Synthesis and evaluation of tetradecyl methacrylate-cyclohexyl vinyl ethers-vanilla acrylate ternary copolymers as bifunctional additives to improve the cold flow properties and oxidative stability of biodiesel-diesel blends

Abstract

Poor cold flow properties (CFPs) and oxidative stability (OS) are the major factors limiting the large-scale commercialization of biodiesel-diesel blends. In this study, the binary copolymers of high carbonyl methacrylate-cyclohexyl vinyl ethers (RMC-CVE, R = -C12, -C14, -C16, -C18) and ternary copolymers of tetradecyl methacrylate-cyclohexyl vinyl ethers-vanilla acrylate (C14MC-CVE-VAA) were synthesized as bifunctional additives of cold flow improver and antioxidant to address the poor CFPs and OS of waste cooking oil biodiesel (WCOB)-diesel blends. The effects of these copolymers on the solid point (SP), cold filter plugging point (CFPP) and induction period (IP) of B20 (20 vol% WCOB + 80 vol% diesel) were systematically studied. Results demonstrated that binary copolymer of C14MC-CVE (9:1) exerted the greatest reductions in SP and CFPP by 15 °C and 10 °C, respectively, at a dosage of 2000 ppm, yet it had no significant improvement in the OS of B20. The introduction of third monomers of VAA obviously enhanced the improvement effect on the CFPs and OS of B20, so the ternary copolymers of C14MC-CVE-VAA seem to be an efficient bifunctional additive for biodiesel-diesel blends. At the same dose of 2000 ppm, C14MC-CVE-VAA (9:1:1) presented the better improvement on SP and CFPP of B20 by 17 °C and 11 °C, respectively. Also, the IP of B20 was improved from 1.50 h to 7.46 h. Lastly, the mechanism of the bifunctional additive on improving the CFPs and OS of B20 was investigated by polarizing microscope, viscosity-temperature curve analysis, differential scanning calorimetry, DPPH radical scavenging experiment, and the Rancimat method.