The catalytic effect of iron oxide on the oxidation kinetics of synthetic char was investigated in a fixed bed reactor and in a conventional thermobalance for comparison. Synthetic char doped with iron oxide was obtained by pyrolyzing hydrochar at 800 degrees C, which had been synthesized by hydrothermal carbonization of cellulose in the presence of iron oxide. Isothermal char oxidation in the fixed-bed reactor resulted in the most reliable kinetic results. According to model-free kinetic analysis of these experiments at 15% conversion, iron oxide decreased the activation energy of char oxidation from 149 kJ/mol to 133 kJ/mol. Modeling of the conversion-time curves was first performed by using the uniform reaction model and then improved by using a n-th order power law. In the temperature range of 440-490 degrees C a very good agreement with the experimental data was achieved using n = 0.6. Activation energies amounting to 149 kJ/mol and 134 kJ/mol were derived for the undoped and iron oxide-doped char, respectively, well in line with the model-free analysis. (C) 2016 Elsevier Ltd. All rights reserved.