USE OF NMR TECHNIQUES FOR STUDYING DEACTIVATION OF ZEOLITES BY COKING

NMR occupies an important place in the study of the deactivation of zeolites by coking. Indeed, association of the resonances of several nuclei has shown that it is possible to investigate: the nature of the carbonaceous deposits; under certain conditions, the coke content; the mode of zeolite deactivation; the exact location of the internal coke and the evolution of its distribution with the coke content, the presence of carbonaceous residues at the crystallite surface; the effect of zeolite structure and the nature of the reactant on coking and regeneration. It also reveals the role of extraframework aluminium species and that of certain lattice Al atoms in the coking process.