Study On Hydrothermal Liquefaction Of Microalgae & Model Compounds In FSCR Combined With Raman Spectroscopy

Recently, the sustainable development has being restricted as a result of climate change, energy crisis and the increasing serious environmental pollution. The long-term sustainable liquid fuels obtained from renewable biomass provided a reliable choice. Many methods of bio oil preparad from biomass was developed by researchers to meet the energy demand. Microalgae was believed to be an ideal raw material for the next generation of energy because of its strong photosynthesis, short growing duration, high growth rate, and arable land-free and high carbon fixation capacity.In this paper, hydrothermal liquefaction phenomena of microalgae and its model compounds in FSCR reactor was observed and recordI of by microscopic imaging system. The products of hydrothermal liquefaction were analysed by Raman Spectroscopy,GC-MS and FT-IR.In the experiment, temperature program of the hydrothermal reaction is as follows:The temperature was rised to 360°C at the heating rate of 50°C/min and retaining time 30 min, and then cooled to room temperature at 10°C/min. The hydrothermal liquefaction process images was collected.The result of hydrothermal liquefaction in FSCR indicated that, the issolution and diffusion of material were main process in the hydrothermal liquefaction with the increase of temperature while the temperature lower than 200°C. different liquefaction phenomena was observed from different raw materials along with the temperature increaseing, which mainly depends on these functional groups. The apparent phenomenon of protein and carbohydrate compounds was more obvious because of its functional groups and polar. The apparent phenomenon of fatty acids were more akin to dissolution and precipitation process of materials with no chemical changes.The chemical information of Dunaliella salina and its liquefaction products were very large and complex.The hydrothermal liquefaction experiment was amplified in quartz glass tube, and the products of hydrothermal liquefaction was analysed by GC-MS and FT-IR. The results of GC-MS show that fatty acidsare the main products, some amides and nitrogen heterocyclic compounds weremixed. The conclusion was also confirmed by FT-IR spectroscopy Hydrothermal liquefaction of model compounds in FSCR was analysed by Raman spectroscopy. The results show that hydrothermal liquefaction of fatty acid without any chemical reaction. Molecular bond of proteins and carbohydrates were destroyed in hydrothermal liquefaction, CO2 was detected in vapor products of glycine and glucose.The results of GC-MS show that fatty acid is high stability in hydrothermal process, and new products was formed in hydrothermal process of glycine and glucose. Co-liquefaction of model compounds shows there was interaction during liquefaction process.Hydrothermal reaction mechanism of microalgae was proposed based on the experiment and related literature: First, amino acids、sugars and fatty acids were obtained from hydrolysis of protein, carbohydrate and lipid. Second, the amino acid, fatty acid and sugar decomposed: gas product CO2 was obtained from decarboxylation reaction of amino acid, epoxidation product was degraded by carbohydrate. Last, the decomposition、 restructuring and polymerization of intermediate product: Gas product CO2 produced by sugar rearrangement, N- heterocycles, pyrrole, pyrazine were obtained from rearrangement of the pyrolysis products from amino acid and carbohydrate, Amide was obtained from rearrangement of fatty acid and the pyrolysis products of amino acid and carbohydrate.