(298c) Elucidating the interactions of H2S and CO2 with transition metal sulfide catalysts for natural gas upgrading

Natural gas reserves contain large concentrations (>10 % mol) of sour gas molecules, 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 have been shown to be 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 with the goal of activating CO₂ molecule in the presence of H₂S. In particular, we will present fixed bed reactor studies and transient kinetics experiment with and without H₂S cofeed to measure apparent barriers and reaction orders. Further, in to complement with the experimental data, we will also present detailed ab initio phase diagrams of MoS₂ edges. Next, we will discuss the effect of acid gases (CO₂,H₂S) on reactivity-selectivity of these transition metal sulfide catalyst for natural gas upgradation. Our results suggest that the presence of H₂S induces change in catalyst structure (active sites) and furthermore, it influences the activity and selectivity towards the reaction.The insights from this work can, therefore, will be used to evaluate a spectrum of transition metal sulfide catalysts for upgrading C₁-C₄ hydrocarbons in the presence of CO₂ and H₂S.

Acknowledgment:

This work was supported as part of UNCAGE-ME, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0012577.