Method for synthesizing ethyl cinnamate by using microporous molecular sieve as catalyst

Abstract

The application discloses a method for catalytically synthesizing ethyl cinnamate by using a microporous molecular sieve, and comprises the following steps: dissolving cinnamic acid in ethanol to obtain an ethyl alcohol cinnamic acid solution, wherein the mass ratio of the cinnamic acid to the ethanol is 1:1.5-50; adding a catalyst into the ethyl alcohol cinnamic acid solution, and reacting at a temperature of 150-300 DEG C for 2-72 h, wherein the catalyst is a microporous hydrogen type molecular sieve or a modified microporous molecular sieve, and the mass ratio of the catalyst to the cinnamic acid is 0.025-1.5:1; and obtaining the ethyl cinnamate by performing vacuum distillation on the reaction product obtained in the step b. The target product has high selectivity, especially the microporous hydrogen type molecular sieve or the modified microporous molecular sieve has high activity, can be repeatedly used and regenerated, and can effectively reduce the preparation cost of the ethyl cinnamate, and can be suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing ethyl cinnamate, and more particularly to a method for synthesizing ethyl cinnamate using microporous molecular sieve catalysis. Background Technology

[0002] Ethyl cinnamate, also known as ethyl β-phenylacrylate or ethyl 3-phenylpropionate, has the molecular formula PhCH=CHCOOEt. It is found in natural plants such as the volatile oil of Elaeagnus angustifolia flowers. It has a pleasant aroma, such as fruit (sweet orange and grape) and floral scents. It is mainly used as a flavoring agent in cigarettes and in the preparation of fragrances.

[0003] Previously, ethyl cinnamate was industrially synthesized via Claisen condensation of ethyl acetate and benzaldehyde under the action of metallic sodium, or via esterification of cinnamic acid and ethanol under sulfuric acid catalysis. However, both methods have their problems. The former involves certain risks due to the instability of metallic sodium; the latter is problematic because concentrated sulfuric acid is highly corrosive, easily corroding equipment and instruments, polluting the environment, and making subsequent product processing difficult and prone to side reactions.

[0004] To overcome the problems of traditional techniques, the preparation of ethyl cinnamate using simple, non-toxic, and non-corrosive solid acids as catalysts has become increasingly popular in recent years. Wang Weihong et al. reported a method for preparing ethyl cinnamate using toluenesulfonic acid as a catalyst: when... n 对甲苯磺酸 : n 肉桂酸 : n 乙醇 The ratio of 0.15:1:10 was used, and the reaction was refluxed for 2 h, resulting in a yield of ethyl cinnamate of 89.1%. However, p-toluenesulfonic acid is readily soluble in the reaction system, making subsequent separation difficult and preventing reuse after recovery, leading to high preparation costs. Peng Anshun et al. studied a method for synthesizing ethyl cinnamate using aminosulfonic acid as a catalyst: when... n 肉桂酸 : n 乙醇 With a ratio of 1:3.5, 1g catalyst, and reflux for 4 hours to remove water, the yield of ethyl cinnamate reached 95.4%. Sulfamic acid is an inorganic solid acid formed by replacing the hydroxyl group of sulfuric acid with an amino group. Compared to sulfuric acid, it is safer to use, less corrosive, and can be reused after recovery. Compared to toluenesulfonic acid, it reduces costs. However, sulfamic acid still has a corrosive effect on the skin, and long-term use can lead to skin ulceration. Deqing et al. used TiCl4 to produce SO4. 2- Ethyl cinnamate was synthesized using TiO2 solid superacid catalysis. n 肉桂酸 : n 乙醇With a ratio of 1:5 and a catalyst concentration of 1.20 g, reflux for 4 h, the yield of ethyl cinnamate reached 89.3%. Furthermore, the catalyst was reused 6 times, and the yield still reached 87.8%. (SO4) 2- TiO2 solid superacid is an acid with a stronger acid strength than 100% sulfuric acid, but it has advantages such as non-corrosiveness to equipment, high reactivity, good selectivity, and easy separation. However, this acid has defects such as small specific surface area, irregular pore structure, and almost non-regenerable catalytic activity, which makes it difficult to use the catalyst in industrial production due to the relatively high production cost.

[0005] Molecular sieve catalysts have a wide range of applications in petroleum refining, petrochemical and fine chemical industries. However, to date, there have been no reports on the preparation of ethyl cinnamate using H-ZSM-5 molecular sieve, HY type molecular sieve, H-β type molecular sieve and their modified microporous molecular sieves as catalysts. Summary of the Invention

[0006] The present invention aims to solve the above-mentioned technical problems existing in the prior art by providing a method for synthesizing ethyl cinnamate using microporous molecular sieve catalysis.

[0007] The technical solution of this invention is: a method for synthesizing ethyl cinnamate using microporous molecular sieve catalysis, comprising the following steps: a. Cinnamic acid is dissolved in ethanol to obtain a cinnamic acid ethanol solution, wherein the mass ratio of cinnamic acid to ethanol is 1:1.5~50; b. Add a catalyst to the cinnamic acid ethanol solution and react at a temperature of 150~300 ℃ for 2~72 h. The catalyst is a microporous hydrogen molecular sieve or a modified microporous molecular sieve, and the mass ratio of the catalyst to cinnamic acid is 0.025~1.5:1. c. The reaction product obtained in step b is subjected to vacuum distillation to obtain ethyl cinnamate.

[0008] The microporous hydrogen-type molecular sieve is at least one of H-ZSM-5 molecular sieve, HY-type molecular sieve and H-β-type molecular sieve.

[0009] The modified microporous molecular sieve is a microporous molecular sieve on which P2O5 or SO3 is loaded, wherein the mass ratio of P2O5 or SO3 to the microporous molecular sieve is 0.5-30%, and the microporous molecular sieve is at least one of ZSM-5 molecular sieve, Y-type molecular sieve and β-type molecular sieve.

[0010] The modified microporous molecular sieve is prepared by the following method: the microporous hydrogen-type molecular sieve is immersed in ammonium phosphate solution or ammonium sulfate solution for 2-48 h, the solid is dried at 80-120 ℃, and then calcined at 300-600 ℃ in air atmosphere for 2-48 h. The microporous hydrogen-type molecular sieve is at least one of H-ZSM-5 molecular sieve, HY type molecular sieve and H-β type molecular sieve.

[0011] This invention uses microporous hydrogen molecular sieves or their modified microporous molecular sieves as catalysts to catalyze the esterification reaction of cinnamic acid and ethanol at relatively low reaction temperatures to synthesize high-value-added ethyl cinnamate. It not only achieves high selectivity for the target product but also solves the problems of corrosion of equipment and human skin, environmental pollution, difficult product handling, and side reactions inherent in existing technologies. In particular, the microporous hydrogen molecular sieves or modified microporous molecular sieves used have high activity, can be reused and regenerated, effectively reducing the preparation cost of ethyl cinnamate and making it suitable for industrial production. Detailed Implementation

[0012] Example 1: a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of three polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.5 g of H-ZSM-5 molecular sieve, 0.5 g of HY molecular sieve and 0.5 g of H-β molecular sieve to the cinnamic acid ethanol solution, and react for 8 h at reaction temperatures of 150 ℃, 160 ℃, 170 ℃, 180 ℃ and 190 ℃, respectively; c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 1.

[0013] Table 1 *: (Result after chromatographic normalization calculation); **: (Result after chromatographic normalization calculation) Example 2: a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of three polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.5 g of modified microporous molecular sieves prepared by different methods and named β-5% P2O5, β-10% P2O5 or β-10% SO3 to the cinnamic acid ethanol solution, and react at 180 ℃ for 8 h. The preparation methods for β-5% P2O5 and β-10% P2O5 are as follows: A strip-shaped H-β type molecular sieve is immersed in an NH4H2PO4 solution for 12 h. The solid is then dried at 100 ℃ and calcined at 550 ℃ for 4 h in air atmosphere to obtain β-5% P2O5 and β-10% P2O5, respectively. The concentration of NH4H2PO4·2H2O is based on a mass ratio of 5.0% and 10.0% of the P2O5 obtained after calcination at 550 ℃ for 4 h to the strip-shaped β type molecular sieve, respectively. The preparation method of β-10% SO3 is as follows: strip-shaped H-β type molecular sieves are immersed in (NH4)2SO4 solution for 12 h, the solid is dried at 100 ℃, and then calcined at 550 ℃ for 4 h in air atmosphere to obtain β-10% SO3. The concentration of (NH4)2SO4 is based on the mass ratio of SO3 obtained after calcination at 550 ℃ for 4 h to strip-shaped β type molecular sieves being 10.0%. c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 2.

[0014] Table 2 *: (Result after chromatographic normalization calculation); **: (Result after chromatographic normalization calculation) Example 3: a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of the six polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.025 g, 0.065 g, 0.125 g, 0.250 g, 0.750 g and 1.000 g of H-β type molecular sieve to cinnamic acid ethanol solution respectively, and react at 180 ℃ for 8 h; c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 3.

[0015] Table 3 *: (Result after chromatographic normalization calculation); **: (Result after chromatographic normalization calculation) Example 4: a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of three polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.5 g of H-β type molecular sieve to the cinnamic acid ethanol solution and react at a reaction temperature of 180 °C for 2, 6, and 12 h, respectively; c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 4.

[0016] Table 4 The results show that using microporous hydrogen molecular sieves or their modified microporous molecular sieves as catalysts, the esterification reaction of cinnamic acid and ethanol can be catalyzed at lower reaction temperatures to synthesize high-value-added ethyl cinnamate. The target product has high selectivity, and the problems of corrosion of equipment and human skin, environmental pollution, difficult product handling, and side reactions caused by existing technologies are solved.

[0017] experiment: 1. Catalyst repeatability experiment The H-β type molecular sieve catalyst used in Example 1 and the β-5% P2O5, β-10% P2O5 and β-10% SO3 catalysts used in Example 2 were dried at 180 °C (one-time drying) and then subjected to the following reactions respectively: a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of four polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.5 g of the dried H-β type molecular sieve, β-5% P2O5, β-10% P2O5 and β-10% SO3 to the cinnamic acid ethanol solution respectively, and react at 180 ℃ for 8 h; c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 5.

[0018] The H-β type molecular sieve, β-5% P2O5, β-10% P2O5 and β-10% SO3 that underwent the above experimental reactions were dried at 180 °C for a second time (double drying), and then the a and b reactions of the above experiments were carried out again. The reaction product obtained in step b was then subjected to vacuum distillation and online analysis by chromatograph to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 5.

[0019] Table 5 *: (Result after chromatographic normalization calculation); **: (Result after chromatographic normalization calculation) 2. Catalyst activity regeneration experiment When the H-β type molecular sieve catalyst used in Example 1 of this invention and the β-5% P2O5 and β-10% SO3 catalysts used in Example 2 lose their activity, they are subjected to the following reactions after calcination at 550 °C for 4 h (one regeneration): a. Add 1.0 g of cinnamic acid and 10.0 g of ethanol to each of four polytetrafluoroethylene-lined reactors to obtain a cinnamic acid-ethanol solution; b. Add 0.5 g of the H-β type molecular sieve, β-5% P2O5 and β-10% SO3 that have been calcined as described above to the cinnamic acid ethanol solution, and react at 180 °C for 8 h. c. The reaction product obtained in step b was subjected to vacuum distillation and then analyzed online by chromatography to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 6.

[0020] The above experimental reaction was repeated. When the H-β type molecular sieve, β-5% P2O5 and β-10% SO3 used lost their activity again, the H-β type molecular sieve, β-5% P2O5 and β-10% SO3 were calcined again at 550 °C for 4 h (secondary regeneration) and the reaction steps a and b of the above experiment were carried out again. Then the reaction product obtained in step b was subjected to vacuum distillation and online analysis by chromatograph to determine that it was ethyl cinnamate. The conversion rate and selectivity of ethyl cinnamate are shown in Table 6.

[0021] Table 6 *: (Result after chromatographic normalization calculation); **: (Result after chromatographic normalization calculation) Experiments show that the catalyst used in the embodiments of the present invention can be reused and regenerated, thus effectively reducing the preparation cost of ethyl cinnamate and making it suitable for industrial production.

Claims

1. A method for synthesizing ethyl cinnamate using microporous molecular sieve catalysis, characterized in that... Follow these steps: a. Cinnamic acid and ethanol are added to a polytetrafluoroethylene-lined reactor to dissolve the cinnamic acid in the ethanol to obtain a cinnamic acid-ethanol solution, wherein the mass ratio of cinnamic acid to ethanol is 1:1.5~50. b. Add a catalyst to the cinnamic acid ethanol solution and react at a temperature of 150~300 ℃ for 2~72 h. The catalyst is a microporous hydrogen molecular sieve or a modified microporous molecular sieve, and the mass ratio of the catalyst to cinnamic acid is 0.025~1.5:

1. c. The reaction product obtained in step b is subjected to vacuum distillation to obtain ethyl cinnamate; The microporous hydrogen-type molecular sieve is at least one of H-ZSM-5 molecular sieve, HY-type molecular sieve and H-β-type molecular sieve; the modified microporous molecular sieve is H-β-type molecular sieve with P2O5 or SO3 loaded on it, and the mass ratio of P2O5 or SO3 to H-β-type molecular sieve is 0.5~30%.

2. The method for synthesizing ethyl cinnamate using microporous molecular sieve catalysis according to claim 1, characterized in that... The modified microporous molecular sieve is prepared by the following method: the microporous hydrogen-type molecular sieve is immersed in ammonium phosphate solution or ammonium sulfate solution for 2-48 h, the solid is dried at 80-120 ℃, and then calcined at 300-600 ℃ in air atmosphere for 2-48 h.

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