阅读说明：本技术 一种采用光敏催化剂生产食品级苯甲酸制备工艺 (Preparation process for producing food-grade benzoic acid by adopting photosensitive catalyst ) 是由 吕海平 张伟 刘德平 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种采用光敏催化剂生产食品级苯甲酸制备工艺,其特征在于,将硫代水杨酸与DMF搅拌反应,待硫代水杨酸完全溶解后加入K-(2)CO-(3)；反应釜内物料全部溶解后计入CuI,溶解后再加入4-溴回香醚；溶解后进行温升反应;再温降加入冷水；过滤收集下层过滤液；用盐酸进行酸化；再进行过滤,得到滤饼,滤饼再次烘干后,得到催化剂半成品,干燥后的滤饼与多聚磷酸混合后,温升反应；温降用水进行淬灭；再次加入DCM进行萃取,得到下层液体；真空干燥,得到白色固体；再次用MeCN溶解温度升再次降温过滤得到微黄色固体；再次真空干燥,得到所需的光敏催化剂2-甲氧基噻吨酮。(The invention discloses a preparation process for producing food-grade benzoic acid by adopting a photosensitive catalyst, which is characterized in that thiosalicylic acid and DMF are stirred to react, and K is added after the thiosalicylic acid is completely dissolved 2 CO 3 (ii) a Adding CuI after materials in the reaction kettle are completely dissolved, and adding 4-bromine retro-fragrance ether after the materials are dissolved; after dissolving, carrying out temperature rising reaction, and then adding cold water after temperature reduction; filtering and collecting lower-layer filtrate; acidifying with hydrochloric acid; filtering to obtain a filter cake, drying the filter cake again to obtain a semi-finished catalyst product, mixing the dried filter cake with polyphosphoric acid, and carrying out temperature rise reaction; quenching with water for temperature reduction; adding DCM again for extraction to obtain a lower layer liquid; vacuum drying to obtainA white solid; the MeCN is used again for dissolving, the temperature is increased again, the temperature is reduced again, and a yellowish solid is obtained after filtration; vacuum drying again to obtain the required photosensitive catalyst 2-methoxythioxanthone.)

1. A process for preparing the photosensitive catalyst used in preparing food-class benzoic acid includes such steps as reaction between thiosalicylic acid and DMF while stirring, adding K after the thiosalicylic acid is completely dissolved₂CO₃(ii) a Adding CuI after materials in the reaction kettle are completely dissolved, and adding 4-bromine retro-fragrance ether after the materials are dissolved; after dissolving, carrying out temperature rising reaction, and then adding cold water after temperature reduction; filtering and collecting lower-layer filtrate; acidifying with hydrochloric acid; filtering to obtain a filter cake, drying the filter cake again to obtain a semi-finished catalyst product, mixing the dried filter cake with polyphosphoric acid, and carrying out temperature rise reaction; quenching with water for temperature reduction; adding DCM again for extraction to obtain a lower layer liquid; vacuum drying to obtain white solid; the MeCN is used again for dissolving, the temperature is increased again, the temperature is reduced again, and a yellowish solid is obtained after filtration; vacuum drying again to obtain the required photosensitive catalyst 2-methoxythioxanthone.

2. The preparation process of the photosensitive catalyst for food-grade benzoic acid according to claim 1, wherein the photosensitive catalyst is prepared from the following raw materials in proportion,

(1) adding 30.8g of thiosalicylic acid into a reaction kettle;

(2) adding DMF300ml into the reaction kettle, starting stirring, heating to 40-50 ℃ until the thiosalicylic acid is completely dissolved;

(3) adding K after the thiosalicylic acid is completely dissolved₂CO₃ 60g；

(4) After all the materials in the reaction kettle are dissolved, adding CuI3.8g, and adding 27.9ml of 4-bromine retro-fragrance ether after the materials are dissolved;

(5) after all the materials in the reaction kettle are dissolved at 50 ℃, the temperature of the reaction kettle is raised to 145 ℃, when the temperature of the reaction kettle is raised to 145 ℃, timing is started, and the reaction is carried out for 3-15 hours;

(6) after the reaction is finished, cooling the temperature of the kettle to 20-70 ℃, and adding 900ml of cold water into the kettle;

(7) mixing the reactant with water, and filtering to collect the lower filtrate;

(8) acidifying the lower-layer filtrate by using 5mol of hydrochloric acid;

(9) filtering after the acidification is finished to obtain a filter cake, and drying the filter cake again to obtain a semi-finished catalyst product;

(10) mixing the dried filter cake with 230g of polyphosphoric acid, heating to 130 ℃, and reacting for 6-8 hours;

(11) after the reaction is finished, the temperature of the kettle is reduced to 80 ℃, and 500ml of water is used for quenching;

(12) adding DCM into the reaction kettle again for extraction to obtain lower-layer liquid;

(13) vacuum drying the lower layer of extract liquor to obtain white solid;

(14) the white solid is dissolved by MeCN again, the temperature is increased to 90 ℃, and the white solid is cooled and filtered again to obtain yellowish solid;

(15) the yellowish solid was again dried under vacuum to give the desired 2-methoxythioxanthone as the photoactive catalyst.

3. A preparation process for producing food-grade benzoic acid by adopting a photosensitive catalyst is characterized in that toluene and photocatalyst 2-methoxy-9-thiophenol are stirred in the air atmosphere, and only one product of benzoic acid is formed by light lamp radiation and HPLC analysis; then adding aqueous sodium hydroxide solution until the pH value is neutral; extracting and recovering photosensitizer with ethyl acetate, diluting water layer with hydrochloric acid, adjusting pH to 1-2, and recrystallizing; vacuum drying and nuclear magnetic identification.

4. The preparation process of food grade benzoic acid with photosensitive catalyst according to claim 3, wherein the preparation process comprises the following steps,

(16) 9 kg of toluene and 2% of photocatalyst 2-methoxy-9-thiophenol are added into a 50L reactor;

(17) irradiating the mixture for 48 hours by 4 800W lamps, and only forming a benzoic acid product by HPLC analysis; the toluene conversion rate is over 99 percent;

(18) then adding aqueous sodium hydroxide solution until the pH value is neutral;

(19) extracting and recovering the photosensitizer by ethyl acetate, diluting a water layer by hydrochloric acid, adjusting the pH value to 1-2, and recrystallizing; vacuum drying and nuclear magnetic identification are carried out, the product quality is 11.8kg, and the yield is 99%.

Technical Field

The invention relates to a preparation process for producing food-grade benzoic acid by adopting a photosensitive catalyst, belonging to the field of chemical synthesis.

Background

Sodium benzoate, also known as sodium benzoate, is an organic substance of formula C₇H₅NaO₂It is a white granular or crystalline powder, has no odor or slight benzoin odor, has slightly sweet taste, astringent taste, relative molecular mass of 144.12, is stable in air, is easily soluble in water, and has pH of 8, and is soluble in ethanol. Benzoic acid and its salts are broad spectrum antimicrobial agents, but its antimicrobial effectiveness depends on the PH of the food product. The sterilizing and bacteriostatic effects are enhanced along with the increase of the acidity of the medium, and the sterilizing and bacteriostatic effects are lost in an alkaline medium. The optimum pH value for corrosion prevention is 2.5-4.0.

In the prior art, CN201910160866.1 discloses an industrial production method of food-grade benzoic acid: adding a raw material toluene solution and a biomimetic catalyst into a reaction kettle together, wherein the concentration of the biomimetic catalyst in the reaction kettle is 5-50ppm, and the materials are uniformly mixed in the reaction kettle; air or oxygen enters a reaction kettle from a gas distributor or a Venturi ejector, a three-stage cascade series equipment flow is adopted, the oxygen concentration in reaction tail gas is controlled to be less than 5%, the reaction temperature is controlled to be 130-170 ℃, the pressure of the reaction kettle is controlled to be 0.6-1.2 MpaG, the reaction residence time is 40-75 minutes, the mass fraction ratio of the air or oxygen to the toluene solution is 35-45%, the one-way conversion rate is 20-30%, and the materials discharged from the reaction kettle are rectified and separated; unreacted toluene is separated from components such as benzoic acid and the like through rectification, the toluene returns to the reaction kettle to be continuously recycled, and other light and heavy components are removed to obtain the food-grade benzoic acid. The biomimetic catalyst is a ligand of iron or cobalt and porphyrin (as described in professor laughing city of the chemical industry institute of university of Hunan).

CN201580005125.6 discloses photoactivators comprising a photoactive moiety and a hydrophilic moiety. The photoactive moiety is selected from 2-methoxythioxanthone and the like.

In view of the continuous development of the preparation technology of the photosensitive catalyst 2-methoxythioxanthone and the preparation process of the food-grade benzoic acid, the invention is also in active innovation.

Disclosure of Invention

The invention aims to provide a preparation process for producing food-grade benzoic acid by adopting a photosensitive catalyst to react at normal temperature and normal pressure.

The purpose of the invention is achieved by the following ways:

a process for preparing the photosensitive catalyst used in preparing food-class benzoic acid includes such steps as reaction between thiosalicylic acid and DMF while stirring, adding K after the thiosalicylic acid is completely dissolved₂CO₃(ii) a Adding CuI after materials in the reaction kettle are completely dissolved, and adding 4-bromine retro-fragrance ether after the materials are dissolved; after dissolving, carrying out temperature rising reaction, and then adding cold water after temperature reduction; filtering and collecting lower-layer filtrate; acidifying with hydrochloric acid; filtering to obtain a filter cake, drying the filter cake again to obtain a semi-finished catalyst product, mixing the dried filter cake with polyphosphoric acid, and carrying out temperature rise reaction; quenching with water for temperature reduction; adding DCM again for extraction to obtain a lower layer liquid; vacuum drying to obtain white solid; the MeCN is used again for dissolving, the temperature is increased again, the temperature is reduced again, and a yellowish solid is obtained after filtration; vacuum drying again to obtain the required photosensitive catalyst 2-methoxythioxanthone.

Further, the preparation process of the photosensitive catalyst according to the proportion is as follows,

(1) adding 30.8g of thiosalicylic acid into a reaction kettle;

(2) adding DMF300ml into the reaction kettle, starting stirring, heating to 40-50 ℃ until the thiosalicylic acid is completely dissolved;

(3) adding K after the thiosalicylic acid is completely dissolved₂CO₃ 60g；

(4) After all the materials in the reaction kettle are dissolved, adding CuI3.8g, and adding 27.9ml of 4-bromine retro-fragrance ether after the materials are dissolved;

(5) after all the materials in the reaction kettle are dissolved at 50 ℃, the temperature of the reaction kettle is raised to 145 ℃, when the temperature of the reaction kettle is raised to 145 ℃, timing is started, and the reaction is carried out for 3-15 hours;

(6) after the reaction is finished, cooling the temperature of the kettle to 20-70 ℃, and adding 900ml of cold water into the kettle;

(7) mixing the reactant with water, and filtering to collect the lower filtrate;

(8) acidifying the lower-layer filtrate by using 5mol of hydrochloric acid;

(9) filtering after the acidification is finished to obtain a filter cake, and drying the filter cake again to obtain a semi-finished catalyst product;

(10) mixing the dried filter cake with 230g of polyphosphoric acid, heating to 130 ℃, and reacting for 6-8 hours;

(11) after the reaction is finished, the temperature of the kettle is reduced to 80 ℃, and 500ml of water is used for quenching;

(12) adding DCM into the reaction kettle again for extraction to obtain lower-layer liquid;

(13) vacuum drying the lower layer of extract liquor to obtain white solid;

(14) the white solid is dissolved by MeCN again, the temperature is increased to 90 ℃, and the white solid is cooled and filtered again to obtain yellowish solid;

(15) the yellowish solid was again dried under vacuum to give the desired 2-methoxythioxanthone as the photoactive catalyst.

Further, a preparation process for producing food-grade benzoic acid by using a photosensitive catalyst, wherein toluene and photocatalyst 2-methoxy-9-thiophenol are stirred in the air atmosphere; then adding aqueous sodium hydroxide solution until the pH value is neutral; extracting and recovering photosensitizer with ethyl acetate, diluting water layer with hydrochloric acid, adjusting pH to 1-2, and recrystallizing; vacuum drying and nuclear magnetic identification.

Further, the preparation process according to the proportion is as follows,

(16) 9 kg of toluene and 2% of photocatalyst 2-methoxy-9-thiophenol are added into a 50L reactor;

(17) irradiating the mixture for 48 hours by 4 800W lamps, and only forming a benzoic acid product by HPLC analysis; the toluene conversion rate is over 99 percent;

(18) then adding aqueous sodium hydroxide solution until the pH value is neutral;

(19) extracting and recovering the photosensitizer by ethyl acetate, diluting a water layer by hydrochloric acid, adjusting the pH value to 1-2, and recrystallizing; vacuum drying and nuclear magnetic identification are carried out, the product quality is 11.8kg, and the yield is 99%.

In the process for preparing the food-grade benzoic acid, the traditional high-temperature and high-pressure equipment is changed into normal-temperature and normal-pressure preparation, the safety coefficient of the process operation is improved, and the equipment investment is reduced; the traditional cobalt catalyst is used for preparing benzoic acid, the problem that the catalyst is difficult to recover is solved, the existing extraction method is used for recovering the catalyst, and the cost is superior to that of the traditional cobalt method.

1. The self-made catalyst of the invention effectively reduces the production cost; the catalyst is a photosensitive catalyst and can be reused, and the method is simpler as the light source is adopted as the reaction condition for extracting the catalyst; because no heavy metal catalyst is used, the standard of food-grade benzoic acid is better met.

2. The invention adopts normal temperature and normal pressure reaction, and can reduce the safety hazard and capital investment in production by reacting with other pressurized and high temperature, and does not need heat energy consumption.

3. The invention has simple process operation and high conversion rate, and the toluene can be completely converted into benzoic acid.

Detailed Description

The technical solution of the present invention is further illustrated by the following examples, however, the scope of the present invention is not limited to the following examples.

Example (b):

preparation of photosensitive catalyst

1. Adding 30.8g of thiosalicylic acid into a reaction kettle;

2. adding DMF300ml into a reaction kettle, starting stirring, heating to 40-50 ℃ until the thiosalicylic acid is completely dissolved;

3. adding K after the thiosalicylic acid is completely dissolved₂CO₃ 60g；

4. After all materials in the reaction kettle are dissolved, CuI3.8g is counted, and 27.9ml of 4-bromine retro-fragrance ether is added after the materials are dissolved;

5. after materials in the reaction kettle are completely dissolved at 50 ℃, the temperature of the reaction kettle is increased to 145 ℃, and when the temperature of the reaction kettle is increased to 145 ℃, timing is started, and the reaction is carried out for 3-15 hours;

6. after the reaction is finished, cooling the temperature of the kettle to 20-70 ℃, and adding 900ml of cold water into the kettle;

7. mixing the reactant with water, filtering and collecting lower filtrate;

8. acidifying the lower-layer filtrate by using 5mol of hydrochloric acid;

9. filtering after the acidification is finished to obtain a filter cake, and drying the filter cake again to obtain a semi-finished catalyst product;

10. mixing the dried filter cake with 230g of polyphosphoric acid, heating to 130 ℃, and reacting for 6-8 hours;

11. after the reaction is finished, the temperature of the kettle is reduced to 80 ℃, and 500ml of water is used for quenching;

12. adding DCM into the reaction kettle again for extraction to obtain lower-layer liquid;

13. vacuum drying the lower layer extract to obtain white solid;

14. the white solid is dissolved by MeCN again, the temperature is increased to 90 ℃, and the white solid is cooled and filtered again to obtain yellowish solid;

15. the yellowish solid was again dried in vacuo to give the desired 2-methoxythioxanthone as the photoactive catalyst.

Secondly, preparing food-grade benzoic acid by using photosensitive catalyst

16. 9 kg of toluene and 2% of photocatalyst 2-methoxy-9-thiophenol are added into a 50L reactor;

17. stirring at 25 ℃ in an air atmosphere and irradiating with 4 lamps of 800W for 48 hours, HPLC analysis showed that only one product, benzoic acid, was formed. The toluene conversion rate is over 99 percent;

18. then adding aqueous sodium hydroxide solution until the pH value is neutral;

19. extracting and recovering photosensitizer with ethyl acetate, diluting the water layer with hydrochloric acid, adjusting pH to 1-2, and recrystallizing. Vacuum drying and nuclear magnetic identification are carried out, the product quality is 11.8kg, and the yield is 99%.

The parameters of the embodiment can be implemented when the parameters adopt range values, and preferably adopt intermediate values; all the raw materials can be amplified or reasonably adjusted according to the proportion, and the method is particularly suitable for guiding industrial production.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.