ADSORPTION AND CATALYTIC PROPERTIES OF MCM-22 - THE INFLUENCE OF ZEOLITE STRUCTURE

A combination of infrared spectroscopy and adsorption and microcalorim etric studies of molecules with different kinetic diameters, such as t oluene, meta- and orthoxylene, and 1,2,4-trimethylbenzene, together wi th consecutive adsorption of these molecules, confirms the presence in MCM-22 of 10-membered ring channels and cavities of larger dimensions , both of which can be reached from the external surface. From the kin etic diameters of the adsorbates the dimension of the two types of voi d species has been estimated. The implications of pore topology on cat alysis have been discussed on the basis of selectivity results obtaine d during alkylation of toluene by methanol and ethanol. The presence o f the two types of unconnected cavities determines the ratios of para- to ortho isomers as well as the ratio of mono- to dialkylates.