A cleaner approach for biodegradable lubricants production by enzymatic glycerolysis of castor oil and kinetic analysis

Monoricinolein (MRO) and diricinolein (DRO) were renewable and biodegradable lubricants. In this paper, MRO and DRO were prepared by the novel cleaner enzymatic glycerolysis of castor oil (CO) in solvent-free system. Three commercial immobilized lipases (Novozym 435, Lipozyme RM IM and Lipozyme TL IM) were screened and compared, and Novozym 435 showed the best catalysis performance among the tested lipases. Effects of reaction variables (reaction pressure, reaction time, temperature, enzyme load, substrate ratio and water content) on the enzymatic glycerolysis of CO were investigated. High conversion of CO (92.48 +/- 1.02%) and the maximum bio lubricants yields (54.47 +/- 0.58% MRO and 38.01 +/- 0.50% DRO) were achieved under the following conditions: enzyme load 5% (w/w, based on the total mass), CO/glycerol ratio at 1:6, 90 degrees C, and 3 h. The activation energies (Ea) for CO conversion and the formation of MRO and DRO were calculated as 33.75 kJ/mol, 22.26 kJ/mol and 24.37 kJ/mol, respectively, and the process showed high selectivity toward the formation of MRO. Reaction kinetic agreed with the ping-pong Bi-Bi mechanism with the inhibition of CO, and the kinetic values (V-max, K-m', and K-IA) were 0.0946 mol/(L.min), 1.6704 mol/L, and 0.89 mol/L, respectively. (C) 2018 Elsevier Ltd. All rights reserved.