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Silicotungstic acid

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(Redirected from Silicotungstate) Chemical compound
Silicotungstic acid
Names
Other names Tungstosilicic acid
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.206.333 Edit this at Wikidata
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/H4O4Si.36O.12W/c1-5(2,3)4;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;/h1-4H;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;Key: CGFYHILWFSGVJS-UHFFFAOYSA-N
  • (hydrate): InChI=1S/H4O4Si.H2O.36O.12W/c1-5(2,3)4;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;/h1-4H;1H2;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;Key: ACTPFSYIGLFGLY-UHFFFAOYSA-N
SMILES
  • (anhydrous): 18%21%24(O%16%18%23(O56(O1)(O247(O9%22(O%12%13(O2)(O3%11%14(O%17%19(O(O3)(O4)(O5)(67%15%2089%10(O(O(O%10)(O%11)(O%12)(%13%14%15))(O%16)(O%17)(%18%19%20))(O%21)(O%22))O)(O%23))))(O%24)O))O))O
Properties
Chemical formula H4[SiW12O40]
Molar mass 2878.2 g/mol
Appearance White solid
Melting point 53 °C (127 °F; 326 K)
Structure
Dipole moment 0 D
Hazards
GHS labelling:
Pictograms GHS05: CorrosiveGHS07: Exclamation mark
Signal word Danger
Hazard statements H314, H315, H319, H335, H412
Precautionary statements P260, P261, P264, P271, P273, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Flash point Non-flammable
Related compounds
Related heteropoly acids Phosphotungstic acid
Related compounds Tungsten trioxide
Tungstic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

Silicotungstic acid or tungstosilicic acid is a heteropoly acid with the chemical formula H4[SiW12O40]. It forms hydrates H4[SiW12O40]·nH2O. In freshly prepared samples, n is approximately 29, but after prolonged desiccation, n = 6. It is a white solid although impure samples appear yellow. It is used as a catalyst in the chemical industry.

Applications

Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene:

C2H4 + CH3CO2H → CH3CO2C2H5

It has also been commercialized for the oxidation of ethylene to acetic acid:

C2H4 + O2 → CH3CO2H

This route is claimed as a "greener" than methanol carbonylation. The heteropoly acid is dispersed on silica gel at 20-30 wt% to maximize catalytic ability.

It has also recently been proposed as a mediator in production of hydrogen through electrolysis of water by a process that would reduce the danger of explosion while allowing efficient hydrogen production at low current densities, conducive to hydrogen production using renewable energy.

Synthesis and structure

The free acid is produced by combining sodium silicate and tungsten trioxide followed treatment of the mixture with hydrochloric acid. The polyoxo cluster adopts a Keggin structure, with Td point group symmetry.

Hazards

Silicotungstic acid is an irritating and odorless substance.

References

  1. ^ Dias, J. A.; Dias, S. C. L.; Caliman, E. (2014). "Keggin Structure Polyoxometalates". Keggin Structure Polyoxoometalates. Inorganic Syntheses. Vol. 36. p. 210-217. doi:10.1002/9781118744994.ch39. ISBN 9781118744994.
  2. ^ Misono, Makoto (2009). "Recent progress in the practical applications of heteropolyacid and perovskite catalysts: Catalytic technology for the sustainable society". Catalysis Today. 144 (3–4): 285–291. doi:10.1016/j.cattod.2008.10.054.
  3. Rausch, Benjamin; Symes, Mark D.; Chisholm, Greig; Cronin, Leroy (September 12, 2014). "Decoupled catalytic hydrogen evolution from a molecular metal oxide redox mediator in water splitting". Science. 345 (6202). American Association for the Advancement of Science: 1326–1330. Bibcode:2014Sci...345.1326R. doi:10.1126/science.1257443. PMID 25214625. S2CID 20572410.
  4. Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.


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