Silicotungstic acid
Silicotungstic acid or tungstosilicic acid is a heteropoly acid with the chemical formula. It forms hydrates. In freshly prepared samples, n is approximately 29, but after prolonged desiccation, n becomes 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:It's 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 was recently 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.