Abstract
The addition of manganese, iron, and cobalt to NOx storage and reduction (NSR) catalysts containing 1% w/w platinum and 15% w/w barium (1Pt/15Ba) on γ-Al2O3 has been studied. Under fuel lean conditions, the addition of Mn or Fe slightly improved the NOx storage, while the addition of Co more than doubled the NOx storage. In addition, a noble metal free 5Co/15Ba catalyst was found to store NOx as efficiently as a 1Pt/15Ba NSR catalyst. This increase in efficiency is associated with the strong oxidizing effect of Co, providing nitric oxide oxidation sites and contact area for NO2 spillover to the Ba NOx storage sites. By utilizing Co as an oxidizing metal instead of Pt, the storage capacity of NSR catalysts can be improved without the need for an expensive noble metal oxidizing catalyst.