Hydrogenolysis and ?–elimination mechanisms for C S bond scission of dibenzothiophene on CoMoS edge sites

Unraveling the mechanisms of hydrodesulfurization (HDS) dibenzothiophene (DBT) and corresponding active sites represents a scientific challenge to improve intrinsic performances Co-promoted MoS2 (CoMoS) catalysts. By using density functional theory calculations, we compare two historical for CS bond scission DBT (direct desulfurization): direct hydrogenolysis ?–elimination ?,?–dihydro-diobenzothiophene (?,?–DHDBT) on four relevant CoMoS M- S-edges. On Co promoted M-edge, ?,?–DHDBT is formed through dihydrogenation which kinetically competing with (both exhibiting activation free energies, ?G‡, smaller than +1.24 eV). S-edge, both exhibit higher ?G‡ (>+1.78 Interestingly, (E2 type) found be (?G‡ = +1.14 The elimination H? atom involves S2 dimer close S-vacancy site where DHDBT adsorbed. Since this leaving distinct from one added at step, may explain why desulfurization 4,6-alkyl substituted compounds hampered according mechanism. We finally discuss possible synergy between edges HDS DBT.