Transformation Of Oxygen During The Catalytic Pyrolysis Of Microalgae Polysaccharides

Microalgae is an abundant,green and renewable energy resource over the world.Microalgae can be friendly used with the advantage of high energy efficient comparing to the fossil fuels.The high-quality biofuels and chemicals can be obtained from pyrolysis of microalgal biomass.Current studies have been carried out to investigate the products and kinetic characteristics of microalgae pyrolysis.Unfortunately,few efforts concerning about the pyrolysis mechanism of the single component of microalgae was performed by researchers.Therefore,the oxygen transformation during chlorella polysaccharides pyrolysis was studied systematically to investigate the pyrolysis mechanism of chlorella polysaccharides in this paper.The main contents with conclusions for this study are as follows.Firstly,the yield and oxygen content of each phase were investigated at different temperatures(300 °C,400 °C,500 °C,600 °C).The pyrolysis mechanism of polysaccharides was deduced by FT-IR,GC-MS and TG-FR.The results show that with the increase of temperature,the yield of the solid phase gradually decreased,the yield of gas always increased,the yield of liquid phase first increased and then decreased and reached the maximum at 500 °C(38.8%).the oxygen of the material gradually transfered to the pyrolysis products with the increase of temperature.Wherein the oxygenated compounds of gas phase main included CO2 and CO,the liquid phase were dominated by furans.Secondly,the pyrolysis deoxidation experiment of chlorella polysaccharides with Ca O was operated in the tube resistance furnace.The path of deoxidation reaction of Ca O was investigated comprehensively by FT-IR analysis of coke,gathered from pyrolysis with or without Ca O at different temperatures.The results show that the addition of Ca O reduced the moisture and oxygen content of bio-oil,and improved the quality of bio-oil.FT-IR results indicate that there are two reaction paths in the deoxidation reaction of polysaccharides with Ca O: one is to play an important role in the fixation of carbonyl(C=O)from pyrolysis of chlorella polysaccharide,and the other is to reduce the moisture of liquid productsby generating Ca(OH)2.Finally,the effects of different catalysts(HZSM-5,Zn Cl2,H3PO4,Cu-based oxygen carriers)on the pyrolysis products of polysaccharides were studied.The effects of different ratios of Zn Cl2 and pyrolysis temperatures on oxygenated compounds were investigated to determine the mechanism of directional regulation with Zn Cl2.The results show that the addition of the catalyst can selectively regulate the kind and content of the pyrolysis products of the biomass,and the addition of Zn Cl2 can be used as an effective means to regulate the content of furfural.The relative content of furfural increased with the increase of Zn Cl2 addition,and reached 76.51% when the amount of Zn Cl2 was 18/100.The relative content of furfural increased first and then decreased with the increase of pyrolysis temperature.and the optimum temperature of pyrolysis was 500 °C.