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High-efficiency pour point depressants (PPDs) for diesel fuel were obtained using a series of tetradecyl methacrylate-N-α-methacrylamide copolymers (C14MC-NMLR) with different molar ratios synthesized through radical polymerization of tetradecyl methacrylate (C14MC) and various forms of N-α-methacrylamide (NMLR, R = -phenyl, -naphthyl, -cyclohexyl, -14a, -16a, -18a). The copolymers were characterized by Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance, and thermogravimetric analysis. Results showed that diesel treated with C14MC-NML-phenyl (9:1) and C14MC-NML-14a (6:1) presented better cold flow properties at 2000 ppm, and the reductions in cold filter-plug point (ΔCFPP) and solid point (ΔSP) were (23 and 10 °C) and (22 and 11 °C) at 2000 ppm, respectively. The depressive effects further improved after compounding. When they were combined at a 1:4 mass ratio, PPDC-6 presented the best depressive effects, and the ΔCFPP and ΔSP reached 25 and 11 °C at 1000 ppm dosage and 28 and 15 °C at 2000 ppm dosage, respectively. Additionally, the crystallization behavior and crystal morphology of each treated diesel were explored.

In this study, various nonionic surfactants (NS) with different ethylene oxide (EO) numbers and tail lengths and its binary blends with anionic surfactants (AS) were used as emulsifiers for naphthenic oil to form the microemulsion metalworking fluids (MWFs), and the effects of them on the stability of the emulsion system were investigated by formulation triangle method. The results indicated that binary complex surfactants of NS and AS as emulsifiers exhibited better emulsifying effect than that of single NS. NS with different EO numbers and tail lengths presented various emulsifying effects. NS (EO = 10) exhibited the greatest number of stable formulations, especially the TX-10, but no linear relationship existed between the number of stable formulations and the tail length of NS. In addition, aromatic primary alcohol ethoxylate (APAE) series surfactants containing benzene groups similar to the cycloalkanes in the naphthenic oil so that presented the best emulsifying affect and the greatest number of stable formulations. The co-surfactant of sodium dodecyl benzene sulfonate (SDBS) binary blends with NS exerted the best synergistic effect, and the stable formulations numbers were ranged from 5 to 7, next sodium stearate (SS) comes last followed by sodium dodecyl sulfate (SDS-1) and sodium dodecyl sulfonate (SDS-2).

The addition of benzyl methacrylate–methacrylate copolymers to diesel significantly improves its cold flow properties, but it is always limited by a large dosage. To improve the depressing efficien...