Influence of mesostructured alumina on the morphology of the active phase in NiWS/Al2O3 catalysts and their activity in hydrotreating of SRGO and VGO

Abstract

Alumina supports were synthesized from aluminum hydroxide produced by the hydrolysis of secondary aluminum butoxide in the presence of the triblock copolymer Pluronic P123 (m-AlOOH) and from the commercial AlOOH pseudoboehmite powder (TH-AlOOH), as well as by mixing of m-AlOOH and TH-AlOOH gel in a ratio of 5:95 (m-TH-AlOOH sample). NiW/Al2O3 catalysts were prepared by impregnation of the synthesized supports with H3PW12O40 heteropolyacid and nickel citrate. Physicochemical properties of the supports and catalysts were investigated by low-temperature nitrogen adsorption, X-ray diffraction, NH3 thermo-programmed desorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Catalytic properties were tested in hydrotreatment of straight-run gas oil and vacuum gasoil on a flow unit. The resulting hybrid support had a non-additively higher average pore radius (75 Å) and surface area (307 m2/g) than a conventional alumina support and hence preferred morphology of NiWS active phase (3.8 nm against 6.6 nm with the same stacking number) and an increase in the W sulfidation degree (68% against 54%) and Ni content in NiWS phase (44% against 26%). Therefore, the catalyst on the hybrid support exhibits higher activity in hydrodesulfurization, hydrodenitrogenation and hydrogenation of petroleum feeds, and a lower degree of deactivation and coke formation.