Effect of tungsten oxide addition on the catalytic activity of gamma-Al2O3 for NOx reduction from fuel-lean gas mixtures

Non-zeolitic catalysts are increasingly being considered as durable alternatives in automotive lean-NOx catalysis. This study focused on increasing the acidity of gamma-Al2O3 through the addition of tungsta (WO3) and increasing the resulting catalytic activity using simulated lean-burn engine exhaust. The effects of WO3 loading, space velocity, catalyst temperature, hydrocarbon and sulfur dioxide concentrations, and hydrothermal aging on the NOx reduction activity of WO3/Al2O3 composite oxides were studied. It was found that tungsta-modified alumina compositions had higher NOx removal activity under lean-burn conditions than the unmodified gamma-Al2O3. Maximum NOx conversion occurred at a 1 wt % loading of WO3 on gamma-Al2O3 at a temperature of 580 degrees C.