Catalytic activity and stability of Pd/Co catalysts in simultaneous selective catalytic reduction of NOx with methane and oxidation of o-dichlorobenzene.

Nitrogen oxides (NOx) and polychlorinated dibenzo- p -dioxins and dibenzofurans (PCDD/Fs) are well known as hazardous pollutants that may be generated during combustion processes, and which simultaneous removal is highly desired. Here the Selective Catalytic Reduction of NO by methane (CH 4 -SCR) with the simultaneous oxidation of 1,2-dichlorobenzene ( o -DCB) was studied over Pd/Co-HMOR and Pd/Co-SZ catalysts under lean, dry and wet conditions. Catalysts were characterized by XRD, BET, TGA, H 2 -TPR, NH 3 -TPD, TEM/EDS and Raman spectroscopy. Pd/Co-HMOR showed better catalytic performance than Pd/Co-SZ in terms of activity and durability under both dry and wet conditions at 500 °C. The presence of Co 2+ ion in both catalysts explains partially the high activity towards o -DCB oxidation. The deactivation of Pd/Co-HMOR for CH 4 -SCR at reaction temperatures above 500 °C may be related with the formation of PdO specie while the loose of sulfate groups of Pd/Co-SZ can be correlated with the deactivation of this catalyst towards CH 4 -SCR. According to NH 3 -TPD analysis, both Pd/Co-HMOR and Pd/Co-SZ catalysts present strong acid sites in the temperature range from 300 to 600 °C, which can be associated with their considerable active towards both reactions. The higher performance of Pd/Co-HMOR compared with Pd/Co-SZ, mainly in the CH 4 -SCR reaction, can be related with the higher total acidity of the catalyst supported on HMOR. The XRD analysis of used samples showed that Pd/Co-HMOR losses crystallinity at reaction temperatures greater than 500 °C and that monoclinic phase appears in Pd/Co-SZ owing to sulfate group loss. [ABSTRACT FROM AUTHOR]