Esterification of levulinic acid to ethyl levulinate: optimization of process conditions using commercial levulinic acid and extension to the use of levulinic acid derived from depithed sugarcane bagasse (original) (raw)

2021, Biomass Conversion and Biorefinery

Oil palm biomass, which is abundantly available in Malaysia, has many types of applications in various industries. In this study, oil palm frond (OPF) was liquefied with 1-butyl-3-methylimidazole hydrogen sulfate ([BMIM][HSO 4 ]) ionic liquid (IL) at optimum conditions. The liquefied OPF-ionic liquid (LOPF-IL) was mixed with furfural at a ratio of 0.8 (w/w), water-tofeedstock ratio of 0.125 (w/w), and sulfuric acid loading of 0.5 mL at 100°C for 1 h to form a gel. Carbon cryogel liquefied oil palm frond (CCOPF) was prepared using a freeze-dryer followed by calcination. CCOPF was further characterized using N 2 sorption, NH 3-TPD, TGA, XRD, FTIR, and FESEM to determine its physical and chemical properties. The thermally stable CCOPF exhibited a large total surface area (578 m 2 /g) and high total acidity (17.6 mmol/g). Next, CCOPF was tested for levulinic acid catalytic esterification by varying the parameters including ethanol-to-levulinic acid molar ratio, catalyst loading, and reaction time at 78°C. At the optimum conditions, the conversion of levulinic acid and ethyl levulinate yield was 70.9 and 71.7 mol%, respectively. CCOPF was reusable up to five runs with no significant conversion drop. Accordingly, CCOPF is conferred as a potential biomass-derived acid catalyst for ethyl levulinate production. Keywords Oil palm frond. Biomass. Liquefaction. 1-Butyl-3-methylimidazole hydrogen sulfate. Carbon cryogel. Ethyl levulinate Highlights • Liquefaction of oil palm frond with [BMIM][HSO 4 ] ionic liquid yielded LOPF-IL mixture. • Synthesis of carbon cryogel liquefied OPF (CCOPF) from LOPF-IL and furfural. • Good surface properties and high thermal stability are exhibited by microspherical CCOPF. • Esterification of levulinic acid is conducted over biomass-derived CCOPF catalyst.