A simplified approach to determine the activation energies of uncatalyzed and catalyzed combustion of soot

Catalyst screening tests for soot oxidation is usually performed in semi-batch mode under a temperature ramp-up. Due to the complexity of soot combustion process, generally the activation energy data are not reported. Rather, the catalyst performances are compared on the basis of temperatures required to achieve a certain conversion. In this study, the Redhead method [Vacuum, 12 (1963) 203] of activation energy determination for temperature programmed desorption processes was adopted for soot combustion processes. The method was applied to extract loose contact activation energies of catalytic oxidation of soot over pure and 1 wt.% Pt/oxide. The oxides investigated in this study are SiO2, gamma-Al2O3, TiO2, ZrO2, CeO2 and La2O3. The dry air activity of pure oxides was screened by thermo-gravimetric analysis (TGA) while the activity tests on Pt/oxide catalysts were performed in a home built temperature programmed oxidation (TPO) set-up. The activation energies for soot oxidation determined for these catalysts by a differential method, by an integral method and by Redhead method indicated that the Redhead method provides reasonable estimates of activation energies from peak temperature data of the temperature programmed experiments such as TGA or TPO. Comparison of the activation energies determined as such revealed little difference in the soot combustion activities of the oxides in the presence of Pt in dry air atmosphere. (C) 2002 Elsevier Science B.V. All rights reserved.