The effects of grafted multiple phenolic antioxidants onto polymethacrylate type pour point depressants on the low-temperature flowability and oxidation stability of biodiesel blends

The enhancement of cold flow properties (CFPs) and oxidative stability (OS) in biodiesel-diesel blends typically involves the use of pour point depressants and antioxidants. However, a scant number of additives are capable of manifesting both pour point depression and antioxidant functionalities concurrently. This study explored the grafting of syringic acid (SA), 3,5-di-tert-butyl-4-hydroxybenzoic acid (DTBHA), and gallic acid (GA) onto polymethacrylate (PMA) type copolymers, culminating efficacious copolymers, namely PTG-SA, PTG-DTBHA and PTG-GA. The findings reveal that with the addition of 1500 ppm of PTG-GA, the CFPP and PP of B20 (20 vol% soybean biodiesel+80 vol% diesel) decrease by 10 and 18 °C respectively, and with the addition of 2000 ppm, the induction period (IP) of B20 can be extended from 1.34 to 8.69 h. In contrast, the application of PTG-SA and PTG-DTBHA to B20 led to inferior OS and CFPs as compared to PTG-GA. The inherent scientific mechanism that underlies this performance discrepancy was thoroughly investigated, scrutinizing it through the lens of co-crystallization and nucleation processes. This research underscores the potential of post-modification of PMA type pour point depressants with antioxidants, a strategy that not only bolsters the CFPs of B20 but also confers antioxidant attributes to the pour point depressants.