Energy-efficient and eco-friendly continuous production of 5-CMF in a UV-ultrasound irradiated catalytic packed bed reactor: heterogeneous kinetics, reactor simulation and LCA analysis

Abstract

For the first time, a reusable heterogeneous Smopex-101 and TiO₂ dual catalytic system was employed successfully for the energy-efficient and eco-friendly synthesis of 5-(chloromethyl) furfural (5-CMF) from soluble starch (SS) under the synergistic photo-thermal effect of UV-ultrasound (US) irradiation. Under mild optimal operating conditions (80 °C, 60 min), the batch (UVUS-BR) and continuous-flow rectangular packed bed reactors (UVUS-RPBR) both resulted in maximum 5-CMF yields of 60.54 mol% and 58.75 mol%, respectively. Significantly, the first-ever heterogeneous surface reaction kinetic model was formulated for the 5-CMF synthesis process, which revealed that the activation energies needed for the different reaction steps involved in the consecutive reaction pathway were 79.04 kJ mol⁻¹ (SS hydrolysis), 61.55 kJ mol⁻¹ (glucose dehydration), and 52.2 kJ mol⁻¹ (5-hydroxymethylfurfural chlorination). RTD analysis and ANSYS fluent simulation study revealed that the utilization of the US energy significantly reduced the non-ideal behavior of UVUS-RPBR (63% reduction in dispersion number). Moreover, the efficacy of UVUS-RPBR in the 5-CMF synthesis process was evaluated, employing the experimentally validated heterogeneous kinetic model parameters. Furthermore, based on comparative LCA analysis, cyclohexane was identified as the most favorable solvent for in situ 5-CMF (purity: 96%) extraction due to its potential environmental advantages over other solvents. The outcomes of the present study can be useful for the scale-up of such reactors for industrial application.