Study on the epoxidation of chain olefins using biquaternary ammonium phosphotungstic acid phase transfer catalysts under no-solvent condition

Graphical A novel phase transfer catalyst comprising phosphotungstic acid and biquaternary ammonium cation salt is synthesized for the epoxidation of long carbon chain olefins under solvent-free conditions, which exhibits high selectivity for epoxides. Different methods are used to characterize the fundamental structure and catalytic mechanism of this catalyst. In this study, we have developed a novel catalyst synthesized by phosphotungstic acid and a gemini quaternary ammonium cation salt. This quaternary ammonium salt not only reduces the interfacial tension between olefins and hydrogen peroxide but also forms a notably stable structure with phosphotungstic acid. Dodecene was successfully epoxidized to epoxy dodecane with a selectivity of 82.9 %. The impact of initial conditions was systematically investigated such as molar ratio, temperature, reaction time, and catalyst dosage on the catalytic performance. Characterization of the catalyst morphology was performed by SEM, TEM and SAXS. Raman spectra, FT-IR and XPS spectra were employed to perform the catalyst transformation during the epoxidation reaction. This catalytic mechanism study could provide the industrial application in the epoxidation of long-chain olefins.