Study of catalyst performance of two inorganic/organic and inorganic/inorganic hybrid catalysts on the CO2cycloaddition to propylene oxide: kinetics and thermodynamics

The behavior of two hybrid catalysts: inorganic/organic (KI/chitin) and inorganic/inorganic (KI/amorphous silica-alumina) on the CO2 cycloaddition to Propylene oxide has been compared. Conversions of KI/chitin and KI/Si-Al were 99 and 97% respectively. KI/Si-Al shows a type IV N2 adsorption isotherm at P0/P of 0.6-0.9 of mesoporous nature with a significant concentration of Lewis acid sites, its FT-IR analysis shows that CO2 can be adsorbed as organic "bridging" carbonate onto the support's surface, which has an important role in the reaction mechanism. Kinetic analysis shows that the organic co-catalyst is up to 1.5 times faster for the CO2 cycloaddition than the inorganic co-catalyst at 160 °C bu both show very similar rate at 120 °C. Both supported catalysts show a significantly lower Ea than that calculated for free KI, although both show comparable activation energies. This insight gives interesting findings on how hybrid catalyst systems behave in an utmost crucial CO2 fixation reaction, being the foundations of future investigation on scale-up applications.