Preparation of NiMo/KIT-6 hydrodesulfurization catalysts with tunable sulfidation and dispersion degrees of active phase by addition of citric acid as chelating agent

• Published in: Fuel (Guildford) 2014-08, Vol.130, p.203-210
• Main Authors: Wu, Huadong, Duan, Aijun, Zhao, Zhen, Qi, Dinghong, Li, Jianmei, Liu, Bing, Jiang, Guiyuan, Liu, Jian, Wei, Yuechang, Zhang, Xiao
• Format: Article
• Language: English
• Subjects: 4,6-Dimethyldibenzothiophene; Applied sciences; Catalysis; Catalysts; Chelating; Citric acid; Dispersions; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fuels; Hydrodesulfurization; KIT-6 mesoporous material; Molybdenum disulfide; NiMo catalysts; Selectivity; X-ray photoelectron spectroscopy
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2014.04.038

Novel NiMo hydrodesulfurization (HDS) catalysts were prepared by using the well ordered 3D cubic Ia3¯d mesoporous KIT-6 silica as support and citric acid (CA) as chelating agent. The highest activity for 4,6-DMDBT HDS was obtained over the NiMoKC2 catalyst with CA/Ni=2 due to the enhancement of the hydrogenation (HYD) activity. [Display omitted] •NiMo catalysts supported on KIT-6 were firstly prepared with citric acid (CA).•Dispersion of metal species was improved and could be tuned by the addition of CA.•NiMoKC2 showed the highest hydrogenation and 4,6-DMDBT HDS activity at CA/Ni=2.•The effects of CA on the characteristics and activities of catalysts were deeply studied. A series of NiMo catalysts supported on 3-Dimension cubic Ia3¯d mesoporous KIT-6 silica were prepared by co-impregnation method using citric acid (CA) as chelating agent to adjust the sulfidation and dispersion degrees of active phase. Dried catalysts without calcination were tested in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT). Impregnation solutions, supports, and catalysts were characterized by means of UV–Vis, Raman, TEM, XRD, N2-physisorption, H2-TPR, elemental analysis, XPS, and HRTEM. The addition of CA results in the formation of MoO3(H2cit)− and Ni(Hcit)(cit)3− complexes, which favors the formation of well dispersed active NiMoS phase. Sulfidation and dispersion degrees of the active phase (average slab length and stacking number of MoS2 particles) could be modulated by adding different amounts of CA. The addition of CA exhibited a promotion effect on hydrogenation (HYD) route and activities and selectivities to HYD of different catalysts were related to the CA contents. NiMoKC2 catalyst with the molar ratio of CA/Ni=2 exhibited the highest reaction rate of 3.1×10−4molg−1h−1 and the highest HYD selectivity of 86% in the HDS of 4,6-DMDBT.