Characterization of NiMoS and CoMoS nano particle supported TiO2 -Al2O3 catalysts and their HDS performance in single and dual catalytic bed systemAuthor(s): A.H.Samia, S.M.Mohsen,A.S.El-sayed
Synthesis, characterization and catalytic evaluation of NiMo and CoMo supported on titania-modified alumina where carried out. For the synthesis of supportedNiMo and CoMo catalysts, amolybdenumprecursor acidic solution and aqueous nickel(cobalt) nitrate solution was used. The morphological as well as microstructural features of the prepared samples were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) Transmission electron microscope (TEM) and temperature programmed reduction (TPR). Textural properties of supports and catalysts were also characterized by nitrogen physic-sorption. The hydrodesulforization(HDS) process was performed in a fixed bed down flow reactor at varying operating conditions,temperature(320-400 °C), LHSV (0.5-4 h-1), H2/ oil ratio of 450v./v.,and 6MPa operating pressure. Each catalyst was evaluated separately. The most active tow catalysts were tested in dual layer catalytic bed system to achieve the sulfur level less than 15 ppm. TPR spectra of the Co and Ni promoted catalyst showed that Ni promotes the easy reduction of Mo species compared to Co. TEM analysis show how the nature of the promoter as well as the support composition affected the morphology of the active MoS2 phase and influenced its catalytic behavior. The experimental results show that The HDS efficiency reaches a maximum at NiMo/ TiO2 -Al2O3 catalysts with Ti content of 15%, which is consistent with the higher reducibility of TiO2- Al2O3 support and the higher CUS proportion. NiMo catalyst was found to be superior to CoMo catalyst for gas oil HDS. The dual catalytic bed system under respective conditions can be a logical approach to achieve the sulfur level lower than 15 ppm at acceptable reaction conditions.