Hydrodesulphurization of dibenzothiophene using carbon supported NiMoS catalysts

Hydrodesulphurization (HDS) is the major process used to remove S from crude oil feedstocks in order to improve fuel quality and meet environmental regulations. The goal of this study was to determine if petroleum coke (petcoke), derived from Alberta oilsands, could be converted into a useful catalyst support. Hence the HDS activity and selectivity of nickel molybdenum sulfided catalysts supported on activated carbon (NiMoS/AC), petroleum coke (NiMoS/PC) and conventional alumina (NiMo/γ-Al₂O₃) have been compared using dibenzothiophene (DBT) as a model reactant. The reactions were carried out in a novel slurry-phase batch microreactor at different reaction times (30-120 min) and temperatures (588-638 K) and a fixed H2 pressure (4.8 MPa). The results showed that NiMoS/PC had higher activity towards the HDS of DBT when compared with NiMoS/AC, although the catalysts had very similar product selectivities. The highest activity for DBT HDS, corresponding to 90% DBT conversion, occurred at 638 K for the NiMoS/AC catalyst and at 623K for the NiMoS/PC catalyst. The reaction proceeded by two pathways: the direct desulphurization (DDS) reaction route and the hydrogenation (HYD) reaction route. The power law pseudo 1st-order kinetic model was applied to the HDS of DBT. The estimated kinetic parameters showed similar magnitudes for the HYD versus the DDS routes over both catalysts, whereas the DDS pathway had higher apparent activation energy compared to the HYD route for both catalysts.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat