Method and architecture for reducing NOX and particulate matter emissions in exhaust gas from hydrocarbon fuel source with a fuel lean combustion mixture

A method for reducing NOx and particulate matter emissions in an exhaust stream comprising:

• passing said exhaust stream through a catalytic oxidation reactor to oxidize carbon monoxide, hydrocarbons, and NO wherein said catalytic oxidation reactor comprises a dual zone type catalytic oxidation reactor in which said exhaust stream first passes through a platinum- and palladium-containing front side, which oxidizes hydrocarbons and carbon monoxide to carbon dioxide, and subsequently passes through a platinum-rich containing rear side, which oxidizes nitrous oxide (NO) to nitrous dioxide (NO2);
• introducing a hydrocarbon stream to said exhaust stream upstream of said catalytic oxidation reactor to raise the temperature of said exhaust stream in said catalytic oxidation reactor;
• passing said exhaust stream through a two-way selective reduction catalyst particulate filter located downstream of said catalytic oxidation reactor, said two-way selective reduction catalyst particulate filter comprising a wall flow filter substrate having internal walls coated with a first selective catalytic reduction catalyst;
• passing said exhaust stream through a cooling pipe located downstream of said two-way selective reduction catalyst particulate filter to cool said exhaust stream;
• passing said exhaust stream through a catalytic reduction reactor located downstream of said two-way selective reduction catalyst particulate filter and said cooling pipe without an intervening catalytic reactor, said catalytic reduction reactor having a second selective catalytic reduction catalyst;
• and
• introducing a stream of ammonia or urea to said exhaust stream upstream of said two-way selective reduction catalyst particulate filter and said catalytic reduction reactor.

A system for reducing NOx and particulate matter emissions in an exhaust stream comprising:

• a catalytic oxidation reactor that oxidizes carbon monoxide, hydrocarbons, and NO wherein said catalytic oxidation reactor comprises a dual zone type catalytic oxidation reactor in which said exhaust stream first passes through a platinum- and palladium-containing front side, which oxidizes hydrocarbons and carbon monoxide to carbon dioxide, and subsequently passes through a platinum-rich containing rear side, which oxidizes nitrous oxide (NO) to nitrous dioxide (NO2);
• a hydrocarbon injector located upstream of said catalytic oxidation reactor that introduces a hydrocarbon stream into said exhaust stream to raise the temperature of said exhaust stream;
• a two-way selective reduction catalyst particulate filter located downstream of said catalytic oxidation reactor, said two-way selective reduction catalyst particulate filter comprising a wall flow filter substrate having internal walls coated with a first selective catalytic reduction catalyst that reduces NOx to N2 in the presence of ammonia;
• a catalytic reduction reactor having a second selective catalytic reduction catalyst that reduces NOx to N2 in the presence of ammonia located downstream of said two-way selective reduction catalyst particulate filter;
• and
• one or more injector devices for injecting ammonia or urea to said exhaust stream located between said catalytic oxidation reactor and said two-way selective reduction catalyst particulate filter and to said exhaust stream located between said two-way selective reduction catalyst particulate filter and said second selective catalytic reduction catalyst.