Preparation method of catalyst for esterification and sulfonation reaction

Abstract

The invention relates to the technical field of catalysts, and particularly discloses a preparation method of a catalyst for esterification and sulfonation reaction, and the preparation method specifically comprises the following steps: S1, dissolving a zirconium source and a cerium source in deionized water, then adding a template agent, stirring and homogenizing, and then adjusting the pH value to 8-9 to obtain sol; s2, transferring the sol into a reaction kettle, carrying out hydrothermal reaction, filtering, and washing to obtain a solid product; and S3, under the protection of inert gas, carrying out heat treatment on the solid product, and naturally cooling to room temperature to obtain the catalyst. The catalyst provided by the invention has bifunctional acidic sites, can efficiently catalyze the esterification reaction of alcohol and acid during the esterification reaction through multi-metal cooperation and surface modification, and can promote sulfonation nucleophilic addition in the subsequent sulfonation reaction; in addition, the catalyst can be easily separated from the reaction liquid after the reaction is finished, so that the cyclic utilization is realized, and the subsequent purification process is simplified.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a method for preparing a catalyst for esterification and sulfonation reactions. Background Technology

[0002] Esterification and sulfonation are two common organic chemical reactions. Under certain industrial or laboratory conditions, esterification and sulfonation reactions need to be combined to achieve multi-step synthesis of multifunctional products. Traditional esterification processes widely employ inorganic acid catalysts, such as concentrated sulfuric acid and p-toluenesulfonic acid. These catalysts are inexpensive and highly active, making them a classic choice for long-term industrial use. However, they have a series of inherent and insurmountable drawbacks: First, strong acidity and high temperatures easily lead to side reactions such as oxidation and polymerization of unsaturated double bonds, as well as dehydration and etherification of alcohols, resulting in products with dark colors requiring subsequent decolorization, high impurity content, and affecting the performance of the final surfactant. Second, they are highly corrosive to reaction equipment, requiring high-quality materials and increasing equipment maintenance and investment costs. Third, post-treatment is complex. After the reaction, neutralization with alkali and washing with water are necessary to remove the catalyst, generating large amounts of saline wastewater, causing environmental pollution, product loss, and complicating the purification process.

[0003] To overcome the drawbacks of traditional catalysts, researchers have dedicated themselves to developing more efficient and environmentally friendly catalytic systems, with solid catalysts being the most actively researched. For example, patent application CN113277964A discloses a vanadium oxide-molybdenum oxide catalytic system. However, the core function of this catalyst is mainly in esterification reactions, lacking optimization for sulfonation reactions. Furthermore, adding another catalyst to the sulfonation reaction would significantly increase production costs. Considering the shortcomings of existing technologies, this invention aims to provide a catalyst that is effective in both esterification and sulfonation systems. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a catalyst with bifunctional acidic sites. When esterification and sulfonation reactions need to be combined, this catalyst can efficiently catalyze the esterification of alcohols with acid anhydrides and promote the nucleophilic addition of sulfonation in the subsequent sulfonation reaction, thus improving the yield. Furthermore, this catalyst can be easily separated from the reaction solution after the reaction, enabling recycling and eliminating the need for alkali neutralization and water washing in traditional processes. This reduces the generation of saline wastewater, lowers environmental pollution, and simplifies the subsequent purification process.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for preparing a catalyst for esterification and sulfonation reactions, specifically comprising the following steps: S1. Dissolve zirconium source and cerium source in deionized water, then add template agent, stir to homogenize, and adjust pH to 8-9 to obtain sol; S2. Transfer the sol to the reactor, perform hydrothermal reaction, filter, wash, and obtain the solid product; S3. Under the protection of an inert gas, the solid product is heat-treated and then naturally cooled to room temperature to obtain the catalyst.

[0006] The catalyst provided by this invention, being a solid heterogeneous structure, can be easily separated from the reaction liquid by vacuum filtration. The recovered catalyst can be regenerated and recycled after drying. This catalyst possesses bifunctional acidic sites, wherein Zr... 4+ It provides Lewis acidity, efficiently catalyzing the esterification reaction of alcohols and acid anhydrides; Ce-OH provides Brønsted acidity, promoting sulfonation. On the other hand, it can suppress side reactions. 3+ / Ce 4+ The redox reaction can consume dissolved oxygen in the reaction system, preventing the sulfonating agent from being oxidized or by other sulfur-containing compounds that cause the product to turn yellow.

[0007] In some embodiments, in step S1, the molar ratio of the zirconium source to the cerium source is (2-5):1.

[0008] In some embodiments, in step S1, the template agent is 2-methyl-1H-imidazol-5-carboxylic acid.

[0009] 2-Methyl-1H-imidazol-5-carboxylic acid possesses both a carboxylate group and a tertiary nitrogen atom, and can react with Zr. 4+ and Ce 4+ Stable bidentate coordination is formed, thereby controlling the hydrolysis-condensation rate during the hydrothermal process and resulting in a uniform mesoporous solid product. Furthermore, during pyrolysis, 2-methylimidazolium-5-carboxylic acid undergoes an intermediate carbonization state, and the resulting reducing carbonaceous intermediate can partially remove Ce. 4+ In-situ restoration to Ce 3+ Thus, the required Ce can be directly constructed. 3+ / Ce 4+ Redox pairs.

[0010] In some embodiments, a lanthanum source is also added in step S1.

[0011] In some embodiments, the amount of lanthanum source used is 1 to 4 mol of the total amount of zirconium and cerium sources.

[0012] This invention introduces a third metal, lanthanum, for doping. 3+ The ionic radius is greater than Ce 4+ and Zr 4+When CeO2 doping occurs, it causes lattice expansion and stress. To compensate for the charge balance and release the stress, it will encourage the addition of more CeO2. 4+ Restored to Ce 3+ and Ce 3+ It stabilizes within the crystal lattice, preventing oxidation during reaction or storage. Simultaneously, lanthanum doping effectively suppresses phase transformation and growth of ZrO2 grains during pyrolysis and use, ensuring structural stability of the catalyst during recycling.

[0013] In some embodiments, the specific conditions for the hydrothermal reaction in step S2 are: reacting at 100-110°C for 8-16 hours, and then naturally cooling to room temperature.

[0014] In some embodiments, step S3 specifically involves heating to 350–390°C at a rate of 4–12°C / min and holding at that temperature for 0.5–1.5 hours.

[0015] This invention satisfies the temperature sensitivity of catalyst heat treatment by programmed temperature rise, thus avoiding pore blockage caused by incomplete decomposition of template agent and the decrease in specific surface area caused by partial sintering collapse of mesoporous structure.

[0016] In some embodiments, in step S3, the catalyst also needs to undergo surface treatment, specifically as follows: the catalyst and silane are refluxed in toluene for 4-8 hours, then filtered and dried.

[0017] In some embodiments, the silane is hexadecyltrimethoxysilane.

[0018] In some embodiments, the amount of silane used is 4 to 8 wt% of the catalyst.

[0019] The long-chain alkyl group of hexadecyltrimethoxysilane provides a strong hydrophobic layer, effectively preventing water molecules from approaching the active sites of the catalyst and preventing hydrolytic deactivation due to water absorption during esterification. During reflux, the methoxy group forms a strong covalent bond with the hydroxyl group on the surface of the porous oxide, resulting in a relatively stable modified layer that is not easily detached during the reaction. Furthermore, the introduction of the long-chain alkyl group also helps to enhance the lipophilicity of the catalyst, making it more dispersible in lipophilic reaction systems.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a solid heterogeneous catalyst for esterification and sulfonation reactions that is easy to filter and recover. The catalyst has bifunctional acidic sites and shortens the total reaction time of esterification-sulfonation through multi-metal synergy and surface modification. At the same time, it can inhibit the premature oxidation of sulfur source during sulfonation and reduce the generation of by-products.

[0021] 2. In the catalyst synthesis process of this invention, 2-methyl-1H-imidazol-5-carboxylic acid, which simultaneously possesses a carboxylate group and a tertiary nitrogen atom, is selected as a template agent, which can react with Zr. 4+ and Ce 4+ This process establishes stable bidentate coordination, thereby controlling the hydrolysis-condensation rate during hydrothermal processes. This results in a uniformly mesoporous solid product. Furthermore, during pyrolysis, 2-methyl-1H-imidazolium-5-carboxylic acid undergoes an intermediate carbonization state, producing a reducing carbonaceous intermediate that can partially release Ce. 4+ In-situ restoration to Ce 3+ Ce formed 3+ / Ce 4+ Redox pairs can consume dissolved oxygen in the reaction system, preventing the sulfonating agent from being oxidized prematurely.

[0022] 3. The present invention obtains long-chain alkyl by further surface modification of the catalyst. The hydrophobic layer brought by the long-chain alkyl can prevent water molecules from approaching the active site of the catalyst, preventing the catalyst from hydrolyzing and deactivating due to water absorption in the esterification reaction. In addition, the introduction of long-chain alkyl also helps to enhance the lipophilicity of the catalyst, making it more dispersed in the reaction system. Detailed Implementation

[0023] The present invention will be described below with reference to specific implementation schemes. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope. It is worth noting that, unless otherwise specified, the raw materials used in the following preparation examples and embodiments can be obtained from any commercially available manufacturer.

[0024] Example 1 A method for preparing a catalyst for esterification and sulfonation reactions specifically includes the following steps: S1. Dissolve 0.4 mol ZrOCl2·8H2O, 0.1 mol (NH4)2Ce(NO3)6, and 15 mmol La(NO3)3·6H2O in 300 mL of deionized water, then add 0.1 mol 2-methyl-1H-imidazol-5-carboxylic acid, stir until homogenized, and adjust the pH to 8.5 with ammonia water to obtain a sol. S2. Transfer the sol to a reaction vessel and hydrothermally react at 105°C for 12 hours. Allow it to cool naturally to room temperature, filter, and wash to obtain the solid product. S3. Under nitrogen protection, the solid product is heated to 378°C at a rate of 8°C / min and held for 1 hour to obtain a porous oxide. 100g of the porous oxide and 5g of hexadecyltrimethoxysilane are refluxed in 500mL of toluene for 6 hours, filtered and dried to obtain the catalyst.

[0025] Example 2 A method for preparing a catalyst for esterification and sulfonation reactions specifically includes the following steps: S1. Dissolve 0.2 mol ZrOCl2·8H2O, 0.1 mol (NH4)2Ce(NO3)6, and 3 mmol La(NO3)3·6H2O in 250 mL of deionized water, then add 0.1 mol 2-methyl-1H-imidazol-5-carboxylic acid, stir until homogenized, and adjust the pH to 8 with ammonia water to obtain a sol. S2. Transfer the sol to a reaction vessel and hydrothermally react at 100°C for 16 hours. Allow it to cool naturally to room temperature, filter, and wash to obtain the solid product. S3. Under nitrogen protection, the solid product is heated to 350°C at a rate of 4°C / min and held at that temperature for 1.5h to obtain a porous oxide. 100g of the porous oxide and 4g of hexadecyltrimethoxysilane are refluxed in 500mL of toluene for 4h, filtered and dried to obtain the catalyst.

[0026] Example 3 A method for preparing a catalyst for esterification and sulfonation reactions specifically includes the following steps: S1. Dissolve 0.5 mol ZrOCl2·8H2O, 0.1 mol (NH4)2Ce(NO3)6, and 24 mmol La(NO3)3·6H2O in 400 mL of deionized water, then add 0.1 mol 2-methyl-1H-imidazol-5-carboxylic acid, stir until homogenized, and adjust the pH to 9 with ammonia water to obtain a sol. S2. Transfer the sol to a reaction vessel and hydrothermally react at 110°C for 8 hours. Allow it to cool naturally to room temperature, filter, and wash to obtain the solid product. S3. Under nitrogen protection, the solid product is heated to 390°C at a rate of 12°C / min and held at that temperature for 0.5h to obtain a porous oxide. 100g of the porous oxide and 8g of hexadecyltrimethoxysilane are refluxed in 500mL of toluene for 8h, filtered and dried to obtain the catalyst.

[0027] Example 4 This embodiment provides a method for preparing a catalyst for esterification and sulfonation reactions. The specific implementation method is the same as in Example 1, except that step S1 is adjusted as follows: S1. Dissolve 0.4 mol ZrOCl2·8H2O and 0.1 mol (NH4)2Ce(NO3)6 in 300 mL of deionized water, then add 0.1 mol 2-methyl-1H-imidazol-5-carboxylic acid, stir until homogenized, and adjust the pH to 8.5 with ammonia water to obtain a sol.

[0028] Example 5 This embodiment provides a method for preparing a catalyst for esterification and sulfonation reactions. The specific implementation method is the same as in Example 1, except that step S3 is adjusted as follows: S3. Under nitrogen protection, the solid product is heated to 378°C at a rate of 8°C / min and held at that temperature for 1 hour to obtain the catalyst for sulfosuccinate.

[0029] Comparative Example 1 This comparative example provides a method for preparing a catalyst for esterification and sulfonation reactions. The specific implementation method is the same as in Example 1, except that step S1 is adjusted as follows: S1. Dissolve 0.4 mol ZrOCl2·8H2O, 0.1 mol (NH4)2Ce(NO3)6, and 15 mmol La(NO3)3·6H2O in 300 mL of deionized water, stir to homogenize, and then adjust the pH to 8.5 with ammonia water to obtain a sol.

[0030] Performance testing Yield testing: The catalysts obtained in Examples 1-5 and Comparative Example 1 were designated as A, B, C, D, E, and F, respectively, while the control group catalyst, p-toluenesulfonic acid, was designated as G. The above catalysts were subjected to a combined esterification and sulfonation reaction, with the specific steps as follows: (1) Esterification reaction: 122 g benzoic acid, 55.2 g ethanol, 6.1 g catalyst (A / B / C / D / E / F / G) and 200 mL chlorobenzene were refluxed at 130°C into a water separator and no water appeared, thus obtaining the esterification product; (2) Sulfonation reaction: Cool the esterification product to 50°C, add 335g of 50wt% sulfuric acid aqueous solution dropwise, and keep warm for 6h after the addition is complete; (3) Post-processing: Cool the reaction system to 45°C, vacuum filter, wash the filter cake, collect the filtrate, concentrate the filtrate, extract the organic phase, wash the organic phase and remove the solvent to obtain the crude product.

[0031] Yield tests were performed on the crude products obtained separately.

[0032] The performance test results are shown in Table 1.

[0033] Table 1 Test Results As shown in Table 1, the crude products obtained in Examples 1-3 have similar yields. Compared with the control group using a conventional catalyst for p-toluenesulfonic acid, the yields of Examples 1-3 are significantly increased. However, p-toluenesulfonic acid remains dissolved in the reaction system after the esterification stage. If sulfuric acid solution is added directly for sulfonation, p-toluenesulfonic acid may decompose and cause the sulfonation reaction system to run out of control, triggering a large number of side reactions and preventing the reaction from proceeding smoothly.

[0034] Compared to Example 1, the catalyst used in Example 4 did not incorporate a lanthanum source, resulting in a lower yield. This may be due to the presence of lanthanum. 3+ The absence of Ce 3+ The reduction in silane content leads to an increase in byproducts. The catalyst in Example 5 lacked further surface modification with silane, resulting in lower yield and reduced cycle stability. This is because hydrophobic surface modification can prevent catalyst deactivation. Compared to Example 1, the catalyst in Comparative Example 1 lacked a template agent, which is detrimental to controlling the hydrolysis-condensation rate during the hydrothermal process and also reduces Ce. 3+ / Ce 4+ The number of redox pairs decreases the yield.

[0035] The embodiments and comparative examples described above do not limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing a catalyst for esterification and sulfonation reactions, characterized in that, Specifically, it includes the following steps: S1. Dissolve zirconium source and cerium source in deionized water, then add template agent, stir to homogenize, and adjust pH to 8-9 to obtain sol; S2. Transfer the sol to the reactor, perform hydrothermal reaction, filter, wash, and obtain the solid product; S3. Under the protection of an inert gas, the solid product is heat-treated and then naturally cooled to room temperature to obtain the catalyst.

2. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, In step S1, the molar ratio of the zirconium source to the cerium source is (2-5):

1.

3. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, In step S1, the template agent is 2-methyl-1H-imidazol-5-carboxylic acid.

4. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, A lanthanum source was also added in step S1.

5. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 4, characterized in that, The amount of lanthanum source used is 1 to 4 mol of the total amount of zirconium and cerium sources.

6. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, In step S2, the specific conditions for the hydrothermal reaction are: reacting at 100-110°C for 8-16 hours, and then naturally cooling to room temperature.

7. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, In step S3, the specific steps of the heat treatment are as follows: heating to 350-390°C at a rate of 4-12°C / min and holding at that temperature for 0.5-1.5 hours.

8. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 1, characterized in that, In step S3, the catalyst also needs to undergo surface treatment. The specific steps are as follows: reflux the catalyst and silane in toluene for 4-8 hours, then filter and dry.

9. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 8, characterized in that, The silane is hexadecyltrimethoxysilane.

10. The method for preparing the catalyst for esterification and sulfonation reactions according to claim 8, characterized in that, The amount of silane used is 4 to 8 wt% of the catalyst.

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