Selective catalytic reduction of NO_x by hydrocarbons over metallo-zeolite based catalysts, which represents one of the new method for NO_x emission control from oxidizing atmosphere, has been described. The main attention is given to the progress in the development of the metallo-zeolite catalysts, active under water vapor presence as existing in real exhaust gases. General aspects and mechanism of the reaction are also described.
High and stable activity in selective catalytic reduction under real conditions of exhaust gasses exhibit only Co-BEA catalyst developed by ENI and Osaka Gas companies. Although, Fe- and Pt-zeolites also show high activity under real exhaust gas, there is produced high concentration of undesirable CO and N₂O. Nevertheless, due to complexity of the reduction of NO with hydrocarbon to nitrogen, the structure and function of the active sites in metallo-zeolites is not completely solved and require further studies.