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

Adding more biodiesel in petrochemical diesel is one of the effective methods to alleviate the global petro-chemical 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 degrees 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-C-14 at 0.15 wt% dosage exhibited the best reduction on CP, CFPP and PP of B30 by 5, 12 and 15 degrees C, respectively. Additionally, the mechanism was discussed by polarizing optical microscopy, rheology analysis, differential scanning calorimeter and low-temperature x-ray diffractometer.