Development of a Butanol Fuel Processor for Person-Portable Fuel Cell Power Systems

A novel partial oxidation (POX) catalyst and butanol-to-hydrogen fuel processor sub-system concept have been developed to fill the need for person-portable power systems with high energy density for extended duration operation.  The system is designed to reform isobutanol through partial oxidation with air.  A multi-stage carbon monoxide removal train was developed to convert the CO present in the reformate stream.  The resulting hydrogen stream is suitable for integration with a PEM fuel cell for person-portable power system applications.

An integrated system design approach was undertaken to optimize the fuel processing system configuration and operating conditions.  Among the available fuel processing options, systems based on both partial oxidation and auto-thermal reforming (ATR) of isobutanol fuel were investigated.  The former, i.e. partial oxidation reforming, results in a simpler but less efficient design to implement.  The latter, i.e. autothermal reforming, is a more efficient approach for conversion of isobutanol to hydrogen for the fuel cell anode.  A systematic design study has determined the optimal operating conditions for the partial oxidation and autothermal-based systems.

Energy density, in terms of W-h/kg and W-h/L, is a critical parameter for person-portable power systems.  These systems must be lightweight and compact, especially for military applications to avoid hindering a soldier’s movements in the field.  The butanol-fueled system under development has an inherent advantage due to the increased energy density of the fuel, as compared to methanol-fueled systems.  A complete, integrated sub-system was designed using 3-D CAD modeling software to minimize the size and weight of the reformer.  3-D CAD renderings were created for both the partial oxidation and autothermal-based butanol fuel processor systems. The POX-based butanol reforming system is estimated to achieve an energy density of 810 W-h/L and 850 W-h/kg, while the ATR-based system is estimated to achieve an energy density of 1,000 W-h/L and 2,000 W-h/kg.

The concept feasibility of reforming isobutanol to a hydrogen-rich stream via partial oxidation was experimentally demonstrated.   Novel catalyst formulations and catalyst support structures have been developed and tested.  A Rh/Ce-based reforming catalyst effectively converted isobutanol to an H₂-rich stream with no coke formation under the desired system operating conditions.  The catalyst was also demonstrated to be regenerable, should carbon deposition occur.  In summary, the concept feasibility of both a novel butanol reforming catalyst and fuel processor sub-system design to effectively convert isobutanol to hydrogen with the potential to be packaged into a compact, high energy density system has been demonstrated.