Preparation Of Unsupported Hydrotreating Catalyst And Ultra Deep Hydrodesulfurization Of Gas Oil

In this paper, porous Ni-Mo-W mixed oxides were synthesized by hydro-thermalsynthesis method, and a series of unsupported hydrotreating catalysts were prepared with theNi-Mo-W mixed oxides as precursors. Deep hydrodesulfurization (HDS) of gas oils on anunsupported Ni-Mo-W catalyst was investigated, which would provide theoretical andtechnological supports for the production of ultra clean gas oil.Firstly, the influences of dispersant on the properties of Ni-Mo-W mixed oxides andperformances of the catalysts were investigated. The results showed that, diatomite couldincrease the surface area of catalyst, but was disadvantageous for the preparation of thecatalyst. Adding some alumina or ethanolamine (MEA) as dispersive medium could increasethe pore surface area and volume efficiently, and also improve the HDS activity of thecatalyst.The effects of preparation technology and binders on the properties and activites wereinvestigated. The results showed that, the improved preparation process greatly simplified theprocedure, decreased the pore structure losses of binders efficiently, helped the disperation ofactive metal in the catalyst, and also improved the catalyst strength and HDS activity. Catalystwith pseudoboehmite as binder showed better disperation and larger surface area, and moreMoS2/WS2stacked layers were found in the HRTEM photographs. While the length ofMoS2/WS2in catalyst with diatomite as binder was shorter, and catalytic activity was higher.XPS analysis showed that, Mo species in catalyst could be transformed from Mo6+to Mo4+ofMoS2totally when the catalyst was sulfided and W could not be sulfided completely.The influences of hydrotreating conditions on the HDS efficiency during the deep HDSof FCC gas oil on an unsupported Ni-Mo-W catalyst were investigated. The kinetics of DBTsHDS was studied by hydrotreating a coker gasline and diesel on commercial NiMo/γ-Al2O3 catalyst, and the order of the apparent reaction rate constant of individual sulfur compoundswas DBT>4-MDBT>4-EDBT>3,6-DMDBT>4-E,6-MDBT>2,4,6-TMDBT>4,6-DMDBT. Properties of gas oils produced by different technologies were analyzed andhydrotreating conditions for producing ultra low sulfur diesel (ULSD) from different gas oilswere concluded. FCC gas oil produced by TSRFCC technology was easier to by hydrotreated,while FCC gas oil with high sulfur content and high density produced by MIP-CGPtechnology and Coking gas oil with high sulfur and nitrogen content required more stringentconditions to produce ULSD. In deep HDS products with less than10μg/g sulfur,4,6-DMDBT and2,4,6-TMDBT were the only organic sulfur compounds.FCC gas oil produced by Shenghua Refinery was hydrotreated in a100ml hydrotreatingunit at conditions of temperature340oC, pressure6.0MPa, liquid hourly space velocity1.5h-1, and H2/oil ratio600. On the unsupported Ni-Mo-W catalyst, the sulfur removal efficiencyof gas oil was99.83%, and the nitrogen removal efficiency could reach up to99.96%, whichwere much higher than that on commercial NiMo/Al2O3catalyst (97.68%and93.11%respectively).