A Novel Kinetic Model of Enzymatic Biodiesel Production in a Recirculating Fixed Bed Reactor

Entrapped lipase derived from Candida rugosa can be used as an alternative for commercial heterogeneous catalysts in the biodiesel synthesis process. The inclination towards a recirculating reactor with lipase-containing beds stems from its capability to simultaneously improve both yield and reproducibility in the biodiesel synthesis process. To industrialize biodiesel production with entrapped lipase in a recirculating reactor, optimization is essential, and this can be estimated using a kinetics model. In this context, a kinetics model based on the Ping-Pong Bi-Bi mechanism was developed for enzyme transesterification. Following this, experiments on biodiesel synthesis were carried out in a fixed-bed reactor with a recirculated substrate, and a biodiesel concentration of 2177.231 mol/m3 was achieved from 917.804 mol/m3 triglyceride. In this study, 3 models, namely Model 1, 2, and 3, were developed based on the Ping-Pong Bi-Bi mechanism, and each has assumptions that determine its complexity. To validate these models, two sets of secondary data were taken and fitted into the respective model. The sum relative error is used to express the differences between model and experimental data. Model 1, predicting each component in transesterification, exhibited the highest error of 1.64, while Model 3, assuming excess alcohol and incorporating a pseudo-steady-state for di- and monoglyceride, yielded the lowest error. Despite these variations, every model demonstrated good agreement in following each component profile accurately, providing a more precise description of the reaction elements.