A study to investigate the capability of adsorbents for reduction of cold-start emissions

Abstract

Most of the emissions (about 60 per cent) from automobiles occur during a cold start before the catalytic converter becomes active. The use of an adsorbent trap for temporary storage of emitted hydrocarbons before catalysts attain the light-off temperature in the converter has been investigated as a means for reduction of cold-start emissions. The hydrocarbon emissions can be reduced significantly if the hydrocarbons are retained by the trap until catalysts reach the light-off temperature. The effect of engine speed on the emission of NO x, CO and hydrocarbons and their subsequent retention in the adsorption trap was studied. A hydrophobic adsorbent, Hisiv-1000, and molecular sieve 13X were used individually and in conjunction in the trap to adsorb hydrocarbons. Although significant amounts of hydrocarbons were adsorbed in the trap initially, they were released from the trap rather quickly even before catalysts reached the light-off temperature.