Structural Studies of Pillared Clays and Modified Pillared Clays

摘要

The long-range order of pillared interlayered clays (PILCs) after acid activation with 0.05N HCl has been investigated by X-ray diffraction (XRD) methods. The data show that long-range order in PILCs decreases as AlCH-PB = ZrCH-PB much greater than Zr/AlCH-PB = Cr/AlCH-PB (PB = pillared bentonite; MCH = metal chlorohydroxy pillaring agent, where M = Al, Zr or Cr). Apparently, pure oxide clusters are more stable than mixed oxide clusters. Treatment of PILCs with dilute HCl at 25 deg C is less damaging than at reflux temperature, and calcined PILCs are more stable than air-dried materials. More structural damage occurs with 3M sulfuric acid treatment than with dilute HCl. Treatment with a weak base also causes some degradation of the pillars. sup 27 Al-MAS NMR has been used to study pillared hectorite (PH), as well as other clay systems. The large increase of the observable octahedral aluminum (Al(VI)) resonance seen after pillaring is explained by loss of water from the (Al sub 13 O sub 4 (OH) sub 24 (H sub 2 O) sub 12 ) sup 7+ (Al sub 13 ) cation. sup 27 Al spectra of PILCs derived from different pillaring agents and exposed to various heat and acid treatments are remarkably similar. 16 refs., 1 fig., 1 tab. (ERA citation 13:018668)