CATALYTIC CRACKING OF DECALIN ISOMERS OVER REHY-ZEOLITES WITH DIFFERENT CRYSTALLITE SIZES

Cracking of a mixture of cis/trans-decalin was carried out over small crystallite rare-earth containing Y zeolites (REHY). Results showed th at, although the reactivity of cis-decalin is much higher than that of trans-decalin, no influence of crystallite size was detected, as an i ndication that differences in reactivity should be attributed to diffe rences in the structure of the reacting molecules, and not to the char acteristics of the zeolite. In fact, deuterium exchange between deuter ated HY zeolite and decalin revealed that cis-decalin is much more rea ctive than its trans-isomer, Trans-decalin, according to its structure minimized by molecular mechanic force field MM2, presents a more hind ered tertiary C-H bond, therefore making protonation and the formation of adsorbed carbocations difficult.