Temperature programmed desorption technique to predict the carbon oxygen reaction

Abstract

The kinetics of the reaction o₂ oxygen with a sucrose char particle size: (88 μ<d_p<105 μrn) has been studied using a thermogravimetric analyzer (TGA) and a mass spectrometer (MS) to measure weight change and CO and CO₂ formation rates during reaction. Experiments were performed to determine the surface oxide formation rate and to determine the mechanism of CO desorption in the temperature range of 762 K to 851 K and for oxygen pressures of 0.04 to 0.3 atm, respectively. When the reaction rate at 30% conversion was used in the Arrhenius plot, an activation energy of 34±3 kcal/mol was obtained and the CO/CO₂ ratio was found to increase with increasing reaction temperature. Analysis of the rate of formation of CO and CO₂ shows the activation energy for CO formation is greater than for CO₂ formation. Temperature programmed desorption (TPD) studies of the surface oxides were made to provide a better understanding of the carbon oxidation process. The activation energy distribution function for desorption was approximately Gaussian and the average activation energy is 55 Kcal/mol for a preexponential factor of 10¹³ 1/sec. The peak of the energy distribution function shifts to higher activation energies for surface complexes formed at higher reaction temperature.