AN EXAFS AND XANES STUDY OF EUROPIUM-NICKEL-EXCHANGED AND EUROPIUM-NICKEL-EXCHANGED Y-ZEOLITE AND THE EFFECTS OF REDUCTION

Eu3+ within the supercages of a ca. 10 wt% europium-exchanged Y zeolite of composition [Eu7.8(NH4)30.5Na0.1Si139Al530384].nH2O can be partially reduced by hydrogen to Eu2+. XANES is shown to be a particularly sensitive means by which the reduction process can be monitored. The Eu3+ in similar sites in a ca. 3 wt% europium-1.5 wt% nickel coexchanged Y zeolite of composition [Eu2.3Ni3.0(NH4)41Na0.1Si141Al51O334].nH2O is also amenable to partial hydrogen reduction to Eu2+. Some of the reduced species, probably located in the smaller cages as a result of migration during the reduction process, are resistant to reoxidation. The Ni2+ in the supercages of the coexchanged Y zeolite is more amenable to hydrogen reduction to metallic nickel than is Ni2+-exchanged Y zeolite in which the Ni2+ is located in the smaller cages.