Thermodynamic equilibrium study of altering methane partial oxidation for Fischer–Tropsch synfuel production

Abstract

Thermodynamic equilibrium assessment for methane partial oxidation (MPO) and concomitant parallel side reactions was conducted by employing the Gibbs free energy minimization approach in order to study the tuning of syngas H2/CO ratio appropriate for downstream Fischer–Tropsch synthesis (FTS). The influences of operating conditions including CH4/O2 ratio (5:1–1:2), pressure (1–50 bar) and temperature (200–1000 °C) on MPO performance in terms of reactant equilibrium conversion, product and side product yields and H2/CO ratio were scrutinized. The results reveal that indirect combustion-reforming pathway was possibly the main contributory factor to the syngas yield during MPO. The lower CH4/O2 ratios possessed a positive effect on syngas yield. Carbon formation was favored at low temperatures but it could be suppressed as CH4/O2 ratios reduced at elevated temperatures. Although a rising pressure was disadvantageous for MPO performance but the quantity of carbon deposit was hindered since these processes involved gas volume expansion. A temperature at least of 800 °C and CH4/O2 ratio of 2:1 or 3:2 are the preferable operating conditions for MPO reaction to achieve the carbon-free region meanwhile maximizing the syngas yield with H2/CO ratio of 2 that appropriate for FTS process.