Sustainable production of levulinic acid and its derivatives for fuel additives and chemicals: progress, challenges, and prospects

Levulinic acid (LA) is one of the most promising biomass-derived platform chemicals owing to its wider convertibility to a large number of commodity chemicals. Numerous LA derivatives have paramount importance in the global economy. In this article, we have comprehensively reviewed various processes that have been developed to produce LA and its derivatives from different sugars and cellulosic feedstocks. These designs are discussed in order to provide comparative information on their chemical mechanisms, process merits, demerits, and scale-up potentials. Monosaccharides such as fructose, glucose, and xylose, and disaccharides such as sucrose are good feedstocks for LA production with Bronsted or Lewis acids as the catalysts in either homogenous or heterogeneous reaction systems. LA yield is in the range of 2–90%, which is greatly dependent on the reaction conditions. Polysaccharides such as cellulose and even lignocellulose are also employed for LA production. Bronsted acids, especially mineral acids, appear to be more efficient than Lewis acids to catalyze the conversion of polysaccharides and lignocellulosic biomass to LA. The important LA derivatives and their preparation reactions such as aminolevulinic acid, diphenolic acid, γ-valerolactone, various alkyl esters, and valerate have also been reviewed. These derivatives have extended utilization in modern industries due to the emergent environmental concerns. Furthermore, the challenges arising during these lab-scale processes are critically unveiled to pave the way for process selection and scale-up study for the production of LA and different derived chemicals. It has been recommended that to improve the production efficiency of LA and its derivatives, efforts should be made to develop robust catalysts and reaction systems in order to improve the reaction selectivity. The mechanisms of LA formation from various feedstocks are also significantly important to guide the intensification of the process. Reactors with potential of industrial application are one of the crucial steps for the scaling up of LA production.