On the Influence of the Catalyst Physical Properties on the Stability of Forced Unsteady-State After-Burners

The influence of the physical and chemical properties of the catalyst on the stability of forced unsteady-state catalytic after-burners has been investigated in detail by numerical simulation, employing either a simplified or a complete two-phase one-dimensional model, having as an objective the optimization of the catalyst. If the aim is to obtain stable operation, feeding cold and lean VOC mixtures without auxiliary fuel, both heat capacity and thermal conductivity of the catalyst have been shown to play a role, not less important than kinetic activity, strongly influencing the minimum inlet VOC concentration required for autothermal operation. Perovskite-type catalysts, even if less active than noble metals over traditional commercial supports, show, for this specific application, better performances because of their high heat capacity and low thermal conductivity. Dilution of the adopted catalyst with an inert material having high thermal capacity has also been considered in order to increase the heat capacity of the bed (and, as a consequence, the ability of the system to keep the heat of reaction inside the catalytic bed).