Adsorption characteristics of HCA(Hydrocarbon Adsorber) catalysts for hydrocarbon and NOx removals under cold-start engine conditions

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 cold-start. 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.