AN ISOTHERMAL FIXED-BED REACTOR WITH NONUNIFORMLY ACTIVE CATALYSTS - EXPERIMENTS AND THEORY

An isothermal fixed-bed reactor packed with supported catalyst pellets, in which the active metal catalyst was deposited as a thin band within the support, was studied experimentally. The purpose was to support our previous related theoretical studies. The oxidation of CO with excess oxygen over Pt catalyst was used as the test reaction. The catalysts were prepared by sequential impregnation of chloroplatinic acid and citric acid on γ-alumina pellets. A thin layer of Pt was achieved within the support to simulate the Dirac delta distribution function. A maximum of two steady states were obtained when only one type of catalyst was packed in the reactor. A 'jump' from the high conversion regime to the low conversion regime occurred when the CO feed concentration was increased from low to high values; as the CO concentration was decreased, a continuous transition from the low conversion regime to the high conversion regime resulted generally. For the reactor packed with two different types of catalysts in series, the importance of their order of packing was demonstrated; also, three stable steady states were observed in some cases. Excellent qualitative agreement between the experiments and the theory was obtained.