The Fundamental Research Of Preparing Biofuels Based On Thermal Liquefaction Of Enteromorpha Prolifera

At present, energy and environmental issues are the focus of global. With theincreasing depletion of fossil energy and the worsening environmental degradation,the development of clean energy has became a pressing global issue of the21stcentury. Biomass energy is a new energy, because of the advantages of renewable andlow pollution, it has became a research focus of today’s new energy field. In recentyears, the algae has attracted people’s attention because of its high efficiency ofphotosynthesis, strong ability to adapt the environment, short growth cycle, highbiological yield and other unique advantages.The major conversion and utilization routes of algae biomass include biologicalconversion, thermal chemical conversion and other conversion technologies. Thethermochemical method includes gasification, pyrolysis and direct liquefaction threetechnologies. Because of it need’t to dry raw materials and could abtain high-qualityliquid fuel, and thus the direct liquefaction technology subject to the attention of thepeople. In this paper, Enteromorpha prolifera which was collected at Qingdao inshorewas used as raw material, studied the process of thermal liquefaction.Firstly, the hydrothermal liquefaction of Enteromorpha prolifera wasinvestigated in this study. The results showed that the liquefaction temperature,liquefaction time, solid-liquid ratio and dosage of Na₂CO₃significantly affect theyield of bio-oil and residue. When at the liquid conditions that solid-liquid ratio was1.2:10（g/mL）, dosage of Na₂CO₃amount of Enteromorpha prolifera quality was5%,300°C liquefaction for30min, the bio-oil yield could reach23.6%. The maincomponent of the gaseous products was CO₂, and also contains a small amount of CO,H₂and alkanes. The primary group of the bio-oil were long-chain alkanes andaldehydes, ketones, carboxylic acids compounds, the C element content of the bio-oilas high as75.32%, the O element content was13.36%, and the heating value was31.62MJ·kg-1. The studied on decomposition process of Enteromorpha prolifera in hydrothermal liquefaction showed that the organic matter in Enteromorpha proliferahas started to decompose at the200°C during liquefaction, and the organic mattercould be decomposed completely when liquefaction at300°C for60min.Then ethanol was used as the solvent to the thermal liquefaction. The resultsshowed that the bio-oil yield could be44.8%when at the conditions that solid-liquidratio of was1.0:10（g/ml）, without catalyst and220°C liquefaction for15min.Compared to hydrothermal liquefaction the main component of the gaseous productswas also CO₂. Because of the main compounds of bio-oil were monosaccharidecompounds and ethyl ester compounds caused O element content of the bio-oil up to23.32%. Liquefaction temperature significantly affect the heat value of the bio-oil, thebio-oil heat value was increased with the rise of liquefaction temperature. When theliquefaction temperature was increased from200°C to260°C, the heat valuementioned by19.07MJ·Kg^-1to29.10MJ· Kg^-1.In order to improve the bio-oil yield and quality, the solid acid SO₄^2-/Fe₂O₃wasused in the thermal liquefaction. The results showed that the solid acid couldsignificantly promote the decomposition of Enteromorpha prolifera, bio-oil yield andheat value.When1%solid acid SO₄^2-/Fe₂O₃was added to the system, and thenthermal liquefaction at220℃for15min, the bio-oil yield reached48.5%and it’s heatvalue reached22.80MJ·Kg^-1, and residue yield was35.0%. Compared to without thiscatalyst the bio-oil’s yield and heat value respectively increased by8.3%and9.7%,and the residue yield reduced by14.0%. The component analysis of bio-oil showedthat solid acid SO₄^2-/Fe₂O₃can promote the process of esterification reaction inthermal liquefaction, result in the esters content of the bio-oil increased significantly.The calcining temperature and calcicing time had a significant impact on acid amountand acid strength on solid acid surface, the solid acid SO₄^2-/Fe₂O₃which was preparedat500℃for5h had the most highly catalytic activity.