Synthesis and characterisation of alumina pillared Texas montmorillonite and determination of the effective Keggin ion charge

Abstract

Controlled calcination of Texas montmorillonite has allowed production of a range of materials of cation exchange capacity from ≈ 70 mequiv./100 g dry clay to virtually zero. Pillaring of these with Chlorhydrol precursor solution has then provided a family of materials of pillar density ranging from about one per six unit cells to zero. The analytical technique based on isomorphous metal dilution (IMD) that follows pillaring is validated. The results provide a consistent value for the precursor (Keggin) ion charge, in the conditions normally used, of 3.15±0.10 rather than the “formal” value of 7. An approach to the attainment of pillar densities consistent with the introduction of shape/size selectivity on pillared layered materials is outlined.