A soft X-ray EXAFS study of the variation of the local aluminium structure on adsorption of bases in various zeolite types

摘要

We report an in situ study of the local structure around aluminium in a number of zeolites, obtained using soft X-ray absorption fine structure spectroscopy of the aluminium K edge at 1567 eV. As found previously for H-FAU and H-ZSM-5, the presence of the acidic proton results in the elongation of one aluminium – oxygen bond in H-FER and H-MOR. The inability of a recent study [1] to identify this longer bond is briefly discussed. Changes resulting from ammonia adsorption on the activated acidic zeolites are presented, and it is shown that the structures relax, the environment around the aluminium atoms becoming much more regularly tetrahedral. Some structural studies of the adsorption of toluene and isopropanol are also presented.