The invention relates to systems for removing
NOx from exhaust. In one aspect of the invention, after adsorption, an
NOx adsorber is isolated from the main exhaust flow and
desorption induced by raising the temperature. The desorbed
NOx is combined with a reductant and reduced over a catalyst. Preferably, the reductant is syn gas produced in an on-board reformer. The catalyst need never be exposed to the main exhaust flow, which is particularly advantageous for catalysts sensitive to water,
oxygen, or
sulfur. In another aspect of the invention, a recirculating flow is induced through an
NOx adsorber during a regeneration cycle. Recirculation can induce greater
desorption at a given temperature, provide a source of heat for the adsorber, and allow a higher conversion rate with a fixed amount of catalyst. A further aspect of the invention relates to a vehicle-mounted adsorbers with provisions for heating.