Catalytic Hydrogenation of Benzaldehyde for Selective Synthesis of Benzyl Alcohol: A Review

In the recent past, various catalysts have been used for hydrogenation of benzaldehyde to benzyl alcohol and the efficiency of the catalysts observed is found to be less. This review focuses on catalytic hydrogenation and their parameters associated with supports, methods of preparation, solvents involved, reaction conditions in converting benzaldehyde to benzyl alcohol. Critical aspect of review is to evaluate activities of various heterogeneous catalysts that can selectively reduce benzalde-hyde to benzyl alcohol. The catalysts include various transition (Ni, Cu, Co) and noble metals (Au, Pt, Pd, Ru), monoliths and metal oxides (MgO, CaO, BaO, Al2O3, CeO2, ZrO2, etc.,), which are all active in the reaction. Among the transition metals, cobalt-based catalysts depicted promising activity, while ruthenium-based systems demonstrated spectacular activity among noble metal series. Hydrogenation by electrochemical reduction using platinum, palladium, nickel has also been reviewed.