Search

In this work, Co-promoted MoS2 catalysts supported on Al-modified mesoporous silica (HMS and SBA-16) have been prepared by the decomposition of ammonium tetrathiomolybdate and cobalt nitrate precursors in a H2S/H2 gas mixture. The effects of the support morphology and Al incorporation method (one-pot synthesis vs. support's grafting) on the catalyst activity were investigated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) conducted in a high-pressure batch reactor at 350 °C and total H2 pressure of 3.3 MPa. The physical and chemical characterization of the oxide precursors and spent catalysts was studied by a variety of several techniques (N2 adsorption–desorption, XRD, SEM, EDS, 27Al MAS NMR, Raman, TG/DTA and DRS UV–vis). The MoS2 phase of all catalysts exhibits similar size (about 2.8 nm) and stacking layers (4). Activity tests showed that CoAT/HMS-Al was most active and selective toward direct desulfurization (DDS) reaction pathway among the catalysts studied. Its catalytic response was similar to that of CoMo/γ-Al2O3 catalyst activated by reductive sulfiding. A linear correlation was found between DBT conversion at a reaction time of 5 h and the specific surface area and mean pore diameter of the catalysts. The best DBT HDS activity showed CoAT/HMS-Al catalyst having the best textural properties among the catalysts studied. Modification of SBA-16 with Al3+ ions by the one-step synthesis method rendered the catalyst more active in the HDS reaction than its modification by grafting. [ABSTRACT FROM AUTHOR]

Abstract: Phosphate-loaded mesoporous SBA-15 and SBA-16 materials were used as supports of novel ternary Co-Mo-W hydrodesulfurization catalysts. The effects of support morphology (SBA-15 against SBA-16) and its modification with variable amounts of phosphorus were studied. The sulfided catalysts were tested in a reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 350°C and 3.1MPa of total H2 pressure. The calcined, fresh sulfided and spent catalysts were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, TPR, TPD-NH3, DRS UV–vis, micro-Raman spectroscopy, XPS, HRTEM and TPO/TGA). Regardless of the support, it was found that the presence of phosphorous inhibited the HDS activity, and the catalytic response of both SBA-15- and SBA-16-based systems did not depend on the support morphology. In terms of the reaction rate constants (k), both CoMoW/SBA-15 and CoMoW/SBA-16 catalysts were more active than a CoMo/Al2O3 commercial catalyst containing a small amount of phosphorous in its formulation. In general, the spent CoMoW/(x)P-SBA-16 catalysts showed a lower coke formation than their SBA-15-based counterparts because the phosphate incorporation to the SBA-16 material led to decrease in coke formation in the final catalysts, as opposite to the behavior of SBA-15-based counterparts. [Copyright &y& Elsevier]

NiMoS/TiMg and NiWS/TiMg nanocatalysts were synthesized, characterized by various techniques and tested in the hydrodesulphurization (HDS) of dibenzothiophene (DBT). TiMg mixed oxides containing 5, 10 or 15 wt% of MgO were prepared by sol–gel and then used as catalyst supports. A constant atomic ratio of Ni/(Ni + M) = 0.5 was kept for all the catalysts (M = Mo or W). The catalysts were first prepared by sequential-wet impregnation. Then, after an ex-situ sulfidation process, they were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and physisorption of N2 following the BET method. The presence of MgO in the NiMoS/TiMg and NiWS/TiMg catalysts resulted in an enhancement in the HDS activity of DBT. In addition, their HDS activities were higher than those observed in the NiMoS/Ti and NiWS/Ti catalysts. Furthermore, higher HDS activity was found for the NiMoS/TiMg compared with their NiWS/TiMg catalysts counterpart. [ABSTRACT FROM AUTHOR]