INFLUENCE OF THE CERIUM CONTENT OF CEHY CATALYSTS ON THEIR PHYSICOCHEMICAL AND CATALYTIC PROPERTIES

The physicochemical and catalytic properties of a stabilized HY zeolite and of CeHY zeolites were compared. The Broensted acid sites of CeHY zeolites are definitely stronger than those of HY whereas their Lewis acid sites are weaker; the total number of acid sites decreases with the cerium content. The strength of protonic sites and the activity for n-heptane cracking at 350 degree C are maximal for an exchange rate of about 45%. For all the samples the cracking activity is clearly related to the strong protonic acidity. The rates and selectivities of the transformations of n-heptane and of its isomers (methylhexanes, 2,4-dimethyl-pentane) were compared.