Keggin heteropolyacid as catalyst for olefin epoxidation: A multiphase approach

Abstract

Keggin-type heteropolyacids have been used as catalyst for the selective oxidation of olefins to the corresponding epoxides in multiphase conditions (isooctane/Aliquat 336/water). Multiphase system allowed achieving a higher conversion (72%) and selectivity (70%) to epoxide than the corresponding homogeneous or biphasic systems in the presence of the same catalyst. Optimization of the multiphase system has been conducted considering reaction time, temperature, amount of the catalysts and quantity of the oxidant. The best-found reaction conditions were then employed for the selective epoxidation of several substrates. Interestingly, it was shown that, in the multiphase system, only an insignificant decomposition of hydrogen peroxide was observed. Furthermore, an environmental assessment has been conducted comparing green metrics related to the homogenous, biphasic and multiphase systems herein investigated.