Selective hydrogenation of cinnamaldehyde to cinnamyl alcohol over BN-supported Pt catalysts at room temperature

Abstract

BN-supported Pt catalysts were prepared by an impregnation method using Pt(NH3)4(NO3)2 as metal precursors and tested in the liquid-phase selective hydrogenation of cinnamaldehyde. It was found that the Pt/BN catalyst exhibited a high performance for the selective CO hydrogenation at room temperature. A selectivity of over 85% towards cinnamyl alcohol at a cinnamaldehyde conversion of over 95% could be obtained. The effects of supports and Pt particle sizes were explored by N2 physisorption, XRD, TEM, HRTEM, HAADF-STEM, TPD, H2-TPR, XPS, CO-DRIFTS, etc. The influences of solvents and operation conditions were investigated, and a simplified kinetics test was also carried out. The comparison of different supports suggested that BN with an inert surface and few acid-base sites possibly favors a simple adsorption mode of cinnamaldehyde dependent only on the supported Pt particles, resulting in a high selectivity to cinnamyl alcohol. While the abundant acid-base surface sites on the Pt/Al2O3 or Pt/SiO2, possibly associated with the multiple adsorption modes of cinnamaldehyde, had an adverse effect on the selective CO hydrogenation. The investigation of Pt size effect showed that large Pt particles with few low coordinated Pt sites displayed a higher selectivity to cinnamyl alcohol than small Pt particles with more low coordinated Pt sites on the Pt/BN catalysts. It was also revealed that water is a suitable solvent, and the presence of water in a mixture solvent is crucial for achieving a high activity of the Pt/BN in cinnamaldehyde hydrogenation.