Dual-Acidity Catalysts for Alkyl Levulinate Synthesis from Biomass Carbohydrates: A Review

To combat the fast-degrading environment in this era, efforts are being made to consider biomass as feedstock for the production of biofuels and biofuel additives. Alkyl levulinates (AL), a good biofuel additive, exhibit excellent performance in improving the flow properties of biofuels. The growing market value of AL makes it highly desirable for large-scale productions. Unfortunately, the highly complex structure of biomass often hinders its conversion to AL, limiting its production. Thus, finding solutions to achieve highly efficient biomass conversion to AL is crucial. Catalyst dual-acidity is important in determining conversion effectiveness. The applications of AL, the roles of the catalyst acidic type in facilitating biomass carbohydrates conversions to AL, the types of catalysts employed and their impact, the prominence of the catalyst dual acidity, and the effect of reaction conditions on the conversion process are discussed. Dual-acidity Brønsted-Lewis catalyst enhances the AL yields and selectivity from carbohydrate conversion. Dual-acidity catalysts in the form of homogenous and heterogenous exhibited several advantages and disadvantages, which are compared in terms of catalytic performance and cost-effectiveness. Carbon-based catalysts are suggested as the prominent choice for large-scale AL production from carbohydrates. The outcome of this review will provide insights into the advancements in AL production from biomass carbohydrates.