Role of water vapor in photocatalytic oxidation of ethylene over titanium dioxide in gas phase

Abstract

The photocatalytic oxidation of ethylene was studied in a packed bed reactor using titanium dioxide that was prepared by a sol-gel method as a catalyst. Effects of several reaction parameters, namely, flow rate of reactant, humidity level, and temperature, on the kinetics of the photocatalytic oxidation process were investigated. Nonlinear regression analysis was employed to fit few proposed rate expression to the kinetic data. A Langmuir-Hinshelwood-Hougen-Watson rate expression was applied to describe the behavior of photocatalytic oxidation of ethylene and could give an adequate fitting to the kinetic data. The reaction rate of ethylene decreased with increasing relative humidity but increased with increasing reaction temperature. Water competes with ethylene for adsorption sites on titanium dioxide surface. The activation energies for the reaction were 25.02 and 6.78 kJ/mol at 0 and 100% relative humidity, respectively. The standard enthalpies ofadsorption for ethylene were -11.3 and -15.8 kJ/mol at 0 and 100% relative humidity, respectively