13^th World Congress on Chemistry April 25-26, 2022 Barcelona, Spain

Hydrotreating (HDT) is considered to be the most direct and effective techniques to realize the efficient conversion of inferior heavy oil into light products and high value-added chemical raw materials. And hydrodenitrogenation (HDN) is regarded as the most difficult and representative reaction in the heavy oil HDT process. In order to further improve the HDN performance of the existing HDT catalysts and explore the structure-activity relationship of the catalysts, γ-Al₂O₃ supports were modified with a Ti/Al molar ratio of 1 by three different methods: the mechanical mixing method, the ion-exchange method and the in-situ synthesis method, and the corresponding NiW supported HDT catalysts were prepared via incipient wetness co-impregnation method. The effects of Ti modification on the physicochemical properties of the prepared supports and catalysts were determined by the characterization techniques such as XRD, FTIR, N₂ physical adsorption-desorption, SEM, Py-FTIR, H₂-TPR, HRTEM and XPS. Finally, quinoline, indole and coker gas oil (CGO) were used respectively as probes to investigate the Ti modification on the HDN performances of the corresponding catalysts. The results show that the introduction of TiO₂ into γ-Al₂O₃ would changes the pore properties and reduces the acid strength of the supports, weakens the interaction between the active metals and the supports (MSI), and can promote the formation of more so-called “type II” NiWS active phases and enhance the sulfidation degrees of active metals. According to the study on different Ti modification methods, we found that the in-situ synthesis method realizes the molecular composition of titanium and aluminum elements, showing the most favorable composite effect, followed by the ion-exchange method, and the mechanical mixing method was found to exhibit the worst composite effect. And Ti³⁺ species were found in the sulfided catalysts prepared by in-situ synthesis method and ion-exchange method. This leads to the fact that in terms of the promotion of active metal dispersion and sulfidation degrees, the in-situ synthesis method is always the best, followed by the ion exchange method and finally the mechanical mixing method. The catalytic assessment results show that the HDN activities of the catalysts were effectively improved after Ti modification and the HDN activities are consistent with the composite effect of titanium and aluminum elements