TiO2-coated CeCoOx-PVP catalysts derived from Prussian blue analogue for synergistic elimination of NOx and o-DCB: The coupling of redox and acidity

Abstract

Achieving efficient selective catalytic reduction (SCR) of NOx and catalytic oxidation of dioxins (o-dichlorobenzene as a model) on one catalyst is still a big challenge. In order to balance the N2 selectivity of SCR and the catalytic oxidation of dioxins, the catalysts with suitable redox properties and acidity need to be designed. Herein, we synthesized Prussian blue analogue (PBA)-derived CeCoOx oxides for the simultaneous removal of NOx and o-DCB by a co-precipitation method. The crystallization rate of PBA was slowed down by the addition of Polyvinylpyrrolidone (PVP), which increased the oxides size, enhanced the crystallinity of oxides and the uniformity of the surface elements distribution. These structural effects enhanced the low-temperature redox performance of the catalysts, and thus improved o-DCB conversion and CO2 selectivity. Furthermore, the PBA structure was coated by introducing TiO2, which improved the amounts of medium-acids and the mobility of oxygen species, thus increasing the mid-and high-temperature SCR performance and N2 selectivity. In addition, the H2O resistance and stability of the catalysts were enhanced due to the protective effect of the TiO2 coating on the PBA core. The optimized CeCoOx-PVP@TiO2 catalyst exhibited stable bifunctional removal efficiencies for NOx and o-DCB, with 90% NOx conversion and 92% o-DCB conversion at 300 ℃. The possible reaction mechanisms for NH3-SCR and the catalytic oxidation of o-DCB over the CeCoOx-PVP@TiO2 catalyst were proposed based on in situ DRIFTS experiments. This work provides an efficient strategy to design advanced catalysts for the elimination of dioxins and NOx.