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 (CH4-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, NH3-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 degrees C. The presence of Co2+ ion in both catalysts explains partially the high activity towards o-DCB oxidation. The deactivation of Pd/Co-HMOR for CH4-SCR at reaction temperatures above 500 degrees 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 CH4-SCR. According to NH3-TPD analysis, both Pd/Co-HMOR and Pd/Co-SZ catalysts present strong acid sites in the temperature range from 300 to 600 degrees 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 CH4-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 degrees C and that monoclinic phase appears in Pd/Co-SZ owing to sulfate group loss.