Preferential oxidation of CO over Au/CuOx–CeO2 catalyst in microstructured reactors studied through CFD simulations

• Gold supported on CuOx–CeO2 is an effective catalyst for the CO-PROX reaction.
• A window of reaction temperatures exists leading to CO contents below 10 ppm.
• Microchannel reactors allow virtually isothermal CO-PROX operation.
• Increasing the microchannel characteristic size lowers the CO removal efficiency.
• A careful control of the coolant flow rate and inlet temperature is necessary.

A computational fluid dynamics (CFD) simulation study of the preferential oxidation of CO (CO-PROX) in microstructured reactors consisting in square and semicircular microchannels coated with an Au/CuOx–CeO2 catalyst is presented. The CO content of the feed stream was set at 1 vol.%. A parametric sensitivity analysis has been performed under isothermal conditions revealing that an optimal reaction temperature exists that leads to a minimum CO content at the microreactor exit. The influence of the space velocity, CO2 concentration and oxygen-to-CO molar ratio in the feed stream (λ), catalyst loading, and microchannel characteristic dimension (d) on the microreactor performance has been investigated. Under suitable conditions, the CO concentration can be reduced below 10 ppm at relatively low temperatures within the 155–175 °C range. A negative effect of the increase of d from 0.35 mm to 2.8 mm on the CO removal efficiency has been found and attributed to a more detrimental effect of the mass transport limitations on the oxidation of CO than that of H2. Non-isothermal CFD simulations have been performed to investigate the cooling of the CO-PROX reactor with air or a fuel cell anode off gas surrogate in parallel microchannels. Due to the very rapid heat transfer allowed by the microreactor and the strong influence of the reaction temperature on the exit CO concentration, a careful control of the coolant flow rate and inlet temperature is required for proper reactor operation. The microreactor behavior is virtually isothermal.

Microchannel reactors allow virtually isothermal CO-PROX operation within the window leading to less than 10 ppm CO.Figure optionsDownload high-quality image (128 K)Download as PowerPoint slide