Effect of interfacial activity of quaternary ammonium cation on kinetics of epoxidation of allyl chloride with hydrogen peroxide

A series of quaternary ammonium phosphotungstic heteropoly acid catalysts with different carbon chain lengths [(CnH2n+1)2(CH3)2N]3{PO4[W(O)(O2)2]4} (n = 8, 10, 12, 14, 16) were synthesized for the epoxidation of allyl chloride with H2O2. The hydrophilic and hydrophobic structure of the catalysts were regulated to optimize the interfacial activity by changing the carbon chain lengths of the quaternary ammonium cations. The reaction system using catalyst [(C10H21)2(CH3)2N]3{PO4[W(O)(O2)2]4} showed the lowest interfacial tension between oil and water, the smallest particle size of emulsion droplets and the largest interfacial area, which resulted in the highest catalytic performance. The reaction kinetics and interface properties studies, including the activation energy, interfacial tension, and microscopic imaging of droplets, were conducted to provide strong proof. The epoxidation reaction rates were significantly associated with the surface activity of different carbon chain length catalysts and their effects on the allyl chloride-H2O2 interfacial properties.