Development of a Magnetically Recyclable Molybdenum Disulfide Catalyst for Direct Hydrodesulfurization

Review of Molybdenum Disulfide Research in Slurry Bed Heavy Oil Hydrogenation

With the growing demand for gasoline and diesel fuel and the shortage of conventional oil reserves, there has been extensive interest in upgrading technologies for unconventional feedstocks such as heavy oil. Slurry bed reactors with high tolerance to heavy oil have been extensively investigated. Among them, dispersive MoS₂ is favored for its excellent hydrogenation ability for heavy oil even under harsh reaction conditions such as high pressure and high temperature, its ability to effectively prevent damage to equipment from deposited coke, and its ability to meet the requirement of high catalyst dispersion for slurry bed reactors. This paper reviews the relationship between the structure and hydrogenation effectiveness of dispersive molybdenum disulfide, the hydrogenation mechanism, and the improvement of its hydrogenation performance by adding defects and compares the application of molybdenum disulfide in heavy oil hydrogenation, desulfurization, deoxygenation, and denitrification. It is found that the current research on dispersive molybdenum disulfide catalysts focuses mostly on the reduction of stacking layers and catalytic performance, and there is a lack of research on the lateral dimensions, microdomain regions, and defect sites of MoS₂ catalysts. The relationship between catalyst structure and hydrogenation effect also lags far behind the application of MoS₂ in the precipitation of hydrogen, etc. Oil-soluble and water-soluble MoS₂ catalysts eventually need to be converted to a solid sulfide state to have hydrogenation activity. The conversion history of soluble catalysts to solid-type catalysts and the key to their improved catalytic effectiveness remain unclear.

Nickel Cobalt Thiospinel Nanoparticles as Hydrodesulfurization Catalysts: Importance of Cation Position, Structural Stability, and Sulfur Vacancy

First-row transition metal-based thiospinels are prepared via a one-pot versatile strategy and for the first time investigated as hydrodesulfurization (HDS) catalysts. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis confirm that these thiospinels consist of agglomerated nanoparticles (NPs) and contain multivalent metal cations. Among the sulfides synthesized at 230 °C, NiCo₂S₄ presents the highest thiophene conversion. This high intrinsic activity is found to be correlated with the normal spinel structure with Ni cations located on the tetrahedral sites and Co cations on the octahedral sites. However, the spent NiCo₂S₄ NPs experience phase transformation because of the relatively low synthetic temperature. Accordingly, six NiCo₂S₄ samples are prepared in the temperature range of 180-350 °C, and their HDS activity increases monotonically with the synthetic temperature, which is attributed to the higher structural stability and more surface sulfur vacancy of the NiCo₂S₄ NPs prepared at higher temperatures. Notably, the NiCo₂S₄ NPs synthesized at 350 °C exhibit a much higher thiophene conversation of 62.9% than the classic MoS₂ catalyst (39.3%) as well as excellent reusability. Our study suggests that the NiCo₂S₄ thiospinels with high activity and stability can represent a new promising class of industrial HDS catalysts.

Towards active macro–mesoporous hydrotreating catalysts: synthesis and assembly of mesoporous alumina microspheres

Stable macro–mesoporous alumina formed via a pore-directing-agent-free molding process shows promise for the hydrotreatment of heavy oils.