Catalytic reactions of alkenes and substituted cyclopropanes on zeolites

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.