Preparation of lactic acid in ethanol

1. Lactic acid and ethanol in the presence of sulfuric acid esterification.
2. To acetaldehyde and hydrocyanic acid as raw materials, the reaction of ethylene cyanohydrin, and then with ethanol in the presence of inorganic acid esterification. [6]
3, metal halide catalyzed method. Ethyl lactate concentrated sulfuric acid with a metal halide Synthesis of ethyl lactate, the yield of 65% -71%. [5]
4, rare earth compounds catalyzed. Ethanol 0.22-0.33mol, lactic 0.11mol, and a rare earth compound with 25mL agent (molar ratio of the acid 1:100) was added to the flask, a reflux reaction 2.5-3h, the reaction solution was evaporated to an excess of ethanol with liquid, and The unreacted lactic acid after vacuum distillation, collecting product, yield 74% -79%. [5]
5, sulfuric acid catalysis. In the sulfuric acid-catalyzed esterification of lactic acid with an excess of ethanol derived ethyl lactate; also be heated in carbon tetrachloride will flow dehydration 24h, atmospheric distillation recycling excess ethanol and then vacuum distilled products. [5]
6, the solid acid catalysis. NaY zeolite was washed with water, dried, high temperature burning, and then impregnated with magnessium lactate concentration of NH4Cl solution was stirred for ion exchange, the NH4Y filtered, washed, dried, 550 ℃ high temperature activation, ie solid acid HY. Then lactic acid, ethanol, benzene, HY added to the reaction flask, HY / lactic acid (mass ratio) = 25/100, acid / ethanol (molar ratio) = 1/3. Refluxing the reaction under 100-160 ℃ 8-10h, the esterification rate of 60% or more. [5]
7, distillation esterification. The 225g80% of lactic acid, 475Ml (380g) 95% ethanol, 100mL of benzene, 2 mL of concentrated sulfuric acid and adding a little water separator distillation apparatus zeolite flask (1000 mL) in. Added to the reaction solution to a boil, steam (ethanol, benzene and water) into the condenser through the distillation column, the water layer was separated and refluxed to the buffered lactic acid column, column top temperature stabilized at 64.9 ℃. When the aqueous layer was 240g (containing ethanol 119g, water, 99g, benzene, 22g), the basic water separation, the column top temperature was raised to 68 ℃, esterification ends. After cooling, the reaction solution 6g of anhydrous sodium acetate and sulfuric acid by distillation under reduced pressure. First total reflux 1h, and then under vacuum in 2.45Kpa control reflux ratio of not less than 5, a head temperature of 58 ℃, distillation clear colorless ethyl lactate 226g, yield 96%. [5]
8, the lactic acid with an excess of alcohol in the esterification catalyst, after refining.