Effect of chlorobenzene on the performance of NH3-SCR over Mn6Co4Ox catalyst

Abstract

The simultaneous removal of nitrogen oxides (NO_x) and volatile organic compounds (VOCs) in NH₃-SCR units can simplify the flue gas treatment process and has great potential for economic and environmental benefits. Mn-based catalysts have shown excellent performance in NO_x/chlorobenzene (CB) synergistic removal, however, the mechanism of CB influence on NH₃-SCR is not clear till now. In this paper, the impact of CB on the performance of NH₃-SCR over Mn₆Co₄O_x catalysts is investigated in detail. The findings demonstrate that while the presence of CB clearly inhibits the adsorption of NH₃ and NO, the Cl-produced during CB breakdown can actually promote the adsorption of them. In addition, the emission of N₂O and NO₂ in the NH₃-SCR reaction with CB participation was significantly reduced, and the N₂ selectivity was significantly improved at the same time. The impact of CB on the NH₃-SCR reaction pathway under 250 ℃ was explored using in situ DRIFT further. It showed that the NH₃-SCR reaction on the Mn₆Co₄O_x catalyst was found to follow both the Eley − Rideal (E-R) and Langmuir − Hinshelwood (L-H) mechanisms. The presence of CB in the reaction accelerated the rate of the nitrate reaction, hindered the synthesis of M−NO₂ nitro compounds, and enhanced the generation of the intermediate product-NH₂ for the improvement of the NH₃-SCR reaction. Conversely, the slow deactivation of the Mn₆Co₄O_x catalysts could be attributed to the by-products of CB decomposition and the unfavorable accumulation of MnCl_x or CoCl_x on the catalyst surface, which inhibited the NH₃-SCR reaction.