Rational selection of Fe2V4O13 over FeVO4 as a preferred active site on Sb-promoted TiO2 for catalytic NOX reduction with NH3

Abstract

FeVO4 (Fe-1) is a particular class of metal vanadate that has recently been highly profiled as an active site to selectively reduce NOX with NH3 (NH3-SCR). This primarily results from NOX/NH3-accessible VO43- anions and an electronic inductive effect between the Fe and V species, leading to the formation of abundant catalytic defects available for NOX turnover. Motivated by a structural inspection of the vanadates reported to date, this study detailed the use of Fe2V4O13 (Fe-2) as a novel active site deposited on anatase (TiO2) for NH3-SCR. While providing the aforementioned structural benefits, Fe-2/TiO2 also enhanced the redox character as well as the number of sites accessible to NOX/NH3 over Fe-1/TiO2 because of the greater electronic inductive effect of Fe-2. Therefore, Fe-2/TiO2 converted NOX better than Fe-1/TiO2 in the presence of H2O. To further improve the NH3-SCR performance of Fe-2/TiO2, its catalytic surface was modified via two steps. The first step was to incorporate 1.9 wt% Sb into Fe-2/TiO2. Sb could promote the redox feature of Fe-2/TiO2 and help its surface to preferentially interact with NH3/NOX, thereby making the resulting Fe-2-Sb-1.9/TiO2 outperform Fe-2/TiO2 during NH3-SCR in the presence of H2O. The second step was to functionalize the Fe-2-Sb-1.9/TiO2 surface with SO32-/SO42- species. The resulting Fe-2-Sb-1.9/TiO2 (S) was validated to further increase redox cycling of Fe-2-Sb-1.9/TiO2, favor NO2 production from NO oxidation for fast NH3-SCR, and hamper surface interplay with SO2. Fe-2-Sb-1.9/TiO2 (S), therefore, showed higher NOX conversions than a control simulating a commercial catalyst during NH3-SCR feeding H2O and SO2. Fe-2-Sb-1.9/TiO2 (S) also showed greater durability than the control because of its enhanced resistance to SO2, ammonium (bi)sulfates, and alkali metals.