Ultrasound-assisted catalytic transfer hydrogenation of fatty acid methyl esters using Ni-La-B/organobentonite composite catalyst: Fabrication, application and mechanisms

Abstract

In this work, an efficient organobentonite-based Ni-La-B composite catalyst (Ni-La-B/OB) was synthesized through impregnation and chemical reduction method using cetyltrimethylammonium bromide (CTAB)-modified bentonite as support and along with the addition of the metal additive La, and then was employed as catalyst for the ultrasound-assisted catalytic transfer hydrogenation (CTH) reaction of fatty acid methyl esters (FAMEs). The characterization results suggested that the inclusion of La resulted in the generation of additional active site. Under the conditions of the mass ratio of solvent water, hydrogen donor isopropanol and FAMEs of 80:28:5 and the catalyst dosage of 10 wt.%, the conversion ratio of C18:2 (CRC182) reached 76.68 %, and the iodine value (IV) decreased from the initial value of 146.7 to 84.01. Kinetics and thermodynamics research showed that ultrasound-assisted CTH of FAMEs followed pseudo-first-order kinetics and was endothermic. Meanwhile, a possible reaction mechanism of the catalyst on CTH of FAMEs was proposed. The Ni-La-B/OB composite catalyst underwent four recirculated cycles, and no significant deactivation was observed. In addition, ultrasound-assisted CTH significantly improved the hydrogenation effect and shortened the reaction time in comparison with the conventional method. The Ni-La-B/OB composite was found to be an efficient hydrogenation catalyst for CTH, and the doping of La significantly enhanced the catalytic activity.