Pd-LaFeO₃ Catalysts in Aqueous Ethanol: Pd Reduction, Leaching, and Structural Transformations in the Presence of a Base

The reactive behavior of three catalysts based on Pd-loaded LaFeO₃ was investigated in terms of the reducibility of Pd and its propensity to leaching into the liquid phase in flowing solutions prototypical of C-C coupling catalysis in a continuous flow reactor cell. In situ quick extended X-ray absorption fine structure spectroscopy showed that Pd remains stable and nonreducible in the flowing ethanol/water solvent mixture under heating to 353 K. However, ex situ transmission electron microscopy, high-energy X-ray diffraction, and fluorescence yield Fe K-edge X-ray absorption near-edge structure show that the addition of a significant amount of base (K₂CO₃, 0.1 M) results in the structural degradation of the perovskite support as well as the mobilization of Pd along the sample bed that is dependent on the structure and crystallite size of the perovskite. The results are discussed in terms of the use of perovskite-type oxides in various areas of research where they are placed in contact with liquid phases of variable temperature and elevated pH.