SCR CATALYSTS HAVING IMPROVED LOW TEMPERATURE PERFORMANCE, AND METHODS OF MAKING AND USING THE SAME

摘要

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.