Selective catalytic reduction of NO in the presence of SO2 and O2: The poisoning effect of SOx under oxygen rich and lean conditions

SOx poisoning has been a critical problem in the chemistry of selective catalytic reduction of NOx, and many fundamental issues surrounding the reactions remain unclear. In this paper, reactions taking place in the (C2H5OH)-C-13-NO-(SO2)-O-18-O-2 system on a platinum single crystal surface were studied. Oxidation of (C2H5OH)-C-13 by (SO2)-O-18 proceeds mainly through O-18-H reaction, and oxidation of the backbone carbon atoms can occur at high (SO2)-O-18 exposures, e.g., 1.6 Ls of (SO2)-O-18 for 0.4 L of (C2H5OH)-C-13. Thus, the presence of (SO2)-O-18 only slightly suppresses the catalytic reduction of NO by (C2H5OH)-C-13. Co-adsorbed O-2 evidently exerts a suppressive effect. When oxygen is lean (relative to (SO2)-O-18), the (SO2)-O-18-O-2 reactions mainly give rise to surface sulphoxy species at temperatures between 400 and 500K and thus, the NO-(C2H5OH)-C-13 reactions can still proceed. The NO reduction reaction is completely suppressed when oxygen is rich, a result of the Pt surface being passivated. This finding provides a valuable guide for optimizing the reaction atmosphere to improve the efficiency of the selective catalytic reduction of NO by hydrocarbons (or oxygen-containing fragments from oxidation of hydrocarbons in this case). (C) 2017 Elsevier B.V. All rights reserved.