| Peach kernel is by-products of processed peach products and is usually discarded.In order to improve the utilization rate of peach kernel,this study with peach kernel as raw material,extracted oil from peach kernel by microwave-assisted extraction(MAE)and ultrasonic-assisted extraction(UAE).Peach kernel oil extraction process was optimized by orthogonal test,and the physicochemical properties,fatty acid composition,structure of main functional groups and thermodynamic properties of peach kernel oil were analyzed in order to compare the effect of different extraction method on composition and properties of peach kernel oil.According to the requirements of biodiesel raw oil,the extracted peach kernel oil was refined by Unilever super degumming and esterification deacidification respectively,and the refining process was optimized by orthogonal test.Using refined peach kernel oil as raw material,biodiesel was produced by homogeneous base alkaline catalytic transesterification,and the preparation process was optimized by response surface method.The characteristics of peach kernel oil biodiesel were characterized by fuel characteristics,GC-MS,FT-IR and DSC,and the properties of various aspects of peach kernel oil biodiesel were tested against the national standard requirements,and the feasibility of producing biodiesel from peach kernel oil was evaluated.This study provides a theoretical basis for improving the comprehensive utilization of by-products of peach processing,developing new biodiesel raw materials and reducing the production cost of biodiesel.The main conclusions of this thesis are as follows:The oil yield of 49.23% was obtained under optimum extraction conditions of extraction time 25 min,extraction temperature 75 ℃,microwave power 400 W and liquid to material ratio of 11:1(mL:g)by MAE.The oil yield of 48.56% was obtained under optimum extraction conditions of extraction time 40 min,extraction temperature 75 ℃,ultrasonic power 500 W and liquid to material ratio of 11:1(mL:g)by UAE.The yield of MAE and UAE was slightly lower than 51.87% of that of soxhlet extraction,But the extraction time of them was shortened and the extraction efficiency of them was improved.The physicochemical properties,fatty acid composition,structure of main functional groups and thermodynamic properties of peach kernel oil by MAE and UAE were not significantly different from that of soxhlet extraction method.Peach kernel oil mainly contains oleic acid,linoleic acid and palmitic acid,among which the GC content of oleic acid and linoleic acid is the highest,the sum of them is more than 93%.The degumming rate of peach kernel oil of 87.13% was obtained under optimum degumming conditions of citric acid addition 4%,water 4%,degumming temperature75 ℃,hydration time 20 min.The esterification rate of peach kernel oil of 92.09%was obtained under optimum deacidification conditions of methanol to oil molar ratio of 12:1,catalyst dosage 5%,reaction temperature 60 ℃,reaction time 60 min.The refined peach kernel oil meets the basic conditions of biodiesel production.The conversion rate of peach kernel oil of 97.42% was obtained under optimum transesterification conditions of reaction temperature 68 ℃,methanol to oil molar ratio 7:1,catalyst concentration 1.1%,reaction time 46 min.Peach kernel oil biodiesel is mainly composed of methyl linoleate,methyl oleate,(Z)-hexadecenoic acid methyl ester,methyl trans oleate,methyl stearate,behenicacid methyl ester.The content of unsaturated fatty acid methyl ester is 93.3%.The product has good oxidative stability and low-temperature fluidity,and various fuel characteristics indicators also meet national standards.Therefore,peach kernel oil is an ideal raw material for biodiesel production. |
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