| Petrochemical energy consumption caused by environmental pollution and energy crisis and other global issues,the development of alternative energy sources of petrochemical energy is the human society and economic sustainable development of the inevitable choice.Biodiesel is a kind of green renewable energy with high calorific value and less pollution.Compared with other biomass,microalgae has the advantages of high carbon sequestration efficiency,short growth period,high oil content,can be large-scale cultivation and not compete with people arable land,and is considered to be the raw material for preparing biodiesel.Nowadays,the preparation of biodiesel based on dry algae has the disadvantages of algal cell collection and drying process is complex and high cost In this paper,We used Chlorella pyrenoidosa(algae mud)as the test material to study the effects of different algae cell wall treatment,algae dehydration,oil extraction and biodiesel preparation methods and related technical parameters,In order to establish an optimized system for the preparation of biodiesel based on algae mud.The main results are as follows:(1)Comparative analysis of six different cell breakage methods,such as freeze-thawing method,acid heat method,biosynthesis method and ultrasonic method,were used to analyze the cell disruption and its lipid extraction rate of C.pyrenoidosa,The result show that ultrasonic method is preferr for C.pyrenoid.(2)we chose the cheap and no secondary pollution of industrial ethanol as dehydrating agent,and systematic optimized C.pyrenoidosa wet algae ethanol dehydration process.Considering the dehydration rate of algae and the loss rate of microalgae fatty acid methyl ester and the cost of preparing biodiesel,the optimum parameters for dehydration of algae(algae mud)were established using ethanol:ethanol concentration 80%,The volume ratio of solution to the volume of algae mud is 1:1.After 1 dehydration,the moisture content of algae mud from 89.04%to 30.52%,can be directly used for subsequent ultrasonic assisted wet extraction of algae oil.(3)The effects of five kinds of algae oil extraction methods on the extraction of C.pyrenoidosa oil(total fat content,fatty acid content,recovery of fatty acids and composition of fatty acids etc.)were studied by using the in situ transesterification method as the reference,and the five methods were compared by Bligh-Dyer method,simplified gravimetric method and ethanol method.etc.)and the relevant parameters(algae powder quality,extraction time,the amount of organic solvents,etc.).The results showed that the improved Bligh-Dyer method not only extracted the total oil and the recovery rate of fatty acid was better than that of other oil extraction methods,but also the fatty acid content and composition of fatty acid were most similar extracted form situ transesterification As the results above,the improved Bligh-Dyer method was used to determine the algae oil of Chlorella pyrenoidosa and the method of determining the total lipid content of algal cells.(4)The optimum technological parameters for the preparation of biodiesel based on the in situ transesterification of C.pyrenoidosa and the dehydration of ethanol were established.We use the biomass of the wet microalgae equivalent to 100 mg of dry algae.that treatment with 400 w for 6 min and then dehydration with 80%ethanol,6 ml of methanol,7 ml of n-hexane,0.5 M H2SO4,reaction temperature of 90? and reaction time of 120 min were added.Using this optimized technology for the preparation of biodiesel based on wet algae,the yield of fatty acid methyl ester was 36.65%(content of cell dry weight). |
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