Temperature and time dependence of the water inhibition effect on supported palladium catalyst for methane combustion

The time constant for equilibration of water adsorption/desorption during methane combustion over zirconia supported palladium catalyst was qualitatively studied at different reaction temperatures under both pulsed and continuous flow experiments. Water inhibition of methane oxidation was found to depend strongly on the time constant for equilibration of the adsorption/desorption of water, which, in turn, is a strong function of temperature. In pulsed experiments, at temperatures below 723 K the water inhibition effect was found to be important, in agreement with previously reported results and consistent with results reported by other authors. This also coincides with the temperature at which the desorption time gap between the measured CO2 and water peaks disappears. Response to changes in water concentration was found to be slow, thus not equilibrated at low temperatures. However, under continuous flow water poisoning is important to higher temperatures due to readsorption. (C) 2001 Elsevier Science B.V. All rights reserved.