X-Ray absorption and photoelectron spectroscopic investigation of vanadium interaction with NH4+- and Eu3+-exchanged zeolite-Y following calcination and steam treatment
Agasi, Lorenza; Berry, Frank J.; Carbucicchio, Massimo; Marco, Jos?? F.; Mortimer, Michael; Vetel, Frederic F. F.; Agasi Lorenza; Dipartimento di Fisica, Università di Parma, and INFM, Parco Area della Scienze 71A; Berry Frank J.; Department of Chemistry, The Open University, Walton Hall; Carbucicchio Massimo; Dipartimento di Fisica, Università di Parma, and INFM, Parco Area della Scienze 71A; Marco José F.; Instituto de QuÃmica-FÃsica â Rocasolanoâ , Consejo Superior de Investigaciones CientÃficas; Mortimer Michael; Department of Chemistry, The Open University, Walton Hall; Vetel Frederic F. F.; Department of Chemistry, The Open University, Walton Hall
Журнал:
Journal of Materials Chemistry
Дата:
2002
Аннотация:
X-Ray absorption near-edge structure, extended X-ray absorption fine structure and X-ray photoelectron spectroscopy have been used to investigate the interaction of vanadium with both NH<sup>4+</sup>- and Eu<sup>3+</sup>-exchanged, dealuminated zeolite-Y. In both cases, samples were subjected to either calcination or steam treatment at temperatures in the range 100 to 800 °C. Following deposition of vanadium, in the form of vanadyl(iv) acetylacetonate, there is evidence of a weak interaction between vanadium and the zeolite-Y framework. Under the conditions used in the work, treatment at increasing temperature, either in air or steam, results in the complete oxidation of V(iv) to V(v) at temperatures in the range 300 to 500 °C. At temperatures exceeding 500 °C, V(v) is present in tetrahedrally-distorted vanadium oxide species containing terminal V.dbd;O bonds, which are highly dispersed but bonded to the zeolite framework. These results show that the migration of vanadium into the zeolite-Y framework is not dependent on the presence of steam, nor is there any detectable influence of the exchanged Eu<sup>3+</sup> cations.
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