CATALYTIC ACTIVITY OF TRANSITION-METAL ZEOLITES

The isomerization of n-butenes proceeds on Ca-A and Co-A zeolites as well as on H- and Ni-clinoptilolites. The oligomerization of isobutene takes place similarly on both Ca-A and Co-A zeolites. On acidic and transition metal forms, however, the reaction mechanisms are different. The activity of different metal forms of zeolites for the addition of H2S to the CC double bond depends on the electronegativity of the cations introduced, and not on the acidity of these zeolites. Small pore zeolites are less active than large pore zeolites. Oligomerization followed by coke formation takes place on zeolites of high Si/Al ratio and on Co and Ni forms. Highest activity and selectivity can be attained with Cd- and Zn-X, FAU. Interconversion of thiols and thioethers can also be performed. Acetylene hydration is catalyzed only by late transition metal ions introduced into the zeolites. High stability is attained when no acid sites are generated by the cations and thus crotonic condensation is avoided; further, the active cations are not reduced during the reaction. The requirements are fulfilled by Cd-clinoptilolite. © 1990.