Chemical Engineering October 2014 - 17

A direct route to organosilicon compounds
R
esearchers from the National Institute
of Advanced Industrial Science
and Technology (AIST; Tsukuba City,
Japan; www.aist.go.jp), with support
from New Energy and Industry Technology
Development Org. (NEDO;
Kawasaki City; Japan; www.nedo.
go.jp) have developed a technology to
efficiently synthesize tetra-alkoxysilane
- a promising raw material
for organosilicon compounds, such as
silicone. Such materials are used in
automobiles and solar cells. Unlike
alternative routes, which either use
a metallic-silicon intermediate, or an
expensive dialkyl carbonate, the new
synthesis process uses inexpensive
raw materials (silica and alcohol).
High temperatures are also avoided,
making the new process a low-cost,
energy-saving alternative to traditional
methods, says AIST.
AIST's reaction process uses an
organic dehydrating agent, which
enables a direct, one-step synthesis
of alkoxy-silane from silica and an
alcohol. Removing the water byproduct
during the reaction suppresses
the reverse reaction. For example, an
18% yield is achieved after 24 h in the
reaction of silica (99.7+%, 75-150µm
dia. particles) and methanol at
242°C using acetone dimethyl acetal
as the dehydrating agent. Without the
agent, a yield of less than 0.1% is observed.
An even higher yield of 48% is
achieved after 24 h (88% yield after 48
h) when introducing tetra-methoxy titanium
and KOH under a CO2 atmosphere
of 2 MPa.
The researchers speculate that CO2
activates the methanol to efficiently
react with silica, while the tetra-methoxy
titanium accelerates the reaction
of methanol and CO2, and the KOH
promotes the decomposition of silica
by cleaving the Si-O bond.
The researchers believe the dehydrating
agent can be easily regenerated and
reused. CO2 is not consumed in the reaction
and can also be reused. Furthermore,
the new process is chlorine-free,
Bio-propane
a team of scientists from imperial College
london (www.imperial.ac.uk) and
the University of Turku (Turun Yliopisto,
Finland; www.utu.fi) has engineered
Escherichia coli bacteria to produce
propane. Using E. coli as a host organism,
the scientists interrupted the
biological process that turns fatty acids
(Fas) into cell membranes. To interrupt
the process, the researchers discovered
a new variant of an enzyme called
thioesterase that specifically targets
Fas and releases them from the natural
process. They then used a second bacterial
enzyme, called Car, to convert
butyric acid into butyraldehyde. Finally,
a hydrocarbon-generating enzyme,
called aldehyde-deformylating oxygenase
(aDo), converts the aldehyde into
propane. The proof-of-concept study is
a first step toward renewable propane. a
commercially viable process may take
5-10 years of further development.
thus avoiding the inevitable chlorinecontamination
that occurs when using
SiCl4 as a raw material. The group is
now working to enhance the efficiency
further, optimize the recycling methods
and scale up the process.
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ChemiCal engineering www.Chemengonline.Com oCToBer 2014 17
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Chemical Engineering October 2014

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