Catalytic Combustion of Premixed Fuel-Rich Methane–Oxygen in a Platinum Microtube

This work examines the catalytic ignition and self-sustained combustion of premixed fuel-rich methane–oxygen mixtures ([Formula: see text]). The experiments used a platinum microtube of 0.6 mm inner diameter with a continuous flow of reactants and subjected it to a linearly ramped power input until ignition was achieved. Following ignition, self-sustained combustion was established without external power input. The influence of the equivalence ratio and flow rate on the power input required to initiate combustion was obtained. Relatively less power was needed to ignite mixtures with increasing equivalence ratios and lower flow rates. Exhaust product analysis was performed during the self-sustaining combustion phase. Fourier transform infrared spectroscopy was employed to quantify the major combustion products, including carbon monoxide and carbon dioxide. Hydrogen production was also quantified using a thermal conductivity detector. Infrared imaging was used to determine the temperature of the catalytic microtube surface and track the postignition movement of the reaction front during the transition to steady combustion. The experimental results for the critical power input required to achieve ignition were compared with numerical simulations. A plug-flow assumption was used to model the microtube reactor, and surface and gas-phase reactions based on an existing kinetic model were included. The simulation results were used to obtain the ignition and hydrogen production maps for this microtube reactor.