NOx ABSORBING AND CLEANING MATERIAL AND EXHAUST GAS CLEANING CATALYST USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide an NOx absorbing and cleaning material excellent in the adsorbability of HC, capable of enhancing the reaction selectivity of NOx and HC or CO and capable of efficiently cleaning up NOx even under an oxygen excessive atmosphere and an exhaust gas cleaning catalyst using the same. SOLUTION: An NOx absorbing and cleaning material contains composite oxide of tungsten, silicon, titanium, sulfur and zirconium. The deporption temp. of NH3 by an NH3 temp. rising desorption method of the composite oxide is 175-225 deg.C and the BET specific surface area thereof is 50-200 m2/g. An exhaust gas cleaning catalyst is constituted by making the NOx absorbing and cleaning material carry noble metals. Further, alkali, metal, alkaline earth metal or a rare earth element may be added.