Catalytic converter system for internal combustion engine powered vehicles

A catalytic converter system suitable for catalyzing the conversion of hydrocarbons, carbon monoxide, nitrogen oxides and other pollutants contained in a flowing exhaust gas stream, the converter system comprising:

• a low temperature conversion catalyst material comprising a platinum group metal component dispersed on a refractory support material, said low temperature conversion catalyst material having a light-off temperature TL of less than about 200° C., and being located relative to the flowing exhaust gas stream such that said low temperature conversion catalyst material is never exposed to a temperature in excess of about 550° C.;
• a hydrocarbon adsorbent material deposited on a refractory carrier, said hydrocarbon adsorbent material being capable of adsorbing hydrocarbons present in said flowing exhaust gas stream and of desorbing the adsorbed hydrocarbons when the temperature of said low temperature conversion catalyst material has exceeded said light-off temperature thereof;
• and
• optionally, an upstream conversion catalyst material, said upstream conversion catalyst material, when present, being located upstream of said low temperature conversion catalyst material relative to the direction of flow of said flowing exhaust gas stream.