Synthesis of ethylidene diacetate from dimethyl ether, CO and H2

Ethylidene diacetate was prepared by reacting dimethyl ether, acetic acid and syngas in the presence of a catalytic system comprising RhI_3, PPh_3 and CH_3I. The effects of reaction temperature, pressure, time and the CO/H_2 molar ratio on the conversion of dimethyl ether and the product selectivity were investigated under the same catalyst formulation. Results showed that a maximum conversion of dimethyl ether was obtained when a mixture consisting of 0.3 mol dimethyl ether and 120 ml acetic acid was reacted at 180 ℃ and 3.0 MPa for 10 h at a stirring speed of 600 rpm under a syngas flow with a CO/H_2 molar ratio of 2.5, which was catalyzed by a catalyst mixture comprising 0.3 g RhI_3, 6 g PPh_3 and 1.3 g CH_3I. The selectivity of ethylidene diacetate increased with temperature, decreased with the CO/H_2 molar ratio and exhibited a maximum with pressure.