silicalite

{{Chembox

| ImageFile = Silicalite MFI framework.png

| ImageSize = 284px

| ImageAlt =

| IUPACName =

| OtherNames =

|Section1={{Chembox Identifiers

| CASNo =

| PubChem =

| SMILES = [Si].[O].[O]

}}

|Section2={{Chembox Properties

| Si=1|O=2

| MolarMass =

| Appearance = white solid

| Density = 1.76 g/cm3

| MeltingPtC = 1300

| MeltingPt_notes = decomposition

| BoilingPt =

| Solubility = }}

|Section3={{Chembox Hazards

| MainHazards =

| FlashPt =

| AutoignitionPt = }}

}}

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.{{cite journal|title=Silicalite, a New Hydrophobic Crystalline Silica Molecular Sieve|author=E. M. Flanigen |author2=J. M. Bennett |author3=R. W. Grose |author4=J. P. Cohen |author5=R. L. Patton |author6=R. M. Kirchner |author7=J. V. Smith |journal=Nature|volume=271|pages=512–516|year=1978|issue=5645|doi=10.1038/271512a0|bibcode=1978Natur.271..512F|s2cid=4266556}}

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.{{cite journal|title=Structural and Physicochemical Features of Titanium Silicalites|author=Georgi N. Vayssilov|journal=Catalysis Reviews|volume=39|pages=209–251|year=1997|issue=3|doi=10.1080/01614949709353777}}

References

{{Silica minerals}}

Category:Polymorphism (materials science)

{{materials-sci-stub}}