Non-catalytic partial oxidation of methane into syngas over a wide temperature range

Noncatalytic partial oxidation of methane has been studied over a wide temperature range from 823 to 1531 K using two flow reactors. Highly diluted fuel-rich CH4/O2/N2 mixtures were reacted in uncoated tubular flow reactors at 1.2 atm. Residence time was varied from 1 to 164 s. Major and minor products of the partial oxidation were measured using a gas chromatograph. Kinetic modeling was performed to simulate experiments and key rate-controlling reactions were revealed by sensitivity analysis. It was found that chain-branching reaction H + O2 = OH + O, recombination CH3 + CH3 (+M) = C2H6 (+M), and methyl radical oxidation CH3 + O2 = CH2O + OH govern the overall rate of the process at short residence times. Recent measurements of these rate constants were analyzed and appropriate modifications in the detailed reaction mechanism were proposed. The model was adjusted to reproduce the measurements accurately at short residence times. At longer residence times, a significant impact of the heterogeneous reactions leading to inhibition of the overall process was observed. The model developed in the present study correctly reproduced temporal profiles and final compositions of the products over the entire range of temperatures and the initial mixture compositions.