Study on kinetics of lactose isomerization producing lactulose and comparison of performance of two reactor models via simulation with Aspen Plus

Lactulose is a non-digestible oligosaccharide with unique functional properties. It could be produced via lactose isomerization catalyzed either by alkaline or enzyme. In this study, kinetics of lactose isomerization to prepare lactulose is investigated assuming the first order reaction. Kinetic parameters are figured out based on Arrhenius equation. The activation energy values are 107.513 (pH = 10), 103.934 (pH = 10.5), and 101.067 kJ/mol (pH = 11), respectively. The activation energy is inversely proportional to pH. Performances of CSTR model and PLUG model are investigated via simulation using Aspen Plus based on the kinetics. The simulation shows that the conversion percentage of lactose in PLUG reactor is greater than that in the CSTR reactor with the same reactor volume and reaction condition. The difference of the conversion percentage becomes larger as the reaction condition becomes severer with the smallest increase of 1.02% and the largest increase of 29.8% among the nine operating conditions.