Core-shell structure CuO-TiO2@CeO2 catalyst with multiple active sites for simultaneous removal of NO, Hg0 and toluene

The core–shell structure CuO-TiO2@CeO2 catalysts with multiple active sites synthesized via a self-assembly method was applied to study the simultaneous removal of NO, Hg0 and toluene. The results indicated that using CeO2 as sheath could remarkably enhance the catalytic performance. The CeO2 shell layer could not only be conducive to the exposure of active sites on the catalyst surface and enhance the adsorption of the toluene, NH3 and NO species, but also produce abundant oxygen vacancy defect sites through the strong interaction between CeO2 shell and CuO-TiO2 core. Coordinately NH3 on Lewis acid sites were the key intermediates for NH3-SCR reaction that takes place both through the Eley-Rideal and Langmuir-Hinshelwood pathways. Gaseous Hg0 was firstly adsorbed over multiple oxidation sites that generated via the redox cycle of Cu2+ + Ce3+ ↔ Cu+ + Ce4+, and then was oxidized to HgO by lattice oxygen species (Oβ). Meanwhile, NO could react with surface chemisorbed oxygen (Oα) to produce NO2, which could oxidize Hg0 into Hg(NO3)2. Toluene could be removed via the reaction path: toluene → benzyl alcohol → benzoate species → maleic acid species → CO2 + H2O. The interaction mechanisms between different gas components on CuO-TiO2@CeO2 were proposed.