Effect Of Fluorine And Phosphorus Promoters On The Hydrodesulfurization Performance Of Nimo Catalysts Prepared By A Complete Liquid-phase Technology

As the diesel vehicles have grown rapidly, the demand on diesel have also increased. But the air pollution caused by diesel fuel consumption is becoming more and more serious. The sulfide in diesel produces SOx compounds through engine which are emitted into the atmosphere. The SOX compounds can cause acid rain and further promote the generation of PM2.5 particles, resulting in serious pollution to the environment. Therefore, the production of ultra low sulfur diesel becomes increasingly important.4,6-Dimethyldibenzothiophene (4, 6-DMDBT) is one of the most refractory molecules to be desulfurized present in the diesel because of its large steric hindrance, so ultra deep hydrodesulfurization of diesel fuel is becoming a hot spot of current research.The catalysts in this article were prepared by complete liquid-phase technology introduced by our research team. Ni-Mo catalysts have poor reproducibility because their materials are easily influenced by the surroundings. Therefore, this paper presents F and P modified catalysts on the basis of previous research. As a result, the dispersion of active components are effectively improved and the generation of unfavorable crystalline phases is restrained, improving the activity and reproducibility of catalysts.Using 4,6-DMDBT as a model reactant, the effect of adding pattern and the amount of fluorine, the amount of phosphorus on performance of NiMo slurry catalysts and the reproducibility of catalysts were studied, the hydrodesulfurization activity of F and P modified catalysts for diesel were also studied. The catalysts were characterized by XRD, NH3-TPD-MASS, H2-TPR, XPS, BET, HRTEM. The main conclusions are as follows:1. In the case of non-existence of nitric acid, the introduction of 3wt.%F or lwt.%P into the slurry catalysts before the introductionof molybdenum and nickel ions can improve the textural property of support and the dispersion of Ni0. The sulfidation degree of Mo and the acid content of catalysts are also raised. So the modified catalysts which exhibit high hydrodesulfurization activity and reproducibility are obtained.2. Adding 3wt.%F into catalyst without the nitric acid before the introduction of active components can improve the dispersion of Ni0 on the surface of catalyst, weaken the interaction between support and mentaland raise the sulfidation degree of Mo and promoting the dispersion of Ni in Mo species, which are helpful to generate the highly active Ni-Mo-S (type â…¡) phase. Also, the catalyst has better textural properties and acid content.3. When the adding amount of P is 1wt.%P, the dispersion of Ni0 on the catalyst surface is greatly promoted, which is beneficial to increasing the hydrogenation activity of catalysts, weakening the interaction between support and mental, improving the sulfidation degree of Mo and the formation of the highly active Ni-Mo-S phase (type â…¡), In addition, the larger surface area, suitable pore structure and the content of acid sites of catalyst are in favor of the adsorption of macromolecular compounds on catalyst surface.4. Repeated experiments have proved that catalysts modified by F and P show good reproducibility and catalysts modified by P exhibit highest activity.5. Catalysts modified by F and P exhibit low activity for diesel fuel compared with simulation process due to the influence of nitrogen compounds. Among them, the catalyst modified by P has higher activity for diesel fuel owing to its high hydrogenation activity and larger surface area.