Cl-Resistant Synergistic Removal of NO_x and Chlorobenzene over SmMn₂O₅-Zeolite Composite Catalysts

Synergistic catalytic removal (SyCR) of NO_x and chlorinated volatile organic compound (CVOCs) emission from nonelectric industries is effective to suppress PM_2.5 and ozone complex air pollution. Catalysts with balanced competence to reduce NO_x and oxidize CVOCs, as well as the resistance to chlorine poisoning, are critical to SyCR. Here, neighboring effects over SmMn₂O₅ mullite (SMO) modified by HZSM-5 composite catalysts (SMO-Z) were demonstrated in the Cl-resistant SyCR of NO_x and chlorobenzene (CB, a representative CVOCs). Characterizations demonstrated that HZSM-5 modification did not alter the crystal structure of SMO and retained Mn-O-Mn-Mn active sites for the SyCR of NO_x and CB. HZSM-5 regulated the redox ability of SMO-Z to reduce the formation of inert nitrate species and to promote the N₂ selectivity. Acidic HZSM-5 acted as dechlorination sites to promote the breakage of the C-Cl bond via the nucleophilic substitution reaction and accelerated the formation of HCl to avoid Cl poisoning on catalysts. The fine-tuned compensation of surface acidity by HZSM-5 suppressed the competitive adsorption of NH₃ and CB on SMO-Z, which promoted NO_x reduction at high temperatures, whereupon neighboring effects between HZSM-5 acidic dechlorination sites and SMO active redox sites on SMO-Z capitally promoted the SyCR efficiency and antichlorination poisoning performance.