Synthesis of Active Hydrodesulfurization Carbon-Supported Co−Mo Catalysts. Relationships between Preparation Methods and Activity/Selectivity

Abstract

Several series of Co−Mo-based carbon catalysts series were synthesized using three methods, successive impregnation, successive impregnation with sulfidation in between, and equilibrium adsorption methods. Co/C and Mo/C were also prepared by impregnation. The activities of sulfided catalysts for hydrodesulfurization of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) as models of the most refractory sulfur-containing compounds found in petroleum oil were studied using an autoclave reactor operating at 2.9 MPa hydrogen pressure. The activity results were found to be highly dependent on the method of preparation. The series that was prepared by impregnation but with the sulfidation step before the cobalt addition exhibited superior activities for hydrodesulfurization (HDS) of DBT and 4,6-DMDBT. The activity results were compared with that of the conventional commercial Co−Mo/Al2O3 catalyst. Co−Mo/C catalysts had about twice the activity of the commercial catalyst. It was found that the activity of HDS depends on the metal loading as well as the order of metal addition during preparation. The highest synergetic effect between Co and Mo for HDS activity was observed at a Co/Mo atomic ratio of 0.325.

Approach to the Prediction of Some Surface Characteristics of Carbon-Supported CoMo- Catalysts from the Adsorption/Desorption Technique

“…The only products detected in all runs were phenyl- cyclohexane, biphenyl, and the partially hydrogenated dibenzothiophene (H4-DBT), in agreement with results found in the literature (1,3,4). The activity of the catalysts for hydrodesulfurization of dibenzothiophene is represented in Table 3.…”

“…Most of these catalysts consist of transition metals or transition metal oxides loaded on an appropriate support and synthesized via the conventional impregnation. The basic role of which is to maintain the catalytically active phase in a highly dispersed state (1)(2)(3)(4).…”

Fuel Formulation Studies

“…benzothiophenes with no substituents in 2-or 7-position 2. dibenzothiophenes with no substituents in the 4-or 6-position 3. dibenzothiophenes with one substituent in the 4-position 4. dibenzothiophenes with two substituents in the 4-and 6-positions For these distillates to meet the mandated sulfur specifications, all compounds in groups 1, 2, and 3 will have to be completely desulfurized, and at least half of those in the least-reactive fourth group will also have to be converted. Several studies using different types of catalysts and operating conditions have identified 4-methyldibenzothiophene (4-MDBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) as the most refractory sulfur compounds which will have to be eliminated to achieve deep desulfurization [49,50,[63][64][65][66][67][68][69][70].…”

Sulfide Catalysts Supported on Porous Aromatic Frameworks for Naphthalene Hydroprocessing

“…In particular, sulfides of Group VIB (molybdenum and tungsten) and Group VIII (cobalt, nickel) are of great industrial interest due to they are widely used in petroleum refining for hydroprocessing applications. Moreover, these sulfides are active in catalytic coal liquefaction [1], i.e., in breaking up macromolecules into low molecular weight fragments.…”