Non-Catalytic direct partial oxidation of methane to methanol in a Wall-Coated microreactor

An integrated mixer-reactor-heat exchanger microtube scalable system for the non-catalytic direct partial oxidation of methane to methanol was developed. With this module one can control the five key parameters (temperature, pressure, residence time, wall inertness and methane:air ratio) to selectively produce methanol at greater than 8 % per-pass yield (product of conversion and selectivity), under optimal conditions. For this module, these conditions were 80 bar, ∼420 °C outer wall temperature, a methane/air molar ratio of 2.9 and a residence time of 0.8 min. At lower methane/air molar ratios good yields were still possible, but at lower methanol selectivities. The walls were rendered inert using a carbiding process based on the decomposition of propane at 700 °C. While this carbide layer is not stable under long-term, repeated use, it is currently stable for about two days of operation.