Aluminosilicates, intercalates

X-ray photoelectron spectra, V3f Alumina-supported metals, multitechnique characterization, 37V-83 Aluminosilicates, Intercalates of, role In heterogeneous catalysis, V72-83 Alumlmin... 

The intercalates of sheet aluminosilicates (clays) and of graphite are demonstrated to be efficient catalysts for a variety of reactions, and results obtained using several analytical techniques, including magic angle spinning KMR, are presented. For the clay family,... 

This i>aper describes two broad types of intercalation conpomds which are based on graphite on the one hand and sheet aluminosilicate (clay) hosts on the other. Taken together these provide a rich veiriety of examples of heterogeneously catalysed reactions. Appropriately cation exchanged clays, for example, act as efficient catalysts for a number of commercially important proton catalysed reactions (10-13) (see Table I). Graphite intercalates, whilst also capable of... 

Swollen clay materials are soft and easy to mould. They serve to produce ceramic materials. High quality fire-clay has a high kaolinite content. Upon firing, the intercalated water is removed first at approximately 100 °C. Then, beginning at 450 °C, the OH groups are converted to oxidic O atoms by liberation of water, and after some more intermediate steps, mullite is formed at approximately 950 °C. Mullite is an aluminum aluminosilicate, Al(4 )/3[Al2 Si,05] with x 0.6 to 0.8. 

In addition to stabilizing organic products by reaction with metal-exchanged clays, as indicated above, aluminosilicate minerals may enable the preparation of metal organic complexes that cannot be formed in solution. Thus a complex of Cu(II) with rubeanic acid (dithiooxamide) could be prepared by soaking Cu montmorillonite in an acetone solution of rubeanic acid (93). The intercalated complex was monomeric, aligned with Its molecular plane parallel to the interlamellar surfaces, and had a metal ligand ratio of 1 2 despite the tetradentate nature of the rubeanic acid. 

Intercalation in layered solids is a long-established phenomenon. It has been suggested [ 1 ] that the first example, dating from over two thousand years ago, involved intercalation in kaolinite (an aluminosilicate clay) and explains the secret behind the production of fine Chinese porcelain, hi modern times, many thousands of papers have been devoted to intercalation chemistry in clays, graphite and other materials. 

Ukrainczyk, L., Chibwe, M., Pinnavaia, T.J. Boyd, S. A. (1994). ESR study of cobalt(II) tetrakis(N-methyl-4-pyridiniumyl)porphyrin and cobalt(II) tetrasulfophthalocyanine intercalated in layered aluminosilicates and a layered double hydroxide. Journal of Physical Chemistry, 98, 2668-76. 

February 29th) into the calendar to make it match the. solar year. Most work on intercalation compounds has been on synthetic systems in which atoms, ions, or molecules have been inserted between layers of the host material. However, some aluminosilicates that we have encountered above provide useful examples. Thus talc and micas form layered structures with ions between the silicate sheets (Fig. 16.3). Some minerals, including all clays, have water molecules intercalcatcd between the framework sheets. In some, such as vermiculile, the water may rapidly and dramatically be evacuated by heating. The water molecules leave faster than they can ditfuse along the layers—exfoliation occurs. The result is the familiar expanded vermiculile used as a packing material and as a potting soil conditioner. 

Zeolites are crystalline, microporous aluminosilicates with molecular-sized intracrystalline channels and cages. Guest molecules with molecular diameters smaller than zeolites (from 3 to 15 A) can enter the interior of zeoUte crystals (intercalation) giving rise to shape and size selective sorption and, consequently, highly selective reactions. 

The diversity of the inclusion of molecules of any type into host lattices which are distinctly inorganic is now becoming apparent [31], Apart from the oxidic zeolites, aluminosilicates and derivatives with other tetrahedral sites, there are the layered silicates and minerals, pillared clays and numerous other intercalation and inclusion systems, including graphite, metal sulfides and metal cyanides [23, 32, 33]. 

A formamide intercalation adduct of dickite, Al2Si20s(0H)4, is the first clay-mineral intercalate that has been shown to possess an ordered structiure of interlamellar molecules. Thus, the formamide molecules lie over vacant octahedral sites in the aluminosilicate layers. 

Tunney. J.J. Detellier, C. Aluminosilicate nanocomposite materials. Poly(ethylene glycol)- kaolinite intercalates. Chem. Mater. 1996, 8. 927-935. 

Clays are colloidal layered hydrous aluminosilicates. There are relatively few examples of porphyrin intercalation into clays reported, mostly with either smectite clays or layered double hydroxides (LDH). Smectite clays consist of negatively charged layered aluminosilicate sheets. These sheets are separated by cations and water molecules. The... 

Chitosan/day nanocomposites represent an innovative and promising class of materials. Potential biomedical applications of chitosan/clay nanocomposites include the intercalation of cationic chitosan in the expandable aluminosilicate structure of the clay is expected to affect the binding of cationic drugs by anionic clay the solubility of chitosan at the low pH of gastric fluid may decrease the premature release of drugs in the gastric environment ... 

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