Carbon Materials Supported Molybdenum Carbide For Hydrodeoxygenation Of Vegetable Oil

In recent years, development and utilization of biomass-based energy resources is a hot domain all over the world. Biodiesel is a clean and renewable source of biomass. Vegetable oils, a rich source of renewable resources and existing widely in nature, have the similar structure of diesel that both contain long carbon chain components. Diesel oil is an excellent fuel, which is primarily a mixture of hydrocarbons containing10-22carbon atoms, high heat value of combustion. Vegetable oils are mainly composed of free fatty acids and their corresponding triglycerides. However, they are not suitable for direct combustion in modern diesel engines due to high oxygen content, high viscosity, high cloud point and low stability. Hence natural oils must be upgraded with decarboxylation, decarbonylation or hydrodeoxygenation to obtained diesel-like hydrocarbons.In the present dissertation, we investigated the selective deoxygenation of vegetable oils over a series of carbon materials supported molybdenum-based catalysts. Detailed analysis of the physical and chemical properties of catalysts including their preparations, characterizations, performance tests and corresponding reaction mechanisms were given in the thesis. Some conclusions drawn from the work are provided as follows:(1) Hydrodeoxygenation and isomerization of maize oil were performed in an autoclave using different carbon materials, such as graphene (rGO), carbon nanotubes (CNTs) graphite (G) and fullerene (C60), as supported molybdenum-based catalysts. Nanostructured molybdenum-based catalysts with different phase compositions were prepared by carbothermal hydrogen reduction (CHR) method at different temperature and characterized by Raman, N2adsorption isotherms, SEM, TEM, XRD, XPS, NH3-TPD and H2-TPD. The sp2hybridized carbon materials (rGO, CNTs, G and C6o) and the sp2and sp3hybridized AC carbon material were selected as supports to compare the catalytic activity of molybdenum-based catalysts. Carbon supports played an important role in participating in the reaction, and the Mo/rGO-700catalyst exhibited the best catalytic activity in the hydrodeoxygenation of maize oil. (2) Three kinds of amorphous carbon material structure, order mesoporous carbon, one kind of activated carbon prepared by hydrothermal synthesis and ordinary activated carbon, supported molybdenum-based catalysts were compared the catalytic activity of deoxygenation of maize oil. A preliminary discussion of the structure of the carbon materials in the corresponding molybdenum carbide catalyst prepared for catalytic activity of the deoxygenation reaction was mentioned.(3) Molybdenum carbide catalyst with different loading on carbon nanofibers (Mo2C/CNF) were successfully prepared by "carbothermal hydrogen reduction method". The high deoxygenation activity was obtained on model compound and real vegetable oil system in supercritical n-hexane process. Fatty acid esters, fatty acid and olefin molecules were selected as probes to explore the reaction process of the fatty acid esters into alkanes on molybdenum carbide catalyst, and there was no deactivation detected after five consecutive tests. Based on comprehensive analysis to gas and liquid products, the deoxygenation mechanism of fatty acid esters was proposed, the hydrodeoxygenation was the main reaction route.(4) With graphite and activated carbon as carbon source, the N-added molybdenum carbide catalysts were synthesized by the "carbothermal hydrogen reduction method" and characterized by XRD, Raman and TEM. Preliminary study of the effects of adding or not adding N element on the formation of molybdenum carbide catalyst was carried out. The corresponding catalytic activity in the hydrodeoxygenation of maize oil were compared, the N-added in the catalysts to some extent in favor to improve the activity of the hydrodeoxygenation of maize oil.