EPR of trans-stilbene radical cations formed in zeolite cavities: a new approach to study the zeolite void space

trans-Stilbene was adsorbed in the cavities of H-ZSM-5, H-MOR and H-BEA zeo lites, originating monomeric and dimeric radical cations that were studied by EPR spectroscopy. The H-BEA samples were pretreated at three progressive ly higher temperatures. Simulation of the spectra allowed the evaluation of the relative amounts of monomers and dimers. The nature, quantity and rela tive amount of monomeric and dimeric radical species were correlated to che mical and dimensional modifications of zeolite channels caused by the dealu mination of the zeolite structure and extra-framework aluminium species for mation.