Methane decomposition : characterization of the carbon produced and possible use in direct carbon fuel cells

[摘要] Investigations into methane conversion (both catalytic and non-catalytic) andcharacterization of the carbon produced for use in high efficiency DCFCs wereperformed. Under non-catalytic processes, a high methane conversion (> 80%) wasachieved at 1200 oC at flow rates of between 10-60 ml/min. Analysis of the carbonusing Raman spectroscopy showed that the carbon was highly disordered and thedegree of disorder increased with increase in methane flow rate (from aD/aG = 1.54at 10 ml to aD/aG = 2.24 at 60 ml/min). Further analysis of the carbon usingthermogravimetric analysis (TGA) demonstrated that the carbon produced at higherflow rates e.g. 100 ml/min were easily oxidized (746 oC) compared with thoseproduced at lower flow rates (10 ml/min, 846 oC). Therefore, a high temperaturecoupled with high flow rates (60-100 ml/min) produced carbon with desired qualities(high disorder, low crystallinity and more thermally reactive) for DCFC uses.In the catalytic decomposition of methane, Ni supported on TiO2 and a 1:1 mixtureof TiO2/Al2O3 gave high and stable methane conversions of about 60% at only 600oC compared to 1200 oC required for the non-catalytic conversion. These catalystswere found to be the best catalyst systems of the tested catalysts.Considering the thermal oxidation and crystallinity data which are some of theproperties of the carbon required for direct carbon fuel cells (DCFCs), the carbonproduced can potentially be used in DCFC systems.

[发布机构] University of the Witwatersrand