Terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride copolymers: A low dosage and high-efficiency cold flow improver for diesel fuel

Abstract

The addition of cold flow improvers (CFIs) is considered as the optimum strategy to improve the cold flow properties (CFPs) of diesel fuels, but this strategy is always limited by the required large dosage. To obtain low-dosage and high-efficiency CFIs for diesel, 1,2,3,6-tetrahydrophthalic anhydride (THPA) was introduced as a third and polar monomer to enhance the depressive effects of alkyl methacrylate-trans anethole copolymers (C₁₄MC-TA). The terpolymers of alkyl methacrylate-trans anethole-1,2,3,6-tetrahydrophthalic anhydride (C₁₄MC-TA-THPA) were synthesized and compared with the binary copolymers of C₁₄MC-TA and alkyl methacrylate-1,2,3,6-tetrahydrophthalic anhydride (C₁₄MC-THPA). Results showed that C₁₄MC -THPA achieved the best depressive effects on the cold filter plugging point (CFPP) and solid point (SP) by 11 °C and 16 °C at a dosage of 1250 mg/L and monomer ratio of 6:1, while 1500 mg/L C₁₄MC-TA (1:1) reached the optimal depressive effects on the CFPP and SP by 12 °C and 18 °C. THPA introduction significantly improved the depressive effects of C₁₄MC-TA. Lower dosages of C₁₄MC-TA-THPA in diesel exerted better improvement effects on the CFPP and SP than that of C₁₄MC-TA and C₁₄MC-THPA. When the monomer ratio and dosage were 6:0.6:0.4 and 1000 mg/L, the improvement effect of C₁₄MC-TA-THPA on diesel reached the optimum level, and the CFPP and SP were reduced by 13 °C and 19 °C, respectively. A 3D nonlinear surface diagram fitted by a mathematical model was also used for the first time to better understand the relationships of monomer ratios, dosages, and depressive effects of CFIs in diesel. Surface analysis results showed that C₁₄MC-TA-THPA achieved the optimum depressive effects at a monomer ratio of 6:0.66:0.34 and dosage of 1000 mg/L, and the CFPP and SP decreased by 14 °C and 19 °C, respectively. The predicted results were consistent with the actual ones. Additionally, the improvement mechanism of these copolymers in diesel was also explored.