Isomorphous substitution liquid-solid

Galliation of Zeolites - Liquid-Solid Isomorphous Substitution... 

At present, this liquid-solid substitution approach has been extended to the secondary synthesis of zeolites containing Si, Fe, Sn, Ti, Cr, and other heteroatoms. An exception is that BF4 cannot be used for liquid-phase dealumination and boron-addition of zeolites to prepare boron-containing zeolites.[33] In the following galliation of NH4Y will be taken as an example to discuss the isomorphous substitution secondary synthesis technique. 

Based on the quite remarkable results obtained with TS-1 we expect that many more examples of microporous solids modified by isomorphous substitution with redox metal ions in the crystal lattice will be described in the future (see Fig. 12). Indeed, the scope for developing unique oxidation catalysts based on the concept of site-isolation in zeolites, silicalites, alpos and sapos is enormous [37], In addition to varying the redox metal the size and hydrophobicity of the cavity can be tuned by, for example, varying Si/Al ratios to provide a variety of unique heterogeneous catalysts for liquid phase oxidation. 

Complete solid solubility for a binary system means that atoms of one constituent can be substituted for the other over the entire range of compositions in both the solid and liquid state without introducing a different phase. Such alloys are said to be isomorphous. Hume-Rothery developed a set of criteria that must be met in order for a system to exhibit complete solid solubility ... 

The liquid L is a homogeneous liquid solution composed of both copper and nickel. The a phase is a substitutional solid solution consisting of both Cu and Ni atoms and has an FCC crystal structure. At temperatures below about 1080°C, copper and nickel are mutually soluble in each other in the solid state for all compositions. This complete solubility is explained by the fact that both Cu and Ni have the same crystal structure (FCC), nearly identical atomic radii and electronegativities, and similar valences, as discussed in Section 4.3. The copper-nickel system is termed isomorphous because of this complete liquid and solid solubility of the two components. 

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