From SiO 2 to Alkoxysilanes for the Synthesis of Useful Chemicals.

The transformation of silica (SiO 2 ) to useful chemicals is difficult to explore because of the strength of the Si-O bond and thermodynamic stability of the SiO 2 structure. The direct formation of alkoxysilanes from SiO 2 has been explored as an alternative to the carbothermal reduction (1900 °C) of SiO 2 to metallic silicon (Si met ) followed by treatment with alcohols. The base-catalyzed depolymerization of SiO 2 with diols and monoalcohols afforded cyclic silicon alkoxides and tetraalkoxysilanes, respectively. SiO 2 can also be converted to alkoxysilanes in the presence of organic carbonates, such as dimethyl carbonate. Alkoxysilanes can be further converted to useful chemicals, such as carbamates, organic carbonates, and chlorosilanes. An interesting and highly efficient pathway to the direct conversion of SiO 2 to alkoxysilanes has been discussed in detail along with the corresponding economic and environmental implications. The thermodynamic and kinetic aspects of SiO 2 transformations in the presence of alcohols are also discussed.