Carbon oxidation kinetics from evolved carbon oxide analysis during temperature-programmed oxidation

Abstract

Temperature-programmed oxidation (TPO) with evolved CO and CO analysis has been used to determine the kinetics of 2 charcoal and graphite combustion at low O partial pressures (1.3–6.1 kPa). Simulations of the TPO profiles provide 2 accurate optimized rate parameters, including oxygen and carbon reaction orders, for four assumed reaction steps. Resultant activation energies indicate that the energy required for stable oxide complex (C(O)) formation decreases in the order graphite, charcoal and unsaturated catalytic coke. When these oxide complexes form, subsequent oxidation is effectively retarded for all carbons. Optimized reaction orders indicate that oxidation in the vicinity of oxygen complexes proceeds via dissociative adsorption. Also temperature-dependent CO/CO ratios are in agreement with literature values.