A method for the synthesis of carboxylic acid esters
By using esterification pre-reaction and reactive distillation esterification reaction of toluenesulfonate catalyst, the problem of difficult catalyst separation and recovery was solved, and efficient and low-energy-consumption carboxylic acid ester synthesis was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING FORESTRY UNIV
- Filing Date
- 2026-03-11
- Publication Date
- 2026-06-09
AI Technical Summary
In existing technologies, homogeneous catalysts are difficult to separate and recover, while heterogeneous catalysts have low reaction efficiency, long reaction time, and high energy consumption.
By using p-toluenesulfonate as a catalyst, a combination of esterification pre-reaction and reactive distillation esterification reaction is adopted to achieve homogeneous reaction of the catalyst and separate and recover it during the distillation process, thereby shortening the reaction time and reducing energy consumption.
This method enables efficient separation and recovery of the catalyst, shortens the reaction time, reduces energy consumption, and improves reaction efficiency.
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Figure CN122167287A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organic synthesis, and more specifically to a method for synthesizing carboxylic esters. Background Technology
[0002] Carboxylic acid esters are compounds formed when the hydroxyl group of the carboxyl group in a carboxylic acid molecule is replaced by an alkoxy group. They are an important class of organic compounds, widely found in nature (such as oils and fragrances) and industrial products. Direct esterification is currently a very mature method for producing carboxylic acid esters. The core of this method is to select a suitable catalyst and azeotropic dehydrating agent, and determine reasonable reaction conditions to improve the activity, selectivity, and yield of the esterification reaction. Based on the phase relationship between the catalyst and the reaction system, catalysts can be divided into homogeneous catalysts and heterogeneous catalysts. These two types differ significantly in their mechanisms of action, application scenarios, and advantages and disadvantages: Homogeneous catalysts mainly include protic acids, Lewis acids, and organometallic compounds. Their advantages include uniform active centers, sufficient contact with reactants, high catalytic efficiency, and wide applicability. However, homogeneous catalysts also have disadvantages such as difficulty in separation and recovery, complex product post-processing, and strong corrosivity. Heterogeneous catalysts mainly include solid acids, metal oxides / composite oxides, and supported metal catalysts. Heterogeneous catalysts are easy to separate and recover, reusable, and have low corrosivity to equipment. However, solid-liquid heterogeneous reactions suffer from interphase mass transfer resistance, reducing the reaction rate. Summary of the Invention
[0003] This invention provides a method for synthesizing carboxylic esters, which shortens the reaction time and facilitates the separation and recovery of the catalyst.
[0004] This invention provides a method for synthesizing carboxylic esters, comprising the following steps: A pre-esterification reaction is carried out by mixing fatty alcohols and / or alcohol ethers, fatty acids and p-toluenesulfonate to obtain a pre-reaction system containing dissolved p-toluenesulfonate; the pre-reaction system contains a portion of carboxylic acid esters, unreacted fatty alcohols and / or alcohol ethers, fatty acids and a portion of by-product water; The pre-reaction system is mixed with an azeotropic dehydrating agent and subjected to reactive distillation esterification to separate byproduct water, thereby obtaining the carboxylic acid ester.
[0005] Preferably, the fatty alcohol includes one or more of isopropanol, butanol, n-pentanol, isoamyl alcohol, hexanol, octanol, and benzyl alcohol; The alcohol ethers include one or more of the following: ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, diethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, and diethylene glycol phenyl ether.
[0006] Preferably, the fatty acid includes one of acetic acid, propionic acid, and butyric acid.
[0007] Preferably, the molar ratio of the alcohol to the fatty acid is 1:0.8~1.5.
[0008] Preferably, the p-toluenesulfonate includes one or more of nickel p-toluenesulfonate, zinc p-toluenesulfonate, calcium p-toluenesulfonate, magnesium p-toluenesulfonate, barium p-toluenesulfonate, cobalt p-toluenesulfonate, aluminum p-toluenesulfonate, and iron p-toluenesulfonate.
[0009] Preferably, the mass of the catalyst is 0.05-1% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids.
[0010] Preferably, the esterification pre-reaction temperature is 60~100℃ and the time is 0.5~4h.
[0011] Preferably, the azeotropic dehydrating agent includes one of ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, and n-butyl ether; The mass of the azeotropic dehydrating agent is 5-35% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids.
[0012] Preferably, the reactive distillation esterification reaction is carried out at a temperature of 100-180°C for 4-5 hours.
[0013] Preferably, after the reactive distillation esterification reaction, the process further includes: removing the azeotropic dehydrating agent and unreacted raw materials from the system obtained by the reactive distillation esterification reaction, and then performing atmospheric or vacuum evaporation in an evaporator; entering the vapor phase obtained by the evaporation into a distillation column for atmospheric or vacuum distillation to obtain a carboxylic acid ester; and recycling the p-toluenesulfonate obtained at the bottom of the evaporator.
[0014] This invention uses p-toluenesulfonate as a catalyst for esterification pre-reaction, resulting in a pre-reaction system containing dissolved p-toluenesulfonate. During the reactive distillation esterification reaction, the reaction system is homogeneous (esterification pre-reaction followed by reactive distillation esterification reaction). After the reaction, p-toluenesulfonate can be fully recovered and recycled. Compared with conventional sulfuric acid and p-toluenesulfonic acid, it has better selectivity and less corrosion to the reactor. In addition, this invention can shorten the reaction time and reduce energy consumption through esterification pre-reaction and reactive distillation esterification reaction.
[0015] Furthermore, this invention adds an evaporator before entering the distillation column to vaporize the crude esterification product of reactive distillation (atmospheric or reduced pressure). The vaporized crude carboxylic acid ester product is then subjected to atmospheric or reduced pressure distillation to obtain the product. The catalyst is separated by precipitating in the evaporator, and the collected catalyst is returned to the pre-reaction system for recycling, thus achieving clean production. Attached Figure Description
[0016] Figure 1 This is a schematic diagram of the synthetic route for carboxylic esters. Detailed Implementation
[0017] This invention provides a method for synthesizing carboxylic esters, comprising the following steps: A pre-esterification reaction is carried out by mixing fatty alcohols and / or alcohol ethers, fatty acids and p-toluenesulfonate to obtain a pre-reaction system containing dissolved p-toluenesulfonate; the pre-reaction system contains a portion of carboxylic acid esters, unreacted fatty alcohols and / or alcohol ethers, fatty acids and a portion of by-product water; The pre-reaction system is mixed with an azeotropic dehydrating agent and subjected to reactive distillation esterification to separate byproduct water, thereby obtaining the carboxylic acid ester.
[0018] This invention involves mixing fatty alcohols and / or alcohol ethers, fatty acids, and p-toluenesulfonate for esterification pre-reaction to obtain a pre-reaction system containing dissolved p-toluenesulfonate.
[0019] In this invention, the molar ratio of the alcohol and / or alcohol ether to the fatty acid is preferably 1:0.8 to 1.5, and in specific embodiments of this invention, it can be 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, or 1:1.4; the fatty alcohol preferably includes one or more of isopropanol, butanol, n-pentanol, isoamyl alcohol, hexanol, octanol, and benzyl alcohol; the alcohol ether preferably includes ethylene glycol methyl ether and ethylene glycol ethyl ether. The fatty acid comprises one or more of the following: ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, diethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, and diethylene glycol phenyl ether; the fatty acid preferably comprises one or more of acetic acid, propionic acid, and butyric acid.
[0020] In this invention, the catalyst is p-toluenesulfonate, and the mass of the catalyst is preferably 0.05-1% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids. In specific embodiments of this invention, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, or 0.9%. The p-toluenesulfonate preferably includes one or more of nickel p-toluenesulfonate, zinc p-toluenesulfonate, calcium p-toluenesulfonate, magnesium p-toluenesulfonate, barium p-toluenesulfonate, cobalt p-toluenesulfonate, aluminum p-toluenesulfonate, and iron p-toluenesulfonate.
[0021] In this invention, the preferred temperature for the esterification pre-reaction is 60~100℃, and the preferred time is 0.5~4h. In specific embodiments of this invention, the preferred temperature for the esterification pre-reaction can be 65℃, 70℃, 75℃, 80℃, 85℃, 90℃ or 95℃, and the preferred time can be 1h, 1.5h, 2h, 2.5h, 3h or 3.5h.
[0022] After obtaining a pre-reaction system containing dissolved p-toluenesulfonate, the present invention mixes the pre-reaction system with an azeotropic dehydrating agent to carry out reactive distillation esterification reaction, separates the by-product water, and obtains the carboxylic acid ester.
[0023] In this invention, the mass of the azeotropic dehydrating agent is preferably 5-35% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids. In specific embodiments of this invention, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, or 32%. The azeotropic dehydrating agent preferably includes one of ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, and n-butyl ether.
[0024] In this invention, the temperature of the reactive distillation esterification reaction is preferably 100~180℃, and the time is preferably 4~5h. In specific embodiments of this invention, the temperature of the reactive distillation esterification reaction can be 110℃, 120℃, 130℃, 140℃, 150℃, 160℃ or 170℃, and the time can be 4.2h, 4.5h or 4.8h.
[0025] In this invention, the reactive distillation esterification reaction is preferably carried out in a distillation apparatus equipped with a distillation column. During the reactive distillation esterification reaction, the water generated in the reaction is continuously discharged from the top of the column, while the azeotropic dehydrating agent is refluxed into the column for continuous azeotropic dehydration.
[0026] After the reactive distillation esterification reaction, the present invention preferably further includes: after the reactive distillation esterification reaction, the azeotropic dehydrating agent and unreacted raw materials in the system obtained by the reactive distillation esterification reaction are removed and then evaporated in an evaporator; The crude carboxylic acid ester obtained from the evaporation is fed into a distillation column for distillation to obtain a carboxylic acid ester, and the p-toluenesulfonate obtained at the bottom of the evaporator is recycled.
[0027] After the reactive distillation esterification reaction, the present invention more preferably includes: first distilling the reactive distillation esterification reactants to remove the azeotropic dehydrating agent and unreacted raw materials (returning them to the reaction system for recycling), removing the crude product, and then evaporating it in an evaporator under atmospheric or reduced pressure. The crude carboxylic acid ester obtained from the evaporation is fed into a distillation column for atmospheric or vacuum distillation to obtain the carboxylic acid ester product. The p-toluenesulfonate obtained at the bottom of the evaporator is recycled.
[0028] The following detailed description of the synthesis method of carboxylic esters provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.
[0029] Figure 1 This is a schematic diagram of the synthetic route for carboxylic esters.
[0030] Example 1 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 324g of diethylene glycol butyl ether, 156g of acetic acid, and 3g of zinc p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 120g of sec-butyl acetate was added. The reaction temperature was controlled at 120~140℃, and the reactants were kept in a boiling state. The reaction was continued for 5 hours to obtain 563g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 2.8g of catalyst was recovered after evaporating the crude product.
[0031] Table 1. Composition and content of the crude product obtained in Example 1
[0032] Example 2 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 433g of 2-ethylhexanol, 230g of acetic acid, and 1.5g of magnesium p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 120g of sec-butyl acetate was added. The reaction temperature was controlled at 120~155℃, and the reactants were kept in a boiling state. The reaction was continued for 5 hours to obtain 723g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 2.8g of catalyst was recovered by evaporation of the crude product.
[0033] Table 2. Composition and content of the crude product obtained in Example 2
[0034] Example 3 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 308g of diethylene glycol ethyl ether, 179g of acetic acid, and 3.1g of aluminum p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 146g of butyl acetate was added. The reaction temperature was controlled at 120~140℃, and the reactants were kept in a boiling state. The reaction was continued for 5 hours to obtain 592g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 2.9g of catalyst was recovered after evaporating the crude product.
[0035] Table 3. Composition and content of the crude product obtained in Example 3
[0036] Example 4 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 291g of propylene glycol ethyl ether, 218g of acetic acid, and 3.3g of aluminum p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 152g of sec-butyl acetate was added. The reaction temperature was controlled at 120~140℃, and the reactants were kept in a boiling state for 5 hours to obtain 610g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 3.1g of catalyst was recovered after evaporating the crude product.
[0037] Table 4. Composition and content of the crude product obtained in Example 4
[0038] Example 5 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 295g of ethylene glycol butyl ether, 195g of acetic acid, and 3.2g of aluminum p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 147g of sec-butyl acetate was added. The reaction temperature was controlled at 120~140℃, and the reactants were kept in a boiling state. The reaction was continued for 4 hours to obtain 591g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 3.1g of catalyst was recovered after evaporating the crude product.
[0039] Table 5. Composition and content of the crude product obtained in Example 5
[0040] Example 6 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 295g of ethylene glycol butyl ether, 195g of acetic acid, and 3.2g of aluminum p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, and then 100g of sec-butyl acetate and 50g of n-butyl acetate were added. The reaction temperature was controlled at 120~140℃, and the reactants were kept in a boiling state. The reaction was continued for 4 hours to obtain 593g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 3.1g of catalyst was recovered after evaporating the crude product.
[0041] Table 6. Composition and content of the crude product obtained in Example 6
[0042] Example 7 In a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), 243g of propylene glycol methyl ether, 260g of propionic acid, and 3.3g of aluminum p-toluenesulfonate were added. The mixture was first reacted at 80℃ for 2 hours, then 151g of n-butyl ether was added. The reaction temperature was controlled at 120-140℃, maintaining the reactants at a constant boiling state for 5 hours, yielding 605g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 3.1g of catalyst was recovered after evaporating the crude product.
[0043] Table 7. Composition and content of the crude product obtained in Example 7
[0044] Example 8 In Example 7, the recovered catalyst was recycled. 243g of propylene glycol methyl ether and 260g of propionic acid were added to a 1000mL three-necked flask equipped with a water separator and a reflux condenser (ɸ20×800 packed column), along with 3.1g of recovered catalyst. The mixture was reacted at 80℃ for 2 hours, followed by the addition of 151g of n-butyl ether. The reaction temperature was controlled at 120~140℃, and the reactants were kept at a constant boiling state for 5 hours, yielding 604g of crude product. The composition of the reaction mixture is shown in the table below. The azeotropic dehydrating agent and unreacted products were recovered by vacuum distillation, and 2.9g of catalyst was recovered after evaporating the crude product.
[0045] Table 8. Composition and content of the crude product obtained in Example 8
[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for synthesizing a carboxylic acid ester, characterized in that, Includes the following steps: A pre-esterification reaction is carried out by mixing fatty alcohols and / or alcohol ethers, fatty acids and p-toluenesulfonate to obtain a pre-reaction system containing dissolved p-toluenesulfonate; the pre-reaction system contains a portion of carboxylic acid esters, unreacted fatty alcohols and / or alcohol ethers, fatty acids and a portion of by-product water; The pre-reaction system is mixed with an azeotropic dehydrating agent and subjected to reactive distillation esterification to separate byproduct water, thereby obtaining the carboxylic acid ester.
2. The synthesis method according to claim 1, characterized in that, The fatty alcohols include one or more of isopropanol, butanol, n-pentanol, isopentanol, hexanol, octanol, and benzyl alcohol; The alcohol ethers include one or more of the following: ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, diethylene glycol phenyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, and diethylene glycol phenyl ether.
3. The synthesis method according to claim 1, characterized in that, The fatty acids include one of acetic acid, propionic acid, and butyric acid.
4. The synthesis method according to any one of claims 1 to 3, characterized in that, The molar ratio of the alcohol to the fatty acid is 1:0.8~1.
5.
5. The synthesis method according to claim 1, characterized in that, The p-toluenesulfonate includes one or more of nickel p-toluenesulfonate, zinc p-toluenesulfonate, calcium p-toluenesulfonate, magnesium p-toluenesulfonate, barium p-toluenesulfonate, cobalt p-toluenesulfonate, aluminum p-toluenesulfonate, and iron p-toluenesulfonate.
6. The synthesis method according to claim 1 or 5, characterized in that, The mass of the catalyst is 0.05-1% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids.
7. The synthesis method according to claim 1, characterized in that, The esterification pre-reaction temperature is 60~100℃, and the time is 0.5~4h.
8. The synthesis method according to claim 1, characterized in that, The azeotropic dehydrating agent includes one of ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, and n-butyl ether. The mass of the azeotropic dehydrating agent is 5-35% of the total mass of fatty alcohols and / or alcohol ethers and fatty acids.
9. The synthesis method according to claim 1 or 8, characterized in that, The reactive distillation esterification reaction is carried out at a temperature of 100-180℃ for 4-5 hours.
10. The synthesis method according to claim 1, characterized in that, The reactive distillation esterification reaction further includes: removing the azeotropic dehydrating agent and unreacted raw materials from the system obtained by the reactive distillation esterification reaction before evaporation in an evaporator; The crude carboxylic acid ester obtained from the evaporation is fed into a distillation column for distillation to obtain a carboxylic acid ester, and the p-toluenesulfonate obtained at the bottom of the evaporator is recycled.