New insights into the cocatalyst-free carbonation of vegetable oil derivatives using heterogeneous catalysts

Cyclic carbonates are important platform molecules with relevant industrial applications such as polymers precursors, fuel additives and solvents. They can be obtained from epoxidized vegetable oils via a carbonation reaction with carbon dioxide. This process is typically performed using homogenous catalyst or co-catalyzed systems, requiring of a homogenous specie. At the present moment very little have been reported regarding fully heterogeneous catalysts applied to the carbonation of epoxidized vegetable oils. In this study, the carbonation of epoxidized methyl oleate was investigated with various heterogeneous catalysts. Diverse nucleophilic organic salts were supported on silica gel and SBA-15 and screened as single component heterogeneous catalysts for the carbonation of epoxidized methyl oleate as a model compound of vegetable oils. The effect of some textural features of the catalytic materials such as the average pore size and surface area were investigated. An improved catalytic performance was observed as the catalytic species were supported on a mesoporous material. The addition of weak Lewis acidity to the support was found to play an important role in the opening of the oxirane ring and its further conversion to a cyclic carbonate, by providing a source of hydrogen bond donor (HBD) to activate the oxirane ring. The methyl esters of oleic acid, tall oil and cottonseed oil were investigated as substrates. A plausible reaction mechanism was proposed.