Synthesis and evaluation of alkyl methacrylate-norbornene anhydride copolymers with various pendants as pour point depressants for soybean biodiesel-diesel blends

Abstract

Adding more biodiesel in petrochemical diesel is one of the effective methods to alleviate the global petrochemical energy shortage, but the high-proportional biodiesel-diesel blends are always limited by the poor cold flow properties. To address this issue, a series of alkyl methacrylate-norbornene anhydride copolymers (CnMC-NA, n = 12, 14, 16, 18) with different molar ratios were synthesized as pour point depressants for B30 (30 vol% biodiesel + 70 vol% diesel). Results showed that C14MC-NA (6:1) presented the best depressive effects at 0.2 wt% dosage, and the cloud point (CP), cold filter plugging point (CFPP) and pour point (PP) of B30 have reduced by 3, 9 and 10 °C, respectively. To further improve their depressive efficiency, nine kinds of alcohols were optimized and grafted modification with C14MC-NA (6:1). The effect of these alcoholysis modified copolymers on CP, CFPP and PP of B30 were systematic researched. Results indicated that long-chain alcohols modified C14MC-NA exhibited better depressive effects on B30 than that of aromatic alcohols and short-chain alcohols. Among that, C14MC-NA-C14 at 0.15 wt% dosage exhibited the best reduction on CP, CFPP and PP of B30 by 5, 12 and 15 °C, respectively. Additionally, the mechanism was discussed by polarizing optical microscopy, rheology analysis, differential scanning calorimeter and low-temperature x-ray diffractometer.