Organic Film Structure Physisorbed Films ESP in SAMS SP in Molecular Films Reforming Catalysts ECH

 

Reformer Development for Solid Oxide Fuel Cells

In collaboration with the Plasma research group at the Université de Sherbrooke, we are developing medium temperature (600oC-750oC) electrochemical fuel cells for distributed power generation.  These will be highly integrated ceramic systems featuring in-situ steam reforming of methane feed stock into hydrogen, the fuel gas.  Our role in this project is to study and optimize the catalytic steam reforming of the methane, in order to minimize coking effects and catalyst poisoning by natural and introduced sulfur products in the feedstock.  We have designed and constructed a mass-spectrometer based system to measure the product yields, feedstock consumption and long-term activity measurements on a multi-cell reactor, and we are now developing infrared spectroscopic systems for the in-situ characterization of the chemical modifications of the catalyst materials as a function of feedstock composition and operating conditions.  We have demonstrated the quantitative agreement between the products of our nickel-based catalyst bed (as a function of temperature and feed gas) and the predictions of our in-house multi-equilibrium model.  This indicates that the reforming reaction is not kinetically limited, and facilitates the study by simple product analysis methods such as those now installed.  We have explored the influence of particle porosity on the reaction yields, and have developed a simple protocol that prevents sintering of the Ni catalyst powder.  We have found that the catalytic activity is remarkably stable in the presence of adsorbed thiols containing fewer than 6 carbon atoms (similar to those used as odour agents in commercial natural gas, and those present naturally), while larger chains rapidly contaminate the surface with coke deposits.  Remarkably, even these coke deposits do not appear to be the major de-activation mechanism, although work is continuing in order to elucidate these effects (and hopefully develop methods by which to mitigate their impact). Exposure to H2S causes catastrophic failure of these catalysts due to the formation of chemically inert Ni3S2 (Heazlewoodite).

 

Where to from here ?

The next phase of this work is to measure the kinetic properties of the reformation yields as a function of the source gas composition and flow rates, in order to more sensitively characterize the accumulation of contaminants and the loss of catalytic activity. 

While the previous work has shown that the activity remains very high (>95% methane conversion over several days of operation), viable fuel cell systems require stable operation over many months of operation under full load.  Accelerated testing of the reformer requires a more sensitive measure of activity than the overall reaction yields.  In addition, the absence of significant sintering of the Ni powders used in these studies is a welcome, yet unexplained result.  The changes in sample morphology will be monitored using SEM, and correlated against the catalytic activity as given by the kinetic properties of the reformer reaction.

 

Relevant Instrumentation (click on image to see apparatus)


Phoenix

Midas

Mercury

Hydra

Jason

Vulcan