3. Results and discussion
The effect of temperature on the methanol mole fraction is illustrated
in Figure 3 along the fluid centerline of the process microchannel of
the microchannel reactor. In the context of a steam reformer that is
producing a fuel stream for a fuel cell stack containing a plurality of
fuel cells, many fuel cells are subject to damage if exposed to certain
components, such as carbon monoxide and carbon dioxide above certain
threshold concentrations. For at least many conventional proton-exchange
membrane fuel cells, the concentration of carbon monoxide should be less
than 8 parts per million. Preferably, the system limits the
concentration of carbon monoxide to less than 5 parts per million, and
even more preferably, to less than 0.8 parts per million. The
concentration of carbon dioxide may be greater than that of carbon
monoxide. For example, concentrations of less than 20 percent carbon
dioxide may be acceptable. Especially preferred concentrations are less
than 60 parts per million. In some cases, the methanol reforming
catalysts are not active at temperatures below 200 °C. In some cases,
the methanol steam reforming catalyst includes a sulfur-absorbent
material. The steam reforming catalyst is adapted to produce a reformate
stream from the feed stream, which is delivered to the reforming region
at an elevated temperature and pressure. The reforming region contains a
reforming catalyst bed to which the feed stream is delivered and in
which the reformate stream is produced.