Supercritical carbon dioxide and poly(ethylene glycol): an environmentally benign biphasic solvent system for aerobic oxidation of styrene

Abstract

Aerobic oxidation of styrene catalyzed by PdCl₂/CuCl can be smoothly performed in the supercritical carbon dioxide and poly(ethylene glycol) biphasic system. A high conversion of styrene and yield of acetophenone were obtained in the presence of a relatively low catalyst loading. This environmentally benign biphasic catalytic system can be applied to the Wacker oxidation of various alkenes. Furthermore, the PdCl₂-mediated oxidation of styrene was preferentially converted into benzaldehyde using a biphasic scCO₂/PEG system. The PEG could effectively immobilize and stabilize the catalysts. The present biphasic system could facilitate product separation and catalyst recycling. The effects of the reaction parameters such as solvent and CO₂ pressure were also investigated in detail.