Supercritical Biodiesel Production from Safflower: Process Optimization and the Impact of Zinc Oxide Nanoparticles on Product Composition

Abstract

The production of biodiesel and valuable products from ground safflower seed using supercritical methanol was investigated, focusing on optimizing biodiesel production through response surface methodology (RSM). It was determined that the optimal conditions for maximizing fatty acid methyl esters (FAMEs) production were 250 °C, 0.25 g ground safflower seed, and 29 min reaction time, achieving a 74% yield. In addition to FAMEs, the reaction resulted in the formation of oxygenated compounds, hydrocarbons, and aromatics, with maximum yields of 56%, 39.3%, and 7.19%, respectively, under different reaction conditions (200 °C, 0.1 g catalyst, 40 min for oxygenates and aromatics, and 200 °C, 0.5 g catalyst, 40 min for hydrocarbons). In the presence of ZnO nanoparticles, the reaction conditions that maximized the yield of FAMEs resulted in a 7% reduction in biodiesel yield, a 52% increase in the yield of hydrocarbons, and an 85% increase in the yield of oxygenates, while there was no apparent effect on the yield of aromatics. The results highlighted the complex role of ZnO in the supercritical methanol process, where it can inhibit biodiesel production while simultaneously aiding in the conversion of biomass into hydrocarbons and oxygenated compounds