Investigation of deep catalytic oxidation of toluene over a Pt-based monolithic catalyst by dynamic experiments

Dynamic techniques were used to investigate the kinetics of deep catalytic oxidation of toluene over a Pt-based monolithic catalyst. Experiments were carried out both in non-reactive and in reactive conditions, in order to study the adsorption properties of the catalyst. The qualitative analysis of the response curves evidenced the formation of irreversibly adsorbed hydrocarbon species (carbonaceous overlayer) both in the presence of oxygen and in its absence. The adsorption of toluene likely occurs on at least two different types of sites, one of them likely being the carbonaceous overlayer. Competition for adsorption affects the behaviour of the reaction only on less active sites, whilst on the more active ones the high turnover frequency avoids any inhibition effect. Anyway, the hydrocarbon seems to be favoured in the competition with respect to oxygen, which is adsorbed in relatively small amount. The results of modelling investigation highlighted the importance of a correct simulation of the dynamics of adsorption and reaction of hydrocarbon species, and showed that a marked improvement of model predictions is possible when taking into account the possibility of adsorption of fresh toluene on the carbonaceous overlayer.