Surface and Bulk Characterisation of Metallic Phases Present during CO Hydrogenation over Pd–Cu/KL Zeolite Catalysts

A series of Pd–Cu/KL zeolites with varying Pd : Cu ratios have been studied by a combination of FTIR and XANES. XANES indicates that only one PdCu alloy is formed for all samples and that the bulk of the alloy is not modified by extended periods under CO/H2at elevated temperatures. A combination of low temperature adsorption studies andin situhigh temperature/high pressure FTIR indicates that an adsorbate induced surface segregation of Pd occurs following exposure of the bimetallic catalysts to a CO/H2reaction mixture under hydrogenation conditions. A progressive loss in Pd three-fold adsorption centres is observed as a function of time in contact with the reaction mixture.