Conversion of Biomass-Derived Molecules into Alkyl Levulinates Using Heterogeneous Catalysts

Abstract

Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in the presence of solid acid catalysts that have abundant Brønsted acid sites. Alkyl levulinates can also be synthesized from other biomass-derived molecules such as furfuryl alcohol and furfural via alcoholysis and one-pot conversion, respectively. Thus far, various heterogeneous catalysts have been developed for the conversion of the biomass-derived molecules (levulinic acid, furfuryl alcohol, and furfural) into alkyl levulinates. To obtain the target products in high yields, numerous strategies have been employed including increasing Brønsted acidity, dispersing and incorporating Brønsted acid sites, inducing the formation of mesopores, and inducing a synergistic effect of metal–Brønsted acid sites that are present on a catalyst surface. Here, we summarily reviewed the performances of the heterogeneous catalysts in the conversions, describing the design and development of the heterogeneous catalysts that ensured the excellent yield of alkyl levulinates.

A Network of Processes for Biorefining Burdock Seeds and Roots

“…Heterogeneous acid catalysts can be easily separated and reused at the end of the reaction cycle. Several catalysts, such as heteropolyacids, metal oxides, zeolites, and ionic liquids, were used to produce ethyl levulinate [ 43 , 44 , 45 ]. However, the synthesis of these catalysts turns out to be very expensive and requires long reaction times, adversely affecting the cost of the final product.…”

Hydrogenation of Ethyl Levulinate to Gamma-Valerolactone with Formic Acid and a Palladium–Manganese Catalyst Immobilized on Dendritic Fibrous Nanosilica (DFNS)

“…It has been proposed that base-mediated enhanced proton transfer through a water bridge causes stabilization of the transition state in the H 2 heterolysis rate-determining reaction step. Ghorbanpour et al showed that in the reaction of decomposition of formic acid, more hydrogen gas is released when sodium formate is used. , Alkyl levulinates (ALs) are biomass-based chemicals with many applications in various fields and can replace chemicals produced from petrochemical pathways. − Among the uses of ALs, one can mention their role as a solvent, additive, and precursor in producing gamma-valerolactone (GVL). Ethyl levulinate (EL) is an ester with a fruity odor and can be prepared from levulinic acid (LA) or the reaction between furfuryl alcohol and ethanol. − Considering the existence of various sources for EL production, it can be pointed out that this combination is a suitable option for biofuel additives .…”