Enhancement of dibenzothiophene hydrodesulphurization via hydrogenation route on NiMoW catalyst supported on HMS modified with Ti

Hydrodesulfurization of Dibenzothiophene over Ni-Mo-W Sulfide Catalysts Supported on Sol-Gel Al2O3-CeO2

To achieve sulfur content in gas oil at a near-zero level, new catalysts with improved hydrogenation functions are needed. In this work, new Ni-Mo-Mo hydrodesulfurization (HDS) catalysts supported by Al₂O₃-CeO₂ materials were synthesized to evaluate their efficiency in the reaction of HDS with dibenzothiophene (DBT). Al₂O₃-CeO₂ supports different CeO₂ loadings (0, 5, 10 and 15 wt.%) and supported NiMoW catalysts were synthesized by sol-gel and impregnation methods, respectively. The physicochemical properties of the supports and catalysts were determined by a variety of techniques (chemical analysis, XRD, N₂ physisorption, DRS UV-Vis, XPS, and HRTEM). In the DBT HDS reaction carried out in a batch reactor at 320 °C and a H₂ pressure of 5.5 MPa, the sulfide catalysts showed a dramatic increase in activity with increasing CeO₂ content in the support. Nearly complete DBT conversion (97%) and enhanced hydrogenation function (HYD) were achieved on the catalyst with the highest CeO₂ loading. The improved DBT conversion and selectivity towards the hydrogenation products (HYD/DDS ratio = 1.6) of this catalyst were attributed to the combination of the following causes: (i) the positive effect of CeO₂ in forcing the formation of the onion-shaped Mo(W)S₂ layers with a large number of active phases, (ii) the inhibition of the formation of the undesired NiAlO₄ spinel phase, (iii) the appropriate textural properties, (iv) the additional ability for heterolytic dissociation of H₂ on the CeO₂ surfaces, and (v) the increase in Brønsted acidity.

Deep desulfurization of alkylated oil by alumina adsorbents: characteristics and mechanism study

Deep desulfurization of alkylated oil is the primary problem that has long plagued the petroleum refining industry. In this study, alkaline alumina adsorbent microspheres were synthesized by carbonization - hot oil column pelletization method. The adsorption desulfurization performance of as-synthesized adsorbent and three commercial alumina-based adsorbents were systematically evaluated and compared. The results showed that alkaline alumina adsorbent had the optimal adsorption performance with a saturated adsorption capacity of 8.604 mg·g^-1. Meanwhile, FTIR and sulfur speciation analysis indicated that the alkaline alumina adsorbent could deeply remove various sulfides (methyl mercaptan, dimethyl disulfide, hexacarbon sulfide, dibenzothiophene, <i>etc.</i>) from alkylated oil. Furthermore, the adsorption kinetics study manifested that the adsorption of sulfide was dominated by chemical adsorption, supplemented by physical adsorption, and accompanied by competitive adsorption among different sulfides. In addition, the regeneration experiment showed that nitrogen (90 °C) could realize the stable regeneration of the alkaline alumina adsorbent. To ensure stable regeneration performance in industry, it is recommended that the alkaline alumina adsorbent be regenerated once with nitrogen at 90 °C. This study will provide theoretical support for the process optimization of deep desulfurization of alkylated oil and contribute to the high-quality production of clean fuels worldwide.

Hydrodesulfurization of dibenzothiophene using NiMoWS catalysts supported on Al–Mg and Ti–Mg mixed oxides

In this work, two series of trimetallic NiMoW sulfide catalysts supported on Al–Mg(x) and Ti–Mg(x) mixed oxides with different content of MgO (x = 5, 10, 15 and 20 wt.% of MgO) were synthesized. The mixed oxides and catalysts were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, N2 physisorption and Diffuse reflectance spectroscopy (DRS UV–Vis); and evaluated during the hydrodesulfurization (HDS) of dibenzothiophene (DBT) reaction. The NiMoW/Al–Mg catalysts showed a higher dispersion of Ni, Mo and W species than NiMoW/Ti–Mg catalysts resulting in higher catalytic activities. Catalysts with 10 wt.% of MgO showed the highest catalytic activity for both series of catalysts. Most of the synthesized catalysts exhibited higher activities than NiMoWS/Al–Ti reference catalyst. The present comparison study clearly showed that NiMoW/Al–Mg and NiMoW/Ti–Mg catalyst with 10 wt.% of MgO might be a promising and effective catalyst for the HDS-DBT reaction.