285
Fuel Production by Supercritical Water
indicates that in general, SCW reduces coking, lowers the required temperature
for the same level of conversion, and modifies the product distribution, particularly
in favor of more production of hydrogen. These results imply the need for a study
of tri-reforming under SCW (critical point 374°C and 22.1 MPa) conditions. It is
expected that the supercritical conditions will bring about significant improvement
on product distributions, reaction temperature severity, and catalyst activity, stability,
and life. Under SCW gasification, syngas is produced directly at high pressure, which
means that a smaller reactor volume and lower energy are needed to pressurize the
gas in a storage tank.
While tri-reforming of methane in SCW has been investigated by a number of
researchers [171–176], these studies have been carried out with conventional Ni or
bimetallic catalysts. The studies have shown that the supercritical conditions lower
the required temperature for gasification, and at high temperatures (>600°C), hydrogen and carbon dioxide are the dominating products. The studies [171–176] have also
shown that the product composition from tri-reforming under supercritical conditions
depends on a number of variables such as temperature, pressure, feedstock and oxygen
concentrations, reaction time, biomass properties, presence of inorganic elements, biomass particle size, and the nature of the catalyst. In the SCW environment, the syngas
composition will heavily depend on the effectiveness of the dry reforming reaction.
More catalytic studies to improve dry reforming reaction are presently being pursued.
The use of nanocatalysts is also very heavily examined. In future, more work on trireforming in SCW environment with practical feedstock needs to be carried out.
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