To meet the SULEV (Super Ultra Low Emission Vehicle) regulations, we have focused on the utilization of HCA (Hydrocarbon Adsorber) in order to adsorb the excess hydrocarbons emitted during a period of engine coldstart. As main recipes of HCA materials, many types of zeolite as well as a combination of alumina and precious metals were used. Representative physico-chemical factors of zeolite such as acidic and hydrophobic properties have been characterized and tried to find the optimum recipe of HCA materials. Among the acid properties of zeolites, the Si/Al ratio has been found to be the most important factor to achieve higher hydrocarbon adsorption capacity.
Paul JA, Todd HB, "Improvements in Pd: Rh and Pt: Rh Three Way Catalyst," SAE 1999-01-308,, 1999
Robert JF, Ronald MH, "The Automotive Catalyst: Its Present and Future Family Free," 15th Meeting of the North American Catalysis Society, Technical Program, 125, 1997