| Biomass energy has the characteristics of renewable and environment-friendly and so on.China is rich and low utilization in biomass resources.Hydrothermal liquefaction technology has a broad development prospect for the preparation of liquid fuel from wet biomass such as algae biomass.In recent years,many scholars have done a lot of research on the preparation of liquid fuel by hydrothermal liquefaction.There is a lack of systematic research on the separation of downstream process products from hydrothermal liquefaction.The recovery of bio-oil from hydrothermal liquefaction is usually separated by organic solvents,which increases the recovery cost.There is no unified reference standard for the separation of hydrothermal liquefaction products.Different product separation modes will lead to different characteristics of bio-oil and aqueous phase products,even if the materials and process parameters are the same.In order to determine the effects of different separation modes on the characteristics of bio-oil from hydrothermal liquefication of biomass.The hydrothermal liquefaction products from four kinds of biomass under four different separation modes were studied experimentally.The yield and physicochemical properties of separated products were determined.Experimental materials include: Corn straw(lignocellulosic biomass),“Dianchi”algae(high ash microalgae),Spirulina(high protein microalgae),Chlorella(high lipid microalgae);the separation modes are: filtration + extraction(M1),centrifugation + ultrasonic assisted extraction(M2),mixed extraction + phase separation(M3),distillation + ultrasonic assisted extraction(M4).the details are as follows:Firstly,the distribution and recovery of hydrothermal liquefaction products of four kinds of materials by different separation modes were analyzed,the results show that: the bio-oil yield of four biomass from high to low is Chlorella(55.98%),Spirulina(36.62%),Corn straw(10.51%),“Dianchi” algae(8.98%).The highest yield of light bio-oil(water-soluble organic phase)from hydrothermal liquefication of high-protein spirulina is 10.9%.The highest yield of residual bio-oil from hydrothermal liquefaction of Dianchi algae is 41.69%(accounts for the total bio-oil content).The effect of separation mode on the yield of bio-oil show that the yield of bio-oil is the highest in M2 and the lowest in M3.There are significant differences in p H value and total dissolved solids of aqueous phase from M3 and M4.Secondly,the HHV(High heating value),elemental composition and chemical components of bio-oil after separation from hydrothermal liquefication of four kinds of materials were compared and analyzed.The HHV of heavy bio-oil from high to low is Chlorella(40.16MJ/kg),Spirulina(36.99MJ/kg),“Dianchi” algae(35.7MJ/kg),Corn straw(32.77MJ/kg).The highest HHV of light bio-oil from algae is spirulina light bio-oil(29.44MJ/kg).The phenols(49.64%)and ketones(19.02%)are rich in the heavy bio-oil from hydrothermal liquefication of Corn straw.The organic acids(31.72%)and phenols(26.38%)are rich in the light bio-oil of Corn straw.The organic acids and nitrogen-containing compounds are rich in heavy bio-oil from hydrothermal liquefication of algae.The content of fatty acids is as high as 63.55% in heavy bio-oil of Chlorella.The results of bio-oil by1H～NMR is consistent with the results of elemental composition and chemical component analysis.Finally,the effects of different separation modes on the bio-oil from hydrothermal liquefaction of four kinds of materials were analyzed.The effect of separation mode on the HHV of bio-oil is as follows: M1 ≈ M2 > M3 > M4.The results of chemical composition analysis of bio-oil from M1,M3 and M4 show that:M3 bio-oil contains light bio-oil from liquid phase,the HHV of bio-oil by mixed extraction is decrease.The separation mode has obvious effect on the HHV and chemical composition of bio-oil from spirulina.The results of different separation modes on the chemical composition of bio-oil from hydrothermal liquefication show that the content of hydrocarbons is low and the content of organic acid is high in bio-oil of M4.The volatilization of low boiling point hydrocarbons in bio-oil may be caused in the process of distillation separation,thus reducing the HHV of bio-oil from M4.The FT-IR analysis of bio-oil shows that: different separation modes under the same material have little effect on the functional group of bio-oil.The 1H～NMR results of bio-oil further verified the difference of bio-oil quality by different separation modes,which was consistent with the results of elemental analysis and GC-MS analysis.The purpose of this study is to clarify the effects of different separation modes on the hydrothermal liquefaction products of biomass and to recover more organic phase.At the same time,it provides some data support and reference for the preparation of bio-oil by hydrothermal liquefaction of biomass. |
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