Selective catalytic reduction catalysts having improved performance at low temperatures, and methods for their manufacture and use

摘要

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.