Computational and experimental study of the second metal effect on the structure and properties of bi-metallic MeMoS-sites in transition metal sulfide catalysts

Effect of Promoter Nature on Synthesis Gas Conversion to Alcohols over (K)MeMoS2/Al2O3 Catalysts

“…Modification by potassium leads to an increase in synthesis gas conversion on both KNiMoS 2 and KCoMoS 2 catalysts. The increase in activity of KNiMoS 2 correlates with the increase in stability of the Mo−H bond on NiMoS sites on the M‐edge shown in our earlier calculations . The increased Mo−H bond energy is likely to imply an increased Mo–CH 3 bond energy.…”

“…Double sulfide vacancies (Scheme b,c) form on the M‐edge at MeMoS (Me=Fe, Co, Ni) and KMeMoS (Me=Co, Ni) sites, which can participate in synthesis gas conversion. We found that sulfur affinity of double vacancies on the M‐edge of KFeMoS sites was much higher than for Co and Ni analogs . All the (Me)MoS 2 catalysts show comparable activities.…”

“…According to Ref., potassium modification of double vacancies of the M‐edge of FeMoS sites results in the sulfur affinity increase (by the [vac][vac]+H 2 S=H 2 +[vac][S] process) from ∼0.7 eV to ∼1.3 eV. Since the reaction energy [Eq.…”

“…Addition of potassium (referred to as a modifier) increased the Me−S bond strength and decreased the number of vacancies for MoS and FeMoS, but not for CoMoS and NiMoS. On the jnl hand, addition of potassium increased the Me−H bond strength facilitating H 2 activation …”

“…Catalysis occurs mainly on coordinative unsaturated sites (CUS) formed on the edges of (Co/Ni)MoS 2 catalysts. [10,[15][16][17][18][19][20][21][22] Co and Ni promoter atoms located on the MoS 2 crystallite edges participate in the CUS formation. [11,12,[22][23][24][25] Addition of potassium to the (Co/Ni)MoS 2 system reduces metal atoms and increases the MoS 2 slab length and stacking degree.…”