Biodiesel is a clean and renewable fuel with similar characteristics to conventional diesel.However,due to the saturated fatty acid ester in biodiesel is very easy to precipitate and crystallize at low temperature,it has poor low temperature fluidity,so it can not be applied in colder climates and regions.Therefore,it is urgent to improve the low temperature fluidity of biodiesel,that is,to greatly reduce its freezing point and cold filtration point.In this study,two new polymethacrylate pour point depressants were developed to improve the flow capacity of soybean oil biodiesel at low temperature.By measuring its influence on the freezing point and cold filter point of biodiesel,the condensation point reduction effect was analyzed.The main content of this paper is summarized as follows:(1)Four kinds of higher alcohol methacrylates were synthesized by direct esterification method to prepare raw materials for subsequent polymerization reactions.The single factor experiment method was used to discuss the main influencing factors of the esterification yield in detail,and the synthesis conditions were optimized.The structure of the synthesized product was confirmed and characterized by Fourier transform infrared.The yield of higher alcohol methacrylate synthesized under optimal conditions can reach 96.55%.(2)According to the mechanism of low temperature depressant in biodiesel,the synthesis method and raw material monomer are selected.The polymer was synthesized by solution polymerization,and then the pour point depressant effects of different higher alcohol methacrylates as raw materials were investigated and the experimental conditions were optimized.The pour point depressant methacrylic acid and hexadecyl ester-hydroxyethyl methacrylate-maleic anhydride copolymer(AHM)and tetradecyl methacrylate-hydroxyethyl methacrylate-vinyl acetate copolymer(AED)were synthesized.Then the most suitable addition amount and stirring temperature in biodiesel were discussed to maximize the effect of pour point depressant.(3)In light of the method of determining the solidifying point and cold filter plugging point,the degree of improvement of the low temperature fluidity of the two polymers AHM and AED on soybean oil biodiesel was measured.AHM can reduce the solidifying point and cold filter point of biodiesel by 12 ℃ and 8 ℃,and AED can reduce the solidifying point and cold filter point of biodiesel by 8 ℃ and 5 ℃。Then the polymer was characterized by Fourier transform infrared,and the change of wax crystal morphology before and after the biodiesel was added with pour point depressant was observed by polarizing microscope.Through experiments,AHM and AED can inhibit the growth and aggregation of wax crystal of biodiesel,change the spatial structure of crystal,and effectively improve the fluidity of biodiesel in low temperature environment. |