NOx storage/reduction catalysts based in cobalt/copper hydrotalcites

The use of materials based on hydrotalcites as NOx storage/reduction (NSR) catalysts has been investigated, examining their activity at low temperature and their resistance to poisons such as H2O and SO2. The results obtained show that catalysts derived from Mg/Al hydrotalcites containing copper or cobalt is active at low temperatures, specially the samples containing 10 or 15% of Co. The addition of 1 wt% of transition metals with redox properties such as Pt, Pd, V and Ru to the hydrotalcite increases its activity because the combination of the redox properties of these metals and the acid-base properties of the hydrotalcite. The best results were obtained with the catalyst derived from a hydrotalcite with a molar ratio Co/Mg/Al = 15/60/25 and containing 1 wt% V. This material shows a higher activity, at low temperatures and in the presence of H2O and SO2, than a Pt–Ba/Al2O3 reference catalyst.