Kinetic modelling of sulfur deactivation of Pt/BaO/Al2O3 and BaO/Al2O3 NOx storage catalysts

In this work, a kinetic model is constructed to simulate sulfur deactivation of the NOx storage performance of BaO/Al2O3 and Pt/BaO/Al2O3 catalysts. The model is based on a previous model for NOx storage under sulfur-free conditions. In the present model the storage of NOx is allowed on two storage sites, one for complete NOx uptake and one for a slower NOx sorption. The adsorption of SOx is allowed on both of these NOx storage sites and on one additional site which represent bulk storage. The present model is built-up of six sub-models: (i) NOx storage under sulfur-free conditions; (ii) SO2 storage on NOx storage sites; (iii) SO2 oxidation; (iv) SO3 storage on bulk sites; (v) SO2 interaction with platinum in the presence of H2; (vi) oxidation of accumulated sulfur compounds on platinum by NO2. Data from flow reactor experiments are used in the implementation of the model. The model is tested for simulation of experiments for NOx storage before exposure to sulfur and after pre-treatments either with SO2 + O2 or SO2 + H2. The simulations show that the model is able to describe the main features observed experimentally.