Kinetically driven instabilities and selectivities in methane oxidation

Journal Article · Fri Aug 01 04:00:00 EDT 1997 · AIChE Journal

DOI:https://doi.org/10.1002/aic.690430816· OSTI ID:556730

Park, Y K; Vlachos, D G ^[1]

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1. Univ. of Massachusetts, Amherst, MA (United States). Dept. of Chemical Engineering

Ignitions, extinctions, and Hopf bifurcations in methane oxidation were studied as a function of pressure and inlet fuel composition. A continuous stirred-tank reactor was modeled with numerical bifurcation techniques, using the 177 reaction/31 species mechanism. Sensitivity and reaction pathway analyses were performed at turning points to identify the most important reactions and reactive species. Then, simulations were compared with experimental data. Multiple ignitions and extinctions as well as oscillations that are purely kinetically driven were found. Ignition to a partially ignited state with considerable reactivity of methane indicates possible narrow operation windows with high selectivities to partial oxidation products. At 0.1 atm, the authors found a selectivity of up to 80% to CO at 70% CH{sub 4} conversion. The ignition to a fully ignited branch is associated with high selectivity to CO{sub 2} and H{sub 2}O. The C2 chemistry inhibits the ignition of methane to the partially ignited branch. The methane ignition temperature exhibits two branches with respect to pressure, with only the low-pressure branch being dominant. Reaction path analysis at ignition conditions shows that the preferred pathway of CH{sub 4} oxidation is to form CO and CO{sub 2} though CH{sub 2}O and CH{sub 2}(s) intermediates. However, at intermediate to high pressures, the recombination of CH{sub 3} to C{sub 2}H{sub 6} also becomes quite significant.

• Sponsoring Organization: Office of Naval Research, Washington, DC (United States); Petroleum Research Fund (United States)
• OSTI ID: 556730
• Journal Information: AIChE Journal, Journal Name: AIChE Journal Journal Issue: 8 Vol. 43; ISSN AICEAC; ISSN 0001-1541
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
CARBON DIOXIDE
CARBON MONOXIDE
CHEMICAL REACTION KINETICS
MATHEMATICAL MODELS
METHANE
OXIDATION
PRESSURE DEPENDENCE
REACTION INTERMEDIATES
WATER VAPOR