An efficient catalyst Co(salophen) for synthesis of diethyl carbonate by oxidative carbonylation of ethanol

The oxidative carbonylation of ethanol to diethyl carbonate (DEC) was investigated by an efficient catalyst system comprising of Co-Schiff base complexes. Effects of Schiff base ligands, reaction time, catalyst concentration, temperature and pressure on the catalytic activity were studied. Co(salophen) [N,N′-bis(salicylidene) o-phenylenediamine cobalt] catalyst exhibited better catalytic activity compared with other Co complexes. When the oxidative carbonylation was carried out at the reaction conditions: 0.12 mol/L Co(salophen), P(CO)/P(O2) = 2:1, 3.0 MPa, 140 °C, 2.5 h, the conversion of ethanol is 15.8%, the selectivity to DEC is 99.5% and the turnover number (TON) is 22.2. The corrosion behavior of Co(salophen) catalyst to the stainless steel reactor was also examined. The corrosion rate to the stainless steel by Co(salophen) catalyst is below 0.005 mm/a. SEM images demonstrated that the pitting corrosion was not observed on the surface of the stainless steel.