Abstract: SCR-active molecular-sieve based catalysts with improved low-temperature performance are made by heating a molecular-sieve in a non-oxidizing atmosphere with steam (hydrothermal treatment), or in a reducing atmosphere without steam (thermal treatment), at a temperature in the range of 600-900° C. for a time period from 5 minutes to two hours. The resulting SCR-active iron-containing molecular sieves exhibit a selective catalytic reduction of nitrogen oxides with NH3 or urea at 250° C. that is at least 50% greater than if the iron-containing molecular-sieve were calcined at 500° C. for two hours without performing the hydrothermal or thermal treatment.

Abstract: SCR-active molecular sieve based-catalysts are produced by combining a molecular sieve with at least one ionic iron species and at least one organic compound to form a mixture, then calcining the mixture to remove the at least one organic compound. This process improves the dispersion of the iron within the molecular sieve compared to an iron-containing molecular sieve that is not treated with an organic compound. Iron-containing ferrierite zeolites exhibit a selective catalytic reduction of nitrogen oxides with NH3 or urea of greater than 25% conversion at 300° C. in exhaust gases prior to ageing or exposure to steam. Iron-containing beta zeolites exhibit a selective catalytic reduction of nitrogen oxides with NH3 or urea of: (a) greater than 40% conversion at 300° C. and (b) greater than 80% conversion at 400° C., in exhaust gases after ageing for 20 hours at 700° C. in the presence of 10% H2O.