NOx storage-reduction catalysts based on hydrotalcite -: Effect of Cu in promoting resistance to deactivation

Novel NOx storage-reduction (NOxSR) catalysts prepared by Pt and/or Cu impregnation of Mg-Al (60:40) hydrotalcite (HT)-type compounds show better performances in NOx storage than Pt-Ba/Al2O3 Toyota-type NOxSR catalysts at reaction temperatures lower than 250 degreesC. The presence of Pt or Cu considerably enhances the activity, with the former more active. The nature of the HT source, however, also influences performance. The co-presence of Pt and Cu slightly worsens the low temperature activity, but considerably promotes the resistance to deactivation after severe hydrothermal treatment and in the presence Of SO2. This effect is attributed to both the possibility of formation of a Pt-Cu alloy after reduction, and the modification of the HT induced during the deposition of Cu. The overall Pt-Cu/HT performances are thus superior to those of the Pt-Ba/Al2O3 Toyota-type NOxSR catalysts. (C) 2002 Elsevier Science B.V. All rights reserved.