Thioreduction of cyclopentanone and hydrodesulfurization of dibenzothiophene over sulfided nickel or cobalt-promoted molybdenum on alumina catalysts

On the hydrodesulfurization of FCC gasoline: a review

“…This is in accordance with results reported recently showing that cobalt had nearly no effect and nickel had clearly a promoting effect on the hydrogenation of cyclopentene (Fig. 2) [108] while both had similar effects on the HDS of dibenzothiophene [98]. This may explain why cobalt-promoted catalysts are more efficient than nickelpromoted catalysts in the selective HDS of FCC gasoline.…”

“…This was found with compounds representative of diesel fuel sulfur impurities such as dibenzothiophene or 4,6-dimethyldibenzothiophene [62,98,102,103] [107] were obtained by sulfiding a blend of the cobalt and molybdenum oxides and although the authors considered that the promoting effects they measured were significant (30-40% enhancement in activity), these effects were much weaker than those reported in other studies made with commercial catalysts [104] or with catalysts where at least both sulfide precursors were deposited on the same support [52,53,104,105,106 and references therein].…”

“…This interpretation was recently updated on the basis of ab initio calculations using the density functional theory and a new metal-sulfur bond energy model was proposed [94]. However, the promoter has also an effect on many other reactions catalyzed by sulfides [71,95 and references therein, [96][97][98][99] including the hydrogenation of olefins [71,95 and references therein, 99]. It was also shown that the synergetic maximum (corresponding generally to a promoter/(promoter + Mo (or W)) atomic ratio of about 0.3) could depend on reaction conditions [100].…”

Highly active MoS2, CoMoS2 and NiMoS2 unsupported catalysts prepared by hydrothermal synthesis for hydrodesulfurization of 4,6-dimethyldibenzothiophene

“…This result is in agreement with previous results showing that Ni or Co promotion favors the DDS pathway [41,44,45]. This effect might be explained by an increase of the basicity of sulfur atoms shared between promoter Mo atoms [46]. If the C-S bond cleavage occurs through the attack of a hydrogen atom at the b position relative to the sulfur atom in the organic sulfur molecule by a sulfur anion acting as a basic site [41].…”

Synthesis, Characterization and Catalytic Activity of Supported NiMo Catalysts

“…This behavior indicates that the principal reaction mechanism was towards direct desulfurization (DDS). The NiMo bimetallic catalysts tend towards the direct desulfurization route (DDS) [32,33]. Higher amount of alumina in the catalyst promotes the reaction toward hydrogenated products of DBT indicated by high concentrations of CHB, which is attributed to a promoted acidity of the catalysts [22].…”