Abstract
Catalytic oxidation of CO over Pd/Al 2O 3 was studied with a novel monolithic reactor, with inside the reactor detection of reactants and products. Periodic switching of the feed between CO/N 2 and O 2/N 2 resulted in time-averaged rates which were more than 40 times the maximum achievable steady-state rate. To our knowledge, these enhancement factors are the highest ever observed for any reaction-catalyst system. Mapping the time-averaged reaction rates in the cycle time-CO duty fraction plane resulted in a unique global maximum at each temperature and flow rate. The ratio of optimum periodic operation rate to steady-state rate does not increase monotonically with decreasing temperature but exhibits a maximum. Transient response experiments show the presence of more than one type of surface species of CO and oxygen taking part in the reaction. While the transient responses for CO and oxygen pretreated catalysts are similar in appearance, step-up and step-down responses to and from the steady state are not. The implications of these observations in terms of the possible surface processes are discussed.
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