Cyclohexane photo-catalytic oxidation on TiO2, an in situ ATR-FTIR mechanistic and kinetic study

Abstract

Chemical processes are generally operated at elevated temperatures and pressures, and energy intensive separations are usually necessary. This thesis focuses on the production of cyclohexanone, which is an intermediate of high commercial importance as a result of its use in nylon-6 and nylon-6,6 production. Using TiO2 based photo-catalysis is a promising alternative to the inefficient commercial process of cyclohexanone production, producing cyclohexanone very selectively at ambient conditions. Furthermore, potentially the catalyst can be activated by a free energy source, i.e. sunlight. However, low yields and severe catalyst deactivation prevent the photo-catalytic alternative to be industrially applied. The work presented in this thesis aims at providing further insight in the mechanism and kinetics of cyclohexane photo-catalytic oxidation to cyclohexanone, by looking closely at the surface phenomena. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy, allows for the analysis of adsorbed reagents, intermediates and products at the catalyst surface. This thesis shows that ATR-FTIR spectroscopy is a very informative technique, especially when combined with isotopic substitution and modeling tools, such as kinetic modeling and DFT calculations.