Effect of Gallium as an Additive Over Corresponding Ni-Mo/γ-Al2O3 Catalysts on the Hydrodesulfurization Performance of 4,6-DMDBT.

ABSTRACT

Experiments were carried out to research the different contents of Ga2O3 modification effects on the hydrodesulfurization (HDS) performance of 4,6-dimethyldibenzothiophene (4,6-DMDBT) catalyzed by the stepwise impregnation method. Characterization techniques such as XRD, BET, HRTEM, NH3-TPD, and Py-FTIR were performed to determine the effects of each modification of the catalyst by Ga on the properties of the prepared supports and catalysts. The catalytic effect of gallium is reflected in the fact that the empty d-orbitals of Ga elements participate in the formation of molecular orbitals in the active center and change their orbital properties, thus generating a direct desulfurization active phase suitable for complex sulfides for endpoint adsorption. The characterization results indicated that the introduction of Ga2O3 with appropriate content (2 wt.%) promoted Ni and Mo species to disperse uniformly and doping of more Ni atoms into the MoS2 crystals, which also increased the average stacking number and the length of MoS2. As a result, more NiMoS active phases were favored to form in the system. The specific surface area and the amounts of acid sites were increased, facilitating the adsorption of reactant molecules and the HDS reactions. The HDS results also suggested the effects of Ga modification play a very important role in the catalytic performance of the corresponding catalysts. The catalyst Ga-Ni-Mo/Al2O3 exhibited the highest conversion rate towards 4,6-DMDBT HDS when the amount of Ga2O3 loading was 2 wt.% with an LHSV of 2.5 h-1 at 290°C and Ga modification also can effectively improve the direct desulfurization (DDS) route selectivity in varying degrees.