In this work, we demonstrate a rapid microwave-irradiated, metal chloride-catalysed one-pot process for converting raw lignocelluloses to furanic fuel precursors by employing Protic Ionic Liquids (PIL). Triethylammonium hydrogen sulfate ([Et₃NH][HSO₄]) and copper chloride have been used as PIL and catalyst, respectively, to convert June grass (Koeleria macrantha, 82.3% cellulose, 1.4% Hemicellulose, and Crystallinity Index 54%) to furanic fuel precursors, such as 5-Hydroxymethylfurfural (HMF), Levulinic acid (LA), and Formic acid (FA). The synthesis of [Et₃NH][HSO₄] comprises of two steps: the mixing of 5M sulfuric acid solution with Triethylamine, followed by the removal of excess moisture by a rotary vacuum evaporator. The acid solution is added drop-wise in Triethylamine inside an ice bath since the reaction is highly exothermic. The PIL rapidly ionizes in the presence of copper chloride (catalyst) and water (cross-catalyst) to form a Lewis acid catalyst, which then creates a polar hexa-aquo complex with cellulose. This polar complex aligns itself along the microwave’s rapidly alternating electromagnetic field, resulting in frequent dipole rotations that lead to molecular collisions, and the dissipation of electromagnetic energy as friction and heat that increases the reaction temperature and the reaction rate, thus rupturing the glycosidic bonds in the cellulose. The reactor parameters, such as catalyst-substrate loading, IL-substrate loading, water concentration, temperature, and time, are optimized to maximize product yields. The raw untreated lignocellulose is converted at 120-200⁰C in only 41 minutes, and the reactor temperature and the water concentration are regulated to maximize the yields of the furanic fuel precursors (34.8% for HMF, 19.3% for LA, and 7.6% for FA). This work also explores the scale-up potential and the economic viability of this rapid, feedstock-agnostic one-pot catalytic process.

Mr. Subhrajit Roy PhD Student

Indian Institute of Technology Kharagpur

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