FUEL PROCESSING FOR FUEL CELLS: EFFECTS ON CATALYST DURABILITY AND CARBON FORMATION

On-board production of hydrogen for fuel cells for automotive applications is a challenging developmental task. The fuel processor must show long term durability and under challenging conditions. Fuel processor catalysts in automotive fuel processors will be exposed to large thermal variations, vibrations, exposure to uncontrolled ambient conditions, and various impurities from ambient air and from fuel. For the commercialization of fuel processors, the delineation of effects on catalyst activity and durability are required. We are studying fuels and fuel constituent effects on the fuel processor system as part of the DOE Fuel Cells for Transportation program. Pure fuel components are tested to delineate the fuel component effect on the fuel processor and fuel processor catalysts. Component blends are used to simulate ''real fuels'', with various fuel mixtures being examined such as reformulated gasoline and naptha. The aliphatic, napthenic, olefin and aromatic content are simulated to represent the chemical kinetics of possible detrimental reactions, such as carbon formation, during fuel testing. Testing has examined the fuel processing performance of different fuel components to help elucidate the fuel constituent effects on fuel processing performance and upon catalyst durability. Testing has been conducted with vapor fuels, including natural gas and pure methane. The testing of pure methane and comparable testing with natural gas (97% methane) have shown some measurable differences in performance in the fuel processor. Major gasoline fuel constituents, such as aliphatic compounds, napthanes, and aromatics have been compared for their effect on the fuel processing performance. Experiments have been conducted using high-purity compounds to observe the fuel processing properties of the individual components and to document individual fuel component performance. The relative carbon formation of different fuel constituents have been measured by monitoring carbon via in situ laser optics, and by monitoring carbon buildup on the catalyst surface. The fuel processing performance of the individual components is compared with the fuel processing performance of blended fuel components and the reformulated gasoline to examine synergistic or detrimental effects the fuel components have in a real fuel blend