Multifunctional catalyst for de-NOx processes: The selective reduction of NOx by methane

A multifunctional catalyst has been applied for the reduction of NOx by methane in excess of oxygen. The catalyst includes a heteropolyacid (HPW) and a noble metal (Pt) deposited on a ceria–zirconia mixed oxide. The presence of hydrogen is necessary for reducing NOx into N2 with methane. During several alternate cycles of NOx storage (2 min) and reduction (1 min), the average NOx reduction percentage into nitrogen was of ca. 60% with a constant storage efficiency of ca.70%. A coherent picture of the catalytic process emerged from two separated experimental tests: water gas shift and steam methane reforming reactions.