Hydrothermal Liquefaction Of Aquatic Biomass And Upgrading Of Their Resulting Liquefied Oil

As an important type of renewable biomass,aquatic biomass been studied in detail due to its wide distribution,high photosynthetic efficiency,strong environment adaptability,and rapid growth cycle.Aquatic biomass contains a high fraction of moisture after direct harvesting;therefore,the sub/supercritical water processing of aquatic biomass is a potential method for the production of biofuels.In this dissertation,high-moisture aquatic biomass was investigated.The material was first hydrothermally liquefied to produce liquefied oil and then was hydrotreated in supercritical water to remove the nitrogen,sulfur,and oxygen to produce high-quality liquid fuel.The primary research contents and results of this study are detailed below:1.Comparative study of the hydrothermal liquefaction of different aquatic biomasses and upgrading of their resulting oils.First,the hydrothermal liquefactions of eight aquatic plants were examined at 350°C for 1 h to assess the yield and qualities of crude bio-oil.The results suggest that microalgae always produces crude bio-oil with a higher yield than macroalgae due to their higher lipid content;thus,the higher lipid content of microalgae tends to produce a higher yield of crude bio-oil.Next,using tetralin as a hydrogen donor,all eight crude bio-oils were treated at 400°C for 2 h with 10 wt.% Ru/C added under a 1-MPa He environment.The results indicate that the yield of the upgraded bio-oils produced by processing crude microalgal bio-oil are generally higher than those produced by processing crude macroalgal bio-oil.All of the upgraded bio-oils exhibited higher energy densities and lower N,O,and S contents than their corresponding crude bio-oils.The upgraded bio-oils produced from the treatment of crude bio-oil produced from Nannochloropsis species and Enteromorpha prolifera contain lower N,O,and S contents.2.Catalytic upgrading of pretreated algal oil with a two-component catalyst mixture in supercritical water.The activities of several different catalyst mixtures for hydrothermal hydrodeoxygenation and hydrodenitrogenation of pretreated algal oil at 400°C for 4 h were determined using a batch reactor.Coke production was controlled in the presence of most of the two-component catalyst mixtures under these hydrothermal conditions.All of the two-component mixtures exhibited excellent performances with respect to deoxygenation,denitrogenation,and,in particular,desulfurization.The mixtures of Ru/C+Mo2C,Ru/C+Pt/?-Al2O3,and Ru/C+Pt/C performed the best with respect to deoxygenation,denitrogenation,and desulfurization,and produced upgraded oils with O,N and S contents of 0.1,1.8,and 0.065 wt.%,respectively.The upgraded oils consisted primarily of saturated hydrocarbons,which accounted for no less than 40% of the total peak area of the majority of the oils.3.Catalytic upgrading of pretreated algal bio-oil over zeolite catalysts in supercritical water.Nine zeolites(H?,HZSM-5(Si O2/Al2O3=25:1),HZSM-5(SiO2/Al2O3=50:1),HZSM-5(SiO2/Al2O3=170:1),HY(5% Na2O),HY(0.8% Na2O),SAPO-11,MCM-41(50% Si),and MCM-41(100% Si))were screened to investigate their effects on the yields of the product fraction and the properties(e.g.,elemental composition,heating value)of the upgraded bio-oil.The reaction was performed at 400°C for 240 min with the addition of 6 MPa H2 and 10 wt.% zeolite catalyst in supercritical water(?H2O=0.025g/cm3).The catalyst type was found to affect the yields of the product fractions:SAPO-11 produced the lowest upgraded bio-oil yield of 42.4 wt.%,and MCM-41 produced the highest yield of 54.5 wt.%.Compared to non-catalytic upgrading reactions,all of the zeolites promoted the denitrogenation,deoxygenation,and desulfurization of the pretreated bio-oil due to the presence of acid sites.The zeolites HY(5% Na2O),HY(0.8% Na2O),and HZSM-5(SiO2/Al2O3=25:1)showed the highest activities regarding denitrogenation,deoxygenation,and desulfurization,respectively.The upgraded bio-oil primarily consisted of hydrocarbons,accounting for 80% in total and as high as 95.6%of the fraction below 400°C.