QXAFS法によるUSYゼオライトを担体としたパラジウムの動的挙動解析

抄録

Dynamic structural change of palladium loaded on USY zeolites was monitored by means of an in situ Quick-XAFS method inthe H₂, O₂ atmosphere and solvents. We found that metal Pd clusters were readily generated on exposure to a H₂ flow at room temperature. The size of the Pd clusters could be regulated simply by changing the number of times that H₂ and O₂ flows were alternately introduced into the in situ cell. Then structural change of Pd was monitored during temperature programmed reduction and oxidation. We could observe the coalescence and dispersion behavior of Pd depending on the temperature and oxidation-reduction cycles. The Pd/USY catalysts exhibited prominent activity in the Suzuki-Miyaura coupling when the reaction was performed in o-xylene. Pd K-edge and Pd L₃-edge XAFS analyses revealed the formation of atomic Pd with a cationic character in the o-xylene as a solvent.