Combined Effects of Ionic Liquid and Tungsten–Halogen Radiation on Heterogeneous Hydrolysis Kinetics of Waste Papaya Epidermis for Production of Total Reducing Sugar

Abstract

This article reports on optimization and kinetic modeling of Amberlyst-36 heterogeneous catalytic hydrolysis of papaya (Carica Papaya) epidermis (PE) in conjunction with ionic liquid (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) for total reducing sugar (TRS) production. The intensification effects in presence of tungsten–halogen radiator (THR) on sequential pretreatment and hydrolysis have been optimized. In pretreatment and hydrolysis, the optimized factors were 70 and 80 °C reactor temperature, 20 and 10 min batch time, water to PE ratio (w/w) of 5 and 20 respectively. An optimum 2.5 (w/w) NH4OH loading in pretreatment while 7.5 wt% catalyst concentration and 20 (w/w) [BMIM]Cl loading in hydrolysis using the tungsten–halogen radiated reactor (THRR) yielded maximum 89.02 mol% TRS which was significantly greater than that obtained (37.41 mol%) through the conventionally heated reactor (CHR). Eley–Rideal mechanism best fitted the hydrolysis kinetics while pseudo-homogeneous model could best represent pretreatment kinetics. Remarkably, the larger activation energy (69.02 kJ/mol) in CHR in comparison with THRR evidently established the greater energy-efficiency of the THRR system. The evaluated kinetic parameters can be useful for reactor design and scale-up studies. The developed energy-efficient, green hydrolysis for optimum TRS synthesis from papaya epidermis also provides sustainable valorization of similar lignocellulosic biomass waste.