Synthesis of methacrylate–vinyl acetate–N-phenylmethylpropionamide terpolymers as pour point depressants and combined with methyl palmitoleate to improve the cold flowability of waste cooking oil biodiesel blends

Abstract

Biodiesel, especially waste cooking oil biodiesel, which is economical and widely sourced, is considered to gradually replace petro-diesel by its blend with diesel in a certain ratio, but poor cold flowability is one of the key factors affecting the generalization and application of biodiesel blends. Therefore, studies should exploit new and efficient pour point depressants (PPDs) that can significantly improve the cold flowability of biodiesel blends at small dosages. Herein, a series of methacrylate–vinyl acetate–N-phenylmethylpropionamide terpolymers (RMC-VA-NPM, R = C12, C14, C16, C18) was synthesized by radical polymerization and characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography as PPDs. Then, these PPDs were applied to 20 vol% waste cooking oil biodiesel and 80 vol% petro-diesel (B20), which contained the optimal blend of biodiesel and petro-diesel. In this work, C14MC-VA-NPM (15:1:1) at 2000 ppm showed the best improvement of effect on improving the cold flowability of B20. Correspondingly, the cold filter plugging point (CFPP) and pour point (PP) were reduced by 14 °C and 16 °C, respectively. Notably, the combined PPDs (PPDC-3) composed of C14MC-VA-NPM (15:1:1) and methyl palmitoleate (a component of biodiesel) at a 4:1 mass ratio had a better depressing effect. The 1000 ppm PPDC-3 reduced the CFPP and PP of B20 by 17 °C and 20 °C, respectively. The depressing effects were also compared with previous reports. In addition, B20 with PPDs was used for in-depth mechanism study using differential scanning calorimetry, rheological analysis, and polarizing optical microscopy.