Chemical Engineering December 2012 - 14

CHEMENTATOR
(Continued from p. 12)
A new photocatalyst
for VOC destruction . . .
A
process for manufacturing fine particles
of titanium dioxide that exhibits a high
level of photocatalytic activity has been developed
by Showa Titanium Co., a subsidiary
of Showa Denko K.K. (SDK, Tokyo; ww.sdk.
co.jp). The product has been developed in collaboration
with professor Bunsho Ohtani at
Hokkaido University with support from the
New Energy and Industrial Technology Development
Organization (NEDO, Kawasaki,
Japan; www.nedo.go.jp). Showa Titanium is
now conducting tests for volume production
at its pilot plant, aiming to commercialize
the product by the end of 2013.
When used as photocatalyst, these titanium-oxide
particles cause strong oxidation
and reduction reactions in the presence of
ultraviolet (UV) light, thereby decomposing
a variety of volatile organic compounds
(VOCs). The TiO2 particles also exhibit ultra
hydrophilicity, causing water to spread as a
thin film, a property that makes the material
useful for solar-powered air purification
in applications such as antifogging window
glass and antifouling coatings for exterior
surfaces of buildings.
Although it is well known that the photocatalytic
properties of TiO2 improve as
the particle size gets smaller, conventional
methods for making fine TiO2 particles
often develop crystal defects, which lowers
the photoconversion efficiency as well as
the catalytic activity. To avoid this problem,
Showa Titanium has developed a gas-phase
production process to make decahedral
titanium-oxide fine particles (photo) with
minimal defects. In addition to the improved
photocatalytic properties, these low-defect
TiO2 products have potential for other applications
as functional materials, such as
for ceramic capacitors.
. . . and another photocatalyst for destroying viruses
M
eanwhile, professor Kazuhito Hashimoto
at the University of Tokyo (Japan;
www.light.t.u-tokyo.ac.jp) has developed
new photocatalyst materials based on copper-titanium
oxide, which exhibits superior
antiviral effectiveness and enhanced
antibacterial properties compared to existing
systems. Developed with support from
NEDO (see story above), this new catalyst
system is capable of reducing the number of
viruses in air by four orders of magnitude
without light in 1 h - a 99.99% viral deactivation
- and by seven orders of magnitude
in the presence of visible light. The
research group also observed similar effecA
BOOST FOR BIO-BUTANOL PRODUCTION
(Continued from p. 13)
Butanol can also be formed directly from
acetyl-coenzyme A (CoA) through butyrylCoA
(hot channel).
The team claims to have reported, for the
first time, the results of systems metabolicengineering
studies of the two butanol-forming
routes and their relative importance in
butanol production. It also claims to have
developed a metabolically engineered C.
acetobutylicum strain capable of producing
butanol with high yield and selectivity, by
Nottingham, researchers are
working to maximize the use of
sustainable forms of energy by
harnessing the ability of certain
bacteria, such as Clostridium
ljungdahlii to consume carbon
monoxide and convert it into
useful chemicals and fuels.
Na-ion batteries
To overcome some of the limitations
of lithium-ion batteries,
such as the relative scarcity
and high cost of lithium and
the fl ammability of the organic
electrolyte currently used, a
group from Murdoch University
(Perth, Western Australia; www.
murdoch.edu.au), led by Manickam
Minakshi, has developed
an alternative aqueous NaOH
battery. The idea was to replace
LiOH with abundantly available
aqueous NaOH electrolyte, and
couple this electrolyte with a Zn
anode and an MnO2 cathode.
Existing sodium technologies
work at high temperatures,
using an anode of molten sodium
and a cathode of molten
sulfur. The group aimed for a
low-temperature storage device.
Minakshi says that simply
tiveness against bacteria, such as E. coli and
Staphylococcus aureus. A system using this
photocatalyst has undergone field testing at
airports and hospitals in Japan.
Together with Showa Titanium, the scientists
have started to develop a mass-production
process for the photocatalyst system.
Also under the NEDO project, applications
development are underway at Seiwa Kogoyo
Co. (for air-cleaning systems); Sekisui Jushi
Corp. (for construction materials for interiors);
Toto Ltd. (for tiles and paints); Nippon
Sheet Glass Co. (for glass); at Panasonic
Corp. (for films); and Taiyo Kogyo Corp. (for
tent canvas materials).
reinforcing the direct butanol-forming flux.
By reinforcing the direct butanol-forming
flux in the bacterium, 18.9 g/L of butanol
was produced, with a yield of 0.71 mol butanol/mol
glucose by batch fermentation.
Those levels are 160% and 245% higher
than those obtained with the wild strain. By
fed-batch culture of the engineered strain
with in situ recovery, 585.3 g of butanol was
produced from 1,861.9 g of glucose, with the
yield of 0.76 mol butanol/mol glucose and
productivity of 1.32 g/L/h. The team believes
this makes the process cost-competitive.
14 CHEMICAL ENGINEERING WWW.CHE.COM DECEMBER 2012
replacing the Li+ with Na+ ions
probably does not work well,
because Na+ ions are 70%
larger than Li+, and do not fi t
well in empty spaces of the
electrode's matrix. Only materials
with 2D layered structures,
or a 3D structure with corner
sharing matrix, or a crystal
structure forming large-size tunnels
can reversibly accommodate
Na+ ions, he says. Hence,
MnO2 was selected as the cathode
material. As sodium is not
involved in the anodic process,
this system is not a " rockingchair
sodium-ion cell " but rather
a NaHO cell - MnO2|NaOH|Zn
- with sodium insertion on the
cathode and zinc dissolution
from the anode.
The discharge capacity of the
MnO2 cathode for the NaOH
cell is 225 mAh/g (300 Wh/kg),
compared with 142 mAh/g (210
Wh/kg) for the LiOH cell using a
1 V cut-off voltage.
Minakshi says the reversibility
of the NaOH cell needs to be
enhanced for practical applications
by incorporating oxide additives
to the host MnO2 matrix.
He says the aqueous sodium
battery could fi nd application in
large-scale energy storage systems,
such as a smart grid.
http://www.co.jp http://murdoch.edu.au http://www.nedo.go.jp http://www.light.t.u-tokyo.ac.jp http://WWW.CHE.COM
Chemical Engineering December 2012

Table of Contents for the Digital Edition of Chemical Engineering December 2012
