CN110003002B

CN110003002B - Production process of high-yield ethyl trifluoroacetate

Info

Publication number: CN110003002B
Application number: CN201910346362.9A
Authority: CN
Inventors: 张依新; 孙宪德
Original assignee: JINAN WANXINGDA CHEMICAL Co Ltd
Current assignee: JINAN WANXINGDA CHEMICAL Co Ltd
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2020-03-17
Anticipated expiration: 2039-04-26
Also published as: CN110003002A

Abstract

The invention relates to a production process of high-yield ethyl trifluoroacetate, which comprises the step of carrying out continuous non-catalytic reaction on trifluoroacetyl chloride and ethanol under the condition of reactive rectification to prepare the ethyl trifluoroacetate. The method can realize the continuous non-catalytic method for preparing the ethyl trifluoroacetate, has high yield of the ethyl trifluoroacetate, effectively recycles the byproduct hydrochloric acid, has convenient and easily obtained used raw materials, simple process, mild reaction conditions, low reaction energy consumption and no waste liquid residue in the process, and is suitable for large-scale production.

Description

Production process of high-yield ethyl trifluoroacetate

Technical Field

The invention relates to a production process of trifluoroacetic acid ethyl ester with high yield.

Background

Ethyl trifluoroacetate is also called as ethyl trifluoroacetate, is a volatile, colorless and transparent liquid, has the smell of ester, is easily soluble in ether and ethanol, is soluble in chloroform and slightly soluble in water, and can be slowly hydrolyzed in water. The vapor of the ethyl trifluoroacetate can form an explosive mixture with air, is easy to combust and explode when meeting open fire and high heat, decomposes to release high-toxicity smoke when meeting the high heat, and has violent contact reaction with an oxidant.

Ethyl Trifluoroacetate (ETFA) is used as an important organic chemical raw material and has wide application in the industries of synthesizing organic fluorine compounds, medicines, pesticides, liquid crystals, dyes and the like, wherein the synthesis of organic fluorine compounds comprises 2-thenoyltrifluoroacetone, ethyl trifluoroacetoacetate, trifluoroacetylacetone and the like; the concrete application is as follows: (1) in the aspect of medicine, the preparation is mainly applied to producing anti-inflammatory drugs for osteoarthritis, anti-tumor drugs for treating colon and rectal cancer, cardiovascular and cerebrovascular drugs, namely laninopril and the like; (2) in the aspect of pesticides, the cell division inhibitor is mainly used for manufacturing cell division inhibitors, and is applied to cotton and peanut fields for removing gramineous weed control and broad-leaved weeds; (3) in the aspect of organic synthesis, ethyl trifluoroacetate is often used for protecting amino groups due to low removal rate under a mild environment.

The trifluoroacetic acid esterification reaction takes trifluoroacetic acid and ethanol as raw materials to synthesize ethyl trifluoroacetate, and the direct esterification method has the advantages that: the raw material trifluoroacetic acid is milder than trifluoroacetyl chloride, has low toxicity, has little harm to human bodies and is easy to obtain. In addition, the esterification synthesis method is mature in research and clear in mechanism, and is the first choice method for synthesizing the ethyl trifluoroacetate. In recent years, the synthesis of ethyl trifluoroacetate by an esterification method is gradually advancing.

The traditional production method takes trifluoroacetic acid and absolute ethyl alcohol as raw materials and concentrated sulfuric acid as a catalyst, and ethyl trifluoroacetate is produced by heating, but the method has low yield, the purification process is complicated, the result is not ideal, and the production method can seriously corrode production equipment, so the production method is gradually eliminated. At present, the main method for producing ethyl trifluoroacetate at home and abroad still uses trifluoroacetic acid and absolute ethyl alcohol as main raw materials, and adopts different catalysts and processes to carry out esterification reaction to generate the ethyl trifluoroacetate.

The method for esterification reaction by using strong-acid cation exchange resin as a catalyst is characterized in that the strong-acid cation exchange resin is used as a novel catalyst, and the mass ratio of ingredients is m (trifluoroacetic acid): m (absolute ethyl alcohol) ═ 1: 0.80 to 3.2; m (trifluoroacetic acid): m (catalyst) ═ 1: 0.3-0.80 ℃, the temperature of the reaction liquid is 40-50 ℃, crude ethyl trifluoroacetate is generated under the condition, the obtained crude ester is placed in a drying tower filled with solid particle silica gel for drying, the residual water is removed, the crude ester is distilled under normal pressure to obtain a fraction of 58-64 ℃, namely the ethyl trifluoroacetate product, the yield is 93.7%, and the product purity can reach 98.0-99.9%. Compared with the traditional concentrated sulfuric acid catalytic reaction method, the technical scheme has great progress in the technical aspect, the quality analysis in the distillation process is simple and reliable, the distilled high-boiling ethanol can be recycled, the environmental pollution is small, and the quality and the yield of the finished product can be improved. However, the process flow is not developed and matured, and the dehydration cost, efficiency and catalyst reuse rate of the drying tower are not considered, so the method has not been adopted in industrial mass production.

Trifluoroacetic acid and absolute ethyl alcohol are used as main raw materials, and a catalyst is prepared by adopting an acidic molecular sieve, so that ethyl trifluoroacetate is prepared, and the method belongs to the field of fine organic chemistry. In the method, the reaction is carried out towards the positive reaction direction, so a water permeable separator is introduced to timely draw out water generated in the esterification reaction. Under the condition that the reaction temperature is 48-50 ℃, n (trifluoroacetic acid): n (absolute ethyl alcohol) is 1: 1.2-1: 5; m (trifluoroacetic acid): and (3) reacting the m (molecular sieve) ═ 1: 0.2-1: 0.5 to obtain the ethyl trifluoroacetate. Extracting the ethyl trifluoroacetate by using a saturated sodium carbonate aqueous solution, washing the ethyl trifluoroacetate by using a saturated sodium chloride aqueous solution, drying the ethyl trifluoroacetate by using solid potassium carbonate, steaming the dried potassium carbonate at normal pressure, collecting fractions, drying the fractions by using phosphorus pentoxide at normal temperature, distilling the fractions at normal pressure, and collecting the fractions to obtain the ethyl trifluoroacetate with the purity of over 99.7 percent.

Considering that ethyl trifluoroacetate has a higher density than water, the mixing of the two phases results in an organic phase below, and the convenience in subsequent separation, a co-solvent is introduced in its production process, the selection of which follows the following principle: 1. a density relative to water of less than 1; 2. can be dissolved in trifluoroacetic acid ethyl ester and trifluoroacetic acid; 3. does not form an azeotrope with ethyl trifluoroacetate; 4. the boiling point is higher than that of the trifluoroacetic acid ethyl ester and the trifluoroacetic acid. In the literature, toluene and xylene are selected as cosolvent, ethanol is 5.5% -9% more than trifluoroacetic acid, so as to improve the conversion rate of trifluoroacetic acid, concentrated sulfuric acid is used as catalyst, the dosage of cosolvent is 300g/(l molTFA), phase separation is carried out through multi-stage reaction, and finally, ethyl trifluoroacetate with the purity of more than 99.5% is obtained through distillation. Most of the processes reported in the above documents have complex flow and high production cost, and the research is only in the experimental stage and is difficult to be applied to large-scale industrialization.

In the traditional synthesis of carboxylic esters, concentrated sulfuric acid is used as a catalyst, but the method has the defects of high corrosion to equipment, easy generation of side reaction, high environmental pollution and the like. Therefore, better catalysts are continuously sought to replace sulfuric acid. At present, many researches on replacing concentrated sulfuric acid as a catalyst have been reported, and the researches can be roughly divided into the following categories, namely, a general acid catalyst, a heteropoly acid catalyst, a solid acid catalyst and a solid super acid catalyst. The selection of a suitable catalyst plays a crucial role in the performance of the esterification reaction.

The acid type catalyst has low catalytic yield, long reaction time and low value. Inorganic acids such as sulfuric acid and phosphoric acid are used as catalysts, so that equipment is seriously corroded, waste liquid formed after reaction is not easy to separate from products, the corrosivity is strong, special 'three wastes' facility treatment is needed, and the environment is polluted if the waste liquid is randomly discharged. But the hydrochloride and the sulfate are used as the catalyst, so the method has good prospect. If solid sulfate is used as the esterification catalyst, the ester yield and the catalytic speed are equivalent to those of the esterification catalyst, but the defect of using concentrated sulfuric acid is overcome, and the esterification catalyst has good stability and can be continuously used.

The autocatalytic reaction refers to a reaction that proceeds with a reactant or a reaction product as a catalyst without an additional catalyst. According to literature reports, most reactions are autocatalytic for the reaction product, and in such reactions, the reaction rate is influenced by both the concentration of the reactant and the concentration of the reaction product. The main characteristics are as follows: (1) the reaction starts to enter an induction period, the reaction rate is slow, the reaction rate is further improved along with the accumulation of products, and the reaction rate is reduced due to the consumption of the reactants; (2) a small amount of product is added for starting the autocatalytic reaction; (3) a fastest reaction rate occurs during the autocatalytic reaction. Typical autocatalytic reaction equation patterns are doubly-curved functions, and if the reactant or product concentrations of the experiment follow a doubly-curved curve, the reaction is likely to be autocatalytic.

Chinese granted patent CN103864615B discloses a method for preparing ethyl trifluoroacetate by a continuous non-catalytic method, which has the following advantages: (1) the method can realize the continuous non-catalytic method for preparing the ethyl trifluoroacetate, has the advantages of convenient and easily obtained used raw materials, simple process, mild reaction conditions, low reaction energy consumption, no waste liquid residue in the process and suitability for large-scale production; (2) the HCl absorption device is used for absorbing the hydrogen chloride gas to produce hydrochloric acid as a byproduct, no waste liquid is generated in the whole production process, and the process has high atom economy and is green and environment-friendly; (3) the reaction and the rectification are carried out in one device simultaneously, and the product generated by the reaction is separated from the reactant in time, so that the yield of the product can be improved, and the product can be separated by utilizing the reaction heat, thereby achieving the purpose of saving energy.

However, the chinese granted patent CN103864615B does not solve two problems: (1) the yield of the ethyl trifluoroacetate prepared by using the continuous non-catalytic reaction of trifluoroacetyl chloride and ethanol is still not high, and the highest yield is only 97.86% (example 4); (2) the application problem of the byproduct hydrochloric acid is not solved, the effective utilization of the byproduct hydrochloric acid is not concerned, and the waste of the whole process is easily caused. Although the Chinese granted patent CN105419403B provides a method for utilizing waste acid, the titanium dioxide prepared by the method is easy to agglomerate and cannot be widely applied.

Disclosure of Invention

In order to solve the following two problems in the prior art: (1) the yield of the ethyl trifluoroacetate prepared by CN103864615B through continuous non-catalytic reaction of trifluoroacetyl chloride and ethanol is still not high; (2) CN103864615B does not solve the application problem of the by-product hydrochloric acid, does not pay attention to the effective utilization of the by-product hydrochloric acid, and is easy to cause the waste of the whole process.

The invention provides the following technical scheme:

a production process of high-yield ethyl trifluoroacetate, under the condition of reactive rectification, trifluoroacetyl chloride and ethanol are subjected to a continuous non-catalytic reaction to prepare the ethyl trifluoroacetate, and the production process comprises the following steps:

(1) adding a small amount of ethanol (2) into the reactor (A), and opening a condenser (C); the adding amount of the ethanol (2) is 0.2-0.4 of the volume of the reactor (A);

(2) the reactor (A) is connected with a rectifying tower (B), the rectifying tower (B) is connected with a condenser (C), and trifluoroacetyl chloride gas (1) is continuously introduced into the reactor (A) at a constant speed at the temperature of 35 ℃ and starts to be stirred;

(3) stirring for 30-60 min, dropwise adding ethanol (2) into the reactor (A), heating to 55-65 ℃ while dropwise adding ethanol, and carrying out reactive distillation, wherein the mass ratio of the flow rate of the trifluoroacetyl chloride to the mass ratio of ethanol is 1: 0.125;

(4) rectifying the reaction product flow (3) by a rectifying tower (B) to obtain a rectified reaction product flow (4), and condensing by a condenser (C) to obtain ethyl trifluoroacetate (5);

(5) absorbing the HCl-containing material flow (6) by an HCl absorption device (D) to obtain hydrochloric acid;

(6) and (5) using the hydrochloric acid obtained in the step (5) as an additive to be used in a titanium dioxide coating process.

The rectification pressure of the rectification tower (B) is normal pressure.

The absorbent in the absorption device (D) is water and/or dilute hydrochloric acid.

Preferably, the specific process of step (6) is:

s1, preparing the hydrochloric acid obtained in the step (5) into a hydrochloric acid solution with the mass concentration of 5% -10% for later use;

s2, adjusting the titanium dioxide slurry to pH not less than 9.5 with sodium hydroxide;

s3 SiO is used according to the mass ratio of sodium silicate to titanium dioxide₂：TiO₂The weight is 1: 50, dropwise adding a sodium silicate solution into the titanium dioxide slurry, homogenizing, dropwise adding a hydrochloric acid solution prepared by S1, controlling the pH to be more than or equal to 9.0, and aging;

s4, and mixing Al with the sodium metaaluminate and the titanium dioxide according to the mass ratio of the sodium metaaluminate to the titanium dioxide₂O₃：TiO₂The weight is 1: 50 of sodium metaaluminate solution is dripped in the proportion; then dropwise adding the hydrochloric acid solution prepared in the step S1, controlling the pH to be more than or equal to 9.0, and aging;

s5, dropwise adding the hydrochloric acid solution prepared in the S1 again, controlling the pH to be more than or equal to 7.0, and aging, washing and drying to obtain inorganic coated titanium dioxide;

s6 adding TiO into the inorganic coated titanium dioxide obtained in S5₂5wt% of dispersant by mass, stirring to obtain the dispersed inorganic coated titanium pigment;

the dispersing agent is composed of carboxymethyl cellulose and sodium methylene dinaphthalene sulfonate according to the mass ratio of 1:1.

The technical scheme of the invention has the following beneficial effects:

(1) aiming at one of the technical problems which are not solved by the Chinese granted patent CN 103864615B: the yield of ethyl trifluoroacetate is still not high. Based on the granted Chinese patent CN103864615B, the applicant has conducted a great deal of experiments by changing various process parameters, and found that the yield of ethyl trifluoroacetate can be greatly improved by adjusting the mass ratio of the flow rate of the trifluoroacetyl chloride to the mass ratio of ethanol to be 1: 0.125. Although the chinese granted patent CN103864615B discloses a wide blending ratio range, it does not disclose the ratio of 1:0.125, and such ratio is not described in examples 1-5 of the chinese granted patent CN 103864615B.

(2) Aiming at the second technical problem which is not solved by the Chinese granted patent CN 103864615B: the application problem of the byproduct hydrochloric acid is not solved. The applicant finds that the byproduct hydrochloric acid can be used in the titanium dioxide coating process, and the pH value and the composition of the dispersing agent involved in the titanium dioxide coating process are controlled through a large number of experiments, so that the titanium dioxide coated with the inorganic substance with excellent dispersibility is finally prepared. The invention also solves the technical problems that the titanium dioxide prepared by the Chinese granted patent CN105419403B is easy to agglomerate and cannot be widely applied.

(3) The invention can realize the continuous non-catalytic method for preparing the ethyl trifluoroacetate, the used raw materials are convenient and easy to obtain, the process is simple, the reaction condition is mild, the reaction energy consumption is low, no waste liquid residue is generated in the process, and the method is suitable for large-scale production; the reaction and the rectification are carried out in one device simultaneously, and the product generated by the reaction is separated from the reactant in time, so that the yield of the product can be improved, and the product can be separated by utilizing the reaction heat, thereby achieving the purpose of saving energy.

Drawings

FIG. 1 is a process flow, wherein: A. the device comprises a reactor, a rectifying tower, a condenser and an D, HCl absorption device, wherein the reactor comprises a reactor A, a rectifying tower B, a condenser C and a rectifying tower C; 1. trifluoroacetyl chloride gas, 2, ethanol, 3, a reaction product stream, 4, a rectified reaction product stream, 5, ethyl trifluoroacetate, 6 and a HCl-containing stream.

Detailed Description

Example 1

(1) adding a small amount of ethanol (2) into the reactor (A), and opening a condenser (C); the adding amount of the ethanol (2) is 0.3 of the volume of the reactor (A);

(3) stirring for 60min, dropwise adding ethanol (2) into the reactor (A), heating to 58 ℃ while dropwise adding ethanol, and performing reactive distillation, wherein the mass ratio of the flow rate of the trifluoroacetyl chloride to the mass ratio of ethanol is 1: 0.125;

The rectification pressure of the rectification tower (B) is normal pressure.

Wherein, the specific process of the step (6) is as follows:

s1, preparing the hydrochloric acid obtained in the step (5) into a hydrochloric acid solution with the mass concentration of 10% for later use;

Example 2

The rectification pressure of the rectification tower (B) is normal pressure.

Wherein, the specific process of the step (6) is as follows:

the dispersant consists only of carboxymethyl cellulose.

Example 3

The rectification pressure of the rectification tower (B) is normal pressure.

Wherein, the specific process of the step (6) is as follows:

the dispersant consists of sodium methylene dinaphthalenesulfonate alone.

Comparative example 1

(3) stirring for 60min, dropwise adding ethanol (2) into the reactor (A), heating to 58 ℃ while dropwise adding ethanol, and performing reactive distillation, wherein the mass ratio of the flow rate of the trifluoroacetyl chloride to the mass ratio of ethanol is 1: 0.1;

Comparative example 2

(3) stirring for 60min, dropwise adding ethanol (2) into the reactor (A), heating to 58 ℃ while dropwise adding ethanol, and performing reactive distillation, wherein the mass ratio of the flow rate of the trifluoroacetyl chloride to the mass ratio of ethanol is 1: 0.155;

The experimental procedure of the present invention was carried out with reference to the chinese granted patent CN103864615B, and the yields of ethyl trifluoroacetate of example 1 and comparative examples 1-2 were measured and recorded in the following table:

numbering	Feeding flow rate mass ratio of trifluoroacetyl chloride to ethanol	Yield of
			Example 1	1:0.125	99.0％
Comparative example 1	1:0.1	98.3％
			Comparative example 2	1:0.155	97.9％

In view of the above detection: the reaction temperature and the mass ratio of the feeding flow rate are optimized through a large number of experiments, the optimal mass ratio of the feeding flow rate is 1:0.125, and the yield of the ethyl trifluoroacetate can reach 99.0%. In addition, the above results show that the mass flow rate of the fed ethanol is not as low as possible, and that the yield is only 98.3% when the mass flow rate ratio of trifluoroacetyl chloride to ethanol is 1: 0.1.

In order to improve the utilization effect of hydrochloric acid and the dispersion effect of titanium dioxide, the titanium dioxide prepared in examples 1 to 3 is subjected to dispersion detection, and the detection method refers to an experimental method recorded in experiment 37 in material science and engineering experiment guidance course (zhou xin cheng hua, 2010.07), that is, the larger the height value of the supernatant liquor is, the worse the dispersion is, the results are as follows:

numbering	Height of supernatant (after 60 min)
		Example 1	43mm
Example 2	59mm
		Example 3	65mm

The results show that the invention well realizes the effective utilization of the hydrochloric acid which is the by-product of the trifluoroacetic acid ethyl ester, and the titanium pigment particles with good dispersibility are prepared. The invention also discovers that the carboxymethyl cellulose and the methylene dinaphthalene sodium sulfonate can synergistically disperse the inorganic coated titanium dioxide by optimizing the composition of the dispersing agent, thereby being beneficial to the utilization of the byproduct hydrochloric acid and improving the quality and application range of the inorganic coated titanium dioxide.

Claims

1. A production process of high-yield ethyl trifluoroacetate is characterized in that under the condition of reactive rectification, trifluoroacetyl chloride and ethanol are subjected to continuous non-catalytic reaction to prepare the ethyl trifluoroacetate, and the production process comprises the following steps:

(6) the hydrochloric acid obtained in the step (5) is used as an additive in a titanium dioxide coating process;

wherein, the specific process of the step (6) is as follows:

s6 adding TiO into the inorganic coated titanium dioxide obtained in S5₂5wt% of dispersant by mass, stirring to obtain the dispersed inorganic coated titanium dioxide；

2. The production process of high-yield ethyl trifluoroacetate of claim 1, wherein the rectification pressure of the rectification column (B) is normal pressure.

3. The process for the production of high yield of ethyl trifluoroacetate of claim 1, wherein the absorbent in the absorption unit (D) is water and/or dilute hydrochloric acid.