Hydrodesulfurization of refractory sulfur species .2. Selective hydrodesulfurization of 4,6-dimethyldibenzothiophene in the dominant presence of naphthalene over ternary sulfides catalyst

The catalytic activities of sulfided Ru-CoMo/Al2O3 were examined for the desulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in decane and decane with naphthalene to find selective catalysts which desulfurize 4,6-DMDBT in the presence of naphthalene through preferential hydrogenation of its phenyl ring, Addition of Ru to CoMo catalyst exhibited an excellent activity for HDS of 4,6-DMDBT and suffered less inhibition by coexisting naphthalene, whereas significant retardation was observed over NiMo/Al2O3 and Ru-NiMo/Al2O3. The ternary combination required much less amount of Ru to maximize the selective HDS reaction, compared to the blend of Ru/Al2O3 and CoMo/Al2O3. Several structural characteristics of the ternary catalyst were revealed according to XPS and HREM: (1) Mo and Ru existed separately on the same alumina support in forms of respective sulfides, (2) crystal size of MoS2 increased when Ru was present on the same support, and (3) MoS2 was easily reduced in the presence of Ru. RuS2 is suggested as the site for the selective hydrogenation of 4,6-DMDBT, the hydrogenated product of which is transferred immediately to the Co-Mo-S active site to be desulfurized.