| abstract |
Abatement of nitrogen oxides in an industrial exhaust gas is effected by reduction of the nitrogen oxides with ammonia in the presence of a catalyst comprising a porous crystalline siliceous solid such as a ZSM-5 type zeolite. Fast responses to changes of NOx load is achieved with a zeolite of low to moderate acid activity. The catalyst may be virgin catalyst, aged catalyst previously used for the conversion of a hydrocarbon or an organic compound, or artifically aged catalyst. |