Hierarchical TS-1 zeolite loaded with NiMo catalysts: Preparation and performance in hydrodesulfurization

The sole micropores strictly restrict the wide utilization of TS-1 zeolite in the catalytic fields, especially in the catalytic conversion of compounds with large molecular sizes. Here, we report a feasible and economical method to overcome this drawback. In this work, the hierarchical TS-1 zeolite was constructed via post-acid treatment, post-alkali etching, and a combination of post-acid treatment and alkali etching methods, after which, the corresponding NiMo-supported catalysts were prepared via the incipient wetness impregnation method. Then, the aforementioned materials were fully characterized using X-ray diffraction (XRD), N-2 adsorption-desorption, pyridine adsorbed Fourier transform infrared spectroscopy (Py - FTIR), H-2 temperature programmed reduction (H-2 - TPR), X-ray photoelectron spectroscopy (XPS), and high-resolution transition electron microscope (HR-TEM) to unravel the changes in the physicochemical properties caused by the post treatments. Finally, the hydrodesulfurization of dibenzothiophene (DBT) was used as a probe to assess the effects of the post-treatments on the catalytic performance of the hierarchical NiMo/TS-1 catalysts. The results showed that the MFI topology of TS-1 zeolite remained undamaged significantly and the serial hierarchical TS-1 zeolites exhibited higher specific surface areas and mesopore structures. Moreover, appropriate amounts of Bronsted acid sites were formed at the surface of the serial hierarchical TS-1 zeolites. The interaction between the active metals and the support materials was also modulated by the post-treatment of TS-1 zeolite, which resulted in better dispersion of Ni promoted MoS2 slabs with a higher proportion of NiMoS active phase, further leading to the enhanced catalytic activity and direct desulfurization pathway selectivity of the corresponding serial hierarchical NiMo/TS-1 catalysts. Among all the prepared catalysts, the catalytic activity was enhanced by approximately 1.2 times over catalyst NiMo/AT-TS-1 obtained by post-acid treatment compared to that over catalyst NiMo/TS-1 without treatment and on which the selectivity of the DDS pathway was 22% higher compared to that over catalyst NiMo/TS-1.