Liquid-phase oxidation of α-pinene with oxygen catalyzed by carbon-supported platinum metals

The liquid-phase oxidation of α-pinene with oxygen at 70–90°C is studied in the presence of Pd, Pt, Ru, Rh, and Ir supported on carbon. The conversion of α-pinene and the selectivity of formation of the main reaction products, namely, verbenol ( 1 ), verbenone ( 2 ), and α-pinene oxide ( 3 ), depends on the nature of the metal, on its oxidation state and extent of dispersion, and on the admixtures introduced into the system. In the presence of the Pt catalysts and promoting admixtures of tetrahexylammonium chloride (Hex 4 NCl), the selectivity of formation of the most valuable oxidation products ( 1 + 2 ) reaches 50% at an α-pinene conversion of 20–30%. The fraction of resinlike oxidation products decreases in the presence of the catalysts. The results obtained are discussed in the framework of the radical mechanism of α-pinene oxidation.