Abstract: By hydrothermal treatment or silicon tetrachloride reaction at a high temperature, we have succeeded in reducing the content of Al atom in zeolite HYand obtained two series of deafuminized Yzeolite named as USY(W) containing nonframework Al and USY(T).USY(W) and USY(T) were characterized by TPD.IRand ESCA.The results shows that the nonframework Al in the USY (W) screens the strong acid sites of the surface and produces weak acid sites.The effects of Si/Al ratio and nonframework Al on the cumene- cracking activity of dealuminated zeolite were examined.The results shows that the higher the Si/Al is, the smaller the catalytic activity is.Besides, the nonframework Al in the USY(W) exerts a influence on the catalytic activity of zeolite in cumene-cracking and coking.The catalytic activity of zeolite decreases with the formation of non-framework Al and the coking amount reduces obviously.

Key words: Dealuminized faujastite, Nonframcvvork aluminium, Surface acidity.Catalytic activity