Thermal management of hybrid LNT/SCR aftertreatment during desulfation

A method of desulfating an NOx adsorber-catalyst in an exhaust aftertreatment system comprising an NOx adsorber-catalyst followed by an SCR catalyst, comprising:

• in a first step, providing a flow of gas heated to at least about 650° C. to the NOx adsorber-catalyst, wherein the flow of gas passes through the NOx adsorber-catalyst and then the SCR catalyst;
• maintaining the flow until a time after the NOx adsorber-catalyst has been heated by the gas to at least about 650° C., but terminating the flow before the SCR catalyst has reached a temperature of 550° C.;
• in a second step, providing a second flow of gas at a temperature of about 500° C. or less to the NOx adsorber-catalyst, wherein the second flow of gas passes through the NOx adsorber-catalyst and then the SCR catalyst;
• maintaining the second flow until a time after the NOx adsorber-catalyst has been cooled by the gas to a temperature at or below about 550° C.;
• repeating the first and second steps at least several times to complete the desulfation.

A method of desulfating an NOx adsorber-catalyst in an exhaust aftertreatment system comprising an NOx adsorber-catalyst followed by an SCR catalyst, comprising:

• cycling the temperature of the NOx adsorber-catalyst;
• creating a reducing environment in the NOx adsorber-catalyst during portions of the cycles where the NOx adsorber-catalyst is at temperatures effective for desulfation;
• wherein the cycles have peak temperatures in a range effective for desulfation and an average temperature that is at least 100° C. lower;
• wherein peak temperature reached by the SCR catalyst during the cycles is at least 100° C. lower than the peak temperature reached by the NOx adsorber-catalyst.