Silicalite

Silicalite is an inorganic compound with the formula SiO2. It is one of several forms (polymorphs) of silicon dioxide. It is a white solid. It consists of tetrahedral silicon centers and two-coordinate oxides. It is prepared by hydrothermal reaction using tetrapropylammonium hydroxide followed by calcining to remove residual ammonium salts. The compound is notable in being ca. 33% porous. It is useful because the material contains (SiO)10 rings that allow sorption of hydrophobic molecules of diameter 0.6 nm.[1]

Silicalite
Identifiers
Properties
O2Si
Molar mass 60.083 g·mol−1
Appearance white solid
Density 1.76 g/cm3
Melting point 1,300 °C (2,370 °F; 1,570 K) decomposition
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

A commercially important modification of silicalite is titanium silicalite. With the formula Si1−xTixO2, it consists of silicalite with Ti doped into some Si sites. Unlike conventional polymorphs of titanium dioxide, the Ti centers in titanium silicalite have tetrahedral coordination geometry. The material is a useful catalyst for the reaction of hydrogen peroxide with propylene to give propylene oxide.[2]

References
  1. E. M. Flanigen; J. M. Bennett; R. W. Grose; J. P. Cohen; R. L. Patton; R. M. Kirchner; J. V. Smith (1978). "Silicalite, a New Hydrophobic Crystalline Silica Molecular Sieve". Nature. 271 (5645): 512–516. Bibcode:1978Natur.271..512F. doi:10.1038/271512a0. S2CID 4266556.
  2. Georgi N. Vayssilov (1997). "Structural and Physicochemical Features of Titanium Silicalites". Catalysis Reviews. 39 (3): 209–251. doi:10.1080/01614949709353777.


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