The Synthesis of Glycolic Acid by Hydrolysis of Chloroactic Acid
|School||Nanjing University of Technology|
|Keywords||Chloroacetic Glycolic Acid Synthesis Hydrolysis Refined|
Glycolic acid, also known as glycolic acid, glycolic acid, is an important organic synthesis intermediates and chemical products, widely used in organic synthesis, cleaning, electroplating, textile, leather, sterilization, and other industries. In recent years, scientific research has found that glycolic acid polymer with a biodegradable, to solve the difficult problem of degradation of traditional plastic products exist to be applied in the medical, packaging, and many other areas. The preparation of a polymer of glycolic acid, glycolic acid monomer purity higher or relatively low molecular weight of the obtained polymer, causing annual growth in demand for high-purity glycolic acid, glycolic acid is not present in the domestic, high purity the formation of industrial-scale production, it is very meaningful to study the synthesis of glycolic acid. Domestic and foreign synthetic glycolic acid glycine oxidation, cyanidation, aldehydes carboxylation coupling method of formaldehyde and methyl formate, oxalic acid, chloroacetic acid hydrolysis method. Glycine oxidation is higher cost and complexity of product; cyanidation is too toxic and unsafe; demanding formaldehyde the carboxylation law of reaction conditions, product purification difficulties, severe corrosion of the equipment; the glyoxal carboxylation law raw material costs are too high; formaldehyde and the low yield of the the methyl formate coupling method, catalyst separation and recovery of difficult; oxalic acid electrolysis method yield lower; chloroacetic alkaline hydrolysis synthesis glycolic acid process route is determined by various synthetic methods, the The process route has a low cost of raw materials, mild reaction conditions, the process is relatively simple, environmental pollution, etc.. Hydrolyzed after synthesis is obtained an aqueous solution of a glycolic acid, which contains a large amount of sodium chloride and a small amount of unhydrolyzed chloroacetate and other impurities, and purified by vacuum distillation and the organic solvent extraction method is more appropriate. Hydroxy acid yield measured by HPLC using Mohr method for quantitative analysis of the content of sodium chloride, and identified by infrared spectroscopy and elemental analysis of the final product. First, factors that influence the reaction: the reaction temperature, reaction time and feed ratio and the quality of sodium hydroxide fraction orthogonal experiment, to obtain the optimum conditions for this reaction, while on a single impact of factors have been studied, obtained optimal conditions: the reaction temperature was 110 ° C, the reaction time was 10 hours, the raw material ratio of 1.2:1 (sodium hydroxide / TCA), and the mass fraction of 45% sodium hydroxide. Purified aqueous solution of glycolic acid on the synthesis of acetone extraction to remove sodium chloride and extracted with ether to remove the chloroacetic acid to be purified by distillation, dehydration under reduced pressure, the yield of the finally obtained solid glycolic acid is greater than 73%, and its purity higher than 97%. In addition, the reaction kinetics explore and study, by nonlinear curve fitting and linear regression to obtain the relationship between the reaction rate and concentration of raw materials, the relationship: r = 2.91 C ~ 2.