Alkali metal-resistant mechanism for selective catalytic reduction of nitric oxide over V2O5/HWO catalysts

A series of V ₂O ₅/HWO catalysts are prepared by hydrothermal and impregnation methods using different precursors, among which the V ₂O ₅/HWO-C catalyst exhibited the optimal NH ₃-SCR performance. Compared to oxalic acid (O) and water (W), commercial bacterial cellulose (C) as a precursor can firstly achieve a more controllable synthesis to form hexagonal WO ₃ (HWO) of V ₂O ₅/HWO-C catalyst. Various characterization (XRD, N ₂-BET, TEM, SEM, XPS, EDX mapping, and NH ₃/NO-TPD-MS) indicate that a higher specific surface area, abundant active oxygen and surface acidity result from the V ₂O ₅/HWO-C catalyst. The reason is that HWO-C has an excellent and smooth rod-shaped morphology, which promotes high dispersion of V ₂O ₅ on its surface. In situ IR results show that the SCR follows the Langmuir-Hinshelwood (L-H) mechanism, where absorbed NO _x intermediate species are formed on the V ₂O ₅ and react with the NH ₄ ⁺ and NH _3abs groups of V ₂O ₅ and HWO. After loading 1.75 wt% K ⁺, the obtained K-V ₂O ₅/HWO-C catalyst exhibits effective resistance to K poisoning and SO ₂, and retains 78 % NO _x conversion efficiency at 360 °C after 10 h, attributed to the effective capture of K ⁺ (1.04 wt%) in HWO-C channels via a new pathway, although approximately 0.71 wt% K ⁺ are located on HWO-C external surface with weak bonding to V ₂O ₅.