Influence mechanism of catalyst morphology on the active sites of Ni-Mo/ Al2O3 catalyst for ebullated bed residue hydrogenation

With the deterioration of crude oil supply and the introduction of strict environmental regulations, fluidized bed residue hydrogenation technology has attracted widespread attention. Cylindrical and spherical Ni-Mo/Al2O3 catalysts were prepared by the extrusion molding method and the special molding method of STRONG fluidized bed, respectively, and the effect of the catalyst particle morphology on the active phase and residual oil hydrogenation performance was systematically studied. Multiple techniques, including X-ray diffraction (XRD), N2 adsorption-desorption, H2 temperature-programmed reduction (H2-TPR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis (EMPA), were employed to determine the physico-chemical properties of the catalysts. It was found that spherical catalyst had more active Type Ⅱ MoS2 phase, excellent textural properties and better fluidization characteristic, which made it exhibited superior hydrogenation activity than that in cylindrical catalyst. The weaker metal-support interaction in spherical catalyst is beneficial for a higher sulfidation degree and the formation of Ni-Mo-S Type Ⅱ active phase with a higher staking degree. Moreover, the spherical catalyst with a larger pore size and pore volume facilitates the diffusion of larger molecular impurities into the pore and adsorption on the catalyst active sites, which results in a uniform distribution of metal deposits in the spherical catalyst rather than concentrated distribution near the pore mouth. Finally, spherical catalyst with a smaller pore size may be easier to be fluidized, enhancing the mass transfer performance of the catalyst. The results provide new ideas for the design and development of more efficient industrial hydrogenation catalyst based on morphology effect. © 2021, Editorial Board of CIESC Journal. All right reserved.