Effect of transition metal dopants (M= Nb, La, Zr, and Y) on the M-TiO2 supported V2O5 catalysts in the selective oxidation of H2S to elemental sulfur

Abstract

P-25 TiO2 was modified by a small amount addition of different transition metal dopants (Nb, La, Zr, and Y) and employed as the supports for preparation of the V2O5/TiO2 catalysts for the selective H2S oxidation at low temperature (130 °C). The H2S removal capability was ranged in the order: V2O5/Y-TiO2 > V2O5/Zr-TiO2 ≈ V2O5/TiO2 > V2O5/La-TiO2 > V2O5/Nb-TiO2, which corresponded well to the chemically adsorbed oxygen on oxygen vacancies at catalyst surface (or surface oxygen) as revealed by XPS results. The Y addition could promote the oxygen vacancies formation because of the Ti4+ substitution by less valence Y3+ cations, leading to the improvement of H2S conversion. Whereas the modification by dopants, which have the extra valence cations or larger ionic radius (i.e., Nb or La) suppressed the oxygen vacancies formation, thus leading to lower activity. Despite the stronger interaction between V and Zr-TiO2, the amount of surface oxygen and H2S conversion of the V2O5/Zr-TiO2 were less than the V2O5/Y-TiO2, suggesting that although the formation of oxygen vacancies depended on the interaction between V and M-TiO2, the effect of Ti4+ substitution by transition metal dopant was more pronounced than the degree of interaction between V and M-TiO2. The H2S removal capability corresponded well to the oxygen vacancies being formed more than the degree of interaction between V and M-TiO2. From this study, the V2O5/Y-TiO2 showed the highest H2S conversion at ∼77% with low SO2 formation (less than 10 ppm).