Superior Ce–Nb–Ti oxide catalysts for selective catalytic reduction of NO with NH3

Abstract

A series of Ce–Nb–Ti oxide catalysts synthesized by a single step sol-gel (SG) method were evaluated and characterized for selective catalytic reduction (SCR) of NO with ammonia. The experimental results showed that the doping of Nb could enhance the catalytic activity of CeO2/TiO2 significantly. Ce20Nb20Ti exhibited the best NH3–SCR activity and great resistance to high gas hourly space velocity (GHSV), H2O, and SO2. Its superior SCR performance could be ascribed to the better dispersion of Ce, more chemisorbed oxygen species and Ce3+/Ce4+ redox pairs on the catalyst surface, increased redox ability and surface acidity, and strong interaction among Ce, Nb, and Ti species after the introduction of Nb2O5. In situ DRIFT results revealed that the doping of Nb was conducive to the adsorption of NOx and NH3 species, and enhanced the reaction of pre-adsorbed NH3 species with NOx species and that of adsorbed NOx species with NH3 species.