Response surface modeling and optimization of heterogeneous methanolysis of beef tallow

Yield of fatty acid methyl ester (FAME) from methanolysis/transesterification reaction is influenced by 5 notable factors: reaction time, temperature, methanol to lipid ratio, catalyst concentration and extent of phase mixing. The aim of this paper is to investigate the optimum conditions for biodiesel production by methanolysis of beef tallow over chicken eggshell derived CaO catalyst, via a 3-level 5-factor modeling using response surface methodology (RSM). Transesterification was performed in 46 duplicated experimental runs. FAME yield was maximized with statistically adequate predictive quadratic model. Interactive parametric effects were studied. An optimum FAME yield of 95.94% was achieved with catalyst concentration of 5.42 wt.%, at 63 °C, methanol to fat ratio of 16.39 mole/mole, reaction time of 3.38 hours and stirring speed of 1300 rpm. The optimally produced biodiesel met European standard. At the established optimum process conditions, the heterogeneous catalyst recoverability, reusability and regeneration ability (RRR) were assessed. Only 85.36% of initial catalyst mass was recovered after 5 catalysis cycles, with resulting biodiesel FAME contents > 96.5% and FAME yields > 80% for each cycle. Regeneration by calcination restored the catalyst’s activity. For modeling and optimization studies, choice of factor range is paramount and no factor should be neglected before modeling.