Catalytic system for efficiently synthesizing methyl cinnamate
By combining a supported solid acid catalyst with a 3A molecular sieve, the problems of catalyst corrosion and coking deactivation in the production of methyl cinnamate were solved, achieving efficient synthesis and good recycling performance, and improving the conversion rate and selectivity of methyl cinnamate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-31
- Publication Date
- 2026-04-03
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
In the existing technology, the production of methyl cinnamate has the problems of strong catalyst corrosivity, complicated post-processing, waste acid emission that pollutes the environment, and solid acid catalysts are prone to carbon deposition and deactivation, resulting in unstable yield and selectivity, and the catalytic system is difficult to recycle.
A supported solid acid catalyst is used in combination with 3A molecular sieve dehydrating agent. The supported solid acid is formed by mixing coprecipitated particles with sulfuric acid and then post-processing. The catalyst is then coated and modified with hexadecyltrimethoxysilane to form a catalytic system with a mesoporous structure. The coprecipitation process of nitrogen-phosphorus complex and silicon-zirconium forms uniform acidic sites, which improves catalytic efficiency and cycle performance.
The efficient synthesis of methyl cinnamate was achieved, with a fast and thorough catalytic reaction rate, good recycling performance of the catalytic system, high conversion rate, and reduced pollutant emissions.
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Figure CN121775744A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid acid catalyst processing technology, and specifically to a highly efficient catalytic system for the synthesis of methyl cinnamate. Background Technology
[0002] Methyl cinnamate is an aromatic organic compound with significant industrial value, widely used in food flavorings, cosmetic additives, pharmaceutical intermediates, and polymer modifiers. The methyl benzoate group in its molecular structure endows it with a unique aroma and biological activity, and market demand continues to grow. Currently, the industrial production of methyl cinnamate mainly relies on esterification, that is, the reaction of cinnamic acid and methanol under the action of a catalyst to generate the target product.
[0003] In existing technologies, the reaction of cinnamic acid with methanol often uses liquid acids such as concentrated sulfuric acid and p-toluenesulfonic acid as catalysts. Although these catalysts have high activity, they have problems such as strong corrosivity, complex post-treatment, and environmental pollution from waste acid emissions. In addition, it is difficult to recycle the catalyst in a homogeneous system, which leads to increased production costs. Traditional solid acid catalysts, such as zeolite molecular sieves and sulfonated carbon materials, although solid acids can reduce pollution and achieve partial recovery, their active centers are prone to deactivation due to carbon deposition, and they have stringent requirements for reaction conditions (such as temperature and pressure), resulting in unstable yield and selectivity.
[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention
[0005] The purpose of this invention is to provide a highly efficient catalytic system for the synthesis of methyl cinnamate, which addresses the technical problem that the conversion rate and recycling performance of the catalytic system for the reaction of cinnamic acid and methanol with solid acid catalysts in the prior art need to be further improved.
[0006] The objective of this invention can be achieved through the following technical solution: a catalytic system for the efficient synthesis of methyl cinnamate, comprising a supported solid acid and a dehydrating agent; The preparation method of the supported solid acid is as follows: coprecipitated particles and sulfuric acid are mixed, the temperature of the reaction system is raised to 70-80℃, the reaction is carried out for 120-160 min, and after post-treatment, a supported solid acid preform is obtained. Then, the supported solid acid preform is coated and modified with hexadecyltrimethoxysilane to obtain the supported solid acid.
[0007] Furthermore, the weight ratio of the supported solid acid to the dehydrating agent is 1:5-7, and the dehydrating agent is 3A molecular sieve.
[0008] Furthermore, the ratio of coprecipitated particles to sulfuric acid is 3g:15mL, and the concentration of sulfuric acid is 2-3mol / L. The post-treatment includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, and the filter cake is transferred to a drying oven at 80-90℃ and dried for 5 hours to obtain dried material. The dried material is then transferred to a muffle furnace, the temperature of the muffle furnace is raised to 550-600℃, and calcined for 5-6 hours. The material is then naturally cooled to room temperature, and the calcined material is washed three times with purified water and anhydrous methanol and then dried to constant weight to obtain a supported solid acid preform.
[0009] Furthermore, the preparation method of the coprecipitated particles is as follows: hexadecyltrimethylammonium bromide, nitrogen-phosphorus complex, and deionized water are mixed and stirred for 8-12 minutes, the temperature of the reaction system is raised to 50-60℃, tetraethyl orthosilicate and zirconium nitrate solution are added to the reaction system, stirred for 3-5 minutes, alkaline solution is added to the reaction system, the reaction is kept at the temperature for 60-80 minutes, crystallization is performed, and post-treatment is carried out to obtain coprecipitated particles.
[0010] Furthermore, the ratio of hexadecyltrimethylammonium bromide, nitrogen-phosphorus complex, deionized water, tetraethyl orthosilicate, zirconium nitrate solution, and alkaline solution is 2-3 g: 1.3-1.5 g: 20 mL: 5-6 g: 10 mL: 5 mL. The zirconium nitrate solution is composed of zirconium nitrate and deionized water at a ratio of 1.2-1.6 g: 5 mL. The alkaline solution is a 4-5 mol / L sodium hydroxide solution. The crystallization temperature is 90-95℃, and the crystallization time is 30 h. The post-processing includes: after the reaction is complete, the temperature of the reaction system is lowered to room temperature, filtered, the filter cake is washed with purified water until neutral and then dried, the filter cake and 10wt% hydrogen peroxide are mixed and stirred at a solid-liquid ratio of 1:10, the temperature of the reaction system is raised to 60-70℃, stirred for 5-6 hours, filtered, the filter cake is washed with ethanol 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80℃ and dried to constant weight, ground, and passed through a 100-mesh sieve to obtain coprecipitated particles.
[0011] Furthermore, the preparation method of the nitrogen-phosphorus complex is as follows: under an inert gas atmosphere, palladium dichloride di(acetonitrile), N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide and methanol are mixed, the temperature of the reaction system is raised to reflux, and the reaction is maintained at this temperature for 8-9 hours. After post-treatment, the nitrogen-phosphorus complex is obtained.
[0012] The synthesis reaction formula for nitrogen-phosphorus complexes is as follows:
[0013] The 1H NMR data for the nitrogen-phosphorus complex are:¹H NMR (400 MHz, ,δ): 8.72 (brs,1H,NH-CONH), 8.38 (brs,1H,NH-CONH), 7.88 (d,J=9Hz,4H,Ar-H), 7.67-7.24 (m,24H,Ar-H), 3.46 (m,2H,CH), 1.98 (m,4H, ), 1.34 (m, 4H, ).
[0014] Furthermore, the molar ratio of palladium dichloride (acetonitrile) to N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is 1:1, and the molar ratio of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide to methanol is 1 g:7 mL. The post-treatment includes: after the reaction is complete, the reaction system is evaporated under reduced pressure to -0.1 MPa to remove low-boiling substances, and a crystallization solution is added to the reaction system at a solid-liquid ratio of 1:3. The temperature of the reaction system is raised to 50-60°C, and the system is stirred until dissolved. The temperature of the reaction system is lowered to room temperature, and the solid precipitates. The solid is filtered, and the filter cake is washed three times with dichloromethane and then dried under vacuum. The filter cake is transferred to a drying oven at 50-60°C and dried under vacuum to constant weight to obtain a nitrogen-phosphorus complex. The crystallization solution is composed of dichloromethane and ethanol at a volume ratio of 1:1.
[0015] Furthermore, the preparation method of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is as follows: under an inert gas atmosphere, 2-diphenylphosphine and tetrahydrofuran are mixed and stirred until the system is dissolved. 1,2-cyclohexanedicarboxyl chloride is added to the reaction system, and the reaction is carried out at room temperature for 10-12 h. After post-treatment, N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is obtained.
[0016] The synthetic reaction formula for N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is as follows:
[0017] The 1H NMR data for N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide are as follows: 1H NMR (400 MHz, , δ): 8.68 (brs, 1H, NH), 8.36 (brs, 1H, NH), 7.78 (d, J=9Hz, 4H, Ar-H), 7.66–7.22 (m, 24H, Ar-H), 3.42 (m, 2H, CH), 1.98 (m, 4H, ), 1.33 (m, 4H, ).
[0018] Further, the ratio of 2-diphenylphosphine to tetrahydrofuran is 1 g:10 mL, and the molar ratio of 2-diphenylphosphine to 1,2-cyclohexanedicarboxyl chloride is 2.1:1. The post-treatment includes: after the reaction is complete, the reaction system temperature is raised to 60°C, the reaction system is evaporated to -0.1 MPa, low-boiling substances are removed by vacuum evaporation, and a crystallization solution is added to the reaction system at a solid-liquid ratio of 1:3. The reaction system temperature is raised to 50-60°C, and the system is stirred until dissolved. The reaction system temperature is lowered to room temperature, the solid precipitates, and the solid is filtered. The filter cake is washed three times with dichloromethane and then dried under vacuum. The filter cake is transferred to a drying oven at a temperature of 50-60°C and dried under vacuum to constant weight to obtain N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide. The crystallization solution is composed of dichloromethane and ethyl acetate at a volume ratio of 2:3.
[0019] The present invention has the following beneficial effects: This invention enhances the esterification reaction rate by using strong acid sites provided by a supported solid acid. Its mesoporous framework promotes the diffusion of substrates and products, while the 3A molecular sieve maintains low water activity to promote equilibrium shift. The combination of these two factors makes the reaction both fast and thorough, improving the catalytic reaction rate of methyl cinnamate. Through sulfuric acid acidification and regeneration, acidic sites can be replenished and impurities can be removed. The molecular sieve adsorption capacity is reactivated during drying, thereby maintaining the recyclability of the catalytic system.
[0020] The supported solid acid of the present invention has an ordered mesoporous or mesomicroporous structure formed by co-precipitation of tetraethyl orthosilicate and zirconium nitrate in the presence of a surfactant template and hydrothermal crystallization. It provides high specific surface area and thermal stability. The system provides sulfatable strong acid sites and enhances mechanical strength. The mesoporous structure reduces diffusion limitations, allowing larger aromatic carboxylic acid molecules to easily access the active sites, thus achieving high conversion in a shorter reaction time. After sulfuric acid impregnation, zirconium sulfate-type acidic sites are formed, forming a bifunctional solid acid possessing both Brønsted and Lewis acid properties. The Brønsted acid sites can protonate the carboxyl carbon-oxygen bond, making it more susceptible to methanol attack; the Lewis acid sites can coordinate and activate the carboxyl carbonyl oxygen. The uniformly distributed acidic sites improve the reaction rate. The long alkane coating modification introduced onto the solid acid surface reduces the adsorption of water generated in the reaction at the acid sites, maintaining site activity while improving the wettability and mass transfer conditions of the organic substrate. Furthermore, the hydrophobic surface layer promotes water migration from the reaction zone, creating conditions for absorption by the 3A molecular sieve, achieving synergistic dehydration both inside and outside the system.
[0021] The nitrogen-phosphorus complex in the supported solid acid of the present invention is obtained by reacting N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide with bis(acetonitrile)palladium dichloride. During the silicon-zirconium co-precipitation process... The hydrolysis rate of is usually faster than the condensation of Si, which easily leads to The formation of rich clusters leads to uneven distribution of acid sites. The P and N atoms in the nitrogen-phosphorus complex have coordinating ability and can temporarily complex. ion, By endowing nitrogen and phosphorus ligands with fixed coordination structures and electronic regulation capabilities, a stable and flexible chelation system is formed, and the phosphine group... Electronic properties and The reverse The acceptance interaction creates electronic complementarity, resulting in a more balanced overall electron distribution in the ligands. This leads to good coordination compatibility of the entire complex when interacting with Zr / Si sol. The hydrolysis reaction is controlled and synchronized with the condensation of the silicon source, thereby achieving... The uniform embedding of Zr atoms in the framework results in a higher specific surface area and a more uniform distribution of acidic sites on the solid acid support. The nitrogen-phosphorus complex molecule contains amide carbonyl and phosphine groups, which can weakly interact with the micellar interface of the surfactant hexadecyltrimethylammonium bromide in the system, synergistically guiding the formation of mesoporous structures. The aromatic framework and polar functional groups work together to slow down phase separation during framework formation, resulting in a more uniform pore size distribution. The induced regular mesoporous structure improves reactant diffusion paths, reduces mass transfer limitations, and increases the apparent reaction rate. Simultaneously, the organic portion of the complex "fine-tunes" the surface polarity of the formed silicon-zirconium network, providing a uniform surface chemical environment for the subsequent organosilane hydrophobicization reaction. The coordination of oxygen at the center and surface increases local electronic defects, enhancing the adsorption capacity of the Lewis acid center for carbonyl oxygen. Polarizing the carboxyl group and protonating the Brønsted acid site both work synergistically to lower the reaction energy barrier, further increasing the reaction rate. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is the FT-IR infrared spectrum of the supported solid acid of the present invention. Detailed Implementation
[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] In this invention, the 3A molecular sieve is a type 3A artificial zeolite molecular sieve with a bulk density of 630-650 (g / l), an effective component content of 99%, and a diameter of 1.5 mm.
[0026] Example 1: This example provides a method for preparing a supported solid acid, including the following steps: S1. Preparation of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide Weigh 58.2 g of 2-diphenylphosphine and 582 mL of tetrahydrofuran into an argon-protected reaction flask and stir until the system dissolves. Add 20.9 g of 1,2-cyclohexanedicarboxylic acid chloride to the reaction flask and react at room temperature for 10 h. After the reaction flask is evacuated to -0.1 MPa, the temperature is gradually increased to 60 °C and the low-boiling substances are removed by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 50°C and stirred until the system dissolved. Then, while stirring, the reaction flask was allowed to cool naturally to room temperature, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and dried under vacuum. The filter cake was transferred to a drying oven at 50°C and dried under vacuum to constant weight to obtain N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide. The crystallization solution consisted of dichloromethane and ethyl acetate in a volume ratio of 2:3.
[0027] In the reaction system, the amino group in the 2-diphenylphosphine molecule acts as a nucleophilic center. Its nitrogen atom, with its lone pair of electrons, attacks the carbonyl carbonyl group of the acyl chloride to form a tetrahedral intermediate. The tetrahedral intermediate is unstable in the system and undergoes rearrangement. While the negatively charged oxygen atom restores the carbonyl π bond, the chloride ion is expelled as a leaving group, resulting in an amide bond. The product obtained is N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide.
[0028] S2. Preparation of nitrogen-phosphorus complexes Weigh out: 25.9 g of palladium di(acetonitrile)dichloride, 69.1 g of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide and 483.7 mL of methanol into an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to reflux and maintain the temperature for 8 h. Then, evacuate the reaction flask to -0.1 MPa and remove low-boiling substances by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 50°C and stirred until the system dissolved. Then, the reaction flask was allowed to cool naturally to room temperature while stirring, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and dried under vacuum. The filter cake was transferred to a drying oven at 50°C and dried under vacuum to constant weight to obtain a nitrogen-phosphorus complex. The crystallization solution was composed of dichloromethane and ethanol in a volume ratio of 1:1.
[0029] The two acetonitrs in bis(acetonitrile)palladium dichloride are easily dissociated neutral ligands. During the reaction, the diphenylphosphine on the N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide molecule undergoes nucleophilic attack on bis(acetonitrile)palladium dichloride with its lone pair electrons. Under the synergistic effect of metal center polarization and chlorine ligands, the amide NH undergoes inner-loop deprotonation. The proton is transferred to the solvent / chlorine by the ortho-chlorine or solvent methanol as the proton acceptor, forming an HCl·solvent or methamide-ammonium type hydrogen-bonded association; subsequently, deprotonation occurs. The amide nitrogen acts as a strong σ donor to bond with Pd, replacing the weakly coordinated solvent / acetonitrile, closing the N,P five-membered (or approximately five-membered) chelate ring, and obtaining the N,P chelate intermediate of dichloro. At the same time, acetonitrile is displaced. Under the operation of methanol reflux and depressurization to remove low-boiling substances, the free acetonitrile and part of the solvent are taken away, reducing the activity of the reactant / intermediate and promoting the coordination equilibrium to shift towards the chelate product. The chelation effect provides additional thermodynamic stability, causing the product to preferentially crystallize in the subsequent dichloromethane / ethanol mixed solvent as the temperature decreases.
[0030] S3. Preparation of coprecipitated particles Zirconium nitrate and deionized water were mixed at a ratio of 1.2 g: 5 mL and stirred until the system was dissolved to obtain a zirconium nitrate solution. Weigh out 40g of hexadecyltrimethylammonium bromide, 26g of nitrogen-phosphorus complex, and 400mL of deionized water and add them to a reaction flask. Stir for 8 minutes, raise the temperature of the reaction flask to 50℃, add 100g of tetraethyl orthosilicate and 200mL of zirconium nitrate solution to the reaction flask, stir for 3 minutes, add 100mL of 4mol / L sodium hydroxide solution to the reaction flask, and keep the reaction at this temperature for 60 minutes. Transfer the reaction solution to a reaction flask lined with polytetrafluoroethylene, seal and stir, raise the temperature of the reaction flask to 90℃, and keep it at this temperature for 30 hours to crystallize. Lower the temperature of the reaction flask to room temperature, filter, wash the filter cake with purified water until neutral, and then dry it. Add the filter cake and 10wt% hydrogen peroxide to the reaction flask at a solid-liquid ratio of 1:10 and stir. Raise the temperature of the reaction flask to 60℃ and stir for 5 hours. Filter, wash the filter cake three times with ethanol, and then dry it. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight. Grind and pass it through a 100-mesh sieve to obtain coprecipitated particles.
[0031] In water, the concentration of hexadecyltrimethylammonium bromide is much higher than the critical micelle concentration, initially forming spherical / rod-shaped micelles that expose the positively charged trimethylammonium head group. Upon addition of NaOH, the pH of the system increases, and tetraethyl orthosilicate undergoes rapid alkaline-catalyzed hydrolysis to generate negatively charged silicate / metasilicate anions. Simultaneously, some... The process involves stepwise hydrolysis into zirconium hydroxide particles. Negatively charged silica species are adsorbed onto the outer layer of hexadecyltrimethylammonium bromide micelles via electrostatic interactions, undergoing initial condensation at the micelle interface to form an "organic template / inorganic precursor" complex core. Zirconium hydroxide complexes with nitrogen and phosphorus compounds also interact with adjacent molecules on the micelle surface. Condensation occurs, forming the initial Under continuous stirring and alkaline conditions, nucleophilic condensation and dehydration occur, and the network gradually grows, constructing a network around the hexadecyltrimethylammonium bromide micelle template. The framework, consisting mainly of zirconium hydroxide and nitrogen-phosphorus complexes, promotes further condensation and rearrangement of the inorganic network during the closed hydrothermal stage, increasing the degree of cross-linking between molecules, resulting in a denser particle structure and improved mechanical / chemical stability. Simultaneously, a more stable interaction is achieved between the template / ligand and the framework, inhibiting ligand loss. After cooling and filtration, free salts are removed by water washing. The alkyl chain of hexadecyltrimethylammonium bromide is oxidized into water-soluble small molecules such as alcohols, ketones, and acids by hydrogen peroxide, which are then carried out by the solvent. After drying, the pore / surface water and solvent are removed, opening the pores and eliminating the organic shielding, resulting in coprecipitated particles.
[0032] S4. Preparation of supported solid acids Weigh out 90g of coprecipitated particles and 450mL of 2mol / L sulfuric acid and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 70℃. Keep the mixture warm and stir for 120min. Lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a drying oven at 80℃ and dry it for 5h to obtain the supported solid acid preform. Weigh out 90g of the supported solid acid preform, 900mL of 60vol% ethanol solution and 21g of hexadecyltrimethoxysilane and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 60℃. Keep the temperature at 60℃ for 40min. Then lower the temperature of the reaction flask to room temperature, filter the mixture, and transfer the filter cake to a drying oven at 80℃ to dry it to constant weight to obtain the supported solid acid.
[0033] When coprecipitated particles come into contact with sulfuric acid, the particle surface... , Protonated by strong acids, residual organic templates and soluble salts are partially removed; simultaneously, the solution... With the surface of the carrier Coordination substitution and dehydration condensation occur, forming surface sulfate coordination species on Zr atoms. This chemically anchors the "sulfate" to the Zr site, laying the foundation for the subsequent formation of strong acid sites, resulting in a supported solid acid preform. The surface of the supported solid acid preform is then alkylated with hexadecyltrimethoxysilane to form a long alkane coating on the surface of the supported solid acid preform, thus preparing the supported solid acid.
[0034] Example 2: This example provides a method for preparing a supported solid acid, including the following steps: S1. Preparation of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide Weigh out 58.2 g of 2-diphenylphosphine and 582 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir until the system is dissolved. Add 20.9 g of 1,2-cyclohexanedicarboxylic acid chloride to the reaction flask and react at room temperature for 11 h. After the reaction flask is evacuated to -0.1 MPa, the temperature is gradually increased to 60 °C. Low-boiling substances are removed by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 55°C and stirred until the system dissolved. Then, while stirring, the reaction flask was allowed to cool naturally to room temperature, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and then dried under vacuum. The filter cake was transferred to a drying oven at 55°C and dried under vacuum to constant weight to obtain N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide. The crystallization solution consisted of dichloromethane and ethyl acetate in a volume ratio of 2:3.
[0035] S2. Preparation of nitrogen-phosphorus complexes Weigh out: 25.9 g of palladium dichloride di(acetonitrile), 69.1 g of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide and 483.7 mL of methanol into an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to reflux and maintain the temperature for 8.5 h. Then, evacuate the reaction flask to -0.1 MPa and remove low-boiling substances by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 55°C and stirred until the system dissolved. Then, the reaction flask was allowed to cool naturally to room temperature while stirring, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and dried under vacuum. The filter cake was transferred to a drying oven at 55°C and dried under vacuum to constant weight to obtain a nitrogen-phosphorus complex. The crystallization solution was composed of dichloromethane and ethanol in a volume ratio of 1:1.
[0036] S3. Preparation of coprecipitated particles Zirconium nitrate and deionized water were mixed at a ratio of 1.4 g: 5 mL and stirred until the system was dissolved to obtain a zirconium nitrate solution. Weigh out 50g of hexadecyltrimethylammonium bromide, 28g of nitrogen-phosphorus complex, and 400mL of deionized water and add them to a reaction flask. Stir for 10min and raise the temperature of the reaction flask to 55℃. Add 110g of tetraethyl orthosilicate and 200mL of zirconium nitrate solution to the reaction flask and stir for 4min. Add 100mL of 4.5mol / L sodium hydroxide solution to the reaction flask and keep the reaction at this temperature for 70min. Transfer the reaction solution to a polytetrafluoroethylene-lined reaction flask, seal and stir. Raise the temperature of the reaction flask to 93℃ and keep it at this temperature for 30h for crystallization. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake with purified water until neutral and then dry it. Add the filter cake and 10wt% hydrogen peroxide to the reaction flask at a solid-liquid ratio of 1:10 and stir. Raise the temperature of the reaction flask to 65℃ and stir for 5.5h. Filter the filter cake and wash it three times with ethanol and then dry it. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight. Grind the filter cake and pass it through a 100-mesh sieve to obtain coprecipitated particles.
[0037] S4. Preparation of supported solid acids Weigh out 90g of coprecipitated particles and 450mL of 2.5mol / L sulfuric acid and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 75℃. Keep the mixture at this temperature and stir for 140min. Then lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a drying oven at 85℃ and dry it for 5h to obtain the supported solid acid preform. Weigh out 90g of the supported solid acid preform, 900mL of 60vol% ethanol solution and 24g of hexadecyltrimethoxysilane and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 65℃. Keep the temperature for 50min and lower the temperature of the reaction flask to room temperature. Filter the mixture and transfer the filter cake to a drying oven at 80℃ to dry to constant weight to obtain the supported solid acid.
[0038] Example 3: This example provides a method for preparing a supported solid acid, including the following steps: S1. Preparation of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide Weigh 58.2 g of 2-diphenylphosphine and 582 mL of tetrahydrofuran and add them to an argon-protected reaction flask. Stir until the system dissolves. Add 20.9 g of 1,2-cyclohexanedicarboxylic acid chloride to the reaction flask and react at room temperature for 12 h. After the reaction flask is evacuated to -0.1 MPa, the temperature is gradually increased to 60 °C. Low-boiling substances are removed by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 60°C and stirred until the system dissolved. Then, while stirring, the reaction flask was allowed to cool naturally to room temperature, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and dried under vacuum. The filter cake was transferred to a drying oven at 60°C and dried under vacuum to constant weight to obtain N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide. The crystallization solution consisted of dichloromethane and ethyl acetate in a volume ratio of 2:3.
[0039] S2. Preparation of nitrogen-phosphorus complexes Weigh out: 25.9 g of palladium dichloride di(acetonitrile), 69.1 g of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide and 483.7 mL of methanol into an argon-protected reaction flask and stir. Raise the temperature of the reaction flask to reflux and maintain the temperature for 9 h. Then, evacuate the reaction flask to -0.1 MPa and remove low-boiling substances by vacuum distillation to obtain the reaction product. The reaction product and the crystallization solution were added to a reaction flask at a solid-liquid ratio of 1:3 and stirred. The temperature of the reaction flask was raised to 60°C and stirred until the system dissolved. Then, the reaction flask was allowed to cool naturally to room temperature while stirring, and a solid precipitated out. The solid was filtered, and the filter cake was washed three times with dichloromethane and dried under vacuum. The filter cake was transferred to a drying oven at 60°C and dried under vacuum to constant weight to obtain a nitrogen-phosphorus complex. The crystallization solution was composed of dichloromethane and ethanol in a volume ratio of 1:1.
[0040] S3. Preparation of coprecipitated particles Zirconium nitrate and deionized water were mixed at a ratio of 1.6 g: 5 mL and stirred until the system was dissolved to obtain a zirconium nitrate solution. Weigh out 60g of hexadecyltrimethylammonium bromide, 30g of nitrogen-phosphorus complex, and 400mL of deionized water and add them to a reaction flask. Stir for 12min and raise the temperature of the reaction flask to 60℃. Add 120g of tetraethyl orthosilicate and 200mL of zirconium nitrate solution to the reaction flask and stir for 5min. Add 100mL of 5mol / L sodium hydroxide solution to the reaction flask and keep the reaction at this temperature for 80min. Transfer the reaction solution to a polytetrafluoroethylene-lined reaction flask, seal and stir. Raise the temperature of the reaction flask to 95℃ and keep it at this temperature for 30h for crystallization. Lower the temperature of the reaction flask to room temperature and filter. Wash the filter cake with purified water until neutral and then dry it. Add the filter cake and 10wt% hydrogen peroxide to the reaction flask at a solid-liquid ratio of 1:10 and stir. Raise the temperature of the reaction flask to 70℃ and stir for 6h. Filter the filter cake and wash it three times with ethanol and then dry it. Transfer the filter cake to a drying oven at 75℃ and dry it to constant weight. Grind the filter cake and pass it through a 100-mesh sieve to obtain coprecipitated particles.
[0041] S4. Preparation of supported solid acids Weigh out 90g of coprecipitated particles and 450mL of 3mol / L sulfuric acid and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 80℃. Keep the mixture warm and stir for 160min. Lower the temperature of the reaction flask to room temperature and filter the mixture. Transfer the filter cake to a drying oven at 90℃ and dry it for 5h to obtain the supported solid acid preform. Weigh out 90g of the supported solid acid preform, 900mL of 60vol% ethanol solution and 27g of hexadecyltrimethoxysilane and add them to the reaction flask. Stir the mixture and raise the temperature of the reaction flask to 70℃. Keep the temperature at 70℃ for 60min. Then lower the temperature of the reaction flask to room temperature, filter the mixture, and transfer the filter cake to a drying oven at 80℃ to dry it to constant weight to obtain the supported solid acid.
[0042] Example 4: This example provides a catalytic system for the efficient synthesis of methyl cinnamate, which comprises the following components by weight: 1 part of the supported solid acid prepared in Example 1 and 5 parts of dehydrating agent; The dehydrating agent is a 3A molecular sieve that has been dried at a constant temperature of 105℃ for 24 hours.
[0043] Example 5: This example provides a catalytic system for the efficient synthesis of methyl cinnamate, which comprises the following components by weight: 1 part of the supported solid acid prepared in Example 2 and 6 parts of dehydrating agent; The dehydrating agent is a 3A molecular sieve that has been dried at a constant temperature of 108℃ for 22 hours.
[0044] Example 6: This example provides a catalytic system for the efficient synthesis of methyl cinnamate, which comprises the following components by weight: 1 part of the supported solid acid prepared in Example 3 and 7 parts of dehydrating agent; The dehydrating agent is a 3A molecular sieve that has been dried at a constant temperature of 110℃ for 20 hours.
[0045] Comparative Example 1 The difference between this comparative example and Example 6 is that, in the preparation of the supported solid acid, steps S1-S2 were omitted, and a nitrogen-phosphorus complex was not added in step S3.
[0046] Comparative Example 2 The difference between this comparative example and Example 6 is that, in the preparation of the supported solid acid, step S2 is omitted, and the nitrogen-phosphorus complex in step S3 is replaced by N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide prepared in step S1.
[0047] Comparative Example 3 The difference between this comparative example and Example 6 is that, in the preparation of the supported solid acid, zirconium nitrate in step S3 is replaced by an equimolar amount of palladium nitrate.
[0048] Comparative Example 4 The difference between this comparative example and Example 6 is that, in the preparation of the supported solid acid, the supported solid acid preform in step S4 is used instead of the supported solid acid.
[0049] Comparative Example 5 The difference between this comparative example and Example 6 is that the amount of dehydrating agent used is reduced to 1 part.
[0050] Performance testing: The catalytic systems prepared in Examples 4-6 and Comparative Examples 1-5 were used to react cinnamic acid with methanol to prepare methyl cinnamate, and the conversion rate of the catalytic system in the reaction of cinnamic acid with methanol to prepare methyl cinnamate was measured. The experimental method for preparing methyl cinnamate by catalyzing the reaction of cinnamic acid with methanol is as follows: 148g of cinnamic acid, 325mL of methanol, and 16g of the catalyst were added to a reaction flask. The reaction flask was then fixed in an oil bath with mechanical stirring. The oil bath temperature was raised to 69-72℃ and the reaction was maintained for 2 hours. The mixture was filtered while hot. The filter cake was washed with dichloromethane and then regenerated to obtain the regenerated catalyst system. The washing solution of the filter cake was mixed with the filtrate and transferred to a rotary evaporator with a water bath temperature of 50℃. Low-boiling substances were removed by vacuum evaporation to obtain the crude product. Sodium hydroxide was added to the flask containing the crude product. The pH of the system was set to 8. The mixture was allowed to stand and separated. The upper organic matter was washed with purified water until neutral and then transferred to a drying oven at 75℃ to dry to constant weight to obtain methyl cinnamate. The regeneration method of the catalytic system is as follows: filter cake and 5 mol / L sulfuric acid are added to the reaction flask at a solid-liquid ratio of 1:8. The temperature of the reaction flask is raised to 60℃ and stirred for 1 hour. After filtration, the filter cake is washed three times with purified water and anhydrous methanol and then transferred to a drying oven at 85℃ for 8 hours. Then it is transferred to a drying oven at 110℃ for 20 hours to obtain the regenerated catalytic system. Repeat the above operation and measure the conversion rate of the regenerated catalytic system obtained in the 10th reaction to prepare methyl cinnamate from cinnamic acid; The conversion rate of the catalytic system for the reaction of cinnamic acid and methanol to prepare methyl cinnamate is shown in the formula. The calculation yields the following result: This represents the actual molar amount of methyl cinnamate obtained during preparation. The molar amount of cinnamic acid used in the reaction process is shown in Table 1 below.
[0051] Table 1 - Performance Test Data of Samples
[0052] Data Analysis: The catalytic system prepared in this invention achieves a conversion rate of 97.5% when catalyzing the reaction of cinnamic acid with methanol to prepare methyl cinnamate. After 10 cycles of regeneration, the conversion rate reaches 96.0%. All performance test data are superior to those of the comparative example, indicating that this invention, through the synergistic effect of nitrogen-phosphorus complexes and Zr-Si framework, combined with the low water activity control of 3A molecular sieves, not only effectively improves the conversion rate of catalyzing the reaction of cinnamic acid with methanol to prepare methyl cinnamate, but also exhibits excellent regeneration performance.
[0053] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A highly efficient catalytic system for the synthesis of methyl cinnamate, characterized in that, Includes supported solid acids and dehydrating agents; The preparation method of the supported solid acid is as follows: coprecipitated particles and sulfuric acid are mixed, the temperature of the reaction system is raised to 70-80℃, the reaction is carried out for 120-160 min, and after post-treatment, a supported solid acid preform is obtained. Then, the supported solid acid preform is coated and modified with hexadecyltrimethoxysilane to obtain the supported solid acid.
2. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 1, characterized in that, The weight ratio of the supported solid acid to the dehydrating agent is 1:5-7, and the dehydrating agent is 3A molecular sieve.
3. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 1, characterized in that, The ratio of coprecipitated particles to sulfuric acid is 3g:15mL, and the concentration of sulfuric acid is 2-3mol / L.
4. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 1, characterized in that, The method for preparing the coprecipitated particles is as follows: hexadecyltrimethylammonium bromide, nitrogen-phosphorus complex, and deionized water are mixed and stirred for 8-12 minutes. The temperature of the reaction system is raised to 50-60℃. Tetraethyl orthosilicate and zirconium nitrate solution are added to the reaction system and stirred for 3-5 minutes. Alkali solution is added to the reaction system and the reaction is kept at a constant temperature for 60-80 minutes. After crystallization and post-treatment, coprecipitated particles are obtained.
5. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 4, characterized in that, The ratio of hexadecyltrimethylammonium bromide, nitrogen-phosphorus complex, deionized water, tetraethyl orthosilicate, zirconium nitrate solution, and alkaline solution is 2-3g:1.3-1.5g:20mL:5-6g:10mL:5mL. The zirconium nitrate solution is composed of zirconium nitrate and deionized water at a ratio of 1.2-1.6g:5mL. The alkaline solution is a 4-5mol / L sodium hydroxide solution. The crystallization temperature is 90-95℃, and the crystallization time is 30h.
6. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 4, characterized in that, The nitrogen-phosphorus complex was prepared by mixing palladium di(acetonitrile)dichloride, N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide and methanol under an inert gas atmosphere. The reaction system temperature was raised to reflux, and the reaction was maintained at this temperature for 8-9 hours. After post-treatment, the nitrogen-phosphorus complex was obtained.
7. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 6, characterized in that, The molar ratio of palladium dichloride (acetonitrile) to N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is 1:1, and the molar ratio of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide to methanol is 1 g:7 mL.
8. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 6, characterized in that, The preparation method of N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is as follows: under an inert gas atmosphere, 2-diphenylphosphine and tetrahydrofuran are mixed and stirred until the system is dissolved. 1,2-cyclohexanedicarboxyl chloride is added to the reaction system, and the reaction is carried out at room temperature for 10-12 h. After post-treatment, N,N′-bis(2-diphenylphosphine)cyclohexane-1,2-dicarboxamide is obtained.
9. The catalytic system for the efficient synthesis of methyl cinnamate according to claim 8, characterized in that, The ratio of 2-diphenylphosphine to tetrahydrofuran is 1 g:10 mL, and the molar ratio of 2-diphenylphosphine to 1,2-cyclohexanedicarboxylic acid chloride is 2.1:1.