Experimental and Mathematical Modelling of Conversion of Animal Fat Oil into Biodiesel Over Waste-Derived Hydroxy Sodalite in a Fixed-Bed Bioreactor

An experimental and mathematical modelling of conversion of animal fat oil (AFO) to biodiesel using waste-derived hydroxy sodalite (HSOD) catalyst in a fixed-bed reactor was conducted. A modified three step Eley-Rideal reaction model was employed and previous studies carried out using a batch reactor with AFO catalyzed by waste-derived HSOD provided some preliminary experimental and reaction kinetics data. A comparism of the kinetic performance of the batch and continuous fixed bed reactor (FBR) processes were investigated to further understand the overall conversion performance with the waste-derived HSOD catalyst. Experimental and mathematical modelling results reveal that the FBR feed rate should be faster than 0.4 ml min^-1 in order to overcome external diffusion limitations. The results indicated that as the diameter of the catalyst particles remain lower than 0.19 mm, the effect of internal diffusion mass transfer difficulties was overcome based on simplifying model assumption. It was also identified that an Eley-Rideal mechanism model was able to describe the kinetic performance of the transesterification in a fixed bed reactor and the system surface reaction of triglyceride with adsorbed methanol assumed to be the rate-determining step (RDS). The kinetics of the transesterification catalysed by waste-derived HSOD in a fixed bed reactor fitted well with the experimental data and in agreement with the literature. From the comparison of the batch and FBR, it was observed that the waste-derived HSOD displayed higher catalytic activity (higher conversion) in the transesterification of AFO to AFOFAME in the FBR than in the batch reactor.