Hydrogen Production from H2S-steam Reforming using Recycled Sour Water: Insights from Thermodynamic and Kinetic Modeling

Given the rising interest in hydrogen economy, alternative feedstocks are explored for their potential use for hydrogen production, such as H2S, a notable byproduct from oil and gas operations. This study presents a computational investigation on the thermodynamics, kinetics and mechanisms of non-catalytic H2S-steam reforming (H2SSR), as a pathway for H2S-to-H2, benchmarked to H2S thermal decomposition (H2SPyrol) (as a limiting case without water). The mechanism integrates key elementary steps form different reaction pathways, including H2S partial oxidation, H2O reduction, and H2S thermal decomposition. Results from the model are validated using available experimental data for H2SPyrol and H2SSR. Homogeneous gas-phase reactions are modelled at different H2O:H2S ratios, reaction temperatures, pressure, and times. Thermodynamically, the H2SSR reaction is unfavorable due to the presence of water and its role in increasing the reaction complexity and endothermicity; however, kinetically, water contributes to increasing the hydrogen yield at least 9 times that from H2SPyrol, achieving 99.23 % H2S conversion at 1473 K with an excess H2O:H2S feed ratio of 200:1. The contribution of water during the H2SSR reaction is interpreted using reaction path and rate of production analyses, demonstrating its role in producing an abundant pool of OH and H radicals. These radicals catalyze the cleavage of H2S-SH bonds, accelerating hydrogen production at an optimal reaction time of 0.07–0.105 s. This study paves the path for future kinetic and catalytic research to optimize the technical viability of H2SSR as a promising H2S-to-H2 conversion pathway for sour wastewater reutilization.