Junxing Han

Nanostructured molybdenum carbides supported on carbon nanotubes as efficient catalysts for one-step hydrodeoxygenation and isomerization of vegetable oils

Nanostructured molybdenum carbides supported on multi-walled carbon nanotubes (Mo2C/CNTs) with different loadings were prepared by carbothermal hydrogen reduction method and characterized with SEM, Raman, HAADF-STEM and XRD. Raman spectra showed that the specific G-band structure of carbon nanotubes promoted the formation of molybdenum carbide at lower temperatures. Compared with noble metals, molybdenum carbide exhibited better catalytic activity and resistance to leaching. The Mo2C/CNTs catalyst also showed high activity and selectivity for one-step conversion of vegetable oils into branched diesel-like hydrocarbons, which provided a promising approach to prepare high-grade diesel fuels from renewable resources.

Carbon-Supported Molybdenum Carbide Catalysts for the Conversion of Vegetable Oils

Ordered mesoporous carbon (OMC)-supported molybdenum carbide catalysts were successfully prepared in one pot using a solvent-evaporation-induced self-assembly strategy accompanied by a carbothermal hydrogen reduction reaction. Characterization with nitrogen sorption, small-angle XRD, and TEM confirmed that the obtained materials had high surface areas, large pore volumes, ordered mesoporous structures, narrow pore size distributions, and uniform dispersions of molybdenum carbide particles. With nitrogen replaced by hydrogen in the carbothermal reduction reaction, the formation temperature of molybdenum carbide could be reduced by more than 100 °C. By changing the amount of molybdenum precursor added from less than 2 % to more than 5 %, molybdenum carbide structures could be easily regulated from Mo(2) C to MoC. The catalytic performance of OMC-supported molybdenum carbide catalysts was evaluated by hydrodeoxygenation of vegetable oils. Compared with Mo(2)C, MoC exhibited high product selectivity and excellent resistance to leaching in the conversion of vegetable oils into diesel-like hydrocarbons.

Palladium-catalyzed decarboxylation of higher aliphatic esters: towards a new protocol to the second generation biodiesel production.

An effective and highly selective decarboxylation approach to convert higher aliphatic esters into diesel-like paraffins has been developed. The results showed that palladium supported on barium sulfate was a potent catalyst to transform aliphatic esters into high-energy alkanes in supercritical hexane at a much lower temperature. Based on the comprehensive analysis to gas and liquid products, a decarboxylation mechanism was proposed. The methodology described in this paper provides a new protocol to the utilization of biomass-based resources, especially to the second generation biodiesel production.

Carbon nanofibers supported molybdenum carbide catalysts for hydrodeoxygenation of vegetable oils

Carbon nanofiber-supported molybdenum carbide catalysts (Mo2C/CNF) with different loadings were prepared by the carbothermal hydrogen reduction method. Characterizations with Raman, XRD, N2-TGA, SEM, TEM and HAADF-STEM confirmed that Mo2C nanoparticles were successfully supported on the carbon nanofibers. The optimal reaction conditions with model compounds on Mo2C/CNF had a conversion of 98.03% and yield of 95.26%. It is interesting to note that a low evaporation rate positions the Mo2C nanoparticles on the outside of the CNF due to the capillary effect and the Mo2C nanoparticles on the outside of the CNFs showed high catalytic activity compared to ones on the inside of the CNFs. The Mo2C/CNF catalyst was recycled 5 times without any apparent loss of catalytic activity. Catalytic performances of Mo2C/CNF, Mo2C/AC (activated carbon) and Mo2C/CNT (multi-walled carbon nanotubes) were examined using methyl palmitate and maize oil. The results showed that molybdenum carbide could be a potential substitute for noble metals in transformation of vegetable oils.