Resumen
Homogeneous base catalysts contained certain limitations including the formation of soap with the usage of high free fatty acid content feedstock and the difficulty of separating the spent catalyst from the biodiesel product. Thus, the research objective was to synthesise the optimum biomass carbon-based solid acid catalyst from pineapple peel for biodiesel production so that the total production cost could be reduced and the synthesised catalyst would be used in interesterification process to reduce the production of glycerol. The biomass was activated using 30 v/v % phosphoric acid and carbonised into carbon-rich compounds at 600 ? for 3 hours. After that, direct sulfonation method was carried out by thermal treatment at sulfonation temperatures varied from 105 to 150 ? and sulfonation durations varied from 4 to 7 h. The catalyst characterisation was analysed via several analytical instruments. The porous structure and sulfur content of catalyst were observed through Scanning Electron Microscopy equipped with Energy-Dispersive X-ray (SEM-EDX). The presence of sulfonic acid group in the catalyst was evaluated by Fourier Transform Infrared Spectroscopy (FTIR) and the acid density was estimated using back titration test. The interesterification reaction was carried out at temperature of 110 ?, reaction time of 8 h, solvent to feedstock molar ratio of 50:1 and 20 wt.% catalyst loading. Then, the biodiesel yield was determined using Gas Chromatography (GC) and the acid value conversion was evaluated using acid value test. After the analysis, the catalyst sulfonated at 135 ? for 6 h provided the highest biodiesel yield and acid value conversion which were 27.58 % and 28.13 % respectively when oleic acid and methyl acetate were employed in interesterification reaction. In conclusion, the usage of biomass waste could significantly reduce the production cost and the synthesised catalyst could produce biodiesel with the most promising yield.