CO Desorption from carbonyl surfaces species in the gasification of coal

Introduction The reactivity behavior of chars and carbons under reaction with oxygen agents has been the focus of many studies due to its practical applications in industry. Characterization of the oxygen complexes in the char surface is very important because its relation with mechanism of gasification and combustion reactions. Studies using transient kinetic have shown that in the char-CO2 and char-O2 reactions, there must be at least two kinds of surface oxygen complexes that release a CO molecule to the gas phase.1-4 Temperature Programmed Desorption (TPD) experiments from oxidized carbons and chars have observed different surface oxygen complexes depending on the temperature at which they are desorbed. It has been suggested that the broad TPD feature in the CO desorption can be due to the surface heterogeneity of the char. Semiquinone and ether groups have been proposed to account for the CO molecule desorption at high temperature5,6 while carbonyl groups for the CO molecule desorption at low temperature.7 Our goal is to employ a state-of-the-art quantum chemistry method to address several fundamental questions regarding the desorption of carbonyl-type surface species. In particular, we examined the effects of the surface inhomogeneity from the presence of different active site structures such as arm-chair, zigzag and tip shapes and how it correlates to the observed TPD peak.