Acid etching-induced Ce3+-O-Mn4+ active sites of SmCe(0.1)Mn(1.9)O(5 )mullite for enhanced elimination of Hg(0 )and chlorobenzene

The efficient control of co-existing Hg0 and chlorobenzene in flue gas through catalytic oxidation is a major challenge in the field of energy-intensive industry. In this study, a porous SmCe0.1Mn1.9O5 catalyst is prepared via a sol-gel method followed with acid etching for the synergistic elimination of Hg0 and chlorobenzene. The optimized Ce-SM-E exhibits near 100% removal efficiency of Hg0 within 100-400 degrees C and 90% chlorobenzene conversion above 275 degrees C as well as excellent performance under complex flue gas conditions. The Ce substituting Mn3+ in the mullite structure enables favorable electron transfers from SmMn2O5 to CeO2 while causing more active defects. Subsequent acid etching removes the surface Sm species and modulates the electronic state of Mn atoms, inducing formation of more Ce3+-O-Mn4+ active sites, consequently enhancing the redox cycle. Especially, the generation of aldehydes, aromatic rings, maleate species and monodentate carbonate species are considered as the main rate-limiting steps in the chlorobenzene degradation path. The influence of complex flue gas components (SO2, NO, H2O, etc) on the distribution of reaction by-products is analyzed. The sulfation poisoning from SO2 consumes reactive oxygen species and promotes more dichlorobenzenes through electrophilic reactions. The presence of NH3/NO and H2O are found to promote the generation of NH4Cl and HCl, respectively, but the addition of which also generates much oxygen-containing byproducts such as acetophenone, benzoyl chloride and benzenecarboxylic acid via the Friedel-Crafts reaction. These results provide a promising approach for engineering efficient catalysts and benefit the evaluation of environmental risk under industrial conditions.

Automated summary

The efficient control of co-existing Hg0 and chlorobenzene in flue gas is achieved through the use of a porous SmCe0.1Mn1.9O5 catalyst prepared via a sol-gel method followed by acid etching. The catalyst exhibits high removal efficiency for Hg0 and chlorobenzene, as well as excellent performance under complex flue gas conditions. The study also analyzes the influence of complex flue gas components on the distribution of reaction by-products.