Structure preparation properties of
Pillared clay
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Yet another approach to the synthesis of pillared clays is the direct intercalation of positively charged metal oxide sol particles. This strategy offers the possibility of forming pillared clays with basal spacings that are substantially larger than the pillared derivatives formed from polycations (Pinnavaia 1995). The height of the interlayer space created by the pillaring sol particles can be substantially larger than the thickness of the layered host. In such cases the intercalates may be described as “supergallery” pillared clays. Especially large surface areas (>500m2g−1) and gallery pore sizes (>20Å) are obtained when organic surfactants are used to order the sol particles in the intragallery space .
The most extensively studied pillared clays are those containing polymeric hydroxy-aluminium species as the pillaring cation. In this paper such Al pillared clays are used to illustrate the nature and properties generally possessed by metal oxide pillared clays. In the non-calcined so-called precursor pillared clay, layer charge is balanced by the pillaring polycations which in the case of Al pillared clays is the Keggin-like [Al13O4(OH)24(H2O)12]7+ ion. On calcination this ion is converted into an oxide with the layer charge balanced by the release of an equivalent number of protons, i.e.
Zirconium-sulfate pillared clay prepared with reaction time of 140 hours and using 0.1 mol /L zirconium acetate solution has been analyzed with mass spectrometry. When the sample was heated in air, masses of 17, 18, 44, 48, 64 and 80 were recorded, corresponding, respectively, to OH+, H2O+, CO2+, SO+, SO2+ and SO3+. Figs. 7, 8 and 9 show the variation of the different masses with heating temperature.
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