Hydrotreating of diesel fuel over in-situ nickel modified Y zeolite supported Ni-Mo-S catalyst

In order to further improve the hydrogenation performance of the existing hydrotreating (HDT) catalysts and explore the structure-activity relationship of the catalysts, a series of Ni modified Y zeolites were successfully synthesized by in-situ synthesis method, and the corresponding NiMo catalysts supported on Ni modified Y zeolites and γ-Al2O3 were prepared for diesel fuel hydrotreating. The effect of Ni modification on the properties of the synthesized xNiY zeolites and the corresponding NiMo/AxNiY catalysts were determined by the characterization techniques such as XRD, ICP-AES, N2 physical adsorption-desorption, SEM, UV-Vis DRS, Py-FTIR, HRTEM and XPS. The results show the in-situ modification method can achieve a favorable composite effect of Ni species and the Y zeolites and Ni modification can affect the physical-chemical properties of the synthesized Y zeolites and the NiMo/AxNiY catalysts in varying degrees. Although Ni modification led to a slight decrease in the specific surface areas and pore volumes of the Y zeolites, it can promote the particle uniformity and improve the number of acid sites of the Y zeolites, which are beneficial to the adsorption of sulfide molecules. Moreover, the incorporation of Ni into Y zeolites can also effectively improve the number of acid sites of the prepared NiMo/AxNiY catalysts and improve the stacking number of MoS2 slabs, and enhance the Mo species dispersion, which promote the adsorption and hydrogenation performances of the reactants on the catalysts. Hence, the catalysts containing Ni modified Y zeolites exhibited higher hydrotreating activity compared with the catalyst containing unmodified Y zeolites. Among the four investigated catalysts, the NiMo/A3NiY was found to be the most favorable for the purpose of preparing highly active hydrotreating catalysts for diesel fuels.