Valence Variation of Yb Encapsulated in the Supercage of Y-Type Zeolite

Abstract

Yb/K-Y exhibits various catalytic reactivities by evacuation at various temperatures. By evacuation with elevating temperature, successive desorption of hydrogen, ammmonia, and hydrogen was observed. Yb L 2 , edge XANES spectra showed that Yb is present as a mixture of Yb 2+ and Yb 3+ . The sample as prepared consists of Yb 3+ species mainly. With elevating the evacuation temperature, the fraction of Yb 2+ increases and reaches a maximum in the vicinity of 500 K. Then, the fraction of Yb 2+ decreases and reaches a minimum at 873 K. The valence variation is in a good accordance with a catalytic variation. Desorption of hydrgen and ammonia corresponds to the chemical change of Yb species: amine → imine → nitride.