Evaluation of tetradecyl methacrylate-hydroxyethyl methacrylate copolymers and their synergies with other polymeric pour point depressants to improve cold flow properties of biodiesel blends

Blending biodiesel with petrochemical diesel is an effective method to alleviate the global petrochemical energy shortage, but the application of biodiesel-diesel blends is always hindered by the worse cold flow properties. To resolve this issue, a series of methacrylate-hydroxyethyl methacrylate copolymers (RMC-HEMA, R= -C12, -C14, -C16, -C18) with different molar ratios were synthesized as pour point depressants (PPDs) for B20 (20 vol% biodiesel + 80 vol% diesel). C14MC-HEMA (9:1) showed better cold flow performance at 1000 ppm, reducing the solid point (SP) and cold filter point (CFPP) of B20 by 14 °C and 6 °C, respectively. To obtain higher-efficiency PPDs, two polymers of poly alpha olefin (PAO) and ethylene vinyl acetate copolymer (EVA), as the assistants, were combined with C14MC-HEMA (9:1) in different mass ratios. Results showed that when the weight ratio of C14MC-HEMA (9:1) to PAO was 5:1, the SP and CFPP of B20 decreased by 18 °C and 14 °C at 1000 ppm. Compared to the single C14MC-HEMA (9:1), the SP and CFPP were decreased by 4 °C and 8 °C, respectively. Subsequently, polarizing optical microscopy, differential scanning calorimeter and viscosity-temperature curves were conducted to explore the anti-coagulating mechanism of these PPDs in improving the cold flow fluidity of B20. •Tetradecyl methacrylate-hydroxyethyl methacrylate copolymers (RMC-HEMA, R= -C12, -C14, -C16, -C18) were synthesized as PPDs for biodiesel blends.•Poly alpha olefin (PAO) and ethylene-vinyl acetate copolymer (EVA) were combined with C14MC-HEMA (9:1) to obtain higher depressive effects.•C14MC-HEMA (9:1) combined with PAO in 5:1 showed the greatest reduction on SP and CFPP of B20 by 18 °C and 14 °C.•The synergistic mechanism of C14MC-HEMA (9:1) and PAO in biodiesel blends was discussed.