Reforming reaction Generation

In a typical PAFC system, methane passes through a reformer with steam from the coolant loop of the water-cooled fuel cell. Heat for the reforming reaction is generated by combusting the depleted fuel. The reformed natural gas contains typically 60 percent H9, 20 percent CO, and 20 percent H9O. Because the platinum catalyst in the PAFC can tolerate only about 0.5 percent CO, this fuel mixture is passed through a water gas shift reactor before being fed to the fuel cell. 

The extent to which anode polarization affects the catalytic properties of the Ni surface for the methane-steam reforming reaction via NEMCA is of considerable practical interest. In a recent investigation62 a 70 wt% Ni-YSZ cermet was used at temperatures 800° to 900°C with low steam to methane ratios, i.e., 0.2 to 0.35. At 900°C the anode characteristics were i<>=0.2 mA/cm2, Oa=2 and ac=1.5. Under these conditions spontaneously generated currents were of the order of 60 mA/cm2 and catalyst overpotentials were as high as 250 mV. It was found that the rate of CH4 consumption due to the reforming reaction increases with increasing catalyst potential, i.e., the reaction exhibits overall electrophobic NEMCA behaviour with a 0.13. Measured A and p values were of the order of 12 and 2 respectively.62 These results show that NEMCA can play an important role in anode performance even when the anode-solid electrolyte interface is non-polarizable (high Io values) as is the case in fuel cell applications. 

Additionally, nickel is a well established steam-reforming catalyst. An ideal SOFC system operated on natural gas applies internal steam reforming, i.e., the reforming of the methane takes place in the anode compartment of the stack. This type of system is favored for system simplicity and costs (no external reformer), and for system efficiency because the heat generated by the cell reaction is directly used by the reform reaction, and hence the cooling requirements of the stack (by air at the cathode side) are significantly reduced. 

Oxidation reactions are much faster than reforming reactions, suggesting that a single stage process for syngas generation would be a viable alternative to steam reforming. 

The objective of tiie research described here is to explore synthesis gas generation by direct oxidation of CH4 (reaction 3). A reactor giving complete conversion to a 2/1 mixture of H2 and CO would be the ideal upstream process for the production of CH3OH or for the Fischer-Tropsch process. As discussed above, currently implemented or proposed processes utilize a combination of oxidation and reforming reactions to generate synthesis gas from CH4 and O2. In this work, we seek a faster, more efficient route of syngas generation in which H2 and CO are the primary products of CH4 oxidation. It is expected that this may be difficult because... 

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