Efficient and selective molybdenum based heterogeneous catalyst for alkene epoxidation using batch and continuous reactors

Abstract

A polystyrene 2-(aminomethyl)pyridine supported molybdenum(VI) complex (Ps·AMP·Mo) has been prepared, characterised and used as a catalyst for epoxidation of 1-hexene and 4-vinyl-1-cyclohexene (4-VCH) using TBHP as an oxidant. The catalytic performance of the polymer supported Mo(VI) complex has been evaluated for epoxidation of 1-hexene and 4-VCH in a classical batch reactor. Experiments have been carried out to study the effect of reaction temperature, feed molar ratio of alkene to TBHP and catalyst loading on the yield of epoxide for optimisation of reaction conditions in a batch reactor. The long term stability of the polymer supported Mo(VI) catalyst has been evaluated by recycling the catalyst several times in batch experiments using conditions that form the basis for continuous epoxidation studies. The extent of Mo leaching from the polymer supported catalyst has been investigated by isolating any residue from reaction supernatant studies after removal of heterogeneous catalyst and using the residue as potential catalyst for epoxidation. The efficiency of Ps·AMP·Mo catalyst has been assessed for continuous epoxidation of 1-hexene and 4-vinyl-1-cyclohexne with TBHP as an oxidant using a FlowSyn reactor by studying the effect of reaction temperature, feed molar ratio of alkene to TBHP and feed flow rate on the conversion of TBHP and the yield of epoxide. The catalyst was found to be active and selective for batch and continuous epoxidation of the substrates using TBHP as an oxidant. The continuous epoxidation in a FlowSyn reactor has shown considerable time savings, high reproducibility and selectivity along with remarkable improvements in catalyst stability compared with the reactions carried out in a batch reactor.