(1) Thick mother liquor 1000L passes through MVR film evaporator in the production of propyl gallate, evaporates and concentrates and obtains condensed water 925L and concentrated solution 75L; content of 20%, propyl gallate content of 35%, gallic acid content of 2% and a mixed solution of water).
(2) Put 300kg of gallic acid, 1200L of n-propanol and 70L of recovered mixed solution (catalyst) into a 2000L enamel reaction kettle as raw materials, heat to reflux, carry out high-temperature esterification reaction at 100°C for 8 hours, and the water generated by the reaction is The kettle is equipped with a membrane dehydration system to separate the water.
(3) Distill and recover n-propanol after the reaction is over. When the recovered solvent amount is 800L, stop the recovery, add 1000L of refined mother liquor to the reaction kettle, and continue to recover the remaining 200L solvent (when the temperature in the kettle reaches 95-99°C, stop the recovery);
(4) The liquid that has recovered the solvent is transferred to a 2000L enamel crystallization kettle for coarse crystallization, and after being cooled to 20°C, it is roughly centrifuged to obtain 422kg of propyl gallate coarse crystals (moisture content 15%) and 940L of thick mother liquor (wherein The content of sulfuric acid is 1.4wt%, the content of propyl gallate is 2.5wt%, and the content of gallic acid is 0.14wt%).
(5) Add 1500L of soft water, 422kg of propyl gallate coarse crystals, 6kg of activated carbon and 0.5kg of disodium EDTA into a 2000L enamel decolorization kettle; heat to 95°C to dissolve, decolorize for 30 minutes, and finely filter;
(6) The fine filtrate is transferred to a 2000L enamel crystallization kettle for fine crystallization, and after being cooled to 20°C, it is finely centrifuged to obtain 394kg (water content 14.5wt%) of propyl gallate fine crystals and 1450L of fine mother liquor (wherein propyl gallate content is 2.5wt%);
(7) Put 394kg of propyl gallate fine crystals into a 2000L enamel cone type rotary vacuum dryer, and dry for 12 hours under vacuum-0.095Mpa to obtain 336kg of propyl gallate, with a content of 99.5% and a conversion yield of 112%; The consumption of n-propanol is 200L (weight 157.1kg); the consumption of sulfuric acid is 14kg.
(8) Evaporated condensed water 925L (chromaticity is 50, pH value is 6, CODcr1000mg/L) reaches “urban sewage recycling, urban miscellaneous water quality” after sewage treatment (chromaticity is 20, pH value is 6.5, CODcr15mg /L).
First select the feed ratio: gallic acid: n-propanol: cyclohexane: arylsulfonic acid = 1: 3: 2.1: 0.1, then accurately weigh 500 g of gallic acid, 1500 g of n-propanol, 1050 g of cyclohexane and arylsulfonic acid according to the ratio. Sulfonic acid 50g.
Operation steps: The first step is to add gallic acid, n-propanol, cyclohexane and arylsulfonic acid into the reaction kettle with overflow pipe at the same time, and carry out esterification reaction at 65 ° C under stirring conditions, and remove water at the same time , The reaction time is 15 hours. In the second step, the reaction materials obtained in the first step are distilled and separated. The temperature of the distillation is gradually increased from 65°C to 100°C, and the temperature at the end of the distillation can reach 110°C to ensure the distillation effect. The crude product of propyl gallate and its trace amount of aromatic sulfonic acid obtained after distillation enters the next treatment process, and n-propanol and cyclohexane are recycled as raw materials again. In the third step, the propyl gallate crude product obtained in the second step and its trace aromatic sulfonic acid are washed with boiling water at 100° C. to remove the aromatic sulfonic acid on the surface of the gallic acid. The feed ratio is: water: crude propyl gallate =1:5. In the fourth step, the material obtained in the third step is cooled and filtered to obtain the crude product of propyl gallate after deacidification, and the temperature of the material during cooling is reduced from 100°C to 15°C. The fifth step is to recrystallize the crude propyl gallate obtained in the fourth step with boiling water at 100°C, and add decolorizing agent activated carbon to decolorize (generally twice), the feed ratio is: crude propyl gallate: water : decolorizer=1: 2: 0.3, the 6th step cools and filters the material that the 5th step obtains, obtains wet propyl gallate refined product, and the temperature during material cooling is dropped to 15 ℃ by 100 ℃. In the seventh step, the wet propyl gallate refined product obtained in the sixth step is dried at 60° C. for 20 hours. Thus obtain propyl gallate finished product 465g, yield reaches 93.0%.
The raw material Galla chinensis is crushed and passed through a 40-mesh sieve. Take 100g of quince powder and 1000ml of n-propanol. Stir and extract at 50°C for 4 hours. minutes, followed by vacuum filtration. Add 25 ml of sulfuric acid with a catalyst concentration of 80% to the filtrate, react at 80°C for 5 hours, cool to 20°C and filter, evaporate and concentrate the filtrate under reduced pressure, recover the evaporated solvent n-propanol; dissolve the concentrated material in 500mL hot water at 80°C , stirred, cooled to 15°C, and centrifuged to filter the crystals to obtain 56.8g of wet crystals of gallic acid propanol. The crude product was heated and dissolved in 750ml of water, decolorized with 2g of activated carbon for 30 minutes, vacuum filtered, and the filtrate was cooled to 10°C to crystallize for 5 hours. Centrifuge and filter, wash the material until the pH is 6.0-7.0, take the filter cake, and vacuum-dry (60° C.) to obtain 32.6 g of propyl gallate finished product, with a content of 99.5%.
Add 9.41g of gallic acid monohydrate, 25mL of n-propanol and 3.68g of N-acetoxypyridinium bisulfate ionic liquid into the reaction vessel, and react at the reflux temperature. After the reaction, change the reaction device into a distillation device, first at normal pressure and then under reduced pressure Excess n-propanol was distilled off, then deionized water was added and slowly cooled to complete crystallization, and a white solid product, namely propyl gallate, was obtained by suction filtration with a yield of 94%. Aqueous ionic liquids can be recycled after dehydration by rotary evaporation and vacuum drying.
