Enhancing biodiesel production: Utilizing sulfonated carbon aerogel as solid acid catalysts for oleic acid esterification

Solid acid catalysts can be utilized during esterification processes to reduce the amount of free fatty acids in non-food oils for the production of biodiesel. In this work, the long chain fatty acid esterification reaction process was investigated using carbon aerogel, a solid acid catalyst support with hydrophobic characteristics obtained from waste coir fiber. Sulfanilic and sulfuric acids were used as sulfonic agents in the hydrophobic sulfonated carbon aerogel, whereas 4-tert-butylaniline (TBA) was applied as a hydrophobic agent. The obtaining catalyst has a high acid density value of 1.19 mmol g^-1, water contact angle of 109°, and a high specific surface area (1051.29-1301.98 m² g^-1). Oleic acid conversion of 93.7% can be achieved under optimized reaction conditions, including a reaction time of 5 hours at a temperature of 65 °C with a catalyst loading of 5 wt % and a molar ratio of methanol to oleic acid of 9:1.