Effect of H₂ in the synthesis of COS using liquid sulfur and CO or CO₂ as reactants

The synthesis of COS from CO, CO₂ and liquid sulfur in the presence and absence of hydrogen was explored. The reaction of H₂ with liquid sulfur produced H₂S and polysulfanes, which increase the reactivity of liquid sulfur and provide alternative complementary reaction routes for the formation of COS. The reaction from CO₂ proceeds by forming CO as intermediate. Elevated pressure favors formation of COS from both carbon oxides due to the increasing residence time and the saturation of gases in the liquid. Above 350 °C, the solubility of H₂S in sulfur and the hydrogenation of COS limit the conversion of CO. The approach provides a highly efficient method for the preparation of COS under mild reaction conditions, without using a catalyst or water adsorbents.