Thermal Stability of Cordierite Supported V2O5‐WO3‐T1O2 SCR CATALYST for Diesel NOx Reduction

Thermal stability of cordierite supported and extruded SCR catalysts was evaluated and a mechanism was developed to explain the observed differences. These catalyst systems are used to reduce NOx in diesel engine exhaustto meet European and US requirements. The cordierite supported catalyst showed significantly better catalytic conversion efficiency after aging at 650°C than the extruded catalyst, although low temperature activity was compromised because of the lower catalyst loading of the cordierite supported catalyst. Characterization of the supported catalyst indicated that the catalyst had very little surface area loss upon aging and maintained most of its acidity. In contrast, the extruded catalyst showed dramatic surface area and acidity loss. The acidity correlates with catalytic activity, confirming that the reaction kinetics are controlled by the availability of V-OH sites at the temperature range.