Resumen
Homogeneous alkali-catalysed transesterification was the typical process used in biodiesel production. However, this method made the downstream separation processes complicated. In this study, the objective was to synthesise cost-effective carbon-based solid catalyst derived from agricultural waste materials. The performances of synthesised catalysts were tested in esterification of palm fatty acid distillate (PFAD) to produce biodiesel. The effects of pretreatment parameters on the effectiveness of carbon based catalyst were investigated by varying the types of biomass precursor and activating agent used, particle sizes, impregnation ratio (1:0.1, 1:0.5, 1:1), impregnation temperature (50°C, 70°C, 90°C) and carbonisation temperature (400°C, 600°C, 800°C). The resulting activated carbon was then sulfonated by direct sulfonation, thermal decomposition of ammonium persulfate and arylation of 4-benzenediazonium sulfonate for comparison study. Scanning electron microscopy micrographs showed that the activated carbon carbonised at 600? had porous structure and exhibited highest surface area. Besides that, energy dispersive X-Ray and Fourier Transform-Infrared Spectroscopy had confirmed the successful attachment of sulfonic groups onto the activated carbon. Thermogravimetric analysis result showed that the catalyst was thermally stable up to the temperature of 225°C. Moreover, it was determined in temperature programmed reduction analysis that 890°C was the most ideal reduction temperature with 1,052 µmol/g of hydrogen gas was consumed. The optimum pretreatment condition obtained was at 600°C carbonisation temperature, 1:0.5 impregnation ratio and at 90°C of impregnation temperature. The optimum catalyst possessed total acid density of 7.36mmol/g and had achieved maximum biodiesel yield of 82.71% and conversion of 93.54% in the esterification reaction. Therefore, the usage of carbon-based solid acid catalyst produced from oil palm frond as catalyst was a promising approach in accelerating the development of biodiesel production from low-value feedstock.