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US 6,607,704 B2Granted
Sulfur tolerant lean NOx trap
AssigneeFord Global Technologies, LLC
InventorsDiane L. Guttridge, Jun (John) Li, Mohinder Singh Chattha, Robert J. Kudla, William Lewis Henderson Watkins
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Abstract
An integrated lean NOx trap. The integrated lean NOx trap includes a lean NOx trap containing a composite metal oxide mixture consisting essentially of about 80-100 wt % stoichiometric spinel MgAl2O4 and between about 0-20 wt % of CeO2 or CeO2—ZrO2. A method for removing NOx and SOx impurities from exhaust gases using the integrated lean NOx trap is also described.
Claims13
An integrated lean NOx trap consisting essentially of:
- about 70 to 98 wt. % of a lean NOx trap;
- and
- about 2 to 30 wt. % of a composite metal oxide mixture consisting essentially of about 80-100 wt % stoichiometric spinel MgAl2O4 and between about 0-20 wt % of CeO2 or CeO2—ZrO2.
A method for removing NOx and SOx impurities from exhaust gases comprising:
- a) providing an integrated lean NOx trap consisting essentially of a lean NOx trap and a composite metal oxide mixture consisting essentially of between about 80-100 wt % stoichiometric spinel MgAl2O4 and between about 0-20 wt % of CeO2 or CeO2—ZrO2;
- b) passing exhaust gas having an air/fuel ratio which is fuel-lean with respect to a stoichiometric air/fuel ratio over the integrated lean NOx trap whereby the integrated lean NOx trap absorbs NOx and SOx from the fuel-lean exhaust gas;
- c) purging the NOx from the integrated lean NOx trap by subjecting the integrated lean NOx trap to exhaust gas having an air/fuel ratio which is the stoichiometric air/fuel ratio or which is fuel-rich with respect to the stoichiometric air/fuel ratio, and absorbing SOx from the stoichiometric or fuel-rich exhaust gas, wherein the NOx is purged from the integrated lean NOx trap and the SOx is absorbed by the integrated lean NOx trap at a temperature in the range of between about 200° C. to about 600° C.;
- d) repeating steps b) and c) until the NOx absorption efficiency of the lean NOx trap has been reduced to a predetermined level;
- and
- e) purging the SOx from the integrated lean NOx trap by subjecting the integrated lean NOx trap to exhaust gas having the air/fuel ratio which is fuel-rich with respect to the stoichiometric air/fuel ratio, wherein the SOx is purged at a temperature in the range of between about 600° C. to about 750° C.
3 more elements
Dependencies are inferred from the claim text.