Release time:2021-03-15  Hits:

• Key Words:Oxidation;Acetic acid - Binary alloys - Bismuth alloys - Catalysis - Kinetic parameters - Kinetic theory - pH - Reaction kinetics - Urea
• Abstract:The chemoenzymatic conversion of cyclohexanone to ϵ-caprolactone (1.25 M) mediated by immobilized lipase from T. laibacchi was successfully achieved with a yield of 98.6%, which is much higher than that in previous studies. A proposed kinetic model consisting of two enzymatic reactions catalyzed by the lipase and one chemical reaction was developed, which fitted the experimental data very well. It was concluded that the enzymatic oxidation of ethyl acetate using urea hydrogen peroxide (UHP) to generate in situ peracetic acid mediated by the lipase may follow an irreversible ping-pong three-four mechanism with substrate inhibitions, which is proposed herein for the first time. Also, the oxidation of cyclohexanone to ϵ-caprolactone by peracetic acid in a chemical fashion may follow a power law. Finally, the reaction of formed acetic acid with UHP to form peracetic acid catalyzed by the lipase may follow an irreversible ping-pong Bi-Bi mechanism with substrate inhibitions. Reaction kinetic data reveal that UHP and acetic acid might have strong substrate inhibition, while peracetic acid might have no product inhibition. Results of enzyme stability test suggest that it is reasonable to adopt a simple exponential equation as the inactivation model of the lipase. The effect of Michaelis-Menten interaction on the reaction rate could be neglected due to the strong substrate inhibition, which makes the constant similar to Michaelis-Menten zero. The yield of in situ polymerization was significantly increased from 61.3% to 92.4% under the optimum conditions obtained in this study.<br/> © 2019 American Chemical Society.
• Volume:7
• Issue:15
• Translation or Not:no