Study On The Synthesis Of The Glycolic Acid

Glycolic is a kind of important intermediates in organic synthesis and chemicalproducts. It is widely used in organic synthesis, chemical cleaning, electroplating, textile,leather, sterilization and other fields.This paper reviews the preparation of the glycolic acid. Analyze the correlatedliterature and design the route of the hydrolysis of chloroacetic acid and the carbonylationof formaldehyde. The hydrolysis of chloroacetic acid with chloroacetic acid as rawmaterials in alkaline water solution of glycolic acid; formaldehyde carbonylation withprarformaldehyde and carbon monoxide as raw materials, concentrated sulfuric acid asreaction medium, cuprous oxide as catalyst under the condition of high pressure, thenobtained glycolic acid.The results show that with the method of chloroacetic acid to prepare glycolic acid,the reaction temperature is100℃, the molar ratio of chloroacetic acid to sodiumhydroxide is1:1.2, the mass fraction of sodium hydroxide is45%, with the reaction of7hours, the yield is93%and the purity was97.5%. with method of carbonylation ofparaformaldehyde to prepare glycolic acid, the reaction temperature is60℃, reactionpressure is3.0MPa, the mole ratio of concentrated sulfuric acid to paraformaldehyde is2.5:1, the molar ratio of paraformaldehyde to cuprous oxide is50:1, the reaction time is3hours, the stirring speed is150r/min, and the yield of glycolic is65.8%.With the purification of glycolic acid dilute solution, the optimum experimentalconditions as follows: The vacuum distillation extracting water vacuum degree is20mmHg,then stop distillation with the reaction liquid temperature about80℃, get the mass fractionof glycolic acid solution is about70%. According to the experiment, we can get the bestconditions to prepare the crystal of glycolic acid, they are as follows: cooling rate is0.5℃/min, stirring speed is60r/min, add the seed crystal temperature is30℃, glycolic acidcrystals in the vacuum drying under the vacuum about20mmHg, then can get the glycolicacid crystal with the purity of more than99.5%, the yield is85%, meltingpoint:79.5~80.6℃.