Periodic operation effects in propane and propylene oxidation over noble metal catalysts

Abstract It had been observed that under cycling conditions, the catalytic activities of three-way automotive catalysts are superior to those under static conditions, and that catalyst performance depends on the cycling period and feedstream conditions. The oxidation of propylene and propane over platinum, palladium and rhodium catalyst under static and periodic conditions was therefore investigated. The results were as follows; (i) the order of catalytic acitivities was Pd>Pt>Rh for propylene—oxygen and Pt>Rh>Pd for propane-oxygen; (ii) the periodic operation effect is dependent on both catalyst species and reaction temperature; (iii) the optimum period for the maximum conversion decreases with increasing temperature; and (iv) from results of the partial reaction order and evolution pattern analysis, either hydrocarbons or oxygen self-poison the reaction on the catalysts. The order of sensitivity to self-poisoning corresponds to the order of the periodic operation effect.