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

• Unsteady-state operation enhances catalytic processes.
• Promoting methane oxidation by transient operation.
• Utilisation of temporary states with high catalytic activity.

Total oxidation of methane over model monolith catalysts with platinum supported on alumina, alumina–ceria and ceria has been studied under unsteady-state 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.