Biomass catalytic conversion to alkyl levulinates under the principles of green chemistry

Nowadays the search of alternative energy and carbon sources is a must. While several alternatives exist for the production of energy based on renewables, the only source of renewable carbon is biomass. As a major form of photosynthetically fixed carbon, lignocellulosic biomass has the potential to furnish a broad range of CO2 neutral materials, fuels and chemicals. Alkyl levulinates (ALs) are versatile bio-based platforms of particular interest due to their specific physicochemical properties. These compounds are regarded as green solvents and find extensive applications as specialty chemicals, in the fine chemical and petrochemical industry. ALs are promising intermediates for the manufacturing of solvents, surfactants, polymers, coatings, drugs, resins, anti-cancer agents, pesticides, flavors and fragrances. These compounds are also ideal oxygenates that can be directly blended with transportation fuels, to reduce the release of harmful gases and the formation of soot in engines. Other excellent fuel additive properties of these materials are their low toxicity, high lubricity, flashpoint stability and moderate flow properties under low temperature conditions, obtaining from their direct mixtures, fuels with reduced SOx and NOx emissions in diesel engines. Three pathways can be mainly followed to produce ALs: 1) esterification of levulinic acid; 2) alcoholysis of furfuryl alcohol, FA; 3) direct hexose alcoholysis. Since levulinic acid is still considered an expensive substrate, this work focused on the production of ALs through the latter two pathways, namely FA alcoholysis and hexose direct alcoholysis using solid catalysts.