Improved promoter effect in NiWS catalysts through a molecular approach and an optimized Ni edge decoration

• Published in: Journal of catalysis Vol. 340; pp. 60 - 65
• Main Authors: Alphazan, Thibault, Bonduelle-Skrzypczak, Audrey, Legens, Christèle, Boudene, Zoubeyr, Taleb, Anne-Lise, Gay, Anne-Sophie, Ersen, Ovidiu, Copéret, Christophe, Raybaud, Pascal
• Format: Journal Article
• Language: English
• Published: San Diego Elsevier Inc 01.08.2016; Elsevier BV; Elsevier
• Subjects: active sites; Catalysis; catalysts; Chemical Sciences; crystallites; heat treatment; hydrogenation; Hydrotreatment; Mixed edge sites; nickel; NiWS; salts; Surface chemistry; temperature; toluene; Toluene hydrogenation; transmission electron microscopy; X-ray photoelectron spectroscopy; Toluene hydrogenation; NiWS; Mixed edge sites; Hydrotreatment; Surface chemistry
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2016.05.004

[Display omitted] •High intrinsic hydrogenation activity of Ni promoted WS2 catalyst.•Efficient preparation method using molecular precursors of tungsten and nickel.•Quasi hexagonal morphology of NiWS crystallites highlighted by HAADF-STEM.•Quantification of Ni distribution by a multi-technique approach.•Distribution of Ni promoter atoms at the edge tuned by the preparation method. An efficient preparation method – based on the grafting and deposition of Ni and W molecular precursors onto partially dehydroxylated amorphous silica–alumina followed by a thermal treatment under H2S/H2 – generates supported NiWS catalysts exhibiting enhanced activities in toluene hydrogenation, by comparison with conventional samples, prepared from metallic salts. A careful analysis of these materials by IR, XPS, TEM, HAADF-STEM, together with DFT calculations, reveals that the improved activity probably originates from the lower sulfidation temperature of W that improves distribution of Ni–W mixed sites at the edges of NiWS crystallites. This provides an optimal compromise between intrinsic activity and surface concentration of active sites.