초록 ▼

The present invention relates to sulfur tolerant catalyst composites useful for reducing contaminants in exhaust gas streams, especially gaseous streams containing sulfur oxide contaminants. More specifically, the present invention is concerned with improved NOx trap catalysts for use in diesel engi

The present invention relates to sulfur tolerant catalyst composites useful for reducing contaminants in exhaust gas streams, especially gaseous streams containing sulfur oxide contaminants. More specifically, the present invention is concerned with improved NOx trap catalysts for use in diesel engines as well as lean burn gasoline engines. The sulfur tolerant NOx trap catalyst composites comprise a platinum component, a support, a NOx sorbent component, and a spinel material prepared by calcining an anionic clay material represented by the formula MmNn(OH)(2m+2n)Aa.bH2O, wherein the formula is defined herein. The sulfur tolerant NOx trap catalyst composites are highly effective with a sulfur containing fuel by trapping sulfur oxide contaminants which tend to poison conventional NOx trap catalysts used to abate other pollutants in the stream. The sulfur tolerant NOx trap catalyst composites are suitable for diesel engines because the composites can be regenerated at moderate temperatures with rich pulses, rather than at high temperatures.

대표청구항 ▼

1. A method for removing NOx and SOx contaminants from a gaseous stream comprising the steps of:(1) heat treating a catalyst precursor to form 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 c

1. A method for removing NOx and SOx contaminants from a gaseous stream comprising the steps of:(1) heat treating a catalyst precursor to form 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 SOx contaminants and thereby provide a SOx depleted gaseous stream exiting the catalyst composite and to sorb and abate at least some of the NOx contaminants in the gaseous stream and thereby provide a NOx depleted gaseous stream exiting the catalyst composite; (3) in a SOx desorbing period, converting 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 provide a SOx enriched gaseous stream exiting the catalyst composite; and (4) in a NOx desorbing period, converting 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 NOx enriched gaseous stream exiting the catalyst composite; wherein the catalyst precursor comprises: (a) a platinum component; (b) a support; (c) a NOx sorbent component; and (d) a spinel material prepared by calcining an anionic clay material represented by the formula MmNn(OH)(2m+2n)Aa.bH2O, wherein M is Co2+; N is a trivalent metal cation; A is a mono-, di-, or trivalent anion which decomposes when heated to a temperature sufficient to form a volatile gas; m and n are such that m/n has values from about 0.5 to about 6; a is a number with the proviso that when A is a monovalent anion, a=n, when A is a divalent anion, a=1/2n, and when A is a trivalent anion, a=1/3n; and b is an integer having a value from 1 to about 10.