System for the removal of particulate matter and noxious compounds from engine exhaust gas

A system for the removal of volatile organic com-pounds, particulate matter and nitrogen oxides from exhaust gas of a compression ignition engine comprising

• an oxidation unit with a catalyst active in oxidation of volatile organic compounds and carbon monoxide to carbon dioxide and water, and nitrogen oxide to nitro-gen dioxide;
• and
• a catalysed wall flow particulate filter downstream of the oxidation unit, the catalysed wall flow particulate filter comprising a plurality of longitudinal inlet flow channels and outlet flow channels separated by gas permeable porous partition walls, each inlet flow channel having an open inlet end and a closed outlet end, and each outlet flow channel having a closed inlet end and an open outlet end;
• wherein the system is adapted for the introduction of a urea solution into the exhaust gas downstream from the catalysed wall flow particulate filter;
• wherein the system further comprises an SCR active catalyst downstream of the catalysed wall flow particulate filter to receive exhaust gas into which urea solution has been introduced, the SCR active catalyst comprising oxides of vanadium and tungsten;
• wherein the system further comprises a three way catalyst unit downstream of the SCR active catalyst, the three way catalyst unit having an NH3-SCR activity, an ammonia oxidation activity, and an adsorption capacity for volatile vanadium and tungsten compounds volatilized off the SCR active catalyst, the three way catalyst unit comprising compounds selected from the group consisting of metal oxides, zeolites, silica, non-zeolite silica alumina, and mixtures thereof.