Water-gas shift conversion in microchannel reactors using noble metal catalysts
Fuel cell technology will play a crucial role in future sustainable energy generation. Different types of fuel cells had been developed, of which Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are the fuel cells of choice for small scale stationary and mobile applications that operate under transient conditions.The feed for PEMFCs is hydrogen. For small scale stationary and mobile applications, the hydrogen, typically, has to be produced on-site from other energy sources, such as fossil fuels or fuel from renewable sources. At present, the most favourable approach appears to be production train that startsith a steam reformer stage, which converts most of the primary fuel to syngas. In the subsequent water-¬‐gas-¬‐shift stage,most of the carbon monoxide in the syngas is converted to additional hydrogen and carbon dioxide. In a last stage, the small amount of carbon monoxide that remains in the stream is reduced to acceptable levels for use in the fuel cell. In large scale industrial hydrogen production, the above concept (steam reforming –water gas-shift-hydrogen purification) is the state of the art, with the units operating under steady conditions for years years once started. In contrast, the said small scale units will typically operate under transient conditions and in on/off mode. This requires catalysts that are stable with respect to occasional contact with air and condensation of the steam co-fed with the primary fuel and which do not require any activation or other conditioning prior to restart. Only noble metal based catalysts meet these requirements at present.This study was aimed at the water-gas-shirhift (WGS) stage within this train. The basis of the study was the comparison of three commercial supported noble metal WGS catalysts and a state-¬‐of-¬‐the-¬‐art industrial iron/chromium high temperature WGS catalyst. All the catalysts were applied washcoated into stainless steel microchannel reactor, either coated in - house or by the catalyst manufacturer, as well as defining an operational window for the noble metal catalysts.
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