Melamine foam-supported ionic liquid catalyst for inulin hydrolysis in micropacked bed reactors

Shrinking fossil fuel reserves and worsening environmental deterioration have spurred exploration on biomass resources. Inulin is an ideal feedstock owing to its ready availability and lack of complex pretreatment. To overcome cumbersome recovery, severe leaching, and low efficiency in batch reactors associated with conventional homogeneous ionic liquid catalysts, sulfonated polysulfone-based ionic liquids (SPSF-ILs) were innovatively immobilized on melamine foam (MF) via impregnation and non-solvent induced phase separation (NIPS) method to fabricate the heterogeneous SPSF-ILs/MF catalyst. The synergistic effect between quaternary ammonium triethylamine sulfonate cations and sulfonated polysulfone anions significantly enhances inulin hydrolysis performance. 99.94% total reducing sugar (TRS) yield was achieved at 90 °C for 150 min in batch reactors. Notably, in micropacked bed reactors (μPBRs), TRS yield of 99.68% was achieved at 90 °C within a 2.0 min residence time, corresponding to a space-time yield (STY) of 6.20 × 10⁻² g·ml⁻¹·min⁻¹·g_cat⁻¹, over 8 times higher than that of the batch reactor. The catalyst exhibited excellent stability, with activity decay of less than 3% after continuous operation for 14 h in μPBRs.