Experimental and kinetic modeling study of C2H4 oxidation at high pressure

A detailed chemical kinetic model for oxidation of C2H4 in the intermediate temperature range and high pressure has been developed and validated experimentally. New ab initio calculations and RRKM analysis of the important C2H3 + O-2 reaction was used to obtain rate coefficients over a wide range of conditions (0.003-100 bar, 200-3000 K).

The results indicate that at 60 bar and medium temperatures vinyl peroxide, rather than CH2O and HCO, is the dominant product. The experiments, involving C2H4/O-2 mixtures diluted in N-2, were carried out in a high pressure flow reactor at 600-900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel-rich conditions.

Model predictions are generally satisfactory. The governing reaction mechanisms are outlined based on calculations with the kinetic model. Under the investigated conditions the oxidation pathways for C2H4 are more complex than those prevailing at higher temperatures and lower pressures. The major differences are the importance of the hydroxyethyl (CH2CH2OH) and 2-hydroperoxyethyl (CH2CH2OOH) radicals, formed from addition of OH and HO2 to C2H4, and vinyl peroxide, formed from C2H3 + O-2.

Hydroxyethyl is oxidized through the peroxide HOCH2CH2OO (lean conditions) or through ethenol (low O-2 Concentration), while 2-hydroperoxyethyl is converted through oxirane.