Synthesis of cyclic carbonate from vinyl cyclohexene oxide and CO2 using ionic liquids as catalysts

Synthesis of cyclic carbonate from 4-vinyl-1-cyclohexene-1,2-epoxide (VCHO) and carbon dioxide was investigated without using any solvent in the presence of ionic liquid as a catalyst. Ionic liquids based on 1-alkyimethylimidazolium salts of different alkyl groups (ethyl, butyl, hexyl, octyl) and different anions (Cl-, BF4-, PF6-) Were used as catalysts. The conversion of VCHO was affected by the structure of the imidazolium salt ionic liquids; the ones with the cations of bulkier alkyl chain length and with more nucleophilic anion showed better reactivity. Reaction temperature, carbon dioxide pressure, and zinc halide cocatalyst enhanced the addition of CO2 to VCHO. Semi-batch operation with continuous supply of carbon dioxide showed higher VCHO conversion than batch operation did. (c) 2007 Elsevier B.V. All rights reserved.