Mixed-metal pillared layer clays and their pillaring precursors

Abstract

Mixed-metal pillared layer clays (Fe,Al-PILCs and Cr,Al-PILCs) of various compositions and the pillaring precursors have been prepared and characterised with a combination of chemical and instrumental methods. Chemical analysis data, IR, ⁵⁷ Mössbauer and ²⁷ Al NMR spectroscopic measurements on the precipitated pillaring precursors and comparison of redox behaviour [temperature-programmed reduction (TPR) results and ⁵⁷ Fe Mössbauer measurements on the heat-treated and the reduced samples] of the ion-exchanged and Al-pillared and mixed-metal pillared clays revealed that isomorphous substitution of Al for Fe or Cr did not occur in either the tetrahedral or the octahedral positions. Heat treatment, however, resulted in mixed-metal pillared clays which were active in both acid-catalysed and redox transformations.