Chemical Engineering April 2019 - 10

tals of TiO2 are interspersed with pinecone-like
polycrystalline structures. The
coating has a surface area 100 times
larger than previous TiO2 coatings made
with nanoparticles, resulting in more
bacteria-killing oxygen. There is carbon
on the crystal surfaces in spaces between
the nanostructures, which helps
absorb visible-light photons, and feeds
them to the TiO2, Krumdieck says.
The team tested the coating by spreading
E.coli culture on a sample and exposing
it to UV light and white light for four
hours. UV exposure killed all of the bacteria
every time, while visible light killed
over 99% of the bacteria.
WASTEWATER TREATMENT
A new pilot plant to treat industrial wastewater
is being built that could potentially
reduce the amount of liquid waste by
over 90%. Located at a semiconductor
manufacturer in Singapore, the new
plant will also recover precious metals
from the treated water. The plant is being
built jointly by the Separation Technologies
Applied Research and Translation
(START) Center - a national-level facility
to develop and commercialize innovative
separation and filtration technologies -
and Memsift Innovations Pte Ltd. (www.
memsift.com), a local water technology
firm specializing in zero-liquid discharge
water-treatment systems.
The pilot plant will use a water-treatment
system that leverages a new type
of hollow-fiber membrane invented by
professor Neal Chung at the National
University of Singapore (NUS; http://nus.
edu.sg). Unlike conventional hollow-fiber
membranes, which resemble spaghetti
noodles with a hollow core, the new tribore
hollow-fiber membranes have three
hollow cores, allowing for a water flowrate
that is about 30% higher.
Under a new research partnership and
licensing agreement, the START Center
and Memsift Innovations will jointly build
the wastewater-treatment plant with the
tri-bore hollow-fiber membranes, which
can treat up to 5,000 L/d. This pilot plant
is expected to help the company save
up to 1.6 million L/yr of water, resulting in
a savings of $250,000 in disposal cost.
The new pilot plant is expected to be
commissioned in the second quarter of
2019, and the piloting results used for
commercializing the technology.
SMART SOLVENT EXTRACTION
At the SME Annual Conference and Expo
(February 24-27; Denver, Colo.), Solvay
S.A.
(Brussels,
Belgium; www.solvay.
com) and Codelco (Santiago, Chile; www.
codelco.com), the world's largest copper
producer, launched SolvExtract - a first(Continues
on p. 11)
10
Mechanochemistry performs
cross-coupling reactions
P
alladium-catalyzed cross-coupling
reactions are one of the
most powerful and versatile
methods to synthesize a wide
range of complex functionalized molecules.
However, the development of solidstate
cross-coupling reactions remains
extremely limited. Now, Hajime Itoh, Koji
Kubota and colleagues at Hokkaido University
(Sapporo, Japan; https://labs.
eng.hokudai.ac.jp/labo/organoelement)
reported a rational strategy that provides
a general entry to palladium-catalyzed
Buchwald-Hartwig cross-coupling reactions
in the solid state. The key finding
of this study is that olefin additives can
act as efficient molecular dispersants for
the palladium-based catalyst in solidstate
media to facilitate solid-state crosscoupling.
Their strategy could inspire the
development
of
industrially
attractive,
solvent-free palladium-catalyzed crosscoupling
processes for other valuable
synthetic targets.
Conventionally, palladium-catalyzed
cross-coupling reactions of liquid and
solid substrates are conducted in organic
solvents. Researchers sought to
re-design palladium-based catalyst systems
for the solid state, which could potentially
unlock versatile applications for
solid-state synthesis.
They have developed a rational strategy
for a potentially general and scalable
solid-state palladium-catalyzed
cross-coupling reaction using mechanochemistry.
Whereas the palladiumcatalyzed
cross-coupling of neat liquids
proceeds readily in ball mills, similar
reactions using solid reactants remain
challenging. However, they discovered
that the addition of small amounts of
olefins dramatically accelerates the C-N
cross-coupling of such solid substrates.
The examination of palladium nanoparticles,
which were obtained from these
reaction mixtures, by transmission electron
microscopy (TEM) suggested that
the olefin additives can act as efficient
molecular dispersants for the palladium
catalysts in solid-state media and thus
facilitate
this
challenging
solid-state
cross-coupling. They expect that the
strategy developed in this study could
unlock broad areas of chemical space
for palladium-catalyzed solid-state syntheses
of valuable synthetic targets in
various scientific fields.
CO2 scrubber supplies raw material for
oxalic acid production
A
novel carbon-capture project at
Michigan Technical University
(MTU; Houghton, Mich.; www.
mtu.edu) couples the collection
of carbon dioxide from power-plant
fluegas with a system to use the captured
CO2 as a raw material to make
oxalic acid, which can be used in the
mining industry to leach rare earth elements
from ore.
" Coal-fired power plants can be acceptable
economically and environmentally
if you can use the CO2 for
a productive purpose, rather than allowing
it into the atmosphere, where
it is harmful, or sequestering it underground,
where it is wasted, " says
MTU professor and project leader
Komar Kawatra.
In the first phase of the project, a sodium
carbonate solution is pumped to
the top of a scrubbing column, where
CO2-rich exhaust gas from the MTU
power plant is bubbled through the
solution. " The scrubber is able to reduce
the CO2 content in the exhaust
gas from 8% to less than 1%, " says
MTU researcher and doctoral student
Sriram Valluri.
Waste heat from the power plant is
used to regenerate CO2 from the sodium
carbonate after it is captured.
The sodium carbonate scrubber is less
expensive than
conventional carboncapture
systems based on amines, and
the chemicals are much less toxic than
amines, the team says.
In the second stage of the project,
the CO2 that has been captured from
the exhaust gas is reacted in an electrolytic
cell to convert it to the two-carbon
dicarboxylic acid known as oxalic acid.
Locally produced oxalic acid could
boost the production of rare-earth elements
in the U.S., says Kawatra.
Currently, the CO2 scrubber is operating
at pilot scale on the MTU power
plant, while the oxalic acid production
system is operating at bench scale,
doctoral student Victor Claremboux
says. The next step in the project is to
scale up the oxalic acid system.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
APRIL 2019
https://labs http://eng.hokudai.ac.jp/labo/organoelement http://www.memsift.com http://nus http://www.edu.sg http://www.mtu.edu http://www.solvay http://www.codelco.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering April 2019

Table of Contents for the Digital Edition of Chemical Engineering April 2019
