Applied Catalysis B: Environmental, Vol.242, 460-468, 2019
Selenite-catalyzed oxidative carbonylation of alcohols to dialkyl carbonates
The oxidative carbonylation of alcohols to prepare corresponding dialkyl carbonates was investigated using alkali metal methylselenite [MSeO2(OCH3)] and alkali metal selenites (M2SeO3, M = Li, Na, K, Cs) as catalysts. Of various alcohols tested, methanol and 2-methoxyethanol (MEG) are found to be highly reactive, affording corresponding dialkyl carbonates in yields of more than 30%, which are significantly higher than those achieved with Cu-based catalysts under similar reaction conditions. XRD and GC-Mass analysis of the spent catalyst recovered from the M2SeO3-catalyzed reaction of methanol revealed that M2SeO3 was converted into elemental selenium and MHCO3 along with the formation of several selenium-containing by-products including malodorous dimethyldiselenide, 1,2-dimethoxydiselane, and O,Se-dimethyl carbonoselenoate. On the contrary, the oxidative carbonylation of MEG with K2SeO3 was highly selective toward the formation of bis(2-methoxyethyl) carbonate (BMEC), without producing any selenium-containing by-products. A plausible mechanism for the MSeO2(OCH3)- and M2SeO3-catalyzed oxidative carbonylation of MEG was suggested on the basis of mechanistic and experimental results.