Reactions of silicon tetrachloride and germanium tetrachloride with oxygen and oxides of nitrogen

Abstract

The reactions of SiCl4 and GeCl4 with oxygen and oxides of nitrogen have been studied in a continuous flow system. SiCl4 is found to react with nitrous oxide at a considerably lower temperature (700 °C vs 1050 °C) than with oxygen. In both cases the formation of silicon oxychlorides (hexachlorodisiloxane and octachlorocyclo-tetrasiloxane) was observed for the first 300 °C after reaction initiates. Activation energies of 115 kcal/mole and 40 kcal/mole were determined for the reactions with oxygen and nitrous oxide, respectively (under conditions of 100-fold excess oxidizer). GeCl4 is also found to react with nitrous oxide at a lower temperature than with oxygen; however, in this case no oxychloride species were observed. Activation energies of 53 kcal/mole and 48.6 kcal/mole were determined for the reactions with oxygen and nitrous oxide, respectively (under conditions of 70-fold excess oxidizer). Reactions of GeCl4 with nitric oxide and nitrogen dioxide are also reported. The use of N2O as an oxidant in optical fiber fabrication processes is discussed.