Influence of maleic anhydride-co-methyl benzyl acrylate copolymers modified with long-chain fatty amine and long-chain fatty alcohol on the cold flow properties of diesel fuel

•The aminated and esterified MB-MA were synthesized and comparative studied.•Esterified MB-MA have better depression effect than that of aminated MB-MA.•C14MA-MB exhibited the best depression on SP and CFPP at 500 ppm addition.•The performance mechanism of these copolymers in diesel fuel was determined. Precipitation of n-alkanes at low temperatures is the main factor that affects the cold flow properties of diesel fuel. In order to improve the clod flow properties of diesel fuel, maleic anhydride-methyl benzyl acrylate copolymer (MA-MB) were synthesized and modified with long-chain fatty amine and long-chain fatty alcohol (RNH2 and ROH, R = C14, C16, C18) to obtain a series of aminated copolymers R1MA-MB (R1 = N14, N16, N18) and esterified copolymers R2MA-MB (R2 = C14, C16, C18). These copolymers were characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, and proton nuclear magnetic resonance (1H NMR), and the oil affinity and oil solubility were studied by the static contact angle. The influences of them used as pour point depressants (PPDs) on the cold flow properties of diesel fuel were investigated. Results indicate that the esterified copolymers exhibit a better depression effect in depressing the solid point (SP) and cold filter plugging point (CFPP) than that of aminated copolymers. Among that, C14MA-MB exhibited the most considerable reduction on the SP and CFPP by 24 and 8 °C at 500 ppm addition, respectively. In addition, the depression mechanism was explored by differential scanning calorimetry, rheological analysis and polarizing optical microscopy. The analysis shows that C14MA-MB changed the crystal behaviors by modifying the crystal growth direction, restraining the crystal accumulation, and retarding the formation of large crystals, thus enhancing the cold flow properties of diesel fuel. Therefore, the synthesized copolymers are the highly effective PPDs of diesel fuels.