Selective hydrogenation of styrene oxide to 2-phenyl ethanol over polyurea supported Pd–Cu catalyst in supercritical carbon dioxide

Abstract

2-Phenyl ethanol (2-PEA) is an important chemical which finds several applications in perfumes, deodorants, soaps and detergents. It is prepared by different polluting and dangerous routes. The current work is concerned with production of 2-PEA by hydrogenation of styrene oxide using polyurea encapsulated catalysts (EnCat) in methanol and supercritical carbon dioxide (scCO₂). Bimetallic Pd–Cu catalyst encapsulated with polyurea, Pd–Cu EnCat, is the best catalyst. The epoxide ring in styrene oxide is selectively hydrogenated to give 2-PEA in scCO₂ without formation of any isomerization or deoxygenated products, which are formed in methanol. A complete conversion of styrene oxide with 100% selectivity to 2-PEA was obtained without addition of any promoter. Effects of various parameters were studied and a bifunctional site Langmuir–Hinshelwood–Hougen–Watson kinetic model was found to be in good agreement with the experimental data. The process is clean and green.