GB654015A - The manufacture of methyl lactate - Google Patents

Abstract

A manufacture of methyl lactate comprises heating lactic acid and/or dehydrated lactic acid and methanol at a temperature between 180 DEG and 235 DEG C. and at a pressure sufficient to keep a major part of the methanol in the liquid phase and maintaining the reaction mixture at said temperature between 30 and 60 minutes. The lactic acid may be anhydrous, dehydrated, i.e. consisting mainly of lactyl and higher polylactyl lactic acids, or contain water, e.g. up to 50 per cent by weight. Acidic esterification catalysts such as boric, phosphoric, toluene sulphonic or sulphuric acids may be present. Entraining liquids such as benzene and toluene present in dehydrated lactic acid are not objectionable. The process may be carried out batchwise, but continuous operation is preferred. In the latter lactic acid and methanol are introduced into a heated reaction zone, most conveniently a long, narrow tube of mild or stainless steel, the rate of flow being adjusted to give a residence time of 30 to 60 minutes. The methyl lactate may be recovered from the reaction mixture by usual methods, e.g. distillation. Methyl lactate is obtained by the rapid fractionation of the products obtained in examples: (1) by passing a mixture of methanol and lactic acid of about 98 per cent concentration through heated mild steel coil under pressure; (2) by passing lactic acid containing 20 per cent by weight of water together with paratoluene sulphonic acid through the same heated coil under pressure.