| With increasing depletion of oil resources and the improvement of the people’s awareness of environmental protection, the process to develop and utilize biodiesel to replace fossil fuels was greatly promoted. As a kind of renewable energy, biodiesel has many advantages such as low environmental pollution, and sustainability, therefore, it arouses significantly concerns of the researchers from various countries.Bio-oils are obtained from biomass which employes rapid pyrolysis processing so that the polymer composition of biomass is broken into low-molecular organic vapor which is condensed into a liquid. With high oxygen concentration in the liquid, the unmodified bio-oil is characterized by poor stability, low calorific value, and high viscosity. Moreover, its acidic oxygen-containing compounds can also cause corrosion of the equipments, which affect their wider application to some extent. Therefore, the bio-oil refining is an urgent problem to solve. The core of the refining technology of bio-oil is to remove the oxygen and improve the ratio of H/C. Therefore, the bio-oil has a sufficiently high heat of combustion value and suitable viscosity and pH value. This article conducted a series of interactions on the microalgae pyrolysis oil catalytic hydrotreating.This study prepared hydrodeoxygenation catalyst (NiCoPd/y-Al2O3) by the methods of incipient impregnation accompanied with step-by-step impregnation. In the test, the reduction temperature was determined by the thermogravimetry experiment (TG), and the impact of the impregnation order and the amount of impregnation on the catalyst activity was evaluated by hydrodeoxygenation of Chlorella pyrolysis oil. The results show that under the same evaluation conditions, the catalyst NiCoPd/y-Al2O3with Ni10%, Co3%(mass percentage accounted carrier γ-Al2O3) and (Ni+Co):Pd is15:1(molar ratio) which was prepared by step-by-step incipient impregnation, has good hydrogenation performance. Finally, XRD and SEM analyses of hydrodeoxygenation catalyst were presented, which provided a theoretical basis for exploring the catalytic hydroconversion mechanism of Chlorella pyrolysis oil.The fast pyrolysis of Chlorella was carried out in a fixed-bed reactor. Firstly, the experiment was performed under thermal cracking conditions (The flow rate of N2is0.1L·min-1. Heating rate is25℃·min-1. The final temperature is550℃). Next, the research removed the water in Chlorella pyrolysis oil and measured its performances before hydrogenation. The experiments showed that Chlorella pyrolysis oil has a high moisture content and the oxygen content is up to8.7%, the calorific value, acid value and cetane respectively are as low as25MJ·kg-1,2.5and24.5. The kinematic viscosity is up to30mm2·S-1. To develop a suitable catalytic hydrotreating process for microalgae pyrolysis oil and improve the heating value and cetane number of oil and reduce its viscosity to produce qualified biodiesel, catalytic hydrogenation of Chlorella fast pyrolysis oil is carried out in a fixed-bed reactor using Ni-Co-Pd/γ-Al2O3catalyst. At low hydrogenation pressure(2×106Pa), the experiments examined the influences of the hydrogenation temperature, and H/Oil ratio on water mass percent, the heating value, the viscosity and the cetane of the refined bio-oil. Further, the elemental analysis and GC-MS analysis of the Chlorella pyrolysis oil were carried out. It indicated that, when H/Oil ratio was equal to120:1at300℃and2℃106pa, the refined oil production rate reached86.1%, the calorific value and cetane number increased by17.94%and71.2%compared with the unrefined oil while the viscosity decreased by66.32%. It found that the H/C ratio increased from1.52to1.97, the content of oxygen, nitrogen and sulfur was significantly reduced, and the deoxidation rate reached up to79.97%. The organic acids, esters, ketones and aldehyde ingredients in refined oils were greatly reduced, while the amount of alcohols and alkanes was significantly increased. The quality of refining oil achieved great improvement. |
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