Monoterpenoid oximes hydrogenation over platinum catalysts

Platinum nanoparticles supported on MgO, Al₂O₃, ZrO₂, TiO₂ were utilized for monoterpenoid oximes hydrogenation. Monocyclic menthone and carvone oximes synthesized from bio-derived monoterpenoids with a different structure were used to explore the effect of substrate structure on the reaction regularities. The oximes hydrogenation was carried out under hydrogen atmosphere at 100 °C using methanol as a solvent. Platinum catalysts were prepared by the impregnation methods. The catalysts were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray fluorescence spectroscopy, nitrogen physisorption. Hydrogenation of carvone oxime containing a conjugated oxime group and several reducible functional groups resulted in both hydrogenation and deoximation giving 5-isopropyl-2-methylcyclohexanamine and carvomenthone over Pt/Al₂O₃ and Pt/ZrO₂ catalysts. Menthone oxime hydrogenation over Pt/Al₂O₃ catalysts with an average particle size of 0.8 nm provided the desired menthylamine formation with the selectivity of 90% at complete oxime conversion. Platinum catalysts based on MgO, ZrO₂ and TiO₂ enhanced menthone oxime deoximation to menthone.