Selective Hydrogenation Of Cinnamaldehyde Over BN Supported Noble Metal Catalysts

Cinnamaldehyde (CAL) is one of the typical representative α, β-unsaturated aldehydes, which can be hydrogenated to cinnamyl alcohol (COL), a widely used chemical in perfume and pharmaceutical industry, or hydrocinnamaldehyde (HCAL), an important intermediate of anti-HIV drug. Further hydrogenation of COL and HCAL leads to the formation of 3-phenyl-1-propanol (PPL). Although the hydrogenation of C=C is thermodynamically favorable than that of C=O group, the mixture of various products is generally obtained in CAL hydrogenation and the mechanism of selecvitity is not clear so far. Therefore, designing the efficient catalyst is of great scientific importance and also of industrial interest for highly selective hydrogenation of cinnamaldehyde.The hexagonal boron nitride (h-BN), also called white graphite, is one of the promising inorganic material with excellent physical and chemical properties. In this thesis, h-BN was used to support Pt and Rh, highly effective metals for catalytic hydrogenation, and the resulting supported catalysts were tested in liquid phase cinnamaldehyde hydrogenation at room temperature. The influence of various noble metals, carriers and reduction conditions on the hydrogenation performance were studied, the reaction conditions such as solvent, temperature, pressure and time were optimized, and the reaction kinetics were investigated as well. The main results are as follows:1. Selective hydrogenation of CAL was studied in the liquid phase over various noble metals supported on h-BN. Pt/BN performed a desired selectivity to COL with a higher activity, while Pd and Rh showed higher selectivity hydrogenation for C=C and little for C=O, and the performance of Ru was in between. Pt(NH3)4·(NO3)2 was selected as Pt precursor to prepare the supported catalysts. Pt/BN performed highest selectivity for cinnamyl alcohol than Al2O3, SiO2 and graphite supported Pt catalysts.1 wt.%Pt/BN exhibits a CAL conversion of 95.8% and a selectivity of 85.2% to COL in the isopropanol/water of 4 at room temperature under 4 MPa H2 pressure with the reaction time of 2 h. The results of kinetic investigation of the Pt/BN reaction system showed that the reaction under constant H2 pressure of 4 MPa followed pseudo first order kinetics for CAL.2. RhCl3 was chosen as Rh precursor to prepare the supported catalyst. Rh/BN performed highest selectivity for hydrocinnamaldehyde than Al2O3, SiO2 and graphite supported Rh catalysts. It may be in relation to the inert surface of h-BN and the Rh particle size.1 wt.% Rh/BN exhibits a CAL conversion of 91.1% and a selectivity of 94.9% to HCAL in the isopropanol/water of 4/1 at 60℃ under 4 MPa H2 pressure after running the reaction for 2 h. The results of kinetic investigation of the Rh/BN reaction system show that the reaction under constant H2 pressure of 4 MPa followed pseudo first order for CAL.