Catalytic esterification, kinetics, and cold flow properties of isobutyl palmitate

Abstract

Isobutyl palmitate was synthesized by the esterification of palmitic acid and isobutanol with pyridine n-butyl bisulfate ionic liquid as the catalyst in a self-designed reactor. The kinetics of the esterification and cold flow properties of biodiesel were also studied. The optimal reaction conditions for the esterification are as follows: catalyst dosage, 6%; reaction time, 60 min; molar ratio of isobutanol to palmitic acid, 5:1; and reaction temperature, 100 °C. The verification test was conducted under the optimal conditions, and the esterification rate was up to 98.79%. The kinetics of catalytic esterification was analyzed. The reaction orders was 1.49; the activation energy Ea was 57.38 kJ/mol; the frequency factor A was 2.70 × 107; and the reaction kinetics model was -dcA/dt=2.70×107e-57.38RTcA1.49. The solidifying point (SP), cold filter plugging point (CFPP), and kinematic viscosity of isobutyl palmitate obtained were 3 °C, 7 °C, and 4.93 mm2 s−1, respectively. Compared to methyl palmitate, the SP decreased by six times, and CFPP decreased by 3.28 times. Therefore, the use of branched-chain alcohol instead of methanol ester exchange descaling method can effectively reduce the SP and CFPP of biodiesel to improve cold flow properties of biodiesel.