Direct Transformation of Biomass into Levulinic Acid Using Acidic Ionic Liquids: An Example of Sustainable and Efficient Waste Valorization

The study highlights the potential of acidic ionic liquids for sustainable and efficient biomass conversion to levulinic acid (LA). The process in the presence of [Hmim] [(HSO₄)(H₂SO₄) _x ], especially with x=1 or 2, can be carried out efficiently under mild conditions. The highest yield of LA is obtained in the conversion of sawmill chips using [Hmim(HSO₄)(H₂SO₄)₂] at 70 °C (64.04 mol% of LA).

The intensification of the use and conversion of renewable raw materials, including plant biomass, into valuable products is one of the major goals of the Sustainable Development Strategy. Levulinic acid (LA), classified as one of the top twelve biobased platform chemicals of the future, can be produced from lignocellulose; however, this process is often complex. Herein, a novel and effective pathway for the direct transformation of lignocellulosic biomass into LA under mild conditions, without pretreatment, is presented. Selected waste lignocellulosic biomass, including sawmill chips, grass, and walnut waste, as well as model cellulose, is converted to LA using acidic ionic liquids (ILs). Among the evaluated ILs, [Hmim(HSO₄)(H₂SO₄)₂] provided the highest product yields even at 50–70 °C. The ILs used herein are significantly more efficient in converting cellulose and biomass compared to conventional sulfuric acid. The highest yield of LA is obtained from sawmill chips, reaching 64.04 mol% of LA.

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