The State of Europium Complexes on Alumina Surface

Abstract
Amide complexes of europium prepared by dissolving Eu in a liquid ammonia were fixed on alumina and heated at various temperatures in vacuo. The activity of the samples for the isomerization of 2,3-dimethylbut-1-ene changed remarkably with the evacuation temperature and the loading amount of Eu. XANES analysis of the samples showed that the Eu species are a mixture of divalent- and trivalent-ion complexes and the samples exhibiting high activity include only divalent Eu species. EXAFS analysis demonstrated that there are two kinds of divalent Eu species in the samples, i. e, the Eu species fixed by OH group on the alumina and the species consisting of Eu ions bridged by nitrogen. EXAFS analysis also revealed that the former is the inactive Eu species, while the latter is the active species for isomerization of 2,3- dimethylbut-1-ene. The catalytic activity closely related to the degree of the aggregation of the latter Eu active species.