Synthesis of Ni-Mo-W sulphide unsupported HDS catalysts from ex-situ activation of trimetallic precursors: effect of preparation method

Abstract

Trabajo presentado en el International Mexican Congress on Chemical Reaction Engineering, celebrado en Acapulco (México) del 07 al 13 de junio de 2014.Unsupported Ni-Mo-W sulphide hydrodesulphurization (HDS) catalysts were prepared by ex-situ decomposition of trimetallic Ni-Mo-W precursors. The effect of the catalyst preparation method was investigated. Firstly, the trimetallic precursors were treated in a stainless steel vessel of 45 mL volume at 523 K for 2 h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H2S/H2 (15 vol.% H2S) from room temperature to 673 K. A series of four catalysts was tested in HDS of dibenzothiophene (DBT). The catalysts were labeled as Ni0.5, Ni1 and Ni2 according with the molar ratio of Ni in the sample. In addition, a precursor with a molar ratio Ni-Mo-W of 2:1:2 was prepared varying the concentration of tungsten, named as W2. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and BET speci¿c surface area measurements. The ex-situ activation method leads to catalysts with a distribution of speci¿c surface areas from 8 to 34 m2/g, showing type IV adsorption¿desorption isotherms of nitrogen typical for mesoporous materials, and poorly crystalline structures with different morphology, and varying phase composition. The Ni:Mo:W atomic ratios for the trimetallic catalysts show variations and are slightly smaller than those expected. The sample labeled as Ni-Mo-W2 showed the highest catalytic activity in the HDS of DBT (k = 12 x 10-7 mol/g s).Peer Reviewe