Synthesis of Dimethyl Carbonate (DMC) by Oxidative Carbonylation of Methanol Using Polymer-Supported CuCl_2 Catalyst

摘要

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 CuCl_2, by oxidative carbonylation of methanol in the liquid-phase. The CuCl_2 complex (Pvypy-CuCl_2) was insoluble in methanol, and the reaction system was heterogeneous. The Pvbpy-CuCl_2 catalyst showed considerable catalytic acivity (DMC yield: 44.4% and DMC selectivity: 92.6%, at methanol, conversion: 1.79%), which is comparable to the previously reported data of poly (vinylpyridine) (PVP)-CuCl_2 catalyst: the Pvbpy-CuCl_2 catalyst could be recycled after filtration and washing thrice, provided, not having lost activity. The corrosion originating from Cl~- was greatly improved by immobilizing the CuCl_2 by Pvbpy. Elimination of CuCl_2 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 secound and the third reactions, 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 support, which demonstrates that the main cause of corrobecame obvious that Cu(II) was gradually reduced to Cu(II) during the reaction.