Composition useful as trap for nitrogen oxides emissions in exhaust gases is based on manganese and alkaline earth or rare earth element

摘要

A manganese-based composition comprises an active phase and a support is effective in absorbing NOx gases in conditions where a stoichiometric excess of O2 is present in exhaust gases, to supplement a conventional 3-way catalyst which is ineffective in reducing NOx in these conditions. A composition which can be used as a NOx absorber comprises a support and an active phase. The active phase is based on Mn and another element A, which is an alkaline earth or rare earth. The product has a surface area of at least 80 m<2>/g after calcination at 800 deg C. for 8 hr Independent claims are also included for the treatment of a gas containing excess O2 and its use in a catalyst system.