Abstract
A general review of molecular sieve zeolites precedes a more
specialised account of the properties of the zeolites omega and erionite.
It is these relatively unstudied zeolites which have been selected for a detailed catalytic characterisation utilising the isomerisation of the
n- butenes and the methyl substituted cyclopropanes as test reactions.
The resulting product distributions for each zeolite were indicative
of carbonium ion type mechanisms. A study of the reaction of specifically
labelled deuteropropene, CD₂= CH-CH₃, on the catalysts confirmed this
mechanism and moreover, demonstrated that the intermediate carbonium ion
was formed in an associative manner involving Brönsted acid sites.
A gravimetric study of the sorption of reactant and product molecules
into the zeolites was also carried out. The wide pore zeolite omega
exhibited rapid sorption and desorption of all three n- butenes and
methylcyclopropane. Conversely, the rates of sorption of the n- butenes
into erionite were a function of their dipole moments and structures,
the order trans but-2-ene > but-1-ene > cis but -2-ene being observed.
Furthermore, the sorption rates shown by erionite were dependent on the
ionic composition of the erionite sample.
