Ambient-temperature α-pinene hydrogenation to cis-pinane over Ru/CeO2-H catalyst via the dimethyl-up configuration

Current industrial catalysts for α-pinene hydrogenation suffer from harsh reaction conditions and poor selectivity to cis -pinane, primarily due to their inability to effectively adsorb α-pinene in a specific favorable configuration on the catalyst surface. In this study, a high-specific-surface-area, rod-shaped CeO 2 -supported ultra-fine Ru nanoparticle (average particle size of 4 nm) catalyst was synthesized via hydrothermal method for the highly stereoselective hydrogenation of α-pinene to cis -pinane. The resulting Ru/CeO 2 -H catalyst achieved an α-pinene conversion of 99.3 % and an impressive cis -pinane selectivity of up to 99.6 % under exceptionally low temperature (30°C), 0.6 MPa H 2 and 0.5 h with high TOF (1236 h −1 ). Density functional theory (DFT) calculations indicated that α-pinene preferentially adsorbs onto the Ru surface via the backside of its intramolecular dimethyl bridge. This particular adsorption mode lowers the energy barriers for further hydrogenation to generate cis -pinane. The oriented dimethyl-up configuration of α-pinene and ultra-low activation energy (12.04 kJ/mol obtained from kinetic tests) enable the highly selective production of cis -pinane at ambient temperature. Furthermore, the strong interaction between the CeO 2 -H support and highly dispersed Ru, combined with the ambient-temperature reaction conditions, effectively prevents metal nanoparticle agglomeration and coking, imparting the catalyst with exceptional stability. Notably, the catalyst was reused at least 15 times without observing any significant deactivation, demonstrating its significant potential for practical applications.