(513s) Probing the Role of H2s on CO2 Hydrogenation on MoS2

Natural gas reserves contain large concentrations (>10 % mol) of sour gas molecules, such as H₂S and CO₂. These streams are treated using energy-intensive separation methods to remove sour gas molecules and to preserve downstream catalysts and equipment. We investigate sour gas tolerant catalysts with emphasis on metal sulfides to devise catalytic processes for sour natural gas monetization without the need for CO₂ and H₂S removal. Metal sulfides are active for methane coupling, alcohol production and alkane dehydrogenation in addition to its traditional use in hydrotreating. Specifically, MoS₂ is used in this work to investigate the reverse water gas shift (rWGS) chemistry to activate the CO₂ molecule in the presence of H₂S. In particular, we will present fixed bed reactor studies and transient kinetics experiments with and without H₂S co-feed to measure apparent barriers and reaction orders. Further, to complement the experimental data, we will also present detailed ab initio thermodynamics analysis of MoS₂ edges. Next, we will discuss the effect of acid gases (CO₂,H₂S) on active sites of MoS₂ catalyst for natural gas up-gradation. Our results suggest that the presence of two sites, a very active sulfur-poor site that is susceptible to H₂S and an H₂S-tolerant sulfur-rich site that has a relatively lower hydrogenation activity. In the present work, the mechanism and active sites of the rWGS reaction on MoS₂ has been explored via kinetic experiments and DFT calculations.