Process for separating azeotropic mixtures of esters of aliphatic carboxylic acids and alcohols

摘要

An ester of an aliphatic, saturated or unsaturated, carboxylic acid and a lower aliphatic alcohol, which forms an azeotrope with the corresponding free alcohol, is separated from admixture with the free alcohol by distilling the mixture in the presence of a halogen derivative of a hydrocarbon, which forms an azeotrope with the alcohol boiling at least 5 DEG C., but no more than 40 DEG C., below the boiling-point of the ester/alcohol azeotrope, and passing the vapours through a fractionating column whereby a mixture of the alcohol and the halohydrocarbon distils over from the top of the column. Water is added to the distillate; and the halohydrocarbon, which separates out, is returned to the distillation zone. The process may be carried out during an alcoholysis reaction. In an example, butyl acrylate is produced by boiling methyl acrylate with butanol in the presence of trans-1,2-dichloroethylene. The reaction mixture also contains p-toluenesulphonic acid and phenothiazine. Another example relates to the preparation of 2-ethylhexyl acrylate by reacting methyl acrylate with 2-ethylhexanol. A further example relates to the hydrolysis of methyl acetate by means of water in the presence of a cation exchange resin; and the separation of methanol from non-hydrolysed ester using dichloromethane as auxiliary.ALSO:An ester of an aliphatic, saturated or unsaturated carboxylic acid and a lower aliphatic alcohol, which forms an azeotrope with the corresponding free alcohol, is separated from admixture with the free alcohol by distilling the mixture in the presence of a halogen derivative of a hydrocarbon, which forms an axeotrope with the alcohol boiling at least 5 DEG C., but no more than 40 DEG C., below the boiling-point of the ester-alcohol azeotrope, and passing the vapours through a fractionating column whereby a mixture of the alcohol and the halohydrocarbon distils over from the top of the column. Water is added to the distillate, and the halohydrocarbon, which separates out, is returned to the distillation zone. In an example methanol is separated from methyl propionate using 2-bromopropane as auxiliary liquid. Trichlorotrifluoroethane may also be used as auxiliary liquid. For the separation of ethanol from ethyl acetate, either trichloroethane or trans-1-bromo-2-chlorethylene may be used as auxiliary liquid. The process may be carried out during an alcoholysis or a hydrolysis reaction (see Division C2).