Mesoporous solid acid catalyst from waste biomass: sustainable application, modeling, and process optimization

Water hyacinth (WH), an invasive aquatic weed, was used as a renewable feedstock for solid acid catalyst development. Among various sulfonated carbon catalysts synthesized, the catalyst prepared via in situ carbonation and sulfonation with chlorosulfonic acid (WHSC-ICl) exhibited the highest acid density (6.72 mmol/g) and fatty acid methyl ester (FAME) conversion efficiency. Structural analysis revealed a porous macro- and mesoporous network (7.2 nm) with graphite-like sheets embedded in amorphous matrix. Thermally stable up to 200 °C, WHSC-ICl showed a total acidity of 16.39 mmol/g and sulfur content of 9.4 wt%, confirming effective sulfonation. Catalytic performance in hemp seed oil transesterification was optimized using response surface methodology (RSM) and artificial neural network (ANN) models. ANN outperformed RSM with an <i>R</i>² of 0.9888. Under optimal conditions (methanol-to-oil ratio 10:1, catalyst loading 10 wt%, 60 min reaction), the FAME yield reached 97.21%. Thus, WH-derived catalyst offers a sustainable waste valorization and renewable energy potential.