Promoting effects of SO on a NiMo/γ-AlO hydrodesulfurization catalyst

This study details the promoting effects that SO 4 2− has on a NiMo/γ-Al 2 O 3 catalyst prepared using NiSO 4 (CAT-Sulf) as a nickel precursor, compared with the Ni(NO 3 ) 2 (CAT-Nit) and the industrial NiMoP-complex (CAT-NiP) after 600 °C calcination. The three catalysts were characterized by virtue of X-ray diffraction (XRD), thermogravimetry mass spectrometry (TG-MS), N 2 adsorption-desorption, hydrogen temperature programmed reduction (H 2 -TPR), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). Hydrodesulfurization (HDS) activity was assessed using dibenzothiophene (DBT) as the feedstock. On the one hand, compared with CAT-Nit, the SO 4 2− anions could be anchored on the catalyst surface due to their thermal stability and strong interaction with Al 2 O 3 , while few NO 3 − anions could be found. These anchored SO 4 2− anions weaken the metal-support interaction and hinder the formation of NiAl 2 O 4 , thereby facilitating both the sulfidation of Mo species and the decoration of Ni atoms and generating more Ni-Mo-S active sites. On the other hand, compared with CAT-NiP, the residual SO 4 2− anions do not impair the support properties and CAT-Sulf maintains excellent textural structure, i.e. high specific surface area and a proper pore structure. Therefore, CAT-Sulf exhibits the highest dibenzothiophene hydrodesulfurization (DBT-HDS) activity out of the three catalysts. Moreover, these anchored SO 4 2− anions effectively hinder the aggregation and growth of the active phases, thus guaranteeing a catalyst with high metal dispersion and good stability. Finally, using the inferior residual oil as a feedstock, the stability of CAT-Sulf was also assessed compared with an industrial catalyst (CAT-Ref), and the results show that during 1500 h on stream, its HDS ratio is maintained at around 78%, while that of the industrial catalyst (CAT-Ref) declined from ca. 82% to ca. 71% after 1200 h, indicating that CAT-Sulf exhibits much better stability and shows excellent industrial potential. The anchored SO 4 2− anions simultaneously endow the NiSO 4 -derived catalyst with excellent physical structure, high intrinsic activity and good stability, indicating that it might be a simple and effective method to balance the activity and stability of the HDS catalyst using thermostable nickel precursor salts. SO 4 2− anchors to a NiMo/γ-Al 2 O 3 catalyst, weakening the metal-support interactions, inhibiting MoS 2 aggregation