(36f) Solvent Effect on Cyclohexene Hydrogenation over Pd

We have studied the effects of different hydrogen solubility, competitive adsorption, and solvation in a model hydrogenation reaction. For this purpose, in-situ spectroscopy is a powerful tool to acquire high time resolution kinetic data. The ATR-IR probe is equipped on a high temperature and high pressure vessel to monitor hydrogenation rate of cyclohexene in different organic aprotic solvents. The reaction is carried out under 70°C over heterogeneous 0.5% Pd/a-Al₂O₃ and homogenous Pd(II) catalyst. The concentration of cyclohexene during reaction is estimated by the intensities of the vibrational mode at 1139cm^-1(wCH2 rock). The scan takes place every one minute so that the reliable kinetic analysis can be modeled. By changing different organic aprotic solvents, the hydrogenation rates are compared to study the solvent effect. The main difference in heterogeneous and homogenous catalysis is that in heterogeneous catalysis reactants are firstly adsorbed on metal surfaces and then go through surface reaction to form products. However, in homogenous catalysis reactants interact strongly with catalyst active sites and they both are solvated in solvents. The study will focus on whether solvation effect and how it affects the cyclohexene hydrogenation rate.