Microchannel Autothermal Reforming of Methane to Synthesis Gas

Autothermal reforming of methane to synthesis gas (CO and H₂) is studied in a microchannel reactor comprised of Pt- and Rh-based catalysts that are coated on opposite walls of the channel. The effects of operating parameters and microchannel catalyst configuration on methane conversion and CO selectivity are analyzed. The parameters considered are the residence time of the reactants (12.9–25.7 ms), reaction temperature (500–650 °C), molar steam-to-carbon (S/C = 0–3.0) and oxygen-to-carbon (O₂/C = 0.47–0.63) ratios at the inlet. Doubling the residence time leads to ca. 10 % increase in methane conversion, but has only a 4 % contribution to the CO selectivity. Higher O₂/C ratios improve extent of methane oxidation, but reduce selectivity due to CO₂ production. When the temperature is raised from 500 to 650 °C, conversion increases from 12.8 to 46.6 % and selectivity increases from 20.1 to 35.7 %. S/C ratio has the greatest effect on the outlet H₂/CO ratio, which is found to vary between 0.93 and 2.68, via the water–gas shift reaction. Comparison of the present catalyst configuration with the use of bimetallic Pt–Rh coating in the microchannel under identical conditions shows that the latter can improve conversion by 20 % and CO selectivity by 33 %.