The Synergistic Catalysis of Chloroaromatic Organics and NOx over Monolithic Vanadium-Based Catalysts at Low Temperature

Abstract

In this study, four monolithic, vanadium-based catalysts in granular (Vox/TiO2), honeycomb-type (Vox-Wox/TiO2 and Vox-MoOx/TiO2), and corrugated forms (Vox-Wox/TiO2) were investigated by multiple characterization methods (BET, XRF, XPS, XRD, H2-TPR, and NH3-TPD). Their catalytic performances were evaluated by the oxidation-reduction performance of ortho-dichlorobenzene (o-DCB) and NO/NH3. The modification of Wox and MoOx could promote catalytic activity by accelerating the transformation of V5+/V4+ and enriching the strong acid sites. The introduction of NO/NH3 significantly impaired the o-DCB oxidation, ascribed to the competitive adsorption of reactants on acid sites. The performance of Vox/TiO2 and Vox-MoOx/TiO2 catalysts indicated that strong acidity could enhance catalytic abilities over o-DCB and Nox. Nevertheless, the CE (conversion efficiency) of o-DCB was more related to a large BET surface area and a high amount of V5+ species, while the CE of Nox was more associated with redox ability and Vox surface density. The V4+/V5+ and OS-A/OS-L ratio increased prominently after the oxidation of o-DCB, indicating that it was the reoxidation of V4+ species, rather than the supplement of oxygen, that limited the reaction rate. This work revealed catalytic activity was positively affiliated with the surface area, amount of V5+ species, transformation rate of V4+/V5+, redox ability, and abundance of strong acid sites. Additionally, the results could guide the selectivity and improvement of industrial low-temperature catalysts for synergistic elimination of chloroaromatic organics and Nox.