Nickel-Molybdenum-Tungsten Sulfide catalysts prepared by in situ activation of tri-metallic (Ni-Mo-W) alkylthiomolybdotungstates

Abstract

Unsupported nickel-molybdenum-tungsten sulphide catalysts were prepared from tri-metallic Ni-Mo-W alkyl precursors by in situ activation during the hydrodesulphurization (HDS) of dibenzothiophene (DBT). The tri-metallic Ni-Mo-W precursors were prepared by reaction of tetraalkylammonium thiomolibdotungstates salts, (R 4 N) 4 MoWS 8 (where R = H, methyl, propyl, butyl, cetyl-trimetyl), with NiCl 2 in water at a Ni/Mo(W) molar ratio of 2. These precursors are named Ni/(NH 4 ) C 1 , NiMoW-C 3 , NiMoW-C 4 and NiMoW-C C catalysts respectively. These catalysts exhibit a ''Swiss-cheese''-like morphology, a wide distribution of specific areas (from 46.9-194.07 m 2 /g) and high content of carbon (C/Mo = 2.5-8.9). The in situ activation of these tetraalkylammonium thiotrimetallates precursors leads to a mesoporous structure with pore size ranging from 10-40 Å and type IV adsorption-desorption isotherms of nitrogen. X-ray diffraction showed that the structure of unsupported nickelmolybdenum-tungsten sulphide catalysts corresponds to a typical structure of 2H-MoS 2 poorly crystalline with low-stacked layers. The nature of the alkyl group strongly affects both the specific area and the HDS activity. The catalytic activity is strongly enhanced when using carbon-containing precursors; the NiMoW catalysts prepared by in situ activation present high HDS activity. The lowest specific area of the catalysts was observed for the NiMoW-H sample.

Hydrodesulfurization of 4,6-DMDBT on a multi-metallic sulfide catalyst with layered structure

“…However, the pore properties of the NiAlMoW catalysts were better than those of the bulk NiMoW catalysts in the Ref. [22]. It should be noticed that the HDS activities changed with the pore size and pore volume.…”

“…Soled et al have synthesized NiMoW sulfide catalysts by sulfidation of an amorphous Ni-Mo-W oxide precursor prepared by the methods of boiling decomposition, direct precipitation or pH-controlled precipitation [19]. Nava et al have prepared unsupported Ni-Mo-W sulfide catalysts by in situ activation of tri-metallic Ni-Mo-W alkyl precursors during the HDS of dibenzothiophene (DBT) [22].…”

Thermal decomposition of ammonium tetrathiotungstate

“…HDS is the central process to remove sulphur from crude oils. There are several ways to prepare these catalysts, like comaceration [29], homogeneous sulphide precipitation [14], hydrothermal and solvothermal processes [30][31][32][33][34], solution reactions [35,36] and thiosalt decomposition [37][38][39]. With the decomposition of thiotungstates a high sulphur content can be achieved in the final WS 2 catalysts [40,41].…”

“…With the decomposition of thiotungstates a high sulphur content can be achieved in the final WS 2 catalysts [40,41]. Also the controlled composition and wide ranges of achievable surface areas [6,[42][43][44][45] made this method promising for preparing WS 2 catalysts. The thiotungstate precursors can be activated by ex situ or in situ methods.…”

Synthesis, Characterization and HDS Activity of Carbon-Containing Ni–Mo Sulfide Nano-Spheres

“…Catalytic desulfurization is the most common technique used to remove organic sulfur compounds from crude oil [2,3]. Hydrodesulfurization of S-containing compounds, such as thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT), is generally performed with molybdenum and tungsten sulfides supported on alumina and promoted by group VIII elements, such as cobalt or nickel [4][5][6]. Generally, molybdenum and tungsten sulfide catalysts are prepared from oxide precursors by reduction-sulfidation.…”