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

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 degrees 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 E-a was 57.38 kJ/mol; the frequency factor A was 2.70 x 10(7); and the reaction kinetics model was -dc(A)/dt = 2.70 10(7)e-57.38/RT x c(A)(1.49). The solidifying point (SP), cold filter plugging point (CFPP), and kinematic viscosity of isobutyl palmitate obtained were 3 degrees C, 7 degrees C, and 4.93 mm(2) 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.