Complete Hydrodesulfurization of Dibenzothiophene via Direct Desulfurization Pathway over Mesoporous TiO2-Supported NiMo Catalyst Incorporated with Potassium

Abstract

Mesoporous TiO2 containing different potassium content was prepared from potassium titanate by mediating the pH value of the ion exchange, which was used as catalytic support to load NiMo for hydrodesulfurization of dibenzothiophene. The as-prepared samples were characterized by X-ray diffraction, N2 physical adsorption/desorption, temperature-programmed reduction, scanning electron microscope/energy dispersive X-ray mapping analysis, high resolution transmission electron microscopy, and pyridine-adsorbed Fourier transform infrared spectroscopy. The characterization results showed that NiO and MoO3 were well dispersed on mesoporous TiO2 with varying potassium content. A crystal NiMoO4 phase was formed on the TiO2 with relatively high potassium content, which could decrease the reduction temperature of oxidized active species. The evaluation results from the hydrodesulfurization displayed that as the potassium content of the catalyst increased, the dibenzothiophene conversion firstly increased and then slightly decreased when potassium content exceeded 6.41 wt %. By contrast, the direct desulfurization selectivity could continuously increase along with the potassium content of catalyst. Furthermore, the change in direct desulfurization selectivity of a TiO2-supported NiMo catalyst was independent of the reaction condition. The mesoporous TiO2-supported NiMo catalyst incorporated with potassium could have near both 100% of dibenzothiophene and 100% of direct desulfurization selectivity. According to the structure–performance relationship discussion, the incorporation of potassium species could benefit the formation of more sulfided active species on mesoporous TiO2. Moreover, excessive free potassium species may poison the active sites of the hydrogenation pathway. Both factors determined the characteristics of complete hydrodesulfurization of dibenzothiophene via a direct desulfurization pathway for potassium-incorporated mesoporous TiO2 supported NiMo catalysts.

Effect of Adding Chelating Ligands on the Catalytic Performance of Rh-Promoted MoS2 in the Hydrodesulfurization of Dibenzothiophene

“…The HDS selectivity correlated linearly with the slab length of the MoS 2 phase (TEM), the longer slab length indicated a high ratio of edge/corner and better HDS selectivity, with RhMo/G-Al 2 O 3 presenting the longest slab length [64,77], and the edge sites only catalysed the HDS reaction [78]. The values presented by the current RhMo catalysts (Table 6) exhibit certain benefits and compare well with the other catalysts reported in the literature [79][80][81][82][83][84]. We concluded that the HDS % conversion and desulfurization route was influenced by the catalyst composition, the electronic properties and the HDS reaction conditions.…”

Effect of Different Catalyst Supports on the Quality, Yield and Morphology of Carbon Nanotubes Produced from Waste Polypropylene Plastics

“…The type-H3 hysteresis loop at high relative pressure P/Po, resulting from complete filling and emptying of mesopores by capillary condensation, indicated that all catalysts had slit-shaped mesoporous structures [26,27]. Apart from the NiMo/TiO 2 and NiMo/CaTiO 3 isotherms, other catalysts' isotherms show steep capillary condensation steps, indicating non-uniformity of their mesopores [28]. It could be seen that there was a sudden intersection of the desorption branch with the adsorption branch at a relative pressure of around 0.63 for the NiMo/MgO catalyst, which may be a result of pore blockage due to the different metal cations present in the bulk surfaces, resulting in pores being inaccessible [29,30].…”

“…A similar low-BET surface area of 23.68 m 2 g −1 was reported by [31] for a NiO/TiO 2 catalyst. Li et al [28] also synthesized NiMo-supported TiO 2 catalysts promoted with potassium via the incipient wet impregnation technique and the authors reported a low BET surface area between 39.7 and 45.7 m 2 g −1 for their catalysts. In our previous study [25], NiMo-supported CaTiO 3 catalysts synthesized by the sol-gel method also showed a low BET surface area between 7.7 and 17.4 m 2 g −1 .…”

“…Therefore, the first shoulder peak could be attributed to the complete reduction of weakly bound nickel species in the NiMo and NiO phases from Ni 2+ to Ni 0 and could also be ascribed to the partial reduction of MoO 3 (Mo 6+ to Mo 4+ ). Li et al [28] stated that the reduction of Mo 6+ to Mo 4+ occurs at temperatures below 450 • C. A welldefined high-temperature peak at 659 • C could be attributed to the complete reduction of the MoO 3 -that is, Mo 4+ to Mo 0 species. For NiMo-supported CaTiO 3 and MgO catalysts, the reduction temperatures for the major reduction peaks shifted to higher temperatures, as shown in Figure 4a,d; these results could be attributed to the increased strong interactions between the support and Ni-Mo oxide catalyst structure, resulting in overlapping phases.…”

Mild Preoxidation Treatment of Pt/TiO2 Catalyst and Its Enhanced Low Temperature Formaldehyde Decomposition

“…The crystal structure of various catalysts is studied by XRD. Figure 2a shows five strong diffraction peaks at 25.4 • , 37.8 • , 48.0 • , 53.9 • , and 55.1 • in all catalysts, corresponding to (101), (004), (200), (105), and (211) planes of the anatase phase [28,29], respectively. There are no signals ascribed to other phases of TiO 2 appearing in the XRD spectra.…”