High temperature oxidation of iron atoms by CO2

Abstract

The reaction of Fe-atoms with CO₂ was studied in the temperature range of 1330 K ⩽ T ⩽ 2650 K at pressures between 1.0 and 1.6 bar in a shock wave reactor. Resonance absorption spectroscopy was applied for time-resolved measurement of Fe-atoms, O-atoms, and CO-molecules in initial gas mixtures containing Fe(CO)₅ and CO₂, highly diluted in argon. The experiments showed at early reaction time an Fe-consumption and a simultaneous CO formation which was interpreted by reaction R2 (explained below):

The rate coefficient was determined to be k₂ = 10^{14.51 ± 0.10} exp(−15 000 ± 400 K/T) cm³ mol⁻¹ s⁻¹. At higher temperatures and longer reaction times a quasi stationary Fe-atom concentration level was observed which could not be explained by (R2) only. Therefore secondary reactions were considered in a simplified reaction mechanism, enabling the simulation of the complete Fe, O, and CO concentration profiles. For the major secondary reaction (R3, explained below): a rate coefficient of k₃ = 10^{15.59 ± 0.46} exp(−23 000 ± 1700 K/T) cm³ mol⁻¹ s⁻¹ was determined, which is regarded more like a fitting parameter than an elementary reaction.