Study On Fine Separation Of Bio-Oil By Cascade Extraction And Its Hydrotreating

Under the background of the world energy crisis,and the long-term goals of"carbon peak"and"carbon neutrality",biomass as the only carbon-containing renewable resource has attracted more and more attention.Bio-oil obtained by rapid pyrolysis of biomass has the potential to be used as green fuel because of its renewability,low sulfur,nitrogen content,and neutral combustion with CO₂balance.However,compared with conventional fuel oil,due to the disadvantages of higher oxygen content,low acidity,viscosity,and calorific value,bio-oil must be upgraded before subsequent application.Because of the complex composition of bio-oil,this paper proposes a new upgrading strategy for the first step-extraction of bio-oil and then hydro-upgrading of the extract phase.The specific research contents and results are as follows:（1）The core of bio-oil extraction and separation is the selection of extractant,and it is necessary to search for a suitable extractant to realize the separation of two-phase bio-oil.After a large number of solvents were screened,water and dichloromethane were finally selected as extractants to achieve step extraction of bio-oil in different extraction sequences,and the bio-oil was divided into twelve extraction phases.A full understanding of the physical properties of the bio-oil extract phase and its composition was accomplished through a series of characterizations.（2）Based on the characterization results of the bio-oil extraction phase,a water-soluble bio-oil phase（WSBO）was selected for the study of catalytic hydrorefining based on thermochemical and electrochemical means.In the process of thermochemical hydrodeoxygenation（HDO）,the Pd/C catalyst enriched the product with alcohol hydroxyl groups,the Pt/C catalyst had the most significant effect on the carbonization and deoxygenation of WSBO,and the Ru/C catalyst could effectively increase the content of low-carbon compounds in the product.Electrochemical hydrogenation（ECH）upgrading using Ru/NF,Pt/NF,and Pd/NF catalysts has a poor reduction effect on sugars in WSBO,but Ru/NF catalysts can significantly improve the corrosion,stability,and coking properties of the oil.（3）Due to the low specific surface area of Ru/NF catalysts,the impregnation method was used to load the Ru active phase onto the Ni-Ni O-Al₂O₃/NF composite support prepared by the evaporation-induced self-assembly method,and smaller Ru particles were successfully prepared and dispersed a high degree of Ru/Ni-Ni O-Al₂O₃/NF catalyst with high specific surface area.The effect of Ni content in the catalyst on the ECH performance of WSBO was also investigated.The catalyst with a Ni content of 10%has the best effect on WSBO hydrogenation,carbonization,and deoxidation,while the catalyst with a Ni content of 30%has the worst conductivity,which makes the hydrogen-to-carbon effective ratio(H/C_eff)of the oil after ECH lower,and when the Ni content is 40%,the content of sugars and carbonyl compounds in the oil can be significantly reduced,the content of alcohol hydroxyl groups can be increased,the stability of the oil can be improved,and the H/C_eff of WSBO after hydrogenation can be the highest.