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

Abstract

Spectroscopy and kinetics of the vapor phase cyclohexane (Cy-H) oxidation over the catalyst 20FeMnOδ/(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 FeMnOδ 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 ∼44, ∼106, and ∼123 kJ/mol, respectively.