Synthesis of dimethyl carbonate (DMC) by oxidative carbonylation of methanol using polymer-supported CuCl2 catalyst

Polymer, including 2,2'-bipyridine, poly(4-methyl-4'-vinyl-2,2'-bipyridine) (Pvbpy), was investigated for the synthesis of dimethyl carbonate (DMC) as a support for CuCl2, by oxidative carbonylation of methanol in the liquid- phase. The CuCl2 complex (Pvbpy-CuCl2) was insoluble in methanol, and the r eaction system was heterogeneous. The Pvbpy-CuCl2 catalyst showed considera ble catalytic activity (DMC yield: 44.4% and DMC selectivity: 92.6%, at met hanol conversion: 1.79%), which is comparable to the previously reported da ta of poly (vinylpyridine) (PVP)-CuCl2 catalyst; the Pvbpy-CuCl2 catalyst c ould be recycled after filtration and washing thrice, provided, not having lost activity. The corrosion originating from Cl- was greatly improved by i mmobilizing the CuCl2 by Pvbpy. Elimination of CuCl2 from the Pvbpy support was observed during the reaction. In the first reaction, about 38% of the initially supported Cl was released, and in the second and the third reacti ons, most of the Cl was retained. The rate of corrosion of stainless steels in the first use of the catalyst (0.6 mg h(-1) for HC276) was greater than that in the rate of the second and the third uses (< 0.1 mg h(-1)). These results are closely related to the amount of Cl- released from the Pvbpy su pport, which demonstrates that the main cause of corrosion in the catalytic system is Cl- released from the Pvbpy-CuCl2 catalyst. From XPS study of th e catalyst, it became obvious that Cu(II) was gradually reduced to Cu(I) du ring the reaction.