Chemical Engineering September 2020 - 11

New fabrication method for fluorinecontaining
carbon-capture membranes
R
ecent work by a team of researchers
from Oak Ridge
National Laboratory (ORNL;
Oak Ridge, Tenn.; www.
ornl.gov) and the University of Tennessee
(Knoxville; www.utk.edu) has
brought cost-effective, fluorinated
carbon molecular-sieve membranes
within closer reach. To make the
membrane, the researchers used
a sol-gel polymerization process
in which a fluorine-containing substrate
that also contains nitrile and
ether groups is polymerized using
strong Brønsted acid (CF3SO3H) as
a promoter/catalyst. The reaction is
performed in a way that allows the
scientists to regulate the size and
thickness of the obtained polymer
membrane. Subsequently, the polymer
film is carbonized in a tubular
oven at 500°C under a slow stream
of nitrogen gas to generate the carbon
molecular-sieve-based membrane,
explains Ilja Popovs, ORNL
Nanomaterials Chemistry Group
scientist. The high fluorine content
in the polymer improves its ability to
adsorb and separate CO2 from nitrogen
and water vapor, which are
prominent components of exhaust
gas, Popovs adds.
By carefully controlling the carbonation
temperature in the oven,
the researchers were able to control
the porosity of the membrane, which
leads to greater permeability, but at
the expense of selectivity. " We were
able to identify a 'sweet spot' in the
temperature and the thickness of
membrane that provides the best
combination of transport properties
(permeability) and separation (selectivity), "
Popovs reports.
The ORNL-led group demonstrated
the effectiveness of their
membrane on a gas stream of nitrogen,
carbon dioxide and water,
simulating industrial fluegas. The
experimental results suggest the
materials are " promising candidates
for CO2 separation. "
n
mine the efficiency of a class of low-cost catalysts,
called spinel oxides. The discovery is said
to break a bottleneck in the production of H2 from
water electrolysis.
Spinel oxides, which are typically made from
inexpensive transition metals, are interesting
as a stable, low-cost catalyst for water splitting,
but the design of high-performing spinel
oxides has been hampered by the lack of
understanding of how they work. Now, NTU
Singapore's associate professor Jason Xu
Zhichuan and his team have made two important
advances. They have unravelled, at
the atomic scale, how spinel oxides work to
speed up water electrolysis, and then used
machine learning to select new spinel oxides
with increased catalytic activity.
Based on key parameters that the team had
identified, the team trained a machine-learning
model with a dataset of over 300 spinel oxides
in order to screen and predict the efficiency of
any spinel oxide catalyst in a matter of seconds.
Using this method, the team found that
a new oxide comprising manganese and aluminum
was predicted to show superior catalytic
activity. This was validated experimentally.
These findings, as described in Nature Catalysis,
have the potential to improve industrial-scale
production of H2 by electrolysis.
(For more on water electrolysis, see the Cover
Story on pp. 26-30.)
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ChemiCal engineering www.Chemengonline.Com September 2020
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Chemical Engineering September 2020

Table of Contents for the Digital Edition of Chemical Engineering September 2020