A kinetic study on CH4 combustion over a very active PdO/ZrO2 catalyst with high Pd loading (10% w/w of Pd) is presented as an example of a demanding problem which requires both the development of appropriate experimental tools and a theoretical insight on surface chemistry. The use of an annular catalytic reactor as a tool to collect kinetic data under unusually severe conditions (high temperature and CH4 concentration) is described in comparison with the use of a conventional packed bed reactor. In particular, problems related to the biasing effects of mass, heat and momentum transfer are addressed. Kinetic data addressing the effects of CH4, O2, H2O and CO2 concentration in a temperature range from 400 to 550 °C are analysed by means of a purely empirical power law model and of a formal kinetic model based on literature indication assuming methane dissociative adsorption as the rate controlling step. |