Mechanisms of soot nucleation in flames—A critical review

Catalytic automotive exhaust aftertreatment

The mechanism of atom formation for a number of elements in a Perkin-Elmer heated graphite atomizer, HGA 2100, has been studied using a combined thermodynamic and kinetic approach. Assuming that an analyte surface-gas phase equilibrium exists within the furnace and the production of observable atoms is characterized by a unimolecular rate constant, a plot of the logarithm of the absorbance as a function of the inverse of the absolute temperature yields a straight line from which the activation energy, E/sub a/, of the limiting step in the atomization pathway can be obtained. These E/sub a/ values reveal that three major atomization mechanisms are operative: thermal dissociation of the analyte oxide or halide, and carbon reduction of the oxide followed by atomization of the free metal.

Studies on the mechanism of atom formation in graphite furnace atomic absorption spectrometry

Soot formation in combustion

Concern about pollutant formation and emissions continues to be a driving force for research in combustion chemistry. Important pollutants include nitrogen oxides (NO x ), sulfur oxides (SO x ), chlorine species, unburned or partly burned fuel components (e.g., UHC, aldehydes, CO), aromatic and polycyclic aromatic compounds, and aerosols (soot, alkaline aerosols). In this review, it is discussed how N, S, Cl, and K/Na species, typically present in small quantities, may affect the overall combustion process, as well as the formation or transformation of each other. Of special interest is their ability to sensitize or inhibit oxidation of fuel and CO, depending on the reaction conditions; the impact of S, Cl and K/Na on formation of NO x , PAH, and soot; and the interaction of sulfur, chlorine and alkali species, which may have significant implications for emissions of SO 2 , HCl, and aerosols.

N.J. Friswell

Papers

The suppression of soot emission from flames by metal additives

Identification of lead compounds in flames and determination of the PbO bond energy