Application of 2-methylfuran and 5-methylfurfural for the synthesis of C16 fuel precursor over fibrous silica-supported heteropoly acid-functionalized ionic liquid

Abstract

Lignocellulosic biomass is the most abundant renewable and sustainable carbon source with great potential for the synthesis of biofuels. In this study fibrous nano-silica (FNS) supported heteropoly acid-functionalized ionic liquid (FNS-ILHPW) catalyst was synthesized for the cross-condensation reaction of 2-MF and 5-MF to produce C16 fuel precursor. 2-MF and 5-MF were utilized in a stoichiometric ratio. The prepared catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The obtained result from the XRD and FTIR suggests that HPW was present as charge compensating anion (H₂PW₁₂O₄₀⁻) of the IL. NH₃-TPD analysis revealed that FNS-ILHPW retains moderate to strong acid sites. FNS-ILHPW shows higher conversion of the reactants and selectivity to C16 (2, 2′,2″-methylidenetris[5-methylfuran]) fuel precursor. 95% yield of C16 fuel precursor was obtained over the optimized reaction conditions. The excellent activity can be attributed to the coexistence of HPW, which provides the catalytically active sites, IL groups, which served as anchors of HPW onto the support, and FNS, which improves dispersion of the active sites and accessibility of the reactant molecules through its fibers. The effects of the reaction conditions on the final yield and the carbon balance of the reaction were studied. Furthermore, the catalyst can be effortlessly recovered and reused without appreciable loss of activity. The post reaction characterizations of the spent catalyst show no significant change from the fresh catalyst.