In situ DRIFT–TRM study of simultaneous NOx and soot removal over Pt–Ba and Pt–K NSR catalysts

The Pt–Ba/γ-Al2O3 and Pt–K/γ-Al2O3 catalysts have been studied in simultaneous NOx and soot removal under cyclic lean-rich conditions. The DRIFT–TRM activity studies were accompanied by a detailed TEM/HRTEM, XRD, and XPS characterization of the catalysts samples. It was found that the alkali component stabilizes the Pt0/Ptox ratio and better catalyst performance during simultaneous removal of NOx and soot was obtained for Pt–Ba, where Pt0/Ptox ratio was close to 0.70. Moreover, the NO to NO2 oxidation rate was higher for the Pt–Ba catalyst than that for the Pt–K catalyst. The study reveals that soot has an influence both on the catalyst accumulation capacity and on the catalyst regeneration. As it is shown in the present work, the amount of NOx stored during the lean phase of TRM increases gradually during soot removal from the catalytic system. The regeneration process depends on alkali element type and is limited for the Pt–K catalyst.