Development of heterogeneous acid catalysts produced from the carbonization of Miscanthus x giganteus for the esterification of butyric acid to butyl butyrate with n-butanol

BACKGROUND: Butyl butyrate is an environmentally friendly biofuel component that can be produced through the esterification of butyric acid with n-butanol, both of which are obtainable from waste products. The reaction can be optimized by commercial catalysts; however they are currently hindered by issues such as environmental sustainability and cost. Thus, efforts have been made to develop catalysts with green characteristics by incomplete carbonization and sulfonation of pyrolysis products. RESULTS: Activated and non-activated catalysts were produced by sulfonation of char obtained from the carbonization of Miscanthus x giganteus to catalyze the production of butyl butyrate. The char surface area increased from 6.4 to 571m²g^-1 after chemical activation at 500°C. Non-activated catalysts derived from char carbonized at 500°C gave a yield of 94.5% after 24h reaction, close to that achieved with H₂SO₄ (96%). Furthermore, the kinetic parameters associated with the production of butyl butyrate were derived with the implementation of a kinetic model. CONCLUSION: Chemical activation increased the surface area of the char but, due to the prolonged treatment at high temperatures, produced less polycyclic aromatic carbons available to be functionalized. This resulted in a lower acid density and an inferior performance. Conversely, activated catalysts displayed better recovery and reusability.