Research on combined-pour point depressant of methacrylate-acrylamide copolymers and ethylene-vinyl acetate copolymers for diesel fuel

Abstract

The combined-pour point depressants (PPDs) have shown potential for the improvement of the cold flow properties of diesel. In this study, free radical polymerization was used to polymerize methacrylate (RMC) and acrylamide (AM) in different molar ratios (1:1, 3:1, 6:1, 9:1, 12:1, 15:1). Methacrylate-acrylamide copolymers (RMC-AM) were synthesized and analyzed through Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and thermogravimetric analysis (TGA) to characterize the copolymers. Through exploring the effect of different chain lengths and different monomer molar ratios on the solid point (SP) and cold filter-plugging point (CFPP) of diesel, C14MC-AM (9:1) showed relatively good performance (ΔSP = 25 °C, ΔCFPP = 10 °C). Then, ethylene–vinyl acetate copolymer (EVA) materials with different VA content were introduced in this study. Diesel treated with 1000 ppm of EVA-2 (VA = 28%) showed relatively good performance (ΔSP = 18 °C, ΔCFPP = 10 °C). C14MC-AM (9:1) was mixed with EVA −2 in different ratios (1:0, 4:1, 2:1, 1:1, 1:2, 1:4, and 0:1, namely, PPDC-1 ~ 7) to produce synergy and improve the cold flow properties of diesel. The ΔSP and ΔCFPP of diesel fuel treated with only 500 ppm PPDC-5 can reach 28 °C and 23 °C, respectively. In addition, the crystallization behavior and crystal morphology of the treated diesel fuel were discussed through differential scanning calorimeter, polarized optical microscope and rheological analysis. The results showed that the combined-PPD made the wax crystals dissolve in the diesel system. The wax crystals became more uniform and denser under the action of AM polar groups.