Study On Hydrothermal Conversion Of Natural Scenedesmus And Its Product Characteristics

In recent years,due to growing concerns about energy issues,investment in new energy development has increased.Biomass energy has attracted much attention due to its high reserves,wide distribution and environmental friendliness.As a third-generation biomass energy,microalgae has many advantages such as high utilization of photosynthesis,high self-cultivation,less reduction of CO₂ emissions and more conversion pathways..Due to the high water content of microalgae,hydrothermal can directly treat wet biomass and become one of the ways to utilize microalgae energy.In addition,the hydrothermal reaction environment is relatively closed,and the presence of ash will affect the whole reaction system.However,there are few studies on the ash effect in the hydrothermal conversion process of natural microalgae.Therefore,in order to explore the effect of ash on hydrothermal system,the natural snails with ash content of 44.47% were used as raw materials.The effects of different hydrothermal process parameters on the distribution and characteristics of tri-state products were analyzed.The hydrothermal conversion reaction pathway and the utilization value of the product.During the hydrothermal conversion of natural Scenedesmus,the temperature has the most significant effect on the whole reaction.Studies have shown that lipids,proteins and carbohydrates decompose into monomeric substances at low temperatures and gradually polymerize to form heavy oils,but too high temperatures can cause secondary cracking of heavy oils.The hydrothermal reaction gas product is mainly composed of CO₂,and a small amount of CO and hydrocarbon gas are generated at the same time.Proteins and acids undergo intense decarboxylation and deamination reactions during hydrothermal processes.The results of FTIR analysis of solid products show that the vibration peaks of O-H,C-H and C-O increase with temperature,and the dehydroxylation,decarbonylation and deamination reactions are severe.If the temperature is too high,the secondary decomposition will lead to a decrease in content.Heavy oils are mostly based on long-chain aliphatic hydrocarbons.They can be considered as raw materials for refining aviation kerosene.Most of the nitrogenous compounds in light oils have potential as nutrient liquids,while heavy oil products contain high levels of insects.Added value industrial compound.Then the optimal hydrolysis conditions of natural microalgae were explored.Hydrothermal experiments were carried out at 300?,15 min⁷5 min dwell time,1:5¹:25 solid-liquid ratio interval,and the protein and lipid were found in the short residence time.The carbohydrate is hydrolyzed into a monomer,followed by decarboxylation,deamination,and decarbonylation to form a heavy oil attached to the solid.A suitable solid-liquid ratio facilitates sufficient contact between the solvent and the reactants,and too high results in a decrease in energy efficiency between the reactants,which is disadvantageous for decomposition.According to the comprehensive experimental results,from the yield point of view,when the temperature is 300 ° C,the solid-liquid ratio is 1:20,the residence time is 30 min,the bio-oil yield is the highest,which is 44.74 wt%,which is beneficial to the heavy mass under the experimental conditions.The formation of oil.However,from the quality of heavy oil,when the temperature is 300 ° C,the residence time is 45 min,and the solid-liquid ratio is 1:20,the heavy oil has high hydrocarbon content and less nitrogen,and the reaction condition is better.The hydrothermal reaction is beneficial to remove metals such as Na and K in the sample,and the water-heating coke has an efficiency of de-ashing of 20.27 to 20.84% based on the original.When the temperature is 300 ° C,the residence time is 30 min,and the solid-liquid ratio is 1:20,the dissolved ash content is the highest,being 14.15 wt%.The degumming efficiency based on the original is up to 31.67%,indicating that the deashing effect is the most under this condition.it is good.Finally,in order to reveal the influence of ash in the hydrothermal process,the natural Scenedesmus was subjected to acid elution ash treatment,and then comparative experiments were carried out.As the ash content of the genus Hyalin increased,the content of organic matter increased,and the yield of heavy oil after hydrothermal was basically the same as the original.However,at the same temperature,the yield of heavy oil of de-ashing algae increased,indicating that the presence of high ash accelerated the progress of chemical synthesis of heavy oil and reduced the rate of secondary decomposition of heavy oil.When the ash content in the sample is reduced,the content of small molecular substances such as pyridine,pyrazine and its derivatives such as pyridine,pyrazine and its derivatives in water-heated oil is significantly increased at 360 ° C.The total amount of ketones reached 50.25%,indicating that ash is beneficial to inhibit the hydrolysis of proteins and carbohydrates.The carboxylic acid content of the de-ashing algae heavy oil increased overall,the ester content decreased,the content of nitrogen-containing small molecular heterocyclic compound decreased,the nitrogen-containing compound mostly consisted of long-chain fatty acid amide,and the ash promoted acid compounds such as palmitic acid.The formation and hydrolysis of the ester inhibits the formation of a nitrogen-containing heterocyclic compound.The reduction of ash is conducive to the stability of product quality.The results of H1 NMR analysis show that the content of aliphatic functional groups in the hydrothermal heavy oil of the sample after deashing generally increases from 50.99 to 62.26%,while the content of organic matter in hydrothermal coke increases,and water heat at 320?.The focal O/C is the lowest,0.13,and the fuel quality is good.