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Esterification of Levulinic Acid to Ethyl Levulinate Using Liquefied Oil Palm Frond-Based Carbon Cryogel Catalyst
- Zainol, Muzakkir Mohammad, Amin, Nor Aishah Saidina, Asmadi, Mohd, Ramli, Nur Aainaa Syahirah
- BioEnergy research 2019 v.12 no.2 pp. 359-369
- Elaeis guineensis, Fourier transform infrared spectroscopy, X-ray diffraction, acidity, biomass, carbon, catalysts, cryogels, esterification, furfural, hydrogen, industry, ionic liquids, levulinic acid, liquids, nitrogen, scanning electron microscopy, sorption, sulfates, sulfuric acid, surface area, thermal stability, thermogravimetry, Malaysia
- 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][HSO₄]) 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-to-feedstock 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 N₂ sorption, NH₃-TPD, TGA, XRD, FTIR, and FESEM to determine its physical and chemical properties. The thermally stable CCOPF exhibited a large total surface area (578 m²/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. Graphical Abstract .