Hydrotalcite as a Support for NOx Trap Catalyst

Hydrotalcite (HT)-based catalysts have been developed to improve NOx storage-reduction (NSR) activity, particularly at low temperature during the cold start period of automotive engines. The content of noble metals, including Pt and Pd, has been optimized and the effect of the K precursors on NSR activity has been extensively examined by a knowledge-based combinatorial approach using colorimetric assay. The optimum noble metal ratio was determined to be 0.5Pt/0.5Pd or 0.25Pt/0.75Pd. Pd is a more effective metal for the high performance of NSR catalyst than Pt, particularly for reducing NOx from the catalyst at 200 °C. Both CH3COOK and KNO3 are the best K precursor in view of the NSR performance at both low (200 °C) and high temperatures (350 °C). HT-based catalysts reveal excellent deNOx performance compared to Al2O3-based catalysts, mainly due to their superior redox property.