Oxidation kinetics of graphite nanoparticles with copper oxide as oxygen carrier

The oxidation characteristics of graphite with copper oxide nanoparticles as oxidizer mixed in stoichiometric proportion were studied using a thermogravimetric analyzer. Progress of reactions was followed by measuring the mass loss, evolved gas analysis, and energy-dispersive X-ray spectroscopy. The samples were heated from room temperature conditions to 975 degrees C at four different heating rates of 5, 10, 15, and 20 degrees C min (-1). The exhaust gas composition was quantified using a non-dispersive infrared analyzer. Experimental results indicate that the system requires a critical CO concentration buildup before the combustion process accelerates. The carbon dioxide production begins and peaks later than carbon monoxide. A total of three peaks occur in both carbon monoxide and carbon dioxide evolution. An Arrhenius dependence for the peak separation times with respect to the starting peak or trough temperature was observed. This work experimentally identifies the various regimes of oxidation chemistry for this fuel oxidizer combination over the entire combustion process via the trajectory of CO and CO2 evolution with temperature. The paths in this trajectory are then mapped onto the mass loss profiles. Modulated TGA experiments were also conducted to obtain the activation energy during the combustion process that shows overlapping mass loss regions. This activation energy is obtained over a wide range of temperatures using this model free-approach. The activation energies obtained using the modulated TGA experiments were also compared to those obtained using the Flynn-Wall-Ozawa method. This work provides new insights into the oxidation kinetics of graphitic carbon with solid copper oxide as an oxidizer.