Hydrothermal carbonization of glucose: experimental data and kinetic modeling

This study investigated the kinetic modeling of hydrothermal carbonization (HTC) of glucose using extensive data on hydrochar yield over time at 160–250 °C and glucose concentrations of 0.1, 0.16 and 0.25 g·mL-¹. More than 250 experimental data points were analyzed and fitted to different kinetic models, confirming the Hill-type sigmoidal model as the most suitable for describing kinetic behavior and determining the formation rate constant. The Arrhenius model confirmed the temperature dependence of the rate constants and revealed two activation energies (E1 below 200 °C and E1 above 200 °C). For example, at a glucose concentration of 0.1 g.mL-1, the activation energies were E1=42.23 kJ.mol-1 and E2=91.54 kJ.mol-1; at a concentration of 0.16 g.mL-1, E1=43.69 kJ.mol-1 and E2=77.11 kJ.mol-1; and at a concentration of 0.25 g.mL-1, E1=48.98 kJ.mol-1 and E2=55.19 kJ.mol-1. The results indicate that the activation energy remains relatively stable below 200 °C, ranging from 42 to 48 kJ·mol−1 with an average of 45 kJ·mol−1. However, above 200 °C, the activation energy decreases markedly, dropping from approximately 92 to 55 kJ·mol−1 as the glucose concentration increases. The study highlights the complex, temperature-dependent kinetics of hydrochar production from glucose. It offers insights into the fundamental processes and establishes a basis for future kinetic modeling.