Silicotungstic acid
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| Names | |
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| Other names
Tungstosilicic acid
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| Identifiers | |
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| 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 | |
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Related heteropoly acids
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Phosphotungstic acid |
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Related compounds
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Tungsten trioxide Tungstic acid |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| 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.
Silicotungstic acid is used to manufacture ethyl acetate by the alkylation of acetic acid by ethylene:
It has also been commercialized for the oxidation of ethylene to acetic acid:
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.
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 Tdpoint group symmetry.
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