Experimental and kinetic study of SO2 oxidation on a Pt/γ-Al2O3 catalyst

Abstract An SO 2 oxidation experimental study was performed and a kinetic model was developed to describe SO 2 oxidation over a Pt/γ-Al 2 O 3 oxidation catalyst. An apparent activation energy of 98.8 kJ mol −1 was measured when SO 3 was present in the feed. Reaction orders of 0.88 and −0.24 were obtained for SO 2 and O 2 , respectively, and the SO 3 reaction order was found to be −0.42. A microkinetic model based on a Langmuir-Hinshelwood mechanism was proposed and a one dimensional steady-state model was developed. A plug flow reactor model was assumed and the set of algebraic differential equations was solved at various temperatures to predict the SO 2 conversion as a function of temperature. The relative importance of each step in the reaction mechanism was studied at different temperatures to identify the rate determining step (RDS). According to the model, at temperatures below 300 °C, O 2 adsorption/desorption and the surface reaction between the adsorbed SO 2 and oxygen control the overall rate, whereas at higher temperatures the surface reaction is the RDS. The model predictions imply that, at low temperatures, SO 3 inhibits SO 2 oxidation through occupation of the active sites required for oxygen adsorption, verifying the higher activation energy observed in the presence of SO 3 in the feed. The modeling results revealed that the relative importance of the individual rates in the mechanism as well as the surface coverages were strongly temperature dependent.