Effect of pore structure of TiO2 on the SO2 poisoning over V2O5/TiO2 catalysts for selective catalytic reduction of NOx with NH3

Abstract

We applied 5wt%V2O5/TiO2 catalysts supported on two types of TiO2 having distinctive pore structure, mesopore (DT-51) and micropore (microporous TiO2; micro) to selective catalytic reduction of NOx with NH3 (NH3 SCR) to investigate the effect of pore structure of TiO2 on sulfur poisoning. During the SCR reaction in the presence SO2 for 12h, 5wt% VT (DT-51) showed more drastic decrease in activity than 5wt% VT (micro). Larger amount of SO2 was desorbed over the post-reaction 5wt% VT (DT-51) sample during the temperature programmed decomposition which was consistent with the elemental analysis. Such larger amount of sulfate formation could be explained by the more active SO2 oxidation on the 5wt% VT (DT-51) than 5wt% VT (micro) because SO2 oxidation is the key step to generate sulfate species on the catalysts. It could be ascribed to the difference in the tendency of oxidation reaction affected by the vanadium species, since it was known that more VOV bonds existed on the surface of 5wt% VT (DT-51) having bulk-like VOx species whereas VO bonds were prevalent on 5wt% VT (micro) having more dispersed VOx. In situ FT-IR results also provided the evidence about the formation of ammonium bisulfate through strong interaction between NH3 and SO3 on 5wt% VT (DT-51), although 5wt% VT (micro) did not. It can be summarized that the different vanadium species determined by the pore structure of TiO2 have a significant effect on the sulfur poisoning during SCR reaction.