Synthesis of supercritical CO2 soluble catalysts and their use in some chemical reactions

In this study, three catalysts which are soluble in scCO2 as an alternative reaction medium of conventional solvents have been synthesized. The synthesized pyridine and phosphiteoxide ligands with perfluoroalkyl groups (-(CH2)n(CF2)7CF3, n=1,3) were used to obtain the Rh(I) and Pd(II) complex catalysts. The activity of the catalysts has been studied for hydrogenation of styrene, 1-octene, t-2-octene and cyclohexene both in scCO2 and organic solvents. Kinetic studies were also carried out on the hydrogenation of styrene catalyzed by perfluoroalkylated pyridine-Pd(II) (pfpy-Pd(II)) complex in scCO2. From the kinetic investigations, it was found that the rate of hydrogenation showed a first order dependence with respect to the concentrations of the catalyst and the substrate and zero order in the partial pressure of dihydrogen. Thermodynamic parameters such as enthalpy, entropy and free energy of the reaction were calculated from the known thermodynamic equations. The experimental results showed that pfpy-Pd(II) is more active catalyst toward hydrogenation of olefins than perfluoroalkylated phosphiteoxide- Rh(I) (pff-Rh(I)) and perfluoroalkylated pyridine-Rh(I) (pfpy-Rh(I)) under similar experimental conditions. Keywords: Supercritical CO2, Perfluoro Pyridine, Perfluoro Phosphiteoxide, Rhodium, Palladium, Hydrogenation