The isothermal differential characteristics of the gas-solid reaction occurring in a micro-fluidized bed reactor were studied using the indigenously developed Micro-Fluidized Bed Reaction Analyzer (MFBRA). The combustion of graphite powder in micrometers was taken as the model reaction because of its negligible internal diffusion and chemical-reaction simplicity. With minimized inhibitions from both the internal and external diffusions, the reaction in MFBRA at a preset temperature was analyzed by using the isothermal kinetic approach, resulting in an activation energy of 165 kJ/mol and a pre-exponential factor of 10(6) 1/s. The reaction was further found to be subject to the nucleation and growth model expressed by G(alpha) = -ln(1 - alpha). Measuring this reaction in TG via the programmed heating method resulted in the similar activation energy and the same reaction function model (by extrapolating to zero conversion). Comparing with the non-isothermal approach for TG that involves complicated mathematical calculations, the isothermal differential approach for MFBRA allowed the separation of the temperature effect (i.e., the reaction rate constant) and kinetic function model, thus providing a simple and reliable determination of the gas-solid reaction kinetics. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.