Silicotungstic acid
 | |
| Names | |
|---|---|
| Other names
Tungstosilicic acid | |
| Identifiers | |
12027-38-2  12027-43-9 (hydrate)  | |
| ECHA InfoCard | 100.206.333 |
| Properties | |
| H4[W12SiO40] | |
| Molar mass | 2878.2 g/mol |
| Melting point | 53 °C (127 °F; 326 K) |
| Structure | |
| zero | |
| Hazards | |
| 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 (also known as tungstosilicic acid) is the most commonly encountered heteropoly acid. It is a pale yellow solid with the chemical formula H4[W12SiO40]. It is used as a catalyst in the chemical industry.[1]
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:[1]
- 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.[2]
Synthesis and structure
The free acid is produced by combining sodium silicate and tungsten trioxide followed treatment of the mixture with hydrochloric acid.[3] The polyoxo cluster adopts a Keggin structure, with Td point group symmetry.
References
- 1 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.
- ↑ 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. American Association for the Advancement of Science. 345 (6202): 1326–1330. doi:10.1126/science.1257443. Retrieved October 6, 2014.
- ↑ Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY.