Magadiite-layered silicates

Figure 6 A conq)arison betweeen the activities of two different layered silicates, magadiite and kenyaite, as a fimction of their interlayer species. Alumina pillared kenyaite appears to have significantly more activity than a comparable pillared magadiite. This indicates a sensitivity towards the layered structure.

In order to systematically change the properties of layered silicate materials, we have investigated the possibility of isomorphous substitution of silicon by aluminum or boron. It is demonstrated that addition of horon and/or aluminum compounds to the reaction mixture leads directly to boron and aluminum containing layered materials in a hydrothermal crystallization process without further treatment. The layered materials obtained were identified as hectorite types, magadiite and kenyaite-like types. The isomorphous substitutions were proven by "B, Al, and Si solid state NMR spectroscopy. 

The layered silicates hectorite and magadiite were synthesized using hydrothermal procedures based on those described in 111. For hectorite which contains lithium and magnesium atoms in octahedral sites between the silicate sheets, this synthesis procedure was modified. The crystallizations were carried out at temperatures ranging from 100°C to 200°C. The compositions of the reaction mixtures (expressed as molar ratios of the oxides) were ... 

Table 1 shows typical compositions of the reaction mixture used for the syntheses of aluminum-containing layered silicates of the M-SH type, in this example magadiite, and their crystallization parameters i.e. the crystallization rates and the incubation periods, to, the time after which the crystallization begins. The presence of AI2O3 in the reaction mixture seems to disturb the seed formation, as reileeted in the inereased ineubation periods. 

P-36 - Hydrothermal transformation of a layered silicate, Na-magadiite, into mordenite zeolite... 

Hydrothermal transformation of a layered silicate, Na-magadiite, into a commercially important mordenite zeolite is achieved, at 175 °C, using tetraethylammonium hydroxide as the intercalating and/or structure directing agent. Samples were characterized by XRD, IR, SEM, DTA and N2 adsorption measurements. The results indicate that the mordenite samples obtained by this new route are highly crystalline, more uniform and smaller in size (0.1 -0.2 pm). 

The hydrous layer silicates are a large family of materials containing two-dimensional tetrahedral silica layers where the individual tetrahedra are linked by the sharing of three comers to form a hexagonal sheet. This family includes such natural minerals as magadiite, kenyaite, makatite, and kanemite, as well as synthetic... 

Finally, the acid- or base-catalyzed reaction of hydrolysis and condensation polymerization of TEOS into a layered silicate gallery could affect the physical properties of silica-pillared magadiite and kenyaite. The samples that were silica-pillared by acid- and base-catalyzed reactions show a large increase in basal spacing. Also, they exhibit relatively narrow pore size distributions and show high surface areas, depending on the type of catalyst and layered silicate. These results indicate that variations in the conditions of gelation contribute to the improvement in the physical properties of silica-pillared molecular sieves. 

Wang, Z., Lan. T. and Pinnavaia,T. (1996), Hybrid organic-inorganic nanocomposites formed from an epoxy polymer and a layered silicate acid (magadiite). Chemistry of Materials, Vol. 8, pp. 2200-2204. 

Li and coworkers chose hydrothermaUy synthesized Na magadiite (Na2Sii4029. nH20) as the source of layered silicate [61]. Upon acidification, Na-magadiite is... 

Layered silicic acids Kanemite, makatite, oaosilicate, magadiite, kenyaite, and layered organo-silicates... 

Amphiphilic cationic azobenzene derivatives (scheme Fig. 14) have been used as the guest species for intercalation into the layered silicates magadiite and montmorillonite (182-185). The azobenzene chromophore photoisomaized effectively in the interlayer space of silicates, despite the fact that the azobenzene... 

Magadiite is a cationic clay of fonnula Na2Sii4C>29 nH20 belonging to the family of layered silicic acids. 

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