A spectroscopic and gravimetric study of the soot- [formula omitted] reaction at various temperatures

Abstract

A study of the hexane soot- NO 2 N 2O 4 reaction, with and without water vapor, over a range of concentrations and temperatures has been conducted. Two types of reaction are evident: activated chemisorption and redox. In the case of activated chemisorption, nitrogen-containing species are formed on the soot resulting in an increase in its mass. The other reaction in which 82–95% of the soot is converted into CO 2 and CO is the major redox reaction, during which NO and N 2O also are formed. This redox reaction commences at temperatures near 60°C. The major redox and activated chemisorption reactions are competitive in the sense that, if activated chemisorption is initiated, it precludes the major redox reaction. The presence of water vapor and dilution of NO 2 N 2O 4 by N 2or air inhibit the major redox reaction and the irreversible activated chemisorption reaction dominates. In addition, a third reaction termed the minor redox reaction occurs under all conditions with the evolution of CO and CO 2. The quantities of effluent gases from this reaction are significantly lower than those evolved during the major redox reaction. The rate equations for the formation of CO 2from the major redox reaction, and CO 2 and CO from the minor redox reaction, have been determined. A mechanism for the major redox reaction is presented. A determining role of NO 2 monomer in redox reactions of soot and NO 2 N 2O 4 is indicated.