Unsteady-state operation of supported platinum catalysts for high conversion of methane

Abstract

Total oxidation of methane over model monolith catalysts with platinum supported on alumina, alumina-ceria and ceria has been studied under unsteadystate operation of the feed gas stoichiometry. The general activity for methane oxidation follows the order Pt/alumina < Pt/alumina-ceria < Pt/ceria. Thanks to high catalytic activity at the gas composition switches, increased cycling frequency between oxygen excess and oxygen free conditions increases the average methane conversion significantly from 11 to 58% for Pt/alumina and from 25 to 87% for Pt/alumina-ceria. The corresponding stationary methane conversion is 10 and 19%, respectively. The underlying reason for the enhanced catalytic activity is likely twofold namely that periods with detrimentally high coverage of either oxygen or carbon are shortened and that the transients induce a highly active (chemical) state of the catalyst, thus, facilitating high average conversion of methane.

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