This study investigates the effect on catalytic activity of inserting tungsten metal (W) into trimetallic W-Mo-Co supported on a Gamma-Alumina (γ-Al2O3) heterogeneous catalyst used for hydrodesulphurisation (HDS) in an oil refinery. Bimetallic Co5Mo15/γ-Al2O3 and a trimetallic Co5Mo14W1/γ-Al2O3 catalysts were synthesised using incipient wetness impregnation. The synthesised trimetallic Co5Mo14W1/γ-Al2O3 catalyst exhibited better catalytic performance, with an 88% hydro-removal percentage of sulphur based on an HDS reaction of petroleum naphtha as compared to the 82% for the bimetallic 5Co-15Mo/γ -Al2O3 catalyst under the same operational conditions at a pressure of 11.5 bar, a temperature 598 K, and a reaction time of 3 hr. This enhanced catalyst activity can be attributed to the presence of tungsten increasing the number of metal sites on the catalyst’s reaction surface.

Bimetallic Co5Mo15 of 5 wt.% Cobalt as a promoter and 15 wt.% Molybdenum as an active metal and trimetallic Co5Mo15-xWx (x = 1, 3, 5 wt.%) heterogeneous catalysts supported on gamma alumina (γ-Al2O3) were synthesized by an incipient wetness co-impregnation process. The structural and the physicochemical characteristics of the prepared bi- and tri-metallic catalysts were evaluated by the XRD, SEM, BET and BJH, respectively. The role of third W active metal on the catalytic activity was determined through a hydrodesulfurization (HDS) reaction of naphtha at four different reaction temperatures (250, 275, 300, 325ºC) and four liquid hourly space velocities, LHSV (3, 4, 5, 6 hr-1) under constant 1.5 MPa H2 pressure. The trimetallic CoMoW5 catalyst exhibited the maximal HDS efficiency at 325ºC and 3 hr-1 liquid flow of 88% sulfur removed compared to the CoMo catalyst. This was ascribed for the role of the highly dispersed active W metal and presence of the sulfided CoMoWS and CoWS sites on the alumina surface that leads to increase the surface area and the porous structure, and enhancing the metal/sulfur bond.

In this study, a bimetallic CoMo spicy supported on γ-Al2O3 heterogeneous catalyst was successfully prepared by an incipient wetness impregnation for Hydrodesulphurization (HDS) reaction of An-Najaf oil refinery heavy naphtha. The structural characteristics of the prepared 5Co-15Mo/γ-Al2O3 catalyst were evaluated by Scanning Electron Microscopy (SEM) and X-Ray Powder Diffraction (XRD) spectroscopies. The surface area, pore volume and pore size were determined by a Brunauer–Emmett–Teller (BET) method. The catalytic activity in the removal of sulphur compound from a heavy naphtha through the HDS at four different reaction temperatures (523, 548, 573, 598 °K) and four different liquid hourly space velocities (3, 4, 5, and 6 hr-1) under a constant ratio of 150 mL H2/1 mL naphtha and a hydrogen gas pressure of 1.5 MPa, has revealed that the prepared catalyst was efficient to remove 82 % of sulphur at 598 °K temperature and 3 hr-1 time. The enhanced selectivity of the CoMo/γ-Al2O3 catalyst through a hydro-treating reaction ascribes to the bimetallic-support interaction and the dispersion of MoS2 particles that leaded to a large edge-to-corner ratio of CoMoS slabs.