A scalable silicon microreactor for preferential CO oxidation: Performance comparison with a tubular packed-bed microreactor

PEM fuel cells utilizing hydrogen and oxygen have shown great promise as future sources of clean, efficient power. Due to difficulties encountered in hydrogen storage and transport, investigation of on-board generation of hydrogen via fuel processing of liquid hydrocarbons has gained prominence. To achieve these goals, the need for compact reactor systems with effective component and heat integration as well as quick start-up times has been observed. This paper underlines the suitability of microreaction technology for the development of compact fuel processing systems as compared to packed-bed reactor technology which does not scale down in a feasible manner. A microchannel reactor was fabricated in silicon using standard microfabrication tools. A 2% Pt/Al₂O₃ catalyst was washcoated on the channel walls. Preferential CO oxidation in H₂ was chosen as a model reaction and the results were compared with those obtained from a conventional packed-bed microreactor. The silicon microreactor performs very well, while offering distinct advantages such as flexibility of reactor design, integration of structural and functional features and low pressure drop. Use of a wall-coated catalyst as compared to a packed-bed catalyst does not introduce any loss of performance efficiency due to external diffusive limitations. Issues of scale-up and efficient heat integration have also been addressed.