Investigation on halloysite nanotube catalysts for heavy oil hydrotreatment

Within the present study, halloysite nanotube-containing clay (Raw clay) and commercial product (Commercial clay) obtained by treatment the Raw clay from the same mine were investigated in the hydrodesulfurization of heavy oil. Two catalysts with approximately the same HNT content were synthesized: CoMoNi/Clay and CoMoNi/Composite. The former contained a Raw clay mineral as a source of HNT, while the latter − a Commercial clay and a binder (Al₂O₃). CoMoNi/Al₂O₃ was synthesized and used as a reference catalyst. The catalysts were characterized by XRD, N₂-sorption, Hg-porosimetry, FTIR, and Raman spectroscopy. It has been found that catalysts from natural clays have heterogeneity of the phase composition (significant variation in phase composition from one sample to another) and are capable of forming macroporosity by sintering of nonporous phases. In turn, β-CoMoO₄ has been preferably formed on HNT-containing catalyst surface. Catalytic test on hydrotreatment (HT) of a real oil feedstock was performed at 390 and 400 °C, hydrogen pressure at 7 MPa, a product collected after the three-stage HT of atmospheric residue was used as the feedstock. Catalytic tests showed the initial specific activity of the HNT-catalysts was higher compared with traditional catalysts but changed due to high density of the acidic sites and undeveloped texture formed by nonporous phases.