Synthesis of Highly Active Co–Mo–S Unsupported Catalysts by a One-Step Hydrothermal Method for p-Cresol Hydrodeoxygenation

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.

Unsupported MoS2-Based Catalysts for Bio-Oil Hydrodeoxygenation: Recent Advances and Future Perspectives

In recent years, unsupported MoS₂-based catalysts have been reported as promising candidates in the hydrodeoxygenation (HDO) of bio-oil. However, preparing MoS₂-based catalysts with both high activity and good stability for HDO reaction is still challenging and of great importance. Hence, this mini-review is focused on the recent development of unsupported MoS₂-based HDO catalysts from the understanding of catalyst design. The three aspects including morphology and defect engineering, metal doping, and deactivation mechanism are highlighted in adjusting the HDO performance of MoS₂-based catalysts. Finally, the key challenges and future perspectives about how to design efficient catalysts are also summarized in the conclusions.

Vacancy Engineering in Transition Metal Sulfide and Oxide Catalysts for Hydrodeoxygenation of Lignin-Derived Oxygenates

The catalytic hydrodeoxygenation (HDO) of lignin has long been a hot research topic and vacancy engineering is a new means to develop more efficient catalysts for this process. Oxygen vacancies and sulfur vacancies are both widely used in HDO. Based on the current research status of vacancies in the field of lignin-derived oxygenates, this Minireview discusses in detail design methods for vacancy engineering, including surface activation, synergistic modification, and morphology control. Moreover, it is clarified that in the HDO reaction, vacancies can act as acidic sites, promote substrate adsorption, and regulate product distribution, whereas for the catalysts, vacancies can enhance stability and reducibility, improve metal dispersion, and improve redox capacity. Finally, the characterization of vacancies is summarized and strategies are proposed to address the current deficiencies in this field.

Low-Temperature Hydrogenation of Toluene Using an Iron-Promoted Molybdenum Carbide Catalyst

As an alternative to noble metal hydrogenation catalysts, pure molybdenum carbide displays unsatisfactory catalytic activity for arene hydrogenation. Precious metals such as palladium, platinum, and gold are widely used as additives to enhance the catalytic activities of molybdenum carbide, which severely limits its potential applications in industry. In this paper, iron-promoted molybdenum carbide was prepared and characterized by various techniques, including in situ XRD, synchrotron-based XPS and TEM. while the influence of Fe addition on catalytic performance for toluene hydrogenation was also studied. The experimental data disclose that a small amount of Fe doping strongly enhances catalytic stability in toluene hydrogenation, but the catalytic performance drops rapidly with higher loading amounts of Fe.

Nanolayered cobalt-molybdenum sulphides (Co-Mo-S) catalyse borrowing hydrogen C-S bond formation reactions of thiols or H2S with alcohols

Nanolayered cobalt-molybdenum sulphide (Co-Mo-S) materials have been established as excellent catalysts for C-S bond construction. These catalysts allow for the preparation of a broad range of thioethers in good to excellent yields from structurally diverse thiols and readily available primary as well as secondary alcohols. Chemoselectivity in the presence of sensitive groups such as double bonds, nitriles, carboxylic esters and halogens has been demonstrated. It is also shown that the reaction takes place through a hydrogen-autotransfer (borrowing hydrogen) mechanism that involves Co-Mo-S-mediated dehydrogenation and hydrogenation reactions. A novel catalytic protocol based on the thioetherification of alcohols with hydrogen sulphide (H2S) to furnish symmetrical thioethers has also been developed using these earth-abundant metal-based sulphide catalysts.

Tailoring the morphology of Co-doped MoS2 for enhanced hydrodeoxygenation performance of p-cresol

Hierarchical Co-doped MoS₂ catalysts with tunable nanostructures were fabricated, which exhibit structure-sensitivity for p-cresol hydrodeoxygenation to hydrocarbons.

MoS2 monolayer catalyst doped with isolated Co atoms for the hydrodeoxygenation reaction

The conversion of oxygen-rich biomass into hydrocarbon fuels requires efficient hydrodeoxygenation catalysts during the upgrading process. However, traditionally prepared CoMoS₂ catalysts, although efficient for hydrodesulfurization, are not appropriate due to their poor activity, sulfur loss and rapid deactivation at elevated temperature. Here, we report the synthesis of MoS₂ monolayer sheets decorated with isolated Co atoms that bond covalently to sulfur vacancies on the basal planes that, when compared with conventionally prepared samples, exhibit superior activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene. This higher activity allows the reaction temperature to be reduced from the typically used 300 °C to 180 °C and thus allows the catalysis to proceed without sulfur loss and deactivation. Experimental analysis and density functional theory calculations reveal a large number of sites at the interface between the Co and Mo atoms on the MoS₂ basal surface and we ascribe the higher activity to the presence of sulfur vacancies that are created local to the observed Co-S-Mo interfacial sites.

Synergistic effect of rare earth metal Sm oxides and Co1−xS on sheet structure MoS2 for photocatalytic hydrogen evolution

The novel composite Sm₂O₃@Co_1−xS/MoS₂ has high photocatalytic activity and stability, the electron transfer and the charge separation were obviously improved with the synergistic effects of Sm₂O₃ and Co_1−xS on the surface of MoS₂.

Highly selective catalytic conversion of phenols to aromatic hydrocarbons on CoS2/MoS2 synthesized using a two step hydrothermal method

CoS₂/MoS₂ composite catalysts were synthesized by two-step hydrothermal method and presented very high hydrodeoxygenation and direct deoxygenation activity in phenols conversion.

Upgrading of anisole using in situ generated hydrogen in pin to plate pulsed corona discharge

In this paper, corona discharge plasma was used for upgrading of anisole as a model compound of lignin derived bio-oil. The required H₂ was generated in situ via methyl decomposition to H₂.