Spectroscopic and Kinetic Study of Cyclohexane Oxidation Reaction in Vapor Phase over the Catalyst 20FeMnOδ/(3CeAl)

Spectroscopy and kinetics of the vapor phase cyclohexane (Cy-H) oxidation over the catalyst 20FeMnO(delta)/(3CeAl) were investigated. An in situ diffuse reflectance Fourier transform spectroscopy adsorption and reaction studies were conducted. The incorporation of ceria into the alumina support facilitated the formation of cyclohexene (Cy-ene) through preferential C-H bond activation at higher temperatures, whereas the FeMnO delta phase enhanced oxygen mobility and loosely bound lattice oxygen species forming of cyclohexanone (Cy-one). The reaction temperature and contact time influenced the product distribution of cyclohexanol (Cy-ol), Cy-one, and Cy-ene. The power law model suggested pseudo-first-order reaction kinetics with Cy-H concentration. The modified Mars-Van Krevelen (MVK) model was validated with the experimental results. The various observed intermediate species cyclohexanolate (Cy-olate*), lattice oxygen, and surface hydroxyl groups play crucial roles in forming various products. The kinetic analysis revealed that the total activation energies for the formation of Cy-ol, Cy-one, and Cy-ene were similar to 44, similar to 106, and similar to 123 kJ/mol, respectively.