US 6,419,890 B1Granted

SOX tolerant NOX trap catalysts and methods of making and using the same

AssigneeEngelhard Corporation

InventorYuejin Li

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Abstract

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.

Claims79

Dependent claims

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=½n, and when A is a trivalent anion, a=⅓n;
and b is an integer having a value from 1 to about 10.

13 more elements

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 a divalent metal cation;
N is selected from the group consisting of Ce3+, Nd3+, Pm3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, and Lu3+;
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 ½n, and when A is a trivalent anion, a=⅓n;
and b is an integer having a value from 1 to about 10.

13 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/634,228Filed 9 Aug 2000
Granted: 16 Jul 2002
Term ends: Not estimatedThe source records don’t support an estimate.

Classification13 codes

B01D 53/9422
Processes characterised by a specific catalyst: for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich…
B01J 23/005
Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00: spinels
B01J 23/8946
Also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36: with alkali or alkaline earth metals
B01D 2255/1021
Platinum group metals: platinum