Trimetallic NiMoW sulfide catalysts by the thermal decomposition of thiosalt blends for the hydrodesulfurization of dibenzothiophene

A series of unsupported trimetallic NiMoW sulfide catalysts were synthesized by ex situ decomposition from mechanically prepared blends of [Ni(en)3]MoS4, a novel precursor, and (NH4)2WS4. N2 adsorption–desorption shows that the NiMoW catalysts are mesoporous materials with characteristic Type IV isotherms, having surface areas of 14.4–52.4 m2/g. Elemental analysis by X-ray energy dispersive spectroscopy (EDS) working in STEM mode finds high carbon/metal ratios (2.3 ≤ C/Mo ≤ 14.2 and 2.2 ≤ C/W ≤ 17.6). The XRD diffractograms of the NiMoW catalysts point to highly dispersed structures, given the absence of the (002) peak, as well as the broad and weakly intense (101) and (110) peaks; the nickel sulfide phase is barely detected. High dispersion is also evidenced by TEM microscopy showing unstacked atomic layers. The catalyst labeled NiMoW-0.20, exhibits the highest catalytic activity (k = 47.7 × 10−7 mol/g s). The NiMoW catalysts follow a zeroth order rate law. Increasing catalyst atomic ratio (more nickel sulfide phase) favors the desulfurization route.