Conversion of furfuryl alcohol to alkyl levulinate fuel additives over Al2O3/SBA-15 catalyst
Alkyl levulinates are promising renewable chemicals in the field of transportation fuels. In this work, the production of alkyl levulinates from furfuryl alcohol was investigated over a series of Al2O3/SBA-15 catalysts prepared by the wet impregnation method. The physicochemical features of the synthesized catalysts were characterized by X-ray diffraction, N2-physisorption, SEM, TEM, temperature-programmed desorption of ammonia, pyridine-adsorbed FT-IR and ICP-OES techniques. These analyses showed that the Al2O3/SBA-15 catalysts maintained the mesoporous structure of parent SBA-15 and that alumina particles were highly dispersed in the uniform pore channels of SBA-15. Al2O3 impregnation over SBA-15 resulted in enhanced acidity and the easy accessibility of active sites to reactants. Among the catalysts, 20 wt% Al2O3/SBA-15 catalyst exhibited the best activity in the alcoholysis of furfuryl alcohol with n-butanol, giving 94% selectivity toward n-butyl levulinate in a batch process. The reaction proceeded via formation of intermediates 2-butoxymethylfuran and 5,5-dibutoxy-2-pentanone, followed by conversion to n-butyl levulinate. The effects of various reaction parameters, including alumina loading, temperature, catalyst amount, n-butanol volume, and different alcohols, were studied. Catalyst recyclability was tested and the spent catalyst characterized. The 20 wt% Al2O3/SBA-15 catalyst was also active in n-butyl levulinate synthesis using a continuous process.