Comparative study of HSOA-/SOA2- versus H3-BPO4B- functionalities anchored on TiO2-supported antimony oxide-vanadium oxide-cerium oxide composites for low-temperature NOX activation

TiO2-supported antimony oxide-vanadium oxide-cerium oxide (SVC) imparts Lewis acidic (L)/Bronsted acidic (B) sites, labile (O-alpha)/mobile oxygens (O-M), and oxygen vacancies (O-V) for selective catalytic NOX reduction (SCR). However, these species are harmonious occasionally, readily poisoned by H2O/sulfur/phosphorus/carbon, thus limiting SCR performance of SVC. Herein, a synthetic means is reported for immobilizing HSOA-/SOA(2)(A= 3-4) or H3-BPO4B- (B= 1-3) on the L sites of SVC to form SVC-S and SVC-P. HSOA- /SOA(2)(-)/H3-BPO4B- acted as additional B sites with distinct characteristics, altered the properties of Oa/OM/OV species, thereby affecting the SCR activities and performance of SVC-S and SVC-P. SVC-P activated Langmuir-Hinshelwood-typed SCR better than SVC-S, as demonstrated by a greater O-alpha-directed pre-factor and smaller binding energy between O-alpha and N-O. Meanwhile, SVC-S provided a larger B-directed pre-factor, thereby outperforming SVC-P in activating EleyRideal-typed SCR that dictated the overall SCR activities. Compared with SVC-S, SVC-P contained fewer O-V species, yet, had higher O-M mobility, thus enhancing the overall redox cycling feature, while providing greater Bronsted acidity. Consequently, the resistance of SVC-P to H2O or soot were greater than or similar to that of SVC-S. Conversely, SVC-S revealed greater tolerance to hydro-thermal aging and SO2 than SVC-P. This study highlights the pros and cons of HSOA-/SOA(2)(-)/H3-BPO4B- functionalities in tailoring the properties of metal oxides in use as SCR catalysts.

Automated summary

This study explores the use of HSOA-/SOA(2)(-)/H3-BPO4B- functionalities to adjust the properties of metal oxides for SCR catalysts. It is found that SVC-P performs better in activating Langmuir-Hinshelwood-typed SCR, while SVC-S excels in EleyRideal-typed SCR. Both variants show different resistance to H2O or soot, with SVC-S exhibiting greater tolerance to hydro-thermal aging and SO2.