Shape selectivity zsm5 and mordenite

One of the paramount advantages of microporous reactors is the influence of geometry/spatial constraints on the reactions of guest species. This gives rise to shape selectivity which is vividly displayed in the products of cyclic olefin reactions on zeolites ZSM5 and Mordenite. The largest contrast is that Mordenite, with its system of 12-ring channels (Table 2), is capable of 

ZSM5 10-ring, straight channels 10-ring, sinusoidal channels 5.3 X 5.6 5.1 X 5.5 

Radiation chemical methods, when coupled with appropriate detection techniques, can be used to study many different aspects of solid heterogeneous catalysis. Ionizing radiation can be used to generate reactive intermediates, to change the oxidation state of metal ions or clusters, to create reactive defects in the solid lattice and to spin label reaction products. When radiolysis and EPR are used together, products of catalysis can be identified in situ and at low temperatures with the excellent structural specificity and sensitivity inherent in the EPR method. 

As always, exceptions to the rule can offer greater insights into chemical mechanisms. Subtle structure/reactivity dependences revealed by radiolysis/EPR experiments carried out under very mild conditions provide interesting examples to theorists in their attempts to learn more about the intimate details of the steric factors and specific interactions of reactant molecules with the catalytically active site. 

We acknowlege the generosity of Chemie Uetikon of Switzerland for the gift of the zeolite materials used in most of our research. 

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