Low-energy-consumption production process for esterification synthesis of ethyl propionate

Abstract

The invention provides a low-energy-consumption production process for esterification synthesis of ethyl propionate. According to the method, propionic acid is added from the middle part or the lower part of an esterification tower, and an ethyl propionate-water-ethanol ternary azeotropic system is broken through the strong association effect of propionic acid and water; in addition, sulfuric acid and propionic acid are fixed at the bottom of the esterification tower and the middle lower part of the esterification tower under the strong complexing action of the acid-binding agent, so that side reaction caused by entrainment of the sulfuric acid and the propionic acid on the upper part of the esterification tower can be reduced; reflux of ethyl propionate at the top of the tower can be effectively reduced by reducing concentration of sulfuric acid and propionic acid at the middle or upper part of the esterification tower, and energy consumption is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of ethyl propionate production, and particularly relates to a production process for esterification synthesis of ethyl propionate with low energy consumption. Background Art

[0002] Ethyl propionate has a fruity fragrance and is widely used in food additives, especially in the preparation of flavors and fragrances. In the coatings and adhesives industries, ethyl propionate can also be used as a diluent and volatilizer to improve its coating property and drying time. In recent years, the application of ethyl propionate has been widely developed and the market has increased. The industrial methods for producing ethyl propionate mainly include the transesterification method and the esterification method. As the name implies, the transesterification method is a reaction in which an ester reacts with a different alcohol / acid / ester in the presence of an acid or base catalyst to form a new ester and a new alcohol / acid / ester. Ethyl propionate is formed by the reaction of methyl propionate and ethyl acetate to produce ethyl propionate and methyl acetate. The esterification method is to synthesize ethyl propionate by the esterification reaction of propionic acid and ethanol under the catalysis of sulfuric acid. Generally, sulfuric acid is selected as the catalyst in industry. The most obvious disadvantage is that the equipment has strong corrosion and is prone to side reactions such as sulfonation, carbonization and etherification, which reduces the product purity and increases the subsequent separation difficulty.

[0003] In the traditional esterification production process, due to the use of sulfuric acid as a catalyst, there are many side reactions, high material consumption, many impurities and complex components, resulting in high energy consumption. Therefore, it is necessary to improve the production of ethyl propionate to achieve the purpose of energy conservation and consumption reduction. Summary of the Invention

[0004] Based on the deficiencies of the prior art, the present invention has developed a production process for esterification synthesis of ethyl propionate with low energy consumption, so as to reduce the phenomenon of many side reactions in the production process of ethyl propionate and reduce the energy consumption and cost of separation and purification.

[0005] The purpose of the present invention is to provide a production process for esterification synthesis of ethyl propionate with low energy consumption, and the production process for esterification synthesis of ethyl propionate with low energy consumption includes the following steps:

[0006] S1. Add propionic acid to the middle or lower part of the esterification tower;

[0007] S2. Add a catalyst, an acid-binding agent and ethanol into the reaction kettle, and after heating through the esterification reboiler, carry out an esterification reaction to obtain a gaseous crude product of ethyl propionate;

[0008] S3. Carry out permeation separation treatment on the gaseous crude product of ethyl propionate through a pervaporation membrane at the top of the esterification tower;

[0009] Wherein, the acid-binding agent is selected from one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and cyclohexanediaminetetraacetic acid.

[0010] Specifically, the crude ethyl propionate product in the gas phase at the top of the esterification tower mainly consists of water, ethyl propionate, and ethanol. The crude ethyl propionate product in this gas phase is subjected to osmotic separation treatment through a pervaporation membrane to separate ethanol, water, and ethyl propionate. The ethyl propionate enters the distillation system for separation. After ethanol and water are separated by the water recovery tower, the ethanol returns to the esterification tower to participate in the reaction again.

[0011] Further, the addition amount of the acid-binding agent is 0.8 - 1.6 wt% of the propionic acid concentration.

[0012] Further, the addition amount of the catalyst is 1.5 - 4.0 wt% of the propionic acid concentration.

[0013] Specifically, by utilizing the strong complexing effect of the acid-binding agent, sulfuric acid and unreacted propionic acid are fixed in the middle and lower parts of the esterification tower, reducing the phenomenon of unqualified product quality caused by sulfuric acid and propionic acid being carried to the upper part of the esterification tower by entrainment. At the same time, the reduction of the sulfuric acid and propionic acid concentrations in the middle and upper parts of the esterification tower can effectively reduce the reflux amount of ethyl propionate at the top of the tower, thereby reducing energy consumption.

[0014] Further, a Venturi nozzle is also provided in the reaction kettle.

[0015] Further, the pressure of the Venturi nozzle is 0.03 - 0.1 MPa.

[0016] Specifically, by setting the Venturi nozzle, the mixing effect of raw materials propionic acid, ethanol, and catalyst sulfuric acid can be improved by utilizing turbulent flow motion, making the reaction more complete, reducing the contact time between the reactants and sulfuric acid, and reducing the generation of side reactions.

[0017] Further, the molar ratio of propionic acid to ethanol is 1.0:1.0 - 1.9.

[0018] Further, in step S2, the catalyst is selected from one or more of sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, and dimethylsulfonic acid.

[0019] Further, in step S1, the feeding temperature of propionic acid is 25 - 45 °C.

[0020] Further, in step S2, the temperature of the esterification reaction is 90 - 120 °C.

[0021] Further, the pervaporation membrane is selected from one or more of polydimethylsiloxane membrane, polytrimethylsilylpropyne membrane, and polyetheramide block copolymer membrane.

[0022] Further, the acidity of the ethyl propionate produced by the production process of low-energy-consumption esterification synthesis of ethyl propionate in the present invention is lower than 0.0040%.

[0023] The beneficial effects of the present invention are as follows:

[0024] In the present invention, propionic acid is added to the middle or lower part of the esterification column, and the strong association between propionic acid and water is utilized to break the ternary azeotropic system of ethyl propionate - water - ethanol. In addition, by using the strong complexation of the acid-binding agent, sulfuric acid and propionic acid are fixed at the bottom and the middle and lower parts of the esterification column, which can reduce the side reactions caused by the entrainment of sulfuric acid and propionic acid to the upper part of the esterification column by entrainment. At the same time, the reduction of the concentration of sulfuric acid and propionic acid in the middle or upper part of the esterification column can effectively reduce the reflux flow rate of ethyl propionate at the top of the column and reduce the energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The flowchart of the production process for the low-energy-consumption esterification synthesis of ethyl propionate according to the present invention is shown.

[0026] In the figure:

[0027] 110, esterification column; 111, Venturi nozzle; 112, esterification reboiler; 113, alcohol-permeable membrane; 114, rectification column; 115, recovery column; 116, reaction kettle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to more clearly illustrate the technical solutions of the present invention, the following examples are listed, but the present invention is not limited thereto.

[0029] The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the following examples can all be obtained from commercial channels unless otherwise specified.

[0030] The production device of the production process for the low-energy-consumption esterification synthesis of ethyl propionate includes an esterification column 110. A reaction kettle 116 is provided at the bottom of the esterification column 110. The reaction kettle 116 communicates with the bottom of the esterification column 110. The reaction kettle 116 is used to input a catalyst, an acid-binding agent, and ethanol. The middle and lower parts of the esterification column 110 are used to input propionic acid. An esterification reboiler 112 is provided outside the reaction kettle 116. The feed end of the esterification reboiler 112 communicates with the reaction kettle 116. After the catalyst, acid-binding agent, and ethanol are input into the reaction kettle 116, they are drawn into the esterification reboiler 112 through the feed end of the esterification reboiler 112.

[0031] A Venturi nozzle 111 is provided in the reaction kettle 116. The input end of the Venturi nozzle 111 communicates with the discharge end of the esterification reboiler 112. The output end of the Venturi nozzle 111 communicates with the reaction kettle 116. The Venturi nozzle 111 conveys the material heated by the esterification reboiler 112 back into the reaction kettle 116.

[0032] An outlet is provided at the upper part of the esterification tower 110. The main components of the crude ethyl propionate in the gas phase at the top of the esterification tower 110 are water, ethyl propionate and ethanol. After the gas phase is discharged from the outlet, it is subjected to pervaporation separation treatment through the pervaporation membrane 113 to separate ethanol, water and ethyl propionate. The ethyl propionate enters the rectification tower 114 for rectification treatment, while ethanol and water are separated by the recovery tower 115 and then ethanol is returned to the reaction kettle 116.

[0033] Example 1

[0034] The low-energy consumption production process for esterifying and synthesizing ethyl propionate includes the following steps:

[0035] S1. At 25 °C, propionic acid is added to the middle part of the esterification tower at a flow rate of 0.55 kg / h.

[0036] S2. A 30 m 3 reaction kettle is provided at the bottom of the esterification tower. 0.3 tons of sulfuric acid catalyst and 0.08 tons of ethylenediaminetetramethylenephosphonic acid acid-binding agent are added to the reaction kettle, and ethanol is added at a flow rate of 0.34 kg / h. The reaction kettle is connected to the esterification reboiler, and the material is transported into the esterification reboiler. After being heated to 95 °C by the esterification reboiler, it is transported back to the reaction kettle through a Venturi nozzle for thorough mixing and reaction. The acid-binding agent forms a complexation with the unreacted propionic acid, enabling the unreacted propionic acid and the catalyst sulfuric acid to be enriched at the lower part of the esterification tower, reducing the content of propionic acid and sulfuric acid in the small liquid droplets entrained by the mist, decreasing the reflux of ethyl propionate at the top of the tower. After the reaction, ethyl propionate, ethanol and water form a ternary azeotrope and are enriched layer by layer in the esterification tower to obtain a crude ethyl propionate product in the gas phase. Part of the gaseous crude product is condensed for reflux, and part of the gaseous crude product directly goes to the pervaporation membrane for subsequent separation.

[0037] S3. The gaseous crude ethyl propionate product at the top of the esterification tower is subjected to pervaporation separation treatment through a polydimethylsiloxane pervaporation membrane. After separation, the ethyl propionate enters the rectification tower for rectification treatment, while ethanol and water are separated by the water recovery tower and then ethanol is returned to the esterification tower.

[0038] Example 2

[0039] The low-energy consumption production process for esterifying and synthesizing ethyl propionate includes the following steps:

[0040] S1. At 35 °C, propionic acid is added to the middle part of the esterification tower at a flow rate of 0.6 kg / h.

[0041] S2. A 30 m 3Reactor, add 0.3 tons of sulfuric acid catalyst and 0.10 tons of ethylenediaminetetraacetic acid acid-binding agent into the reactor, add ethanol at a flow rate of 0.56 kg / h. The reactor is connected to an esterification reboiler, and the material is transported into the esterification reboiler. After being heated to 100 °C in the esterification reboiler, it is transported back to the reactor through a Venturi nozzle for full mixing and reaction. The acid-binding agent forms a complexation with unreacted propionic acid, causing unreacted propionic acid and catalyst sulfuric acid to accumulate at the lower part of the esterification column, reducing the content of propionic acid and sulfuric acid in the small droplets entrained by the mist, and reducing the reflux of ethyl propionate at the top of the column. After the reaction, ethyl propionate, ethanol, and water form a ternary azeotrope and are enriched layer by layer in the esterification column to obtain a gaseous crude product of ethyl propionate. Part of the gaseous crude product is condensed for reflux, and part of the gaseous crude product directly goes to a pervaporation membrane for subsequent separation;

[0042] S3. At the top of the esterification column, the gaseous crude product of ethyl propionate is subjected to pervaporation separation through a polytrimethylsilylpropyne pervaporation membrane. After separation, ethyl propionate enters the distillation column for distillation, while ethanol and water are separated by a water recovery column, and the ethanol is returned to the esterification column.

[0043] Example 3

[0044] The low-energy-consumption production process for esterifying and synthesizing ethyl propionate includes the following steps:

[0045] S1. At 45 °C, add propionic acid into the middle of the esterification column at a flow rate of 0.6 kg / h;

[0046] S2. There is a 30m 3 Reactor, add 0.3 tons of sulfuric acid catalyst and 0.11 tons of ethylenediaminetetraacetic acid acid-binding agent into the reactor, add ethanol at a flow rate of 0.68 kg / h. The reactor is connected to an esterification reboiler, and the material is transported into the esterification reboiler. After being heated to 100 °C in the esterification reboiler, it is transported back to the reactor through a Venturi nozzle for full mixing and reaction. The acid-binding agent forms a certain complexation with unreacted propionic acid, causing unreacted propionic acid and catalyst sulfuric acid to accumulate at the lower part of the esterification column, reducing the content of propionic acid and sulfuric acid in the small droplets entrained by the mist, and reducing the reflux of ethyl propionate at the top of the column. After the reaction, ethyl propionate, ethanol, and water form a ternary azeotrope and are enriched layer by layer in the esterification column to obtain a gaseous crude product of ethyl propionate. Part of the gaseous crude product is condensed for reflux, and part of the gaseous crude product directly goes to a pervaporation membrane for subsequent separation;

[0047] S3. At the top of the esterification column, the gaseous crude product of ethyl propionate is subjected to pervaporation separation through a polyether amide block copolymer pervaporation membrane. After separation, ethyl propionate enters the distillation column for distillation, while ethanol and water are separated by a water recovery column, and the ethanol is returned to the esterification column.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 lies in that in step S2, no acid-binding agent is added, and other components and preparation methods are the same.

[0050] Test Example 1

[0051] The crude ethyl propionate products in step S2 of Example 1 and Comparative Example 1 were respectively taken for detection, and the total acid content in the crude ethyl propionate products at different reflux ratios in the crude ethyl propionate products in step S2 of Example 1 and Comparative Example 1 was detected.

[0052] Among them, the total acid content required for the quality of ethyl propionate products needs to be lower than 0.0040%;

[0053] The reflux ratio is the ratio of the amount of reflux liquid at the top of the tower to the amount of product withdrawn at the top of the tower per unit time, and the reflux ratio is controlled by controlling the reflux and the discharge amount during the production process.

[0054] The test results are shown in Table 1.

[0055] Table 1 Performance test results of the production processes of Example 1 and Comparative Example 1

[0056]

[0057] From the data comparison in Table 1, it can be seen that in Example 1, an acid-binding agent was added, and the acid-binding agent forms a complexation effect with the unreacted propionic acid and the acidic catalyst, causing the unreacted propionic acid and the catalyst to accumulate in the lower part of the esterification tower, reducing the content of propionic acid and sulfuric acid in the small droplets entrained by the mist. When the reflux ratio is 1:1, the total acidity in the crude ethyl propionate product can be reduced to below 0.0040%, meeting the product acidity requirements. However, in Comparative Example 1 without the addition of an acid-binding agent, it is necessary to have a reflux ratio of 1.5:1 to meet the requirements. The reduction of the reflux of ethyl propionate at the top of the tower can significantly reduce the energy consumption.

[0058] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.

[0059] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A production process for esterifying and synthesizing ethyl propionate with low energy consumption, characterized in that, The production process for low-energy-consuming esterification synthesis of ethyl propionate comprises the following steps: S1. Add propionic acid to the middle or lower part of the esterification tower; S2. Add a catalyst, an acid-binding agent and ethanol into the reaction kettle, heat it through an esterification reboiler, and carry out an esterification reaction to obtain a gaseous crude product of ethyl propionate; S3. Carry out permeation separation treatment on the gaseous crude product of ethyl propionate through a permeable alcohol membrane at the top of the esterification tower; Among them, the acid-binding agent is selected from one of ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetraacetic acid, ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid, cyclohexanediaminetetraacetic acid.

2. The production process of ethyl propionate by low-energy esterification synthesis according to claim 1, characterized in that, The addition amount of the acid-binding agent is 0.8-1.6 wt% of the propionic acid concentration.

3. The production process for synthesizing ethyl propionate with low energy consumption according to claim 1, characterized in that, A Venturi nozzle is further arranged in the reaction kettle.

4. The production process of ethyl propionate by low-energy esterification synthesis according to claim 3, characterized in that, The pressure of the Venturi nozzle is 0.03-0.1 MPa.

5. The production process for synthesizing ethyl propionate with low energy consumption according to claim 1, characterized in that, The molar ratio of propionic acid to ethanol is 1.0:1.0-1.

9.

6. The production process of ethyl propionate by low-energy esterification synthesis according to claim 1, characterized in that, In step S2, the catalyst is selected from one or more of sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, dimethylsulfonic acid.

7. The production process of ethyl propionate by low-energy esterification synthesis according to claim 6, characterized in that, The addition amount of the catalyst is 1.5-4.0 wt% of the propionic acid concentration.

8. The production process of ethyl propionate by low-energy esterification synthesis according to claim 1, characterized in that, In step S1, the feeding temperature of propionic acid is 25-45 °C.

9. The production process of ethyl propionate by low-energy-consuming esterification synthesis according to claim 1, characterized in that, In step S2, the temperature of the esterification reaction is 90-120 °C.

10. The production process of ethyl propionate by low-energy esterification synthesis according to claim 1, characterized in that, The permeable alcohol membrane is selected from one or more of polydimethylsiloxane membrane, polytrimethylsilylpropyne membrane, polyether amide block copolymer membrane.

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