Development of an online refractive index monitoring system to detect the end point of transesterification reaction

Abstract

Refractive index is a physical property which can be used in determining the end point of transesterification in producing biodiesel. The traditional method in acquiring refractive index measurements takes place outside of a transesterification reactor making remote sensing impossible. In this study, a fiber optic cable was used to identify the appropriate wavelength to acquire the refractive index measurement of the mixture as well as fuzzy logic using proportional and derivative errors as its input in determining the end point of transesterification reaction. The different components are used to address real time data acquisition and processing in controlling the continuation or termination of the reaction. It showed that the transesterification reaction of refined, bleached, deodorized coconut oil and methanol using 1∶6 molar ratio and 0.003 (by weight of oil) of sodium hydroxide has a mean termination time of 80 minutes with +/− 10 minutes deviation and the percent error compared with measurements from traditional refractometer was less than 0.24%. In doing so, an online system for real time data acquisition and processing was established. The study provides an alternative way to automatically identify the end point of transesterification and successfully presents a method for remote sensing identifying the reaction termination timely to the mixture condition.