Chemical Engineering July 2012 - 20

Oxford Catalysts
Newsfront
Microchannel reactors
Microchannel reactors are compact reactors
that have channels with diameters
in the millimeter range. These
small channels dissipate heat more
quickly than conventional reactors
with larger channel diameters, so more
active catalysts can be used. Mass- and
heat-transfer limitations reduce the
efficiency of the large conventional reactors
used for Fischer-Tropsch (F-T)
and steam methane reforming (SMR)
reactions and hydroprocessing. So, the
use of microchannel processing makes
it possible to greatly intensify chemical
reactions, enabling them to occur
at rates 10 to 1,000 times faster than
in conventional systems.
Microchannel Fischer-Tropsch reactors,
developed by Velocys (Plain
City, Ohio) and using a new, highly active
F-T catalyst developed by Oxford
Catalysts (Oxfordshire, U.K.) are now
available for the small-scale distributed
production of fuels. These reactors
exhibit conversion efficiencies in
the range of 70% per pass, and are designed
for economical production on a
small scale. A single microchannel-reactor
block produces some 30 barrels
of synthetic fuels per day. In contrast,
conventional FT plants are designed to
work at minimum capacities of 30,000
barrels per day or higher.
Because microchannel reactors have
the potential to unlock the distributed
product of fuels and other materials
on a small, decentralized scale, Oxford
Catalysts has been working to
develop catalysts for these applications,
says Kai Jorosch, manager of
catalyst and material sciences with
Oxford Catalysts. " We've developed a
series of catalyst platform technologies
for the production of superactive
catalysts for use in microchannel reactors, "
he says.
Among them is the organic matrix
combustion (OMX) method, which
makes it possible to produce catalysts
with higher metal loadings, while still
maintaining optimal crystalline sizes.
Compared to conventional catalystproduction
methods, such as incipient
wetness impregnation, OMX produces
more active and stable catalysts.
Catalysts for FT reactions are also
being developed. In the FT process,
a syngas consisting of a mixture of
Microchannel Fischer-Tropsch reactors exhibit conversion efficiencies in the range of
70% per pass, and are designed for economical production on a small scale
Oxford Catalysts
Oxford Catalysts' technology allows the typically cobalt catalysts to be produced with
a reduced need for precious metal promoters, without any loss of performance and
with superior activity, selectivity and stability to conventional catalysts
carbon monoxide and hydrogen is
converted into hydrocarbons over a
catalyst. Oxford Catalysts' technology
allows the typically cobalt catalysts
to be produced with a reduced need
for precious metal promoters, without
any loss of performance and with
superior activity, selectivity and stability
to conventional catalysts, notes
Jorosch. It is now possible to use feedstocks
such as natural gas and biogas,
as well as coal, for the production of
synthetic fuels.
SMR is another area of development
for Oxford Catalysts. In SMR,
methane gas is mixed with steam
and passed over a catalyst to produce
a syngas consisting of hydrogen
and carbon monoxide. The reaction is
highly endothermic, so it requires the
input of heat. This can be generated
by the combustion of excess methane
20 CHEMICAL ENGINEERING WWW.CHE.COM JULY 2012
and hydrogen produced. In microchannel
SMR reactors, the heat-generating
combustion and steam methane reforming
processes take place in adjacent
channels.
Overcoming heat and mass transfer
limitations allows near-equilibrium
conversion and selectivity at millisecond
contact times. The high heat
transfer properties of the microchannels
and the close integration between
combustion and reforming channels
make this process very efficient. The
microchannel SMR exhibits high mechanical
strength, low pressure drop
and excellent safety as no premixing
between fuel and air is required. In
the same way as superactive FT catalysts
can unlock the potential of microchannels
FT, the same applies with
a superactive SMR catalyst.
■
Joy LePree
http://WWW.CHE.COM
Chemical Engineering July 2012

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