ELECTROLYTIC CARBONYLATION OF METHANOL OVER THE CUCL2 ANODE IN THE GAS-PHASE

Electrolytic carbonylation of CH3OH in the presence of CO over a CuCl2-added graphite anode was studied in the gas phase at <101 kPa and ambient temperature. No reaction proceeded at applied voltages lower than 1.0 V across the cell (cathode: He). The formation of dimethyl carbonate (DMC) and CO2 started at >1.0 V. The rates of these formations showed maxima at ca. 1.4 V. Electrolysis of CH3OH to dimethoxymethane (DMM) and methylformate (MF) started at >1.4 V, reducing the formation of DMC and CO2 markedly. Replacement of He in the cathode compartment with O-2 decreased the applied voltage needed for the formation of DMC by ca. 0.6 V. The results of the electrolysis of CH3OH alone suggested that DMM and MF were formed directly from CH3OH. However, the formation of CO2 at an applied voltage less than or equal to 1.4 V (cathode: He) originated from the same precursor of DMC. The anode potentials measured during the reaction suggested that the electrolytic carbonylation of CH3OH as well as the electrolysis of CH3OH occur on Cu(II) cations. The reaction scheme assuming a methoxide radical and a carbomethoxide species as the reaction intermediates is suggested on the basis of kinetic studies on the formation of each product.