First-principles microkinetic study of methane and hydrogen sulfide catalytic conversion to methanethiol/dimethyl sulfide on MoS clusters: activity/selectivity of different promoters

A large fraction of the global natural gas reserves is in the form of sour gas, i.e. contains hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ), and needs to be sweetened before utilization. The traditional amine-based separation process is energy-intensive, thereby lowering the value of the sour gas. Thus, there is a need to find alternative processes to remove, e.g. , hydrogen sulfide. Mo 6 S 8 clusters are promising candidates for transforming methane (CH 4 ) and hydrogen sulfide into methanethiol (CH 3 SH) and dimethyl sulfide (CH 3 SCH 3 ), which are high-value sulfur-containing products that can be further used in the chemical industry. Here first-principles microkinetics is used to investigate the activity and selectivity of bare and promoted (K, Ni, Cl) Mo 6 S 8 . The results show that methanethiol is produced via two different pathways (direct and stepwise), while dimethyl sulfide is formed via a competing pathway in the stepwise formation of methanethiol. Moreover, there is an increase in activity and a decrease in selectivity when adding an electropositive promoter (K), whereas the reverse behaviour is observed when adding an electronegative promoter (Cl). When adding Ni there is also a decrease in activity and an increase in selectivity; however, Ni is acting as an electron donor. The results provide insights and guidance as to what catalyst formulation is preferred for the removal of hydrogen sulfide in sour gas. A large fraction of the global natural gas reserves is in the form of sour gas, i.e. contains hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ), and needs to be sweetened before utilization.