Heat-resistant hydrocarbon adsorber to restrict exhaust gas emissions

摘要

A heat-resistant hydrocarbon (HC) adsorbent to restrict exhaust gas emissions contains a heat-resistant, modified zeolite. This modified zeolite is prepared by subjecting an unmodified zeolite to a dealuminising treatment. The molar ratio of SiO2/Al2O3 of the unmodified zeolite is termed Mr1 and the molar ratio Mr2 of SiO2/Al2O3 of the modified zeolite is equal to or greater than 1.2 Mr1 (Mr2 >/= 1.2 Mr1). The modified zeolite has the same basic framework structure as the unmodified zeolite. Such a hydrocarbon adsorbent has an excellent heat resistance and high hydrocarbon adsorption capacity.