HEAT-RESISTANT HC ADSORBENT FOR PURIFICATION OF EXHAUST GAS

摘要

PURPOSE:To obtain excellent HC absorptibity and durability against high temp. exhaust gas by carrying a specified amt. of Ag or Cd on a heat-resistant reformed zeolite. CONSTITUTION:Reformed ZSM-5 zeolite as a reformed zeolite is produced by treating unreformed ZSM-5 zeolite containing Na with acid to remove Al. Then at least one kind of metal element selected from Ag and Cd is carried by an amt. C satisfying 0.5wt.%<=C<=11wt.% to prepare various kinds of adsorbents. The figure indicates that a HC adsorbent (1) comprising reformed ZSM-5 zeolite and Ag shows significant improvement in the HC adsorption with smaller amt. of Ag compared to an adsorbent (2) comprising unreformed ZSM-5 zeolite and Ag. Further, the HC adsorbent (1) has excellent heat resistance so that when the HC adsorbent (1) is kept at 900 deg.C for 20 hours to obtain an adsorbent (1a), it shows high adsorption.