PURPOSE: To obtain a carbonic acid ester in high efficiency by carrying out the ester interchange of dimethyl carbonate with a hydroxy compound and distilling out the by-produced methanol by using the dimethyl carbonate raw material as an azeotropic agent.
CONSTITUTION: A carbonic acid ester is produced by the ester interchange of dimethyl carbonate with a hydroxy compound (e.g. phenol) in a reactive distillation column 4 in the presence of an ester interchange reaction catalyst (e.g. dibutyltin oxide). In the above process, the methanol produced in the reaction zone at the lower part of the reactive distillation column 4 is mixed with dimethyl carbonate in the reactive distillation zone to form an azeotropic mixture, transferred from the column top through a line 5 and condensed by a condenser 6. The distillate from a line 8 consisting of an azeotropic mixture of dimethyl carbonate, and methanol is separated and purified by a permeating evaporation membrane 9 and the methanol is recovered from the line 10. The dimethyl carbonate is recovered from the line 2 and returned to the reactive distillation column 4 through the line 1. Methanol can be removed in high efficiency by this process to enable the effective progress of the reaction in a short time and the production of a carbonic acid ester at a low cost.
MAEDA YASUSHI
HORIGUCHI AKIRA
SUGIMOTO MASAHIKO
