Optimisation of corncob based heterogeneous acid catalysed biodiesel synthesis using response surface methodology

Biodiesel, which is also known as fatty acid methyl ester (FAME) can be produced through esterification reaction of vegetable oil or animal fats catalysed by heterogeneous acid catalyst. The objective of this study was to synthesise a corncob derived carbon based heterogeneous acid catalyst functionalised by the arylation of 4-benzenediazonium sulfonate (4-BDS) for biodiesel production by using palm fatty acid distillate (PFAD) as feedstock for the esterification reaction. Subsequently, the biodiesel production reaction was optimised by using response surface methodology (RSM). RSM was employed to study the interaction between the primary factors: reaction time (2.5-6.5 h), temperature (60 to 100 °C), oil to methanol molar ratio (1: 13 to 1: 29) and catalyst loading (5 to 11 wt.%) in esterification reaction. The five-level, four factors central composite design (CCD) consisted of 30 experiments was chosen in this investigation. The predicted optimum reaction conditions was 6.48 h reaction time, 89.21 °C reaction temperature, 1 to 21.94 molar ratio of PFAD to methanol and 11 wt.% catalyst loading with 85.94% of predicted biodiesel yield. The actual optimum biodiesel yield of 83.48% was successfully achieved at the corresponding optimum operating conditions which proved the validity of the statistical optimisation model. (paper)