Kinetic study of oxidation of cyclohexane using complex catalyst



With an effort to use a multimetallic catalyst system for oxidation of cyclohexane using oxygen, a binuclear monometallic macrocyclic ZrZr complex was prepared and covalently bonded to modified alumina support. The complex catalyst thus prepared was found to be thermally stable and was completely characterized by CHN, SEM-EDAX, TGA, and FTIR analysis. We carried out liquid phase oxidation of cyclohexane using molecular oxygen without any solvent, coreactant, or cocatalyst at considerably mild reaction conditions (150°C, 27 atm) with extremely high selectivity. The GC-MS of the liquid product formed showed the total conversion of as much as 19% having cyclohexanone and cyclohexanol in the ratio of 16:1. To explain the experimental data, a possible reaction mechanism has been proposed and rate constants (assuming single phase) at different temperatures were determined using an optimal curve fitting by applying genetic algorithm. We showed that the steady state approximation cannot be assumed, and for the pressure range studied (7–35 atm), the rate constants thus determined were found to be a function of temperature only. From experiments carried out at different temperatures, we found that for every rate constant, an Arrhenious type relation could be established. © 2007 American Institute of Chemical Engineers AIChE J, 2007