Patent ID: 6585945
Filing Date: 2003-07-01
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 a first metal oxide and a second metal oxide, wherein the metal in the first metal oxide is selected from the group consisting of aluminum, titanium, zirconium, silicon, and composites thereof, and the metal in the second metal oxide is a Group IIA metal selected from the group consisting of Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium; a Group IIIa Metal selected from the group consisting of Scandium, Yttrium, Lanthanum, Cerium, Praeseodymium, Neodymium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Lutecium a Group IIIb Metal selected from the group consiting of Boron, Aluminium, Gallium, Indium, and Thallium; a Group IVa Transition Metal selected from the group consisting of Titanium, Zirconium, Hafnium, and Thorium; and a Group IVb element selected from the group consisting of Carbon, Silicon, Germanium, Tin, and Lead; rare earth metals; and transition metals; wherein the metal in the first metal oxide is different from the metal in the second metal oxide; 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 first and second metal oxides, or precursors thereof, or both, wherein the precursors of the first and second metal oxides are metal salts which when hydrolyzed produce the respective metal oxides; (ii) subjecting the suspension or solution of the first and second metal oxides, or precursors thereof, 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.