Surface and Catalytic Elucidation of Rh/γ-Al2O3 Catalysts during NO Reduction by C3H8 in the Presence of Excess O2, H2O, and SO2

The Present study aims at exploring the surface and catalytic behavior of Rwh/gamma-Al2O3 catalysts during the selective reduction of NO by C3H8 in the presence of excess oxygen, H2O, and SO2 with particular emphasis oil identifying the elementary steps that describe the reaction mechanism. To this end, detailed activity and stability tests were employed and I precise kinetic analysis was carried Out at differential Conditions 10 elucidate the effect of each reactant, including H2O and SO, on the total reaction rate. At the same time, temperature programmed desorption (TPD) studies in combination with in situ diffuse reflectance infrared Fourier transform (DRIRFT) spectroscopy were carried out under various reaction conditions to correlate the catalytic performance of Rh/gamma-Al2O3 catalyst With its corresponding surface chemistry. The results reveal that in the absence of H2O and SO2 the reaction follows a typical "reduction" type mechanism, where the active intermediates (NOx, carboxylates, isocyanates) are interacting to yield the final products. In this reaction sequence the formation of carboxylate (CxHyOz) species is considered as the rate determining step. Water affects in a different way the NO and C3H8 Conversion performance of Rh/gamma-Al2O3 catalyst its effect is totally reversible in the case of C3H8 oxidation, while the NO reduction was permanently affected Mainly due to the oxidation of Rh active sites. Ill contrast, SO, poisons both reactions irreversibly via the formation of strongly adsorbed sulfate compounds, which hinder the adsorption and consequently the activation of reactants.