Chemical Engineering March 2021 - 6

monia to impart strengthened
π-π
interaction. By
applying
nanosheet coatings with intercalation
of porphyrin-based planar
molecules (with charged groups
and a conjugated π system) to
the surface of a porous membrane,
the research group was
able to construct an ultrathin
(50 nm) desalination membrane
layer. This layer demonstrated
high ion-blocking functionality
because the size of the nanochannels
could be controlled
within 1 nm.
The study was published recently
in the Journal of Materials
Chemistry A.
ENERGY HARVESTING
Scientists of Karlsruhe Institute
of Technology (KIT; Germany;
www.kit.edu) have developed
three-dimensional component
architectures for thermoelectric
generators (TEGs) based on
novel, printable thermoelectric
materials. The results are reported
in npj Flexible Electronics
and ACS Energy Letters.
TEGs directly convert thermal
into
electrical
energy. " This
technology enables operation
of autonomous sensors for
the internet of things (IoT) or
in wearables, such as smart
watches, fitness trackers or
digital glasses without batteries, "
says professor Uli Lemmer,
head of the Light Technology
Institute of KIT. In addition,
they might be used for the recovery
of waste heat in industry
and heating systems or in
the geothermal energy sector.
" Conventional TEGs have to
be assembled from individual
components using relatively
complex manufacturing methods, "
Lemmer says. " To avoid
this, we studied novel printable
materials and developed two
innovative processes and inks
based on organic, as well as on
inorganic nanoparticles. " These
processes and inks can be used
to produce inexpensive, threedimensional
printed TEGs.
The first process uses screen
printing to apply a 2-D pattern
onto an ultrathin flexible substrate
foil using thermoelectric
printing inks. Then, a generator
about the size of a sugar cube is
folded by means of an origami
technique. This method has
been developed jointly by KIT
researchers, the Heidelberg In(Continues
on p. 8)
6
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2021
New process for synthetic eugenol
available to fragrance market
S
olvay S.A. (Brussels, Belgium; www.
solvay.com) recently announced a
new commercial process for synthetic
eugenol (diagram), a derivative
of phenol, whose natural version is extracted
from clove oil obtained from dried
flower buds of clove trees grown in Indonesia
and Madagascar. Synthetic eugenol
offers a cost-effective alternative supply of
the compound for applications that do not
specifically require natural origins, and also
offers protection from price volatility of natural
clove oil for fragrance formulators.
As Corinne Duffy, the eugenol project
manager at Solvay Aroma Performance,
explains, the synthetic route for eugenol
was first imagined by scientists at Solvay
affiliate Rhône-Poulenc in the early 2000s,
but the process never progressed beyond
the pilot stage because the purification is
very challenging, rendering the process
economically unattractive. In the past two
years, Solvay scientists, driven by strong
demand for eugenol, revisited the process,
focused on increasing yields and improving
the separation stage.
The resulting process begins with phenol,
which is converted into catechol, and then,
X
ylene isomers are usually derived from
the catalytic reforming of crude oil, and
require costly methods to separate
them from each other, including distillation,
fractional crystallization and adsorption
in high-temperature and high-pressure environments.
" The separation of xylene's isomers
requires much energy and is a difficult process
due to the isomers' overlapping physiochemical
properties, " says Abdul-Hamid Emwas,
staff scientist in nuclear magnetic resonance
(NMR) from the Imaging and Characterization
Core Lab (IAC) at the King Abdullah University
of Science and Technology (KAUST; Thuwal,
Saudi Arabia; www.kaust.edu.sa). " These include
identical molecular weights, close boiling
points and similar structures. "
KAUST associate professor Niveen Khashab
and her research group recently
teamed up with IAC and an international
group of scientists to find a new and less
energy-consuming method to separate and
purify the isomers for the petrochemical industry.
Their work is described in a recent
issue of the journal Chem.
To separate the isomers, the research team
took advantage of the properties of cucurbiturils,
which are organic macrocyclic molecules
made of glycoluril monomers linked
from that, into the intermediate
guaiacol.
" Guaiacol is a key
product in our chain,
as it can be used for
many applications, "
Duffy says. These
applications include
using guaiacol as an
intermediate in the
production of the
Solvay
flavor molecule vanillin and the cough suppressant
guaifenesin, as well as the main
raw material for the production of eugenol.
The synthetic eugenol process features a
carefully designed distillation stage to separate
the desired end-product (para-eugenol)
from the various co-products and byproducts
with similar boiling points that result
from the reaction of guaiacol to eugenol,
Duffy explains.
Synthetic eugenol is now available to the
fragrance market, Duffy says, but in the
near future, the product could be incorporated
into oral care products (toothpaste
and mouthwash) for its antiseptic properties,
once the company secures the necessary
certifications.
Separate xylene isomers with less energy
by methylene bridges. They are shaped like
pumpkins, with their hydrophobic central
cavity able to hold smaller molecules.
The researchers used an aqueous solution
of cucurbit[7]uril (or CB7), which " has strong
and distinctive binding affinity with xylene
isomers in water, " says Gengwu Zhang, a
postdoctoral fellow and the lead author of the
paper. " Using liquid-liquid extraction (at room
temperature and pressure), we showed that
the hole in the middle of CB7 can selectively
host o-xylene from mixtures of xylene isomers, "
explains Zhang. " We could separate
o-xylene with selectivity of more than 92%
after one extraction cycle. "
Because the three isomers have different
NMR spectra, NMR was used to perform the
study: high-resolution 1-D NMR was used
for quantitative analyses, and advanced
2-D NMR experiments were used to probe
the separation mechanism that explains the
novelty of the separation process using CB7.
The researchers showed that CB7 can
separate xylenes from commercial oil samples
at scales of up to 0.5 L. Also, laboratory
scale-up experiments using commercial
xylenes and C8 aromatic fraction of pyrolysis
gasoline proved that CB7 is able to separate
o-xylene with a selectivity of up to 83%.
http://www.solvay.com http://www.kit.edu http://www.kaust.edu.sa http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2021

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