Development of Predictive Model Equation for Hydrogen Production from Hydrothermal Reaction of Sulfide

摘要

Our previous studies have demonstrated hydrogen production from hydrothermal reaction of sulfide [1, 2]. At temperature range of 280-320 °C and pH 9-13, the hydrogen yield was found to be increased with temperature and/or pH [3]. It was discovered that hydrogen production was accompanied by formation of polysulfide, S_n~(2-), with n=2-5 [4] and/or sulfur oxyanion, S_Xo_y~(2-), as represented by Eqs. (1) and (2) respectively, in which the predominant reaction mechanism was temperature- and pH-dependent. According to these mechanisms, if hydrogen was produced according to Eq. (1), the ratio of hydrogen produced per sulfide consumed (H2/S~(2-)) is at least 0.5 mol/mol if n=2, and at most 0.8 mol/mol if n=5. If hydrogen was produced according to Eq. (2), the H2/S~(2-) ratio is at least 2 mol/mol if the oxidation state of sulfur changes from S~(2-) to only S~(2+) (i.e. S2O3~(2-)), and the H2/S~(2-) ratio is at most 4 mol/mol if the oxidation state of sulfur changes from S~(2-) to S~(6+) (i.e. SO4~(2-)).