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

Abstract

The simultaneous removal of nitrogen oxides (NOx) 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 NOx/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 Mn6Co4Ox 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 Mn6Co4Ox 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 Mn6Co4Ox catalysts could be attributed to the by-products of CB decomposition and the unfavorable accumulation of MnClx or CoClx on the catalyst surface, which inhibited the NH3-SCR reaction.