Formation and Performance of Monolithic Catalysts for Selective Catalytic Reduction of Nitrogen Oxides: A Critical Review

Elimination of PCDD/Fs over Commercial Honeycomb-Like Catalyst of V2O5-MoO3/TiO2 at Low Temperature: From Laboratory Experiments to Field Study

With the need for ultra-low emissions and the strict regulation of PCDD/Fs from MSWI plants, traditional SCR catalysts have been applied to remove PCDD/Fs. In this study, we compared one typical commercial V2O5-MoO3/TiO2 catalyst’s performance in removing PCDD/Fs under laboratory and industrial conditions. Various characterization methods like XRF, XPS, BET, and H2-TPR were applied to analyze the catalyst’s properties. The laboratory results showed that the adsorption could significantly affect the removal at low temperatures. The RE on PCDD/Fs was 59.4% (55.0% for toxicity RE), 88.5% (90.3%), and 78.0% (76.0%) at 160 °C, 180 °C, and 200 °C, respectively, showing that 180 °C is the most suitable operation temperature for this V2O5-MoO3/TiO2 catalyst. The field study was conducted at 180 °C, and the results revealed that the competition between water vapor and the interaction of SO2 could lower the RE. However, comparisons between laboratory and field conditions showed that this V2O5-MoO3/TiO2 catalyst still showed good stability, with only a 6.8% drop.

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

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.