Study On Structure Design,Preparation And Effect Of Bifunctional Additives On Cold Flow Properties And Oxidation Stability Of Biodiesel Blends

In recent years,the global awareness of sustainable development and the government’s vigorous promotion make the petrochemical energy gradually replaced by renewable energy.Among all kinds of liquid alternative energy sources,biodiesel has attracted wide attention due to its higher flash point than petrochemical diesel fuel,non-toxic,biodegradable,renewable and abundant raw materials.The raw materials for preparing biodiesel include oil plant,animal fat or waste cooking oil.Waste cooking oil is more economical to use as biodiesel than other plant and animal feedstocks and is easily available from everyday life,and its properties as a fuel have been heavily studied.In this research,using waste cooking oil biodiesel as raw material,blending method and additive method are used to improve the cold flow properties and oxidation stability of biodiesel blends.The mechanism of the improvement of the cold flow properties of biodiesel blends was explained by means of rheometer,differential scanning calorimeter,and low temperature polarized optical microscope.Rancimat method and 1,1-diphenyl-2-picryl-hydrazyl（DPPH）radical scavenging experiment were used to evaluate the oxidation stability of biodiesel blends,which laid a theoretical foundation for promoting the wide application of biodiesel.（1）A series of copolymers(C₁₄MC-NA)with different molar ratios were synthesized.When C₁₄MC-NA（3:1）was added at 2000ppm,the reduction values of the cloud point（CP）,cold filter plugging point（CFPP）,and pour point（PP）were 3°C,9°C,and 12°C,respectively,but there was no antioxidant effect.C₁₄MC-NA（3:1）was modified with four amines containing antioxidant groups,including 4-aminophenol,4-amino-2-hydroxytoluene,2,2,6,6-tetramethylpiperidine,and 4-aminopperidine,and a bifunctional additive of B20（20 vol%waste cooking oil biodiesel+80 vol%petrochemical diesel fuel）was synthesized.The optimal dosage of C₁₄MC-NA-3 at 2000ppm showed better effects on cold flow properties and oxidation stability.CP,CFPP,and PP were reduced by 5°C,12°C,and 13°C,respectively,and the induction period（IP）was increased from 1.81h to 9.22h.In addition,rheological analysis,differential scanning calorimetry（DSC）analysis,and polarizing optical microscopy（POM）analysis were used to investigate the mechanism of cold flow properties.The antioxidant activity of the bifunctional additive was analyzed by DPPH free radical scavenging experiment.（2）3,5-di-tert-butyl-4-hydroxybenzoic acid（DTBHA）and gallic acid（GA）were grafted onto ethylene-vinyl acetate（EVA）copolymers with different VA contents,and the grafted EVA was used as bifunctional additive of B20（20 vol%waste cooking oil biodiesel+80 vol%petrochemical diesel fuel）.When EVA with 25%VA content（EVA-2）was added at 1500ppm,CP,CFPP,and PP were reduced by 5°C,10°C,and 7°C,respectively.EVA can inhibit the cold flow properties of B20,but has no effect on oxidation stability.GA from natural extraction produced better bifunctional improvement on B20 than EVA grafted by commercial DTBHA.The optimal dosage of EVA-GA-2 was 1000ppm,and the results showed that CP,CFPP,and PP were reduced by 5°C,11°C,and 10°C,respectively.The IP was increased from 1.66h to25.56h.In addition,the mechanism of cold flow behavior was investigated by DSC analysis and POM analysis.The antioxidant activity of the bifunctional additive was analyzed by DPPH free radical scavenging experiment.