Promotion of C-S Bond Scission over Solid Catalytic Sulfides by Aromatics and Nitrogen Heterocycles

The competitive adsorption of aromatics and nitrogen heterocycles on the active sites of solid catalytic sulfides (Ni(Co)-MoS2 dispersed over oxidic carriers) typically causes inhibitory effects during the hydropurification of sulfur heterocycles. Contrary to this typical behavior, we report herein that it is possible to promote the scission of the C-S bond of refractory dibenzothiophene by co?feeding the above compounds during hydropurification over a conventional Ni-MoS2/Al2O3 catalyst. Particularly, we prove that at temperatures between 240 and 300°C and concentrations of dibenzothiophene between 1.0 and 3.7 wt.%, the desulfurization of dibenzothiophene is promoted by increasing its conversion up to 370% when either naphthalene, indole, or quinoline are co-fed to the reaction system. The work highlights the following: (i) lower temperatures and higher concentrations of the sulfur heterocycle enhanced the cleavage of the C-S bond from dibenzothiophene; (ii) it is possible to promote hydropurification reactions regardless of the nature of the of co-reactants; namely: a fused aromatic ring -naphthalene-, or a fused nitrogen heterocycle with a lone pair belonging to the pi-system -quinoline- or not -indole-.