Catalytic NOx removal with H 2 in the presence of an excess of oxygen was studied. A Pt/zeolite catalyst has a high
NOx conversion efficiency, but has the disadvantages of being strongly poisoned by CO and HCs such as C3H 6 and the
formation of N20 as a byproduct from NOx. By reducing the oxidation efficiency of Pt, we have developed an improved
catalyst, Pt-Mo-Na/SiO 2, which has a higher temperature range of NOx conversion and a lower N20 byproduct formation,
than conventional Pt catalysts. This idea was supported by IR and XPS data of the catalyst.