Separation Analysis And Liquefaction Research Of Seaweed Polysaccharides

Energy reserves are dramatically reduced with the rapid development of society.However,the excessive use of fossil energy has caused serious energy crisis and environmental pollution.Under the dual pressures of energy crisis and environmental protection,people find that biomass energy is a new form of energy which is clean,pollution-free,abundant and renewable.Terrestrial plants and seaweed are used as raw materials during Biomass conversion and utilization.Algae has many advantages,such as strong photosynthesis,short regeneration period and no occupation of cultivated land.Therefore,it is feasible economicly on the transformation and utilization.In recent years,the thermochemical conversion of algae to produce high-quality fuel oil has became a hot spot of widespread concern.There is high content of protein in seaweed.This will lead to a large amount of nitrogen-containing compounds in liquid fuel abtained from algae.Nitrogen-containing compounds can not only influence fuel properties but also produce much NO_x,that will aggravate environmental pollution.In this study,Enteromorpha prolifera polysaccharides were extracted from Enteromorpha prolifera and protein was removed during extraction.Direct deoxy-liquefaction of Enteromorpha polysaccharides was carried out at 350?.The results showed that compared with the liquid oil from Enteromorpha prolifera liquefaction,the content of oxygen and nitrogen in the liquid oil from polysaccharide liquefaction decreased greatly,and the higher heating value increased from 40.29MJ/kg to 44.26MJ/kg.Therefore,it is feasible to prepare biofuels which contain large amounts of alkanes by pyrolysis and recombination of algal polysaccharides.The compositions of polysaccharides from different species of algae are different,which can result in the different components and properties of liquid fuel.In this study,Green algae polysaccharides,carrageenan and sodium alginate were extracted from Ulva vulgaris,Cauliflower and Undaria pinnatifida,separately.Three kinds of polysaccharides were converted into liquid oils by deoxy-liquefied,which were analysed by using GC-MS and FTIR.Based on the comparison of higher heating value,oxygen content,alkane content,nitrogen content of the three liquid oils and the difficulty of polysaccharide purification,it can be concluded that sodium alginate is more suitable for preparing liquid biofuels.Catalysts have great influence on the efficiency of algae deoxygenation,the yield and quality of liquid oils.In this paper,HZSM-5/MCM-41 composite zeolite catalyst was synthesized using HZSM-5 microporous molecular sieve.HZSM-5/MCM-41 was modified by Ni and Mo,respectively.The catalysts were characterized by SEM,FTIR,N₂ adsorption-desorption and NH₃-TPD,respectively.Then,all catalysts were used in deoxy-liquefaction of Enteromorpha prolifera.The results showed that the qualities of liquid oils were obviously improved by using molecular sieve catalysts.Among the sts,liquid oils catalized by NiMoHZSM-5/MCM-41 had the lowest nitrogen?0.38%?and oxygen?4.97%?contents,the highest heating value?45.80 MJ/kg?and alkane content?27.30%?.