Silicotungstic acid

Silicotungstic acid
Names
	Other names Tungstosilicic acid
Identifiers
CAS Number	(anhydrous): 12027-38-2 ; (hydrate): 12027-43-9 ;
3D model (JSmol)	(anhydrous): Interactive image;
ChemSpider	(anhydrous): 21241680; (hydrate): 30782693;
ECHA InfoCard	100.206.333
PubChem CID	(anhydrous): 90478850; (hydrate): 71307034;
UNII	(anhydrous): HC56ET3NXY ; (hydrate): 26XKI06R59 ;
CompTox Dashboard (EPA)	(anhydrous): DTXSID50923295 ;
	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): [W]18!$(O[W]#(O[W]56(O1)(O[W]247(O[W]9"(O[W](O2)(O[W]3(O[W](O[W](O3)(O4)(O5)([O ]67[Si] [O ]89[W](O[W](O[W](O)(O)(O)([O ])[O-])(O)(O)([O ] )[O-])(O!)(O")[O-])O)(O#)[O-])[O-])[O-])(O$)O)[O-])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
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 [77 °F], 100 kPa). verify (what is ?) Infobox references

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.^[1] It is a white solid although impure samples appear yellow. It is used as a catalyst in the chemical industry.^[2]

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:^[2]

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.^[3]

Synthesis and structure

The free acid is produced by combining sodium silicate and tungsten trioxide followed treatment of the mixture with hydrochloric acid.^[1]^[4] The polyoxo cluster adopts a Keggin structure, with T_d point group symmetry.

Hazards

Silicotungstic acid is an irritating and odorless substance.

References

^ ^a ^b 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.
^ ^a ^b 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.
^ 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.
^ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.

This inorganic compound–related article is a stub. You can help Wikipedia by expanding it.

[Dias-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.

[Misono-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.

[1]

[2]

[3]

[4]