| 摘要 |
PURPOSE:To obtain a superb NOx purification performance, increase heat resistance and thereby achieve the compatibility of enhanced purification capability with improved heat resistance by permitting a precious metal active species which decomposes NOx by combustion of HC carried by a specific metal- containing silicate. CONSTITUTION:The subject exhaust gas purification catalyst consists of a precious metal active species which decomposes NOx by combustion of HC carried by a metal-containing silicate with an acidity function Ho of Ho<=-3.0 and solid acid properties such that the acid amount is 0.04 to 0.55mmol/g. Further, as a model shows in the figure, Pt 2 and Ir 3 as precious metal active species are carried as metals by an aminosilicate 1, and an acid site 4 is formed on the aminosilicate 1 by control of solid acid properties. Consequently, HC in an exhaust gas which flows in comes in contact with the acid site 4, to begin with, to excite HC to be made into free radical. On the other hand, NOx is adsorbed on the surface of Ir3 as a metal, then HC which becomes a strong attacking species to NOx attacks NOx and NOx is efficiently decomposed as N2 and O2 in an oxygen-rich atmosphere. |
