Integrating ionic liquids and catalytic processes for enhanced biomass conversion technologies

Abstract

Lignocellulosic biomass is an abundant, renewable feedstock for the sustainable production of fuels and high-value chemicals. Ionic Liquids (ILs), with their low vapor pressure, adjustable polarity, and ability to breakdown resistant biopolymers, have emerged as “designer” solvents and catalysts for biomass processing. This review begins by surveying the key physicochemical features and classifications of ILs: protic, aprotic, acidic, basic, neutral, and functionalized, before delving into their involvement in biomass breakdown, pretreatment, and solution-state characterisation. The following sections examine IL-mediated hydrolysis and dehydration strategies for converting cellulose, hemicellulose, and simple sugars into platform molecules such as 5-hydroxymethylfurfural (HMF), furfural, levulinic acid, and formic acid, emphasizing typical yields (up to 99% for HMF and 96.6% for levulinic acid) and reaction conditions (80–180 °C, minutes to hours). In parallel, this paper discussed about catalytic systems polyoxometalate (POM) acids, vanadium salts (e.g., NaVO₃–H₂SO₄, VOSO₄), aluminium-based Lewis acids, zeolites, polymeric solid acids, metal chlorides, and Brønsted acidic ILs that facilitate selective C–C bond cleavage, oxidation, and dehydration under IL and aqueous conditions. The recyclability of ILs, problems in solvent recovery, catalyst separation, and environmental consequences are all examined. Finally, in this paper are highlighted prospects for developing low-cost, scalable IL-based processes and hybrid catalytic techniques to improve the commercial feasibility of biomass-to-chemical technologies.