Comparison of Carbon-Based Heterogeneous Acid Catalyst from Water Hyacinth and Coconut Shell for Biofuel Production

Biofuels are one of the renewable fuels needed to replace fossil fuels. Making biofuels requires an acid/base catalyst to speed up the reaction, one of which is esterification. This study aimed to produce sulfonated carbon from coconut shells and water hyacinth, which was carbonized at 300 °C for 6 h. It was reacted with 96 % sulfuric acid at 150 °C with variations in sulfonation times and variations in sulfonation cycles. The highest acid concentration catalyst results were obtained on water hyacinth raw materials at 1.2 mmol/g and coconut shells at 1.215 mmol/g. The more sulfonation cycles will increase the acid concentration value. The value of the catalyst activity test in the esterification reaction of the water hyacinth catalyst can convert Free Fatty Acid (FFA) better than the coconut shell catalyst. Conversion of esters in the esterification process is 75.28 % in the water hyacinth catalyst and 57.62 % in the coconut shell catalyst. The coconut shell and water hyacinth catalysts were sulfonated in the presence of Fourier Transform Infra-Red (FTIR) absorption spectra at wave numbers 1,035.77 cm–1 for the coconut catalyst and 1,033.85 cm–1 for the water hyacinth catalyst, which is a strong S=O group. The Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analysis results indicate that the carbon sulfonate acid catalyst is amorphous. The constant kinetics of the water hyacinth catalyst reaction is 0.0139 L/mol.h, while for the coconut shell catalyst, it is 0.0045 L/mol.h. Coconut shell and water hyacinth raw materials can be used as heterogeneous acid catalysts after sulfonation. HIGHLIGHTS The problem of less and less fossil energy, so alternative energy is needed, one of which is biodiesel as a substitute for fossil energy In making biodiesel, a catalyst is needed to speed up the reaction In this study compared the carbon sulfonate catalyst derived from coconut shells and water hyacinth. Therefore, this paper should be of interest to readers in advanced materials chemistry GRAPHICAL ABSTRACT