Propylene carbonate and γ-valerolactone as green solvents enhance Sn(IV)-catalysed hydroxymethylfurfural (HMF) production from bread waste

摘要: Two green solvents, namely propylene carbonate (PC) and γ-valerolactone (GVL), were examined as co-solvents in the conversion of bread waste to hydroxymethylfurfural (HMF) over SnCl4 catalyst under microwave heating at 120 °C, their performances compared with water acetone a common solvent. The results showed that HMF yield ∼20 mol% was achieved 7.5 20 min PC/H2O GVL/H2O (1 : 1 v/v) systems, respectively, implying tandem reactions (starch hydrolysis, glucose isomerisation, fructose dehydration) efficient. systems played critical role maintaining effective Lewis acid sites, i.e., Sn4+, greater extent acetone/H2O water, where loss Sn4+ from liquid phase colloidal SnO2 particles via hydrolysis evidenced by X-ray diffraction analysis. In comparison, utilisation (47–59 starch within 10 min) appeared rate-limiting step systems. When comparing GVL/H2O, kinetics overall former more favourable, which associated high in-vessel pressure developed liberation CO2 PC. addition, dipole moment dielectric constant solvents may also account for respective performance. This study elucidates multiple roles interplay catalysts, advocates application facilitate catalytic biomass lower energy requirement.