Abstract
The formation and aggregation of wax crystals at low temperatures impair the flow and filtration properties of diesel fuel. Comb-like copolymers containing long alkyl side chains can modify wax crystallization and improve the low-temperature performance of diesel fuel. This study aimed to synthesize octadecyl methacrylate-vinylimidazole (ODMA-VI) copolymers with different monomer feed ratios and evaluate their effects on the cold filter plugging point (CFPP), cloud point (CP) and pour point (PP) of diesel fuel. Results and Discussion. ODMA-VI copolymers with ODMA:VI monomer feed ratios of 9:1, 6:1 and 4:1 were synthesized by free-radical solution copolymerization and characterized by 1H NMR, FTIR spectroscopy and gel permeation chromatography. Their effects on the low-temperature properties of diesel fuel were evaluated at dosages ranging from 1000 to 3000 ppm. The observed changes depended on the monomer feed ratio and additive dosage. Among the investigated samples, the copolymer prepared at an ODMA:VI monomer feed ratio of 4:1 resulted in the largest reductions at 3000 ppm, decreasing the CFPP from -7 to -10 °C, the CP from -3 to -8 °C and the PP from -10 to -18 °C. Optical microscopy showed that the copolymer reduced the size and aggregation of wax crystals and promoted their more uniform dispersion in diesel fuel. Conclusion. The results indicate that the ODMA:VI monomer feed ratio influences the depressant performance of the synthesized copolymers. Among the investigated samples, the copolymer prepared at an ODMA:VI monomer feed ratio of 4:1 showed the most pronounced effects on wax-crystal morphology and the measured low-temperature properties of diesel fuel.