanced. Then, sulfonation introduces sulfonic acid groups. The resulting solid acid resin catalyst exhibits good stability and high activity in sustained high-temperature environments, while also extending its service life.

[0035] 4. This application provides a method for preparing a solid acid resin catalyst, wherein the sulfur content of the resin catalyst after sulfonation is controlled at 5wt%-12wt%. Unlike traditional sulfonated resins that pursue high exchange capacity, this application adopts a "shallow sulfonation" strategy, introducing an appropriate amount of sulfonic acid groups as active centers on the surface of resin particles and the inner wall of pores. This ensures sufficient catalytic activity while avoiding excessive sulfonation that leads to increased skeletal swelling and decreased thermal stability of the groups, thus achieving the optimal balance between activity and stability under high-temperature reaction conditions.

[0036] 5. The application of the solid acid resin catalyst and the method for preparing the solid acid resin catalyst provided in this application in the synthesis of diisopropyl maleate. The solid acid resin catalyst provided in this application can improve the conversion rate of maleic anhydride and the selectivity of diisopropyl maleate, thereby increasing the yield. Due to the good stability of the catalyst itself and the few side reactions during the reaction process, the product does not contain sulfur impurities introduced by the catalyst. The resulting diisopropyl maleate product has a light color and high purity, and can be directly used in fields with high purity requirements.

[0037] 6. This application discloses a solid acid resin catalyst and its preparation method. The solid acid resin catalyst obtained is used in the synthesis of diisopropyl maleate. After the esterification reaction, solid-liquid separation is performed to obtain the solid acid resin catalyst and the reaction solution. The separated solid acid resin catalyst is then reused. The solid acid resin catalyst provided in this application is a solid particle catalyst. After the reaction, the catalyst and product can be separated through simple solid-liquid separation, avoiding the cumbersome post-processing steps and wastewater discharge problems in homogeneous acid catalysis processes. The separated catalyst can be recycled multiple times, exhibits slow activity decay, has a long service life, and significantly reduces production costs and environmental pollution. Detailed Implementation

[0038] The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0039] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0040] Preparation Example 1 This preparation example provides a method for preparing a solid acid resin catalyst, the specific preparation method and operating parameters of which are as follows: (1) In a reactor equipped with a stirrer, condenser and thermometer, add 100g styrene, 10g divinylbenzene (crosslinking degree about 15%), 1g hexafluorobutyl acrylate, 20g liquid paraffin and 0.5g azobisisobutyronitrile. Under a nitrogen atmosphere, heat the above materials in a water bath to 80°C and react for 6 hours, then heat to 85°C and react for 2 hours, and finally heat to 95°C and mature for 6 hours. During the reaction, stir continuously at 150 rpm.

[0041] After the reaction was completed, the polymer white spheres were filtered out, and the liquid paraffin was removed by extraction with petroleum ether and then vacuum dried.

[0042] (2) Place the dried polymer white balls obtained in step (1) into a photochlorination reactor, introduce chlorine gas under light-proof conditions, control the reaction temperature at 15°C, take intermittent samples to detect the chlorine content, stop the gas supply when the chlorine content reaches 20%, purge the residual chlorine gas with nitrogen gas to obtain chloromethylated resin.

[0043] (3) Add the chloromethylated resin to an excess of 92wt% concentrated sulfuric acid and react at 40℃ for 8 hours. After the reaction is complete, slowly pour the mixture into ice water to dilute it, filter to obtain the resin, and wash repeatedly with deionized water until the effluent is neutral.

[0044] Finally, the catalyst was vacuum dried at 60°C for 12 hours to obtain a light yellow granular solid acid resin catalyst.

[0045] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.5% according to elemental analysis.

[0046] Preparation Example 2 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1. The difference is that the amount of divinylbenzene added in step (1) is 20g (the degree of crosslinking is about 30%).

[0047] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.2% according to elemental analysis.

[0048] Preparation Example 3 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1, except that the amount of hexafluorobutyl acrylate used in step (1) is 0.5g.

[0049] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.7% according to elemental analysis.

[0050] Preparation Example 4 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1, except that the amount of hexafluorobutyl acrylate used in step (1) is 2g. Elemental analysis of the solid acid resin catalyst prepared in this example shows that its sulfur content is 8.4%.

[0051] Preparation Example 5 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1, except that the amount of hexafluorobutyl acrylate used in step (1) is 5g.

[0052] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.3% according to elemental analysis.

[0053] Preparation Example 6 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1. The difference is that the concentration of concentrated sulfuric acid in step (3) is 87 wt%. After vacuum drying at 60°C for 12 hours, a light yellow granular solid acid resin catalyst is obtained.

[0054] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 5% according to elemental analysis.

[0055] Preparation Example 7 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1. The difference is that the concentration of concentrated sulfuric acid in step (3) is 95 wt%. After vacuum drying at 60°C for 12 hours, a light yellow granular solid acid resin catalyst is obtained.

[0056] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 12% according to elemental analysis.

[0057] Preparation Example 8 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1. The difference is that trifluoroethyl methacrylate of equal mass is used to replace hexafluorobutyl acrylate in step (1).

[0058] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.5% according to elemental analysis.

[0059] Preparation Example 9 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are the same as those in Preparation Example 1. The difference is that an equal mass of dodecafluoroheptyl methacrylate is used to replace hexafluorobutyl acrylate in step (1).

[0060] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.4% according to elemental analysis.

[0061] Preparation Example 10 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are as follows: (1) In a reaction vessel equipped with a stirrer, condenser and thermometer, add 100g styrene, 30g divinylbenzene (crosslinking degree about 25%), 1g hexafluorobutyl acrylate, 15g liquid paraffin and 1g benzoyl peroxide. Under a nitrogen atmosphere, heat the above materials in a water bath to 75°C and react for 10 hours, then heat to 90°C and react for 4 hours, and finally heat to 85°C to mature for 6 hours. During the reaction, stir continuously at 150 rpm.

[0062] After the reaction was completed, the polymer white spheres were filtered out, and the liquid paraffin was removed by extraction with petroleum ether and then vacuum dried.

[0063] (2) Place the dried polymer white balls obtained in step (1) into a photochlorination reactor, introduce chlorine gas under light-proof conditions, control the reaction temperature at 25°C, take intermittent samples to detect the chlorine content, stop the gas supply when the chlorine content reaches 15%, purge the residual chlorine gas with nitrogen gas to obtain chloromethylated resin.

[0064] (3) Add the chloromethylated resin to an excess of 92wt% concentrated sulfuric acid and react at 30℃ for 10 hours. After the reaction is complete, slowly pour the mixture into ice water to dilute it, filter to obtain the resin, and wash repeatedly with deionized water until the effluent is neutral.

[0065] Finally, the catalyst was vacuum dried at 60°C for 12 hours to obtain a light yellow granular solid acid resin catalyst.

[0066] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 8.1% according to elemental analysis.

[0067] Preparation Example 11 This preparation example provides a method for preparing a solid acid resin catalyst. The specific preparation method and operating parameters are as follows: (1) In a reactor equipped with a stirrer, condenser and thermometer, add 100g styrene, 5g divinylbenzene (crosslinking degree about 10%), 1g hexafluorobutyl acrylate, 15g dioctyl phthalate and 0.2g azobisisobutyronitrile. Under a nitrogen atmosphere, heat the above materials in a water bath to 85°C and react for 6 hours, then heat to 100°C and react for 2 hours, and finally heat to 100°C for aging for 2 hours. During the reaction, stir continuously at 250 rpm.

[0068] After the reaction was completed, the polymer white spheres were filtered out, and the dioctyl phthalate was removed by extraction with petroleum ether and then dried under vacuum.

[0069] (2) Place the dried polymer white balls obtained in step (1) into a photochlorination reactor, introduce chlorine gas under light-proof conditions, control the reaction temperature at 10°C, take intermittent samples to detect the chlorine content, stop the gas supply when the chlorine content reaches 15%, purge the residual chlorine gas with nitrogen gas to obtain chloromethylated resin.

[0070] (3) Add the chloromethylated resin to an excess of 92wt% concentrated sulfuric acid and react at 50℃ for 8 hours. After the reaction is complete, slowly pour the mixture into ice water to dilute it, filter to obtain the resin, and wash repeatedly with deionized water until the effluent is neutral.

[0071] Finally, the catalyst was vacuum dried at 60°C for 12 hours to obtain a light yellow granular solid acid resin catalyst.

[0072] The solid acid resin catalyst prepared in this example was found to have a sulfur content of 11.3% according to elemental analysis.

[0073] Example 1 This embodiment provides a method for synthesizing diisopropyl maleate, the specific preparation method and operating parameters of which are as follows: In a 500 mL three-necked flask, 100 g of cyclohexane, 49 g (0.5 mol) of maleic anhydride, 180 g (3.0 mol) of isopropanol and 4.9 g (10% of the mass of maleic anhydride) were added sequentially to prepare the solid acid resin catalyst prepared in Example 1.

[0074] Install the stirrer, thermometer, and water-return condenser. Turn on the stirrer at 300 rpm. During stirring, heat the mixture to 110°C using an oil bath, and then reflux the reaction at this temperature for 6 hours. During the reaction, observe that no water is being produced using the water separator. After the reaction is complete, filter the reaction mixture while it is still hot to separate and recover the solid catalyst.

[0075] The filtrate was distilled under normal pressure to recover excess isopropanol (approximately 150 g). The remaining crude product was distilled under reduced pressure, and the fraction collected at 105-108 °C / 1.33 kPa was used to obtain a colorless, transparent liquid product, diisopropyl maleate.

[0076] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 99.2%, the selectivity of diisopropyl maleate was 99.5%, and the product yield (based on maleic anhydride) was 98.7%.

[0077] Example 2 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the oil bath heating temperature is adjusted to 80°C.

[0078] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 85.3%.

[0079] Example 3 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the oil bath heating temperature is adjusted to 100°C.

[0080] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 96.8%.

[0081] Example 4 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the oil bath heating temperature is adjusted to 120°C.

[0082] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 99.3%.

[0083] Example 5 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the oil bath heating temperature is adjusted to 130°C.

[0084] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 99.4%.

[0085] Example 6 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the molar amount of isopropanol is 3.5 mol, or 210 g.

[0086] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 99.36%.

[0087] Example 7 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1, except that the molar amount of isopropanol is 2 mol (120 g).

[0088] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 96.12%.

[0089] Examples 8-17 This embodiment provides a method for synthesizing diisopropyl maleate. The specific preparation method and operating parameters are the same as those in Example 1. The difference is that the solid acid resin catalysts prepared in Preparation Examples 2-10 are used instead of the solid acid resin catalysts prepared in Preparation Example 1.

[0090] Gas chromatography analysis revealed the following conversion rates of maleic anhydride synthesized in Examples 8-17: The catalyst used to synthesize diisopropyl maleate in Example 8 was the solid acid resin catalyst prepared in Preparation Example 2, with a maleic anhydride conversion rate of 96.7%. The catalyst used to synthesize diisopropyl maleate in Example 9 was the solid acid resin catalyst prepared in Preparation Example 3, with a maleic anhydride conversion rate of 99.4%. The catalyst used to synthesize diisopropyl maleate in Example 10 was the solid acid resin catalyst prepared in Preparation Example 4, with a maleic anhydride conversion rate of 99.6%. The catalyst used to synthesize diisopropyl maleate in Example 11 was the solid acid resin catalyst prepared in Preparation Example 5, with a maleic anhydride conversion rate of 99.5%. The catalyst used to synthesize diisopropyl maleate in Example 12 was the solid acid resin catalyst prepared in Preparation Example 6, with a maleic anhydride conversion rate of 95.3%. The catalyst used to synthesize diisopropyl maleate in Example 13 was the solid acid resin catalyst prepared in Preparation Example 7, with a maleic anhydride conversion rate of 99.7%. The catalyst used to synthesize diisopropyl maleate in Example 14 was the solid acid resin catalyst prepared in Preparation Example 8, with a maleic anhydride conversion rate of 99.2%. The catalyst used to synthesize diisopropyl maleate in Example 15 was the solid acid resin catalyst prepared in Preparation Example 9, with a maleic anhydride conversion rate of 98.8%. The catalyst used to synthesize diisopropyl maleate in Example 16 was the solid acid resin catalyst prepared in Preparation Example 10, with a maleic anhydride conversion rate of 95.4%. The catalyst used to synthesize diisopropyl maleate in Example 17 was the solid acid resin catalyst prepared in Preparation Example 11, with a maleic anhydride conversion rate of 99.5%.

[0091] Example 18 This embodiment provides a method for synthesizing diisopropyl maleate, the specific preparation method and operating parameters of which are as follows: In a 500 mL three-necked flask, 100 g of cyclohexane, 49 g (0.5 mol) of maleic anhydride, 240 g (4.0 mol) of isopropanol and 2.45 g (5% of the mass of maleic anhydride) were added sequentially to prepare the solid acid resin catalyst prepared in Example 1.

[0092] Install the stirrer, thermometer, and water-return condenser. Turn on the stirrer at 300 rpm. During stirring, heat the mixture to 80°C using an oil bath, and then reflux the reaction at this temperature for 10 hours. During the reaction, observe that no water is being produced using the water separator. After the reaction is complete, filter the reaction mixture while it is still hot to separate and recover the solid catalyst.

[0093] The filtrate was distilled under normal pressure to recover excess isopropanol. The remaining crude product was distilled under reduced pressure, and the fraction collected at 105-108℃ / 1.33kPa was used to obtain the colorless and transparent liquid product diisopropyl maleate.

[0094] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 99.5%, the selectivity of diisopropyl maleate was 99.6%, and the product yield (based on maleic anhydride) was 98.9%.

[0095] Example 19 This embodiment provides a method for synthesizing diisopropyl maleate, the specific preparation method and operating parameters of which are as follows: In a 500 mL three-necked flask, 100 g of cyclohexane, 49 g (0.5 mol) of maleic anhydride, 90 g (1.5 mol) of isopropanol and 7.35 g (15% of the mass of maleic anhydride) were added sequentially to prepare the solid acid resin catalyst prepared in Example 1.

[0096] Install the stirrer, thermometer, and water-return condenser. Turn on the stirrer at 300 rpm. During stirring, heat the mixture to 130°C using an oil bath, and then reflux the reaction at this temperature for 4 hours. During the reaction, observe that no water is being produced using the water separator. After the reaction is complete, filter the reaction mixture while it is still hot to separate and recover the solid catalyst.

[0097] The filtrate was distilled under normal pressure to recover excess isopropanol. The remaining crude product was distilled under reduced pressure, and the fraction collected at 105-108℃ / 1.33kPa was used to obtain the colorless and transparent liquid product diisopropyl maleate.

[0098] Gas chromatography analysis showed that the conversion rate of maleic anhydride synthesized in this embodiment was 93.5%, the selectivity of diisopropyl maleate was 97.3%, and the product yield (based on maleic anhydride) was 89.83%.

[0099] Comparative Example This comparative example provides a method for synthesizing diisopropyl maleate, the specific preparation method and operating parameters of which are as follows: In a 250 mL three-necked flask, add 49 g (0.5 mol) of maleic anhydride, 180 g (3.0 mol) of isopropanol and 4.9 g (10% of the mass of maleic anhydride) of concentrated sulfuric acid (98 wt%).

[0100] Install the stirrer, thermometer, and water reflux condenser. Turn on the stirrer and heat the oil bath to 110°C. At this temperature, reflux the reaction for 6 hours.

[0101] After the reaction, the reaction solution was neutralized to pH 7 with sodium carbonate solution, and then purified by distillation after separation, washing with water, drying, and distillation to obtain diisopropyl maleate.

[0102] Gas chromatography analysis showed that the final product yield was 89.4%, and the product was slightly yellow. However, the process generated a large amount of saline wastewater.

[0103] Experimental Example The solid acid resin catalysts recovered in Examples 1 and 8-17 were washed twice with a small amount of isopropanol and dried in an oven at 60°C for 4 hours. Subsequently, without adding new catalyst, the next batch of catalytic reaction was carried out under the same feed ratio and reaction conditions as in Example 1. The conversion rate of maleic anhydride, the selectivity of diisopropyl maleate, and the product yield were measured for each cycle. The experimental results for different cycle numbers are shown in Table 1.

[0104] Following the steps of Example 1, commercially available conventional styrene-divinylbenzenesulfonic acid resin (type D001) was used to replace the solid acid resin catalyst to synthesize diisopropyl maleate. The recovered catalyst was washed twice with a small amount of isopropanol and dried in an oven at 60°C for 4 hours. Subsequently, without replenishing the catalyst, the next batch of catalytic reaction was carried out under the same raw material ratio and reaction conditions as in Example 1, and the conversion rate of maleic anhydride was measured for each cycle. The experimental results for different cycle numbers are shown in Table 1.

[0105] Table 1. Experimental results for different number of cycles

[0106] As shown in Table 1, the commercially available conventional styrene-divinylbenzene sulfonic acid resin (such as type D001) exhibited good conversion in the initial catalytic synthesis. However, after multiple cycles, its catalytic activity decreased sharply, indicating that repeated use in high-temperature alcohol solutions resulted in severe loss of sulfonic acid groups, a significant decrease in sulfur content, and a shortened service life for the commercially available conventional styrene-divinylbenzene sulfonic acid resin. In contrast, the solid acid resin catalyst prepared in this application maintained excellent catalytic performance even after five cycles of reuse, with only a small decrease in conversion and selectivity, demonstrating good stability during repeated use.

[0107] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A solid acid resin catalyst, characterized in that, Raw materials include, Styrene; Divinylbenzene; Fluorinated acrylate monomers.

2. The solid acid resin catalyst according to claim 2, characterized in that, Based on the mass of styrene, the mass fraction of fluorinated acrylate monomers is 0.5wt%-5wt%, and the mass fraction of divinylbenzene is 5wt%-30wt%.

3. The solid acid resin catalyst according to claim 2, characterized in that, The fluorinated acrylate monomer includes at least one of hexafluorobutyl acrylate, trifluoroethyl methacrylate, and dodecafluoroheptyl methacrylate. And / or, based on the mass of styrene, the mass fraction of fluorinated acrylate monomers is 1wt%-3wt%.

4. The method for preparing the solid acid resin catalyst according to any one of claims 1-3, characterized in that, Includes the following steps, Styrene, divinylbenzene, and fluorinated acrylate monomers are sequentially polymerized and sulfonated.

5. The method for preparing the solid acid resin catalyst according to claim 4, characterized in that, The polymerization reaction, followed by the sulfonation reaction, also includes a chlorination reaction. And / or, the specific steps of the polymerization reaction include, in an inert atmosphere and in the presence of an initiator, initiating a reaction of styrene, divinylbenzene and fluorinated acrylate monomers at a first temperature, reacting at a second temperature for a second time, and then performing a aging reaction. The first temperature is 75℃-85℃, the initiation reaction time is 6h-10h, the second temperature is 85℃-100℃, the second time is 2h-4h, and the aging reaction temperature is 90℃-100℃, the aging reaction time is 2h-6h.

6. The method for preparing the solid acid resin catalyst according to claim 5, characterized in that, The specific steps of the sulfonation reaction include reacting the product after polymerization or chlorination with 85wt%-98wt% concentrated sulfuric acid at 30℃-60℃ for 6h-10h. And / or, the sulfur content of the resin catalyst after sulfonation is controlled at 5wt%-12wt%; And / or, the polymerization reaction further includes a porogen; And / or, the chlorination reaction is carried out at a temperature of 10°C-25°C, and the chlorine content of the chlorination product after the chlorination reaction is 15wt%-25wt%; And / or, after the polymerization reaction, the degree of crosslinking of the polymer product is 15%-30%; And / or, the initiator includes at least one of benzoyl peroxide or azobisisobutyronitrile.

7. The method for preparing the solid acid resin catalyst according to claim 6, characterized in that, The pore-forming agent includes at least one of liquid paraffin, dextrin powder, and dioctyl phthalate. And / or, based on the mass of styrene, the pore-forming agent has a mass fraction of 15wt%-25wt%, and the initiator has a mass fraction of 0.2wt%-1wt%; And / or, the concentration of concentrated sulfuric acid in the sulfonation reaction is 90wt%-95wt%; And / or, the sulfonation reaction is carried out at a temperature of 40°C-50°C.

8. The application of a solid acid resin catalyst prepared by any one of claims 1-3 or any one of claims 4-7 in the synthesis of diisopropyl maleate, characterized in that, The method for synthesizing diisopropyl maleate includes the following steps. In the presence of the solid acid resin catalyst, maleic anhydride and isopropanol are subjected to an esterification reaction.

9. The application according to claim 8, characterized in that, The solid acid resin catalyst has a mass fraction of 5wt%-15wt% based on the mass of maleic anhydride, preferably 8wt%-12wt%. And / or, the molar ratio of maleic anhydride to isopropanol is 1:3-8, preferably 1:4-6; And / or, the specific steps of the esterification reaction include, under stirring conditions, refluxing the solid acid resin catalyst, maleic anhydride and isopropanol at 80°C-130°C for 4-10 hours. And / or, after the esterification reaction is completed, solid and liquid are separated to obtain a solid acid resin catalyst and a reaction solution. The separated solid acid resin catalyst is reused, and the reaction solution is distilled under normal pressure to recover isopropanol, and then distilled under reduced pressure to obtain diisopropyl maleate.

10. The application according to claim 9, characterized in that, The esterification reaction is carried out in a solvent environment, the solvent including at least one of cyclohexane, methyl isobutyl ketone or benzene; And / or, the esterification reaction temperature is 100℃-120℃; And / or, the reflux time is 5-7 hours; And / or, the solid-liquid separation step includes at least one of filtration or sedimentation.

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