Soybean oil-based monoacylglycerol synthesis using bio-compatible amino acid ionic liquid as a catalyst at low temperature

Abstract

Monoacylglycerol (MAG) from edible oil is one kind of green and safe food additive. This project mainly focused on a nontoxic and biodegradable catalyst, amino acid-based ionic liquids (AAILs), for the glycerolysis of soybean oil triacylglycerol (TAG) to prepare MAG at low temperature. Seven AAILs, from arginine, lysine, histidine, tryptophan, or glutamic acid and choline hydroxide, tetramethylhydroxide ammonium, or tetrabutylammonium hydroxide, were successfully synthesized in this work. The effects of substrate ratio, AAIL load, temperature, and reaction time on AAIL-catalyzed the glycerolysis of soybean oil were evaluated. Moreover, the activation energy of MAG formation was explored and reaction mechanism was also proposed. Finally, reaction conditions were optimized by response surface methodology. Results showed that, among all tested AAILs, [TMA][Arg] prepared by arginine (Arg) and tetramethylhydroxide ammonium (TMAOH) showed the outstanding catalytic performance for the glycerolysis of soybean oil. The maximum MAG yield (64.89 ± 1.26%) and TAG conversion (86.31 ± 1.68%) were achieved under the optimized conditions: 105 °C, 0.5 h, [TMA][Arg] load 10%, and substrate molar ratio 1:2 (soybean oil/glycerol). Moreover, the activation energies of MAG formation and TAG conversion were 44.22 kJ/mol and 37.58 kJ/mol, respectively.