Steam reformation of hydrogen sulfide

A modified version of the Sulfur–Iodine cycle, here called the Sulfur–Sulfur Cycle, offers an all-fluid route to thermochemical hydrogen and avoids implications of the corrosive HI–H2O azeotropic mixture:equation(1)4I2(l) + 4SO2(l) + 8H2O(l) ↔ 4H2SO4(l) + 8HI(l) (120 °C)equation(2)8HI(l) + H2SO4(l) ↔ H2S(g) + 4H2O(l) + 4I2(l) (120 °C)equation(3)3H2SO4(g) ↔ 3H2O(g)+3SO2(g) + 1½O2(g) (850 °C)equation(4)H2S(g) + 2H2O(g) ↔ SO2(g) + 3H2(g) (900–1500 °C)The key step in the Sulfur–Sulfur cycle is the steam reformation of hydrogen sulfide, which is highly endothermic and has a positive Gibbs free energy change. The steam reformation of hydrogen sulfide was investigated under favorable circumstances (excessive dilution with steam and inert carrier) over a variety of catalytic and non-catalytic settings in a quartz tube. Successful results were obtained by pretreating a molybdenum wire with H2S at high temperature. Apparent Arrhenius parameters for both thermal splitting and steam reformation of hydrogen sulfide were determined.

► Steam reformation of H2S was successfully carried out at temperatures between 700 and 900 °C.
► Increasing the ratio of H2O to H2S increases H2 and SO2 production.
► Apparent Arrhenius parameters were estimated based upon kinetic data.