PROPOSED PORE VOLUME TOPOLOGY OF ZEOLITE MCM-22 BASED ON CATALYTIC TESTS

The void structure of zeolite MCM-22 is discussed on the bases of cata lytic reaction tests. The isomerization/disproportionation of m-xylene on the acidic zeolite, and the hydroisomerization of n-decane on bifu nctional Pt/zeolite catalysts have been used as model reactions. The c onversion of n-decane has been carried out under more realistic hydroi somerization conditions, i.e., higher pressure and lower H-2/n-decane ratio, as compared to the original work. Under these conditions it has been shown that the n-decane test is also a useful reaction to differ entiate between different zeolite structures. From both reaction model s it is concluded that zeolite MCM-22 shows features of both 10 MR and 12 MR zeolites depending on the different selectivity criteria used. This could be explained, in principle, by assuming the presence of bot h types of channels in the structure of MCM-22 which are probably leav ing free spaces of a higher diameter than the channels.