Active hydrocarbon trap for reduction of emissions from internal combustion engines using a three-valve configuration

A method for reducing emissions from an internal combustion engine having a close-coupled catalyst, using a system comprising:

• an underbody catalyst disposed downstream of the close-coupled catalyst;
• a hydrocarbon trap disposed downstream of the close-coupled catalyst;
• and
• a three-valve system to optimize performance of the underbody catalyst and the hydrocarbon trap, wherein the three-valve system comprises:
• a first flow line from the close-coupled catalyst to the underbody catalyst;
• a second flow line from the underbody catalyst to an ambient environment with a first valve disposed in the second flow line;
• a third flow line from the underbody catalyst to the hydrocarbon trap with a second valve disposed in the third flow line;
• a fourth flow line from the hydrocarbon trap to the ambient environment with a third valve disposed in the fourth flow line;
• and
• a fifth flow line from the hydrocarbon trap to the internal combustion engine, the method comprising:
• feeding an exhaust gas from the internal combustion engine to the close-coupled catalyst, producing a catalyzed exhaust gas;
• flowing the catalyzed exhaust gas from the close-coupled catalyst to the three-valve system;
• during a first period of time corresponding to a cold engine condition having a temperature less than 125° C.:
• closing the first valve;
• opening the second valve and third valve;
• flowing the catalyzed exhaust gas to the underbody catalyst, producing a cold underbody catalyst effluent;
• flowing the cold underbody catalyst effluent to the hydrocarbon trap through the second valve, producing a cold hydrocarbon trap effluent;
• and
• ejecting the cold hydrocarbon trap effluent to the ambient environment through the third valve;
• during a second period of time corresponding to a warm engine condition having a temperature in a range of 125 to 300° C.:
• opening the first valve;
• partially closing the second valve;
• closing the third valve;
• flowing the catalyzed exhaust gas to the underbody catalyst, producing a warm underbody catalyst effluent;
• ejecting a first portion of the warm underbody catalyst effluent to the ambient environment through the first valve;
• flowing a second portion of the warm underbody catalyst effluent to the hydrocarbon trap through the second valve, producing a warm hydrocarbon trap effluent;
• and
• recycling the warm hydrocarbon trap effluent to the internal combustion engine for reuse;
• during a third period of time corresponding to a hot engine condition having a temperature in a range above 350° C.:
• closing the second valve;
• flowing the catalyzed exhaust gas to the underbody catalyst, producing a hot underbody catalyst effluent;
• and
• ejecting the hot underbody catalyst effluent to the ambient environment through the first valve.