Study On Preparation Of Bio-oil By Thermochemical Conversion Of Microalgae Through Catalytic And Co-pyrolysis

Energy is the basic driving force of the development of human society,the traditional petrochemical energy has disadvantages of not renewable and overused to bring a series of environmental problems,so the developing renewable energy is the key to achieve sustainable development.Biomass is the only renewable energy that can be converted into liquid fuels as well as fixing carbon dioxide,microalgae has broad prospects for development because of its fast growth cycle,no need for land,high photosynthetic efficiency.Bio-oil is a liquid product obtained by thermochemical conversion of biomass,which has been hindered by its shortcomings such as high acid content,high oxygen content,low calorific value and large viscosity.Thermochemical conversion is the most commonly used microalgae conversion method,which includes thermal cracking and hydrothermal liquefaction.In view of the complexity of microalgae components,it is a very effective method to prepare bio-oil by designing appropriate multifunctional catalyst to convert microalgae by catalytic hydrothermal liquefaction;The co-pyrolysis of biomass and other waste polymers has also obtained a wide range of concerns,studying the co-pyrolysis behavior of microalgae and waste plastics as well as other polymers can not only effectively solve environmental pollution problems,but also to enhance the quality of bio-oil.In this paper,we mainly selected microalgae to carry out catalytic hydrothermal liquefaction study,and explored the co-pyrolysis process of the mold compound of D.tertiolecta polysaccharides and plastic in order to find the optimal conditions for the thermochemical conversion of microalgae.The main results are as follows:（1）The multifunctional SBA-15 catalyst,which combines metal,acidic and basic organic functional groups,was successfully synthesized by impregnation-precipitation method and post-grafting method.Among them,Co-SBA-15,SO₃H-Co-SBA-15 and NH₂-SO₃H-Co-SBA-15 have high hydrothermal stability and can maintain intact mesoporous structure at hydrothermal treatment under a maximum of 573K for 1h.（2）When SO₃H-Co-SBA-15 and NH₂-SO₃H-Co-SBA-15 were used as catalysts,the microalgae was catalyzed by hydrothermal liquefaction at 533 K to produce more furfural and its derivatives（up to 35%）,while the contents of acids and N-containing substances were significantly decreased,indicating that these catalysts are conducive to the directional conversion of carbohydrate components.The selectivity of SO₃H-Co-SBA-15and NH₂-SO₃H-Co-SBA-15 to furfural derivatives was enhanced by 16.8%and 9.7%,respectively,by further studying the catalytic effect of multifunctional SBA-15 on the hydrothermal liquefaction of glucose.（3）During the co-pyrolysis process,the pyrolysis interval of PP was determined to be 380-500℃and cellulosic to be 240-380℃by means of thermogravimetric analysis,of which the coincidence degree was low.When PP and cellulose were mixed in solid,the cellulose pyrolysis temperature decreased while PP pyrolysis temperature increased,the interactions were most obvious in the cellulose:PP=5:5.The reactor was designed for investigating the solid-solid,gas-solid and gas-gas reaction of cellulose with PP,and the components of the obtained bio-oil were analyzed.It was found that when cellulose and PP was mixed by gas-gas and solid-solid,the distribution of the product and the distribution of the oil phase components are basically the same,which proves that the synergistic effect is mainly related to the mutual reaction of the gas phase intermediates.The gas phase intermediates produced by the pyrolysis of cellulose may be absorbed by the solid phase PP and lead to the liquid phase yield reduction.