On the origin of power-law kinetics in carbon oxidation

摘要: Abstract Many experimental studies report high fractional orders for the global carbon/oxygen reaction, including several that cover wide ranges in oxygen partial pressure and observe power-law kinetics with a constant apparent order over entire range. This persistent n th-order behavior is inconsistent simple Langmuir kinetic model also challenge more elaborate multi-step models of elementary reactions on ideal surfaces. The power law form attractive rate law, but without fundamental basis, it will remain empirical ultimately controversial. present paper evaluates effect surface or site heterogeneity as an explanation paradox behavior. Simple intrinsic induced are used to show indeed expected when desorption adsorption activation energy distributions broad. Examination TPD data shows broad enough be generally disordered carbons. particular formulation Haynes was evaluated candidate framework describing main features carbon oxidation database at temperatures below 1000 K pressures above 0.01 bar. turnover predicts gives promising description absolute reaction orders, energies, near-atmospheric rates coal polymer chars. It low its weak variation graphitized black Tyler coworkers. origin discussed terms detailed three classes active sites: reactive bare sites, partially covered stable oxide, approximate analytical expression derived relates distribution.