Patent ID: 6699448
Filing Date: 2004-03-02
Classification: B01D

Abstract:
A method for removing NOx contaminants from a SOx containing gaseous stream comprising the steps of:(1) providing a catalyst composite; (2) in a sorbing period, passing a lean gaseous stream comprising NOx and SOx within a sorbing temperature range through the catalyst composite to sorb at least some of the NOx contaminants and thereby provide a NOx depleted gaseous stream exiting the catalyst composite and to sorb and abate at least some of the SOx contaminants in the gaseous stream and thereby provide a SOx depleted gaseous stream exiting the catalyst composite; (3) in a NOx desorbing and abating period, changing the lean gaseous stream to a rich gaseous stream to thereby reduce and desorb at least some of the NOx contaminants from the catalyst composite and thereby provide a reduced NOx enriched gaseous stream exiting the catalyst composite; (4) in a SOx desorbing period, changing the lean gaseous stream to a rich gaseous stream and raising the temperature of the gaseous stream to within a desorbing temperature range to thereby reduce and desorb at least some of the SOx contaminants from the catalyst composite and thereby regenerate the catalyst composite and provide a reduced SOx enriched gaseous stream exiting the catalyst composite; and wherein the catalyst composite comprises:(a) a platinum component; (b) a support; and (c) a NOx sorbent component comprising the following constituents: (i) Na2O in an amount up to about 0.1%; (ii) MgO in an amount up to about 1%; (iii) Fe2O3 in an amount from about 10% to about 30%; (iv) SrO in an amount from about 0.5% to about 15%; (v) Y2O3 in an amount up to about 5%; and (vi) the remainder of the NOx sorbent component being Al2O3; wherein the NOx sorbent component is prepared by a hydrothermal synthesis process comprising the steps of:(i) providing an aqueous suspension or solution of the constituents of the NOx sorbent component; (ii) subjecting the suspension or solution of the constituents of the NOx sorbent component to a temperature from about 150Â° C. to about 300Â° C. in an autoclave under pressure for a time sufficient to produce a precipitate having an average particle size from about 0.001 to about 0.2 micron in a mother liquor; and (iii) separating the precipitate from the mother liquor.