X-Ray absorption and photoelectron spectroscopic investigation of vanadium interaction with NH4+- and Eu3+-exchanged zeolite-Y following calcination and steam treatment

Abstract

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 NH⁴⁺- and Eu³⁺-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 VO 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 Eu³⁺ cations.