Supported and bulk phase catalysts are both extensively used in hydrogenation reactions, possess distinct strengths and limitations. Aiming to create a catalyst that combines the benefits of both, a series of NiMoW/SiO 2 catalysts were synthesized with varied metal loadings using SiO 2 supports characterized by different pore structures. The catalytic activities of these catalysts were evaluated using 1-methylnaphthalene, dibenzothiophene and quinoline as model compounds. Comprehensive microstructural characterization was performed through ICP-OES, N 2 physisorption, HRTEM, SEM, and XPS techniques. The investigation revealed that both the catalytic and microstructural properties of the catalysts gradually changed from the supported catalysts to the bulk catalysts with the gradual increase of the metal loadings. This transition was accompanied by a significant enhancement in activity and hydrogenation selectivity compare to the supported catalysts. Nonetheless, this catalyst preserved the benefits of a superior pore structure, straightforward preparation methods and excellent regeneration.
The petroleum refining industry faces increasing challenges in processing sulfur-rich crude oils while meeting stringent environmental regulations. Increasing the metal loading is the most straightforward approach to enhancing catalyst activity. However, under high metal loading conditions, the catalyst tends to form a significant amount of isolated low-activity NiS x and NiO x species. This study presents an effective " sulfidation-oxidation-secondary sulfidation" reconstruction process to enhance the hydrogenation performance of high-loading sulfide NiMoW/SiO 2 catalysts. The migration of active species on the metal surface was induced through high-temperature calcination and sulfur-oxygen transformation processes, leading to the conversion of isolated NiS x and NiO x species into a distinctive NiMoWS/NiS x -SiO 2 composite active phase, with NiS x functioning as a secondary support. Extensive characterization using XRD, HRTEM-EDS, XPS, and DFT calculations revealed that this structural modification substantially increased metal dispersion, sulfidation degree, and hydrogen spillover effects. The optimized NiMoW-300(S) catalyst displayed excellent hydrodesulfurization (HDS) activity and hydrogenation selectivity, with a relative volumetric activity (RVA) 2.49 times higher than that of the conventional NiMo/γ-Al 2 O 3 catalyst, while also demonstrating outstanding stability.
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