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.