Heterogeneous catalytic production of elemental sulfur from hydrogen sulfide and carbon dioxide

The purpose of this study was to experimentally and theoretically investigate the feasibility of producing elemental sulfur, carbon monoxide (CO), hydrogen (H{dollar}sb2{dollar}) and possibly methane (CH{dollar}sb4{dollar}) from hydrogen sulfide (H{dollar}sb2{dollar}S) and carbon dioxide (CO{dollar}sb2{dollar}) through catalytic reactions at moderate temperatures around 550{dollar}spcirc{dollar}C. Novel experimental systems that could evaluate potential catalysts and adsorbents under controlled laboratory conditions were designed and constructed. Additionally an effective simulation program capable of providing valuable thermodynamic information on the reaction system was compiled.; The experimental results indicated that the Co-Mo sulfided catalyst was a good candidate for the decomposition of H{dollar}sb2{dollar}S to elemental sulfur. In the presence of CO{dollar}sb2{dollar}, the conversion of H{dollar}sb2{dollar}S to elemental sulfur increased significantly and an appreciable amount of sulfur, CO and H{dollar}sb2{dollar} were produced by the present catalytic process. The experimental values were reasonably close to the thermodynamic equilibrium limits. A recycle and/or a hybrid system of catalysis and adsorption may be required for commercial applications. The results also indicated that activated carbon was the best of four tested adsorbents based on the experiments of sulfur vapor adsorption. However, it may be a poor choice of adsorbent since the activated carbon in the reacting environment may participate in the reaction moving the equilibrium in an unfavorable direction. Other non-reacting sorbents may still be applicable since solid powders could be easily transported through the catalytic packed-bed with the proper use of vibrators.; The thermodynamic simulation showed that at least two reaction zones were required for production of any appreciable amount of CH{dollar}sb4{dollar}. The first reaction zone should be composed of multiple stages to recover the elemental sulfur in order to avoid the equilibrium limitations. With an optimum temperature in each zone, the conversion of H{dollar}sb2{dollar}S was increased significantly and less amount of by-products such as COS, CS{dollar}sb2{dollar} and SO{dollar}sb2{dollar} were produced. The results illustrated that the H{dollar}sb2{dollar}S conversion and sulfur yield increased following a logarithmic pattern with the number of stages. The simulation results also indicated that the multiple stage system became more effective at high reaction temperatures.