Application of Heteropolyacid H 4 SiMo 3 W 9 O 40 for the Preparation of Bimetallic MoWS 2 /Al 2 O 3 Hydrotreatment Catalysts

The bimetallic MoWS2/Al2O3 catalyst was synthesized using the Keggin-type mixed heteropolyacid H4SiMo3W9O40. The monometallic catalysts SiMo12/Al2O3 and SiW12/Al2O3 based on the H4SiMo12O40 and H4SiW12O40 acids are prepared as reference samples. The sulfidized catalysts are analyzed by temperature-programmed reduction with hydrogen, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Their catalytic properties are studied in the cohydrotreatment of dibenzothiophene (DBT) and naphthalene on a flow-type setup. The introduction of three molybdenum atoms into the structure of an oxide precursor is shown to increase the degree of sulfidation of the tungsten particles by 20% in comparison with SiW12/Al2O3. The DBT turnover frequency in the hydrodesulfurization (HDS) on the sites on the edges of the active phase of the SiMo3W9/Al2O3 catalyst is shown to be 5.5 times higher than in the presence of SiW12/Al2O3. The bimetallic sample demonstrated the highest selectivity in the preliminary DBT hydrogenation route and activity in the prehydrogenation of naphthalene. The high level of activity of the SiMo3W9/Al2O3 catalyst was due to the formation of a mixed Mo x W(1–x)S2 active phase with a MoW oxide precursor, whose structure contained both metals bonded at the molecular level.