Performance Evaluation of Carbon-based Heterogeneous Acid Catalyst Derived From Hura crepitans Seed Pod for Esterification of High FFA Vegetable Oil

Efficient and recyclable heterogeneous catalysts from low-cost material is a research target in biodiesel industry to reduce production cost and minimize waste generation. The performance of carbon-based heterogeneous acid catalysts prepared from Hura crepitans seed pod via partial carbonization and sulfonation was evaluated in this study. Different catalysts, 0HuSO(3)H, 30HuSO(3)H, 60HuSO(3)H, 90HuSO(3)H, and 120HuSO(3)H, obtained by varying preparation conditions were characterized using emission scanning electron microscope, Fourier transform infrared spectroscopy, X-ray powder diffraction, and thermogravimetric and titrimetric analyses. The activity of the catalysts towards esterification of high free fatty acid-containing H. crepitans seed oil was assessed. Effects of process parameters, temperature, catalyst load, methanol/oil ratio, reaction time, and their various optimum levels on the esterification reaction, were investigated using Taguchi L9 orthogonal array method of optimization. The results showed that the H. crepitans seed pod-derived solid acid catalysts exhibited superior catalytic properties primarily due to high acid density (2.0 mmol/g). The resident time of carbonization before sulfonation showed a strong influence on the acid site density, pore sizes, hydrophobicity, and acid site retention capacity. The optimum process conditions as predicted by the optimization model gave 94.81% ester conversion. The catalyst was effective up to four cycles with only 1.44% decrease in activity.