High Zr-loaded SBA-15 cobalt catalyst for efficient NOx reduction in lean-burn exhaust

Abstract

A high Zr-loaded SBA-15 mesoporous material with high surface area, well-ordered structure, homogeneous Zr dispersion and high surface acidity has been prepared by a novel direct-post synthesis technique (DP). While maximum Zr loadings of 5.1wt% and 16.7wt% have been achieved in direct and post synthesis methods, respectively, the support synthesized by the DP method (ZrSBADP2) has yielded a Zr loading of 32.1wt%. Also, a high acidity of 136μmolg−1, favorable for catalysis reactions, has been reached for ZrSBADP2. The effect of cobalt concentration on the catalyst has also been examined on the NO to N2 conversion via selective reduction (C3H8-SCR) with propane. It has been demonstrated that the catalyst with 2wt% cobalt has shown the highest N2 yield (70%) at 400°C in the presence of 6vol% O2. The catalyst performance has significantly improved in the presence of water vapor where the N2 yield increased to 54% and 70% at 300°C and 350°C, respectively, compared with 18% and 34% in the absence of water vapor. Also, at high temperatures (≥400°C), the presence of water vapor has not resulted in any decrease in the catalyst performance. The long term stability test has proved that the catalyst structure is retained in extreme prolonged reaction conditions, making it a suitable catalyst for real applications.