Kinetics of CH4 complete oxidation on CuH-ZSM-5 catalyst

Abstract

Publisher Summary In the past few years, copper—containing zeolites of ZSM-5 type—has been examined in a lot of works because of its unusual activity in different redox reactions. In particular, the activity of Cu-ZSM-5 in complete oxidation of CH 4 and C 2 H 6 was correlated with the concentration of coordinatively unsaturated square-planar Cu 2+ cations. At the same time, little is known about the kinetics of these processes occurring on the active sites located inside the zeolitic channels. The chapter provides kinetic data about the methane complete oxidation on the Cu-ZSM-5 characterized in previous works. Upon the study of methane oxidation in a flow system at much lower CH 4 concentration (265 ppm), it is shown that the reaction occurs in the external diffusion region. For checking the possible influence of mass-transfer on the reaction kinetics, the circulation rate was changed from 200 to 500 l/h at 490oC and the mixture flow 18 1/h. No change of reaction rate is registered. Besides, the change-over to the conditions of a flow reactor results in a small rise in the conversion degree despite of the deterioration of the external mass-transfer conditions. Therefore, the external diffusion retardation was negligible even at 490oC much less at lower temperatures.