A novel molecular-structure-based formulation representation for the H2S decomposition reaction equilibrium constant

The decomposition of hydrogen sulfide (H2S) into hydrogen (H2) and sulfur (S2) is a promising approach for hydrogen production and sulfur recovery. How to predict accurately the H2S decomposition reaction equilibrium constant has always been a perplexing problem. Here, based on the molecular-structure-based Gibbs free energy formulation expressions subject to the reactant and products, we establish a novel explicit formulation for the equilibrium constant regarding H2S thermal decomposition reaction. The developed molecular-structure-based equilibrium constant model (MSBECM) only incorporates standard experimental data of three, four, and six molecular constants, respectively, for three components H2, S2, and H2S, and overcomes the drawback of traditional empirical correlations containing multiple adjustable parameters determined from fitting plenty of the measured experimental data. The average absolute errors of the theoretical values predicted with the MSBECM from six sets of experimental data are 2.035 %, 1.093 %, 1.809 %, 1.922 %, 2.072 %, and 1.473 %, respectively. Comparing the experimental data and theoretical values, we validate the reliability of the MSBECM. In addition, it has an advantage over the conventional empirical models in that it can predict the impact of pressure changes on the equilibrium constant. As the pressure increases, the forward reaction equilibrium constant value in H2S decomposition decreases.