Synthesis of dispersed molybdenum disulfide nano-catalysts and their performance in the hydrogenation of simulated oil slurry

A series of dispersed nano molybdenum disulfide (MoS₂) catalysts were prepared with molybdenum dialkyl dithiocarbamate (Mo-DTC) and molybdenum hexacarbonyl (Mo(CO)₆) as the precursors by hydrothermal methods and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (NH₃-TPD). By using a simulated oil slurry containing three kinds of olefins (octane, styrene and trans-dibenzylethene), benzothiophene and anthracene, the catalytic performance of nano MoS₂ in the hydrogenation was investigated, with the help of gas chromatography-mass spectrometry (GC-MS). The results indicate that all the prepared catalysts are in the form of 2H-MoS₂; however, their crystallinity, particle size, vulcanization degree, and acid property are influenced by the pretreatment conditions; the preferred vulcanization conditions for the Mo-DTC-and Mo(CO)₆-based MoS₂ catalysts are 380 ℃/30 min and 370 ℃/30 min, respectively, to achieve a relatively high activity in the hydrogenation of olefins and benzothiophene. Over the Mo-DTC-based nano-MoS₂ catalyst, the saturation conversion of olefins hydrogenation is 98.10% and the hydrodesulfurization rate is 94.51%, whereas the saturation conversion of anthracene hydrogenation is 29.47%, without forming octahydroanthracene (8HN) or perhydroanthracene. In contrast, the activity of Mo(CO)₆-based nano-MoS₂ catalyst is slightly lower, with the saturation conversion of olefins hydrogenation being 94.01% and the hydrodesulfurization rate being 89.01%; similarly, the saturation conversion for anthracene hydrogenation is 24.20%, without 8HN or perhydroanthracene in the product. As a whole, in comparison with the Mo(CO)₆-based MoS₂ catalyst, the nano MoS₂ catalyst derived from Mo-DTC displays higher efficiency in both olefins saturation and sulfur-containing compounds desulfurization, and low degree hydrogenation of aromatic hydrocarbons; moreover, it also exhibits higher hydro-treating selectivity for the catalytic cracking slurry and higher stability during hydrogenation.