Hydrodeoxygenation Of Soybean Oil To The Second Generation Biodiesel Over NiMo/La-Al₂O₃ Catalysts

In order to relieve the dependency on fossil fuels, much attention has been attracted for exploring the development and application of new energy as biodiesel. Until now, biodiesel has been classified into three generations, and especially, the second generation biodiesel has been widely used. Biodiesel is composed of C10-C22 diesel components, which is mainly obtained through hydrogenation of vegetable oil. The hydrotreating process for vegetable oils has been commercialized using a metal sulfide catalyst. Nevertheless, the traditional sulfided catalysts require the addition of sulfur compounds in order to avoid the catalyst deactivation, which also leads to the pollution of products. Therefore, it is worthy for developing an environmental friendly and stable catalyst with high activity and alkanes selectivity.In this thesis, the non-sulfide NiMo catalysts on La modified Al2O3 with different Ni/Mo molar ratios was prepared by impregnation. The structural characterization of the catalysts was performed using X-ray diffraction (XRD), transmission electron microscope (TEM) and N2 physisorption. The results showed that the active species mainly existed in the form of Ni and MoO2 with excellent dispersion. In addition, all of catalysts with a mesoporous structure in the range of 5 to 10 nm were observed.Catalytic distillation of soybean oil was performed for obtaining an overhead oil, which was chose as the feedstock. From the results of infrared spectroscopy (IR) spectra, it was obvious that fatty acids as well as short chain alkanes, and deoxygenated compounds are the main compositions in overhead oil, and the products obtained from hydrodeoxygenation, respectively. The catalytic activities were evaluated in hydrogenation of the overhead oil to investigate the effect of reaction temperature on product distribution and reaction pathway. For all these catalysts, the dominant product was diesel components, and high selectivity of biodiesel (55%-65%) could be achieved. In addition, with increasing reaction temperature, the DCO/DCO2 (Decarbonylation/Decarboxylation) and cracking reaction were enhanced, resulting in an increase in the corresponding products selectivity. The effect of LHSV on products distribution was further explored on NiMo/La-Al2O3(Ni:Mo=8:1) catalyst. Results showed that the catalyst gave the highest selectivity (64%) to biodiesel at 5 MPa, H2/Oil ratio of 600, LHSV of 1.6 h-1,340℃. In addition, it was noteworthy that the addition of Mo led to the enhancement of DCO/DCO2 reaction.In conclusion, the non-sulfide NiMo catalysts exhibited excellent reactivity and biodiesel selectivity in the hydrodeoxygenation of soybean oil, and higher activity and stability for the bimetallic catalysts was also determined. Non-sulfide catalysts are worthy to develop and apply, which plays an important role in the green development of biodiesel.