A method for catalytically reducing nitrogen oxide compounds (NO.sub.x,
defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a
material comprising a base metal consisting essentially of CuO and Mn, and
oxides of Mn, on an activated metal hydrous metal oxide support, such as
HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be
added and has been shown to increase conversion efficiency. This method
provides good conversion of NO.sub.x to N.sub.2, good selectivity, good
durability, resistance to SO.sub.2 aging and low toxicity compared with
methods utilizing vanadia-based catalysts.
