Chemical Engineering April 2020 - 11

Semiconducting material combines
handedness and polarity
A
E
material synthesized by researchers
at Rensselaer Polytechnic Institute
(RPI; Troy, N.Y.; www.rpi.edu) could
enable new ways of manipulating
electronic materials remotely using light. The
material, explains RPI professor of materials
science and engineering Jian Shi, derives its
unique capabilities from the co-existence of
both macroscopic electrical-field-switchable
polarity and chirality. This combination of
material properties in semiconductors has
not been previously demonstrated. The new
material's pyroelectricity (spontaneous electric
polarization that can be reversed through
the application of an electric field) combined
with chirality (a spatial property of molecules
or crystals that are non-superimposable with
their mirror images) yields unprecedented material
tunability when exposed to light sources
of different polarization. This means that the
material can be remotely manipulated to produce
specific electric and magnetic properties,
which could be especially advantageous
in semiconductor applications.
The organic-inorganic hybrid crystal is
made of carbon, iodine and lead and is synthesized
via a wet-chemistry method with
special precursors designed to enable both
polarity and chirality. " Currently, the materials
are synthesized in a laboratory beaker, but it
would be easily scaled up, " explains Shi, noting
that scaleup would involve delicate control
of parameters like nucleation and growth
rate. The most promising electronics applications
for this material, says Shi, include sensing,
logic switching and memory.
Wood-supported catalyst safely keeps fruit fresh
Empa
thylene is a
multifunctional
phytohormone
that regulates
growth, ripening and
other functions in plants.
For
example,
bananas
stored next to apples will
ripen quickly due to the
ethylene released from
the apples, which in turn
are triggered to release
more ethylene. This can
cause a loss of food in
the entire supply chain, from importer to the
wholesale and retailer.
To counteract the accelerated
specific surface area
(photo) - properties
that make the delignified
wood a perfect natural
scaffold for a catalyst.
The delignified wood is
then put into two different
solutions: The first
creates a cerium-doped
TiO2 foundation that
serves as the support
for the platinum particles
on the cell walls of the
wood; the second contains
the platinum particles, which then enter
the wood structure.
ripening
process, ethylene must be kept away from
fruits and vegetables. For this purpose, researchers
from the Swiss Federal Laboratories
for Materials Science and Technology
(Empa; Dübendorf; www.empa.ch) and ETH
Zurich (www.ethz.ch) are developing a new
catalyst that degrades ethylene, released by
fruits and vegetables, into water and CO2.
The concept is based on a catalyst support
made of delignified wood, which is then enriched
with a platinum catalyst that is dispersed
at an atomic level.
Wood consists of three basic substances:
cellulose, hemicellulose and lignin. The researchers
used a protocol developed in the
Wood Materials Science professorship at
ETH Zurich and Empa, and dissolved with the
help of an acid solution both lignin, wood's
binding substance, and a part of the hemicelluloses.
This makes the remaining cellulose
structure extremely porous with a very large
The Empa team demonstrated that the catalyst
decomposes virtually all of the emitted
ethylene at room temperature. If the temperature
drops to 0°C, however, water - one of
the reaction products - can no longer evaporate,
sticking to the catalyst and preventing
any further chemical reaction. To rid the
catalyst from the condensed water layer and
make it work again, it is sufficient to warm up
the entire structure for a few minutes every
two hours, Lukovic says.
The concept of catalytically degrading ethylene
to extend the shelf life of fruit is not new,
since Hitachi (Tokyo, Japan; www.hitacji.com)
has been producing refrigerators equipped
with platinum catalysts since 2015. However,
the Empa researchers have improved this
concept by using a wood-based support instead
of silica, and a more efficient utilization
of the (rather expensive) platinum catalyst.
The study was reported in a recent issue of
the journal ACS Nano.
n
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
APRIL 2020
11
veloped a new, stable SAC
for performing chemoselective
hydrogenation of
nitroarenes. The researchers
were able to stabilize
single platinum atoms
within sub-nanometer
surface cavities in well-defined
12CaO·7Al2O3 crystals
(designated C12A7),
using a combination of
both theoretical prediction
and experimentation. This
approach utilizes the interaction
of isolated metal
anions with the positively
charged surface cavities
of C12A7, which allows
for severe reduction conditions
at temperatures up
to 600°C. The resulting
catalyst, 0.1Pt/C12A7,
is said to be stable and
highly active toward the
selective hydrogenation of
nitroarenes to anilines, with
a much higher turnover frequency
(up to 25,772 h−1)
than well-studied Ptbased
catalysts.
AMMONIA
Tsuyoshi Nagaoka and
colleagues at Nagoya
University (Japan; www.
nagoya-u.ac.jp)
have
demonstrated that the
ammonia synthesis activity
per weight of catalyst
of Ru/Ba/LaCeOx, prereduced
at 700°C, has the
highest reported oxidesupported
Ru catalysts,
52.3 mmol h-1 gcat-1
at 350°C, 1.0 MPa. The
turnover frequency of Ru/
Ba/LaCeOx at 350°C was
more than 8 times that of
Cs+/Ru/MgO, which is a
well-known active catalyst
used as a benchmark. Furthermore,
hydrogen poisoning
- a typical drawback
for oxide-supported
Ru catalysts - was effectively
suppressed.
CO2 UTILIZATION
VTT (Espoo, Finland;
www.vtt.fi) and partners
have started a two-year
project to develop a process
to capture and utilize
CO2. For the BECCU
project, researchers are
focusing on polyols as the
primary end product. ❑
http://www.rpi.edu http://nagoya-u.ac.jp http://www.empa.ch http://www.ethz.ch http://www.hitacji.com http://www.vtt.fi http://WWW.CHEMENGONLINE.COM
Chemical Engineering April 2020

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