Formation, mobilité et réactivité d'espèces paramagnétiques adsorbées sur zéolithes H—Y irradiées. Une étude par résonance paramagnétique électronique

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Abstract
Use of γ radiation as an ionizing source has been successfully applied to an epr study of adsorption sites and of adsorbed species in the case of H—Y zeolites. Adsorption sites have appeared to be mainly oxygen nuclei from the lattice. It has been observed that molecular hydrogen neutralizes paramagnetic sites while molecular oxygen gives rise to O2−-type radicals which have nearly equal unpaired spin density on the two nuclei (43 and 57%). Carbon monoxide gives rise to a species assigned to C+O which reacts very easily at 77 K with molecular oxygen to yield an O2−-type species for which the spin density distribution is not equivalent on the two oxygen nuclei [Formula: see text] The nature and the mobility of OH• and NH2• radicals have been studied in detail. They arise from the ionization of physisorbed H2O and NH3, the better yield being obtained at a monolayer coverage. This study leads to an original approach to the study of the adsorptive properties of zeolites.

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