| abstract |
The invention relates to a novel catalyst having excellent activity, selectivitynand stability for reducing nitric oxide to gas nitrogen, with hydrogen beingnused as a reducing agent, in the low temperature range 100-200 °C and innthe presence of an excess of oxygen (e.g. 5 % vol), H 2 O (5 % vol) and/or SO 2 n(20 ppm) in the supply. The inventive catalyst consists of platinum crystalsnwhich are in contact with the phases of a mixed MgO and CeO 2 medium or innthe form of platinum supported on the mixed MgO-CeO 2 medium which hasnalready been sulphated in a selective manner. The Pt/MgO-CeO 2 catalyst cannbe used to obtain NO conversion levels which are greater than 40 % andnnitrogen selectivity values of greater than 80 % under NOx oxidationnconditions in the 100-400 °C temperature range and for a surface contactntime of 0.045 s. In particular, full NO conversion is obtained as well as N 2 nselectivity levels of 83 % at 150 °C with a reaction mixture of 0.25 % NO / 1 %nH 2 / 5 % O 2 / 5 % H 2 O / He. |