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Water for Energy and Fuel Production
Besides Cu/ZnO catalyst, Pd/ZnO catalyst has also been effective in methanol
partial oxidation reaction. For 1 wt% Pd/ZnO catalyst, methanol conversion reaches
40–80% within the 230°C–270°C range. Methanol conversion and H 2 selectivity increase with an increase in temperature. The nature of support also affects
the kinetics. Pd/ZrO 2 catalyst, while producing hydrogen and carbon dioxide, also
shows a significant increase in the decomposition reaction.
A combination of steam reforming and partial oxidation results in an auto-thermal
operation. Under this condition, the following reaction
CH 3 OH + (1 − 2n) H 2 O + nO 2 → CO 2 + (3 − 2n)H 2 (0 < n < 0.5) (4.60)
with copper-based catalysts also perform well. On Cu/ZnO catalyst, initially methanol is combusted by oxygen and water is produced. When oxygen is depleted,
methanol conversion and the production of hydrogen and carbon monoxide increase,
and the water production goes down. When Al 2 O 3 is added to the catalyst, better
performance for steam reforming is obtained. Purnama et al. [119] also found the
beneficial effect of oxygen addition to the feed during steam reforming of methanol
on Cu/ZrO 2 catalysts. In the auto-thermal operation, the relative ratio of oxygen,
methanol, and steam plays an important role on hydrogen production. For Cu–ZnO
(Al) catalyst, the best feed ratio of oxygen/methanol/steam was found to be 0.3/1/1.
In general, oxy reforming of methanol is complex, but it also strongly interacts with
water–gas shift reaction.
The auto-thermal operation of methanol for FC application in vehicles has been
adopted by DaimlerChrysler, Toyota, and Nissan. Small-scale hydrogen production
by reforming methanol is also commercialized. For its application in refueling station, hydrogen purification step is needed. This is generally carried out by either
pressure swing adsorption (PSA) or membrane separation technology. In general,
the cost of hydrogen production from methanol reforming is higher than that from
methane reforming. The Mercator project funded by the European Commission is an
integrated methanol steam reformer and selective oxidation system. The FC contains
a series of catalytic plates with combustion of anode off-gas on one side and steam
reforming of methanol on the other side.
A number of studies examined the metal-supported catalyst systems for steam
reforming of methanol for FC applications [120–134]. Such catalysts overcome
the slow heat transfer of packed-bed systems by integrating endothermic steam
reforming with exothermic hydrogen combustion. A wash-coated aluminum heat
exchanger showed the best performance using a suspension of commercial reforming catalysts. With an aluminum foam, 90% methanol conversion was achieved for a
sustainable period of time (about 450 h). Lindström [120], Lindström and Pettersson
[121–124,126,127], Lindström et al. [125,129], and Kolb et al. [128] examined methanol reforming over copper-based catalysts for FC applications.
A novel technology of steam reforming of methanol accompanied by palladium
membrane separation to produce pure hydrogen was investigated by Pan and Wang
[131,132] and Pan et al. [133]. This technique provides a possibility for bypassing the
technical problems of storage and delivery of hydrogen by delivering methanol to
forecourt hydrogen-dispensing stations and on-site hydrogen productions. Li et al.