Synthesis Of Pour Point Depressants Based On Maleic Acid Structure And Corresponding Mechanism Analysis

Biodiesel is considered an alternative to traditional fossil fuels because it is environmentally friendly,easy to prepare and renewable.However,because the main component of biodiesel is fatty acid methyl ester,which is easy to denaturate,the cold flow performance of biodiesel is worse than that of fossil diesel at low temperature,which is easy to lead to the generation of sediment,which will block the fuel filter in the vehicle or cause fuel blockage in the fuel pipeline,resulting in fuel shortage in engine operation.In order to solve this problem,the methods of mixing with petrochemical diesel and adding point depressant are mainly adopted.In this paper,biodiesel blended oil（B20）obtained by blending soybean oil biodiesel and diesel oil was taken as the research subject.In order to explore the influence of coagulant on the fluidity of B20 at low temperature,a series of binary copolymers were independently synthesized using methacrylic acid and maleic acid monomers as the coagulant of biodiesel.Through a series of modern testing techniques,the action mechanism of the coagulant in biodiesel mixture was thoroughly explored.（1）Polymers of C₁₄MC-MA,C₁₄MC-MH and C₁₄MC-DM were prepared by free radical polymerization reaction and added as the coagulant of B20.The results show that C₁₄MC-MA,C₁₄MC-MH and C₁₄MC-DM can inhibit the formation and aggregation of wax crystals in B20 at low temperature to a certain extent.Among them,C₁₄MC-MA has the best effect.When the monomer polymerization ratio is 9:1 and the addition amount is 2000 ppm,ΔSP andΔCFPP can reach the maximum value of 14℃and 11℃.DSC,POM and rheological analysis all show that B20 has a great difference before and after adding coagulant.Adding polymer can change the morphology and size of wax crystal in B20,delay the initial precipitation temperature of wax crystal,so as to improve the cold filter point of B20 and reduce the viscosity of B20.（2）In order to further improve the effect and explore the influence of anhydride structure differences on the cold flow performance of B20,C₁₄MC-IA and C₁₄MC-CA were synthesized and added to B20.C₁₄MC-CA had the best performance when the molar ratio was 9:1 and the dosage was1000 ppm,and the CFPP and SP were reduced by 12℃and 14℃,respectively.The inhibition mechanism of copolymer on eutectic reaction was investigated by polarized light microscopy,differential scanning calorimetry and viscosity-temperature curve.The experimental results well support the conclusion that the combination of aldehyde group in C₁₄MC-CA with the long side chain alkyl group given by methacrylic acid has a strong coagulant effect.The unique outer ring methyl group of CA has excellent polarity and solubility,which not only enhances the ability of PPD to adsorb wax crystals,but also changes the crystallization habit and shape of wax crystals,making wax crystals smaller and more uniform.（3）Based on previous studies,we would like to continue to investigate whether it can be combined with many other types of point depressants,dispersants and surfactants to further improve the efficiency without increasing the dosage and explore the effect of different types of point depressants on the low-temperature fluidity of biodiesel blended oil.C₁₄MC-CA with low addition amount and significantly reduced cold filtration point was selected to be mixed with Span series dispersant,EVA coagulant and nano-silica.Only a few C₁₄MC-CA compounds with Span series dispersants and nano silica produced beneficial effects.Among them,Span 80 combined with C₁₄MC-CA at a ratio of 6:1 had the best effect,which could reduce the cold filtration point and condensation point of biodiesel by 16℃ and 17℃.The combination of Nano-silica and C₁₄MC-CA at a ratio of 9:1 has the best effect,which can reduce the cold filtration point and condensing point of biodiesel by 13℃ and 15℃.The combination of C₁₄MC-CA and VA with 25%EVA had the best filtration reduction effect.When the combination ratio was 6:1,the cold filtration point and condensation point of biodiesel could be reduced by 17℃ and 19℃.