Hetero-/homogeneous combustion of ethane/air mixtures over platinum at pressures up to 14 bar

The hetero-/homogeneous combustion of fuel-lean ethane/air mixtures over platinum was investigated experimentally and numerically at pressures of 1–14 bar, equivalence ratios of 0.1–0.5, and surface temperatures ranging from 700 to 1300 K. Experiments were carried out in an optically accessible channel-flow reactor and included in situ 1-D Raman measurements of major gas phase species concentrations across the channel boundary layer for determining the catalytic reactivity, and planar laser induced fluorescence (LIF) of the OH radical for assessing homogeneous ignition. Numerical simulations were performed with a 2-D CFD code with detailed hetero-/homogeneous C₂ kinetic mechanisms and transport. An appropriately amended heterogeneous reaction scheme has been proposed, which captured the increase of ethane catalytic reactivity with rising pressure. This scheme, when coupled to a gas-phase reaction mechanism, reproduced the combustion processes over the reactor extent whereby both heterogeneous and homogeneous reactions were significant and moreover, provided good agreement to the measured homogeneous ignition locations. The validated hetero-/homogeneous kinetic schemes were suitable for modeling the catalytic combustion of ethane at elevated pressures and temperatures relevant to either microreactors or large-scale gas turbine reactors in power generation systems. It was further shown that the pressure dependence of the ethane catalytic reactivity was substantially stronger compared to that of methane, at temperatures up to 1000 K. Implications for high-pressure catalytic combustion of natural gas were finally drawn.