Optimization and kinetics of biodiesel production from soybean oil using new tetraethylammonium ionic liquids with amino acid-based anions as catalysts

Abstract

By using amino acids (AAs) as anions, eleven ionic liquids composed of tetraethylammonium (N2222) as a cation were synthesized, namely, [N2222][AA]s. Their structures were characterized by FT-IR and NMR. The alkalinity of the synthesized AAILs was measured using a pH meter. In the transesterification reaction of soybean oil with methanol, tetraethylammonium arginine ([N2222][Arg]) presented the best catalytic capability. The optimal reaction conditions for the transesterification reaction of soybean oil to achieve 98.4% biodiesel conversion were a methanol/oil of 10:1 mol/mol, reaction temperature of 100 °C, catalyst dosage of 20 wt% (based on the oil weight) and reaction time of 60 min. The kinetics study was evaluated and followed the pseudo-first order reaction mechanism, and the activation energy and pre-exponential factor were 34.53 kJ/mol and 1.21 × 104 min−1, respectively. [N2222][Arg] is a promising, operationally simple, sustainable, biodegradable and possibly renewable catalyst for the conversion of vegetable oil or animal fat into biodiesel.