Exhaust gas treatment system and method with four-way catalyzed filter element

An exhaust gas treatment system for an internal combustion engine, the exhaust gas treatment system comprising:

• an exhaust gas pathway configured to receive exhaust gas from the internal combustion engine;
• a first injector configured to selectively introduce a first reductant into the exhaust gas pathway in response to a sensed temperature of the exhaust gas being within a predetermined temperature range;
• a first treatment element positioned within the exhaust gas pathway downstream of the first injector, the first treatment element including
• a selective catalytic reduction (SCR) layer,
• a porous filter substrate, and
• a precious metal catalyst layer,
• a second treatment element positioned within the exhaust gas pathway downstream of the first treatment element, the second treatment element including a SCR element;
• and
• a controller configured to periodically initiate a desulfuring regeneration cycle by increasing a concentration of hydrocarbons in the exhaust gas and increasing the flow of the first reductant through the first injector to oxidize sulfur contamination in the first treatment element at temperatures between 400 and 500 degrees Celsius.

An exhaust gas treatment system for an internal combustion engine, the exhaust gas treatment system comprising:

• an exhaust gas pathway configured to receive exhaust gas from the internal combustion engine;
• a first injector configured to introduce a first reductant into the exhaust gas pathway;
• a first treatment element positioned within the exhaust gas pathway downstream of the first injector, the first treatment element including
• an inlet channel,
• an outlet channel,
• a selective catalytic reduction (SCR) layer,
• a NOx storage layer coated under or over the SCR layer,
• a porous filter substrate including a porous filter wall separating the inlet channel and the outlet channel such that the exhaust gas is configured to flow from the inlet channel to the outlet channel through the porous filter wall, and
• a precious metal catalyst layer coated on the porous filter substrate such that the precious metal catalyst layer fully infiltrates the porous filter wall;
• and
• a controller configured to periodically initiate a desulfuring regeneration cycle by increasing a concentration of hydrocarbons in the exhaust gas and increasing the flow of the first reductant through the first injector to oxidize sulfur contamination in the first treatment element at temperatures between 400 and 500 degrees Celsius,
• wherein the porous filter substrate is configured to capture soot from the exhaust gas, and
• wherein the precious metal catalyst layer is configured to exothermically react hydrocarbons from the exhaust gas to promote oxidation of the captured soot on the porous filter substrate through active regeneration.