Chemical Engineering September 2023 - 5

Chementator
Direct-air capture of CO2 via a liquid-based, lowtemperature,
thermochemical system
W
ith global temperatures likely to
rise beyond the 1.5°C target
set by climate experts, negative
emissions technologies - most
notably direct air capture (DAC) - become
increasingly important for addressing CO2
already in the atmosphere. A new DAC approach
is being pursued by Holocene Climate
Corp. (Knoxville, Tenn.; www.theholocene.co).
Holocene's system is unique in its
ability to operate at low temperatures, while
still employing an aqueous-based approach
amenable to traditional chemical-engineering
scaling benefits.
Leveraging technology licensed from Oak
Ridge National Laboratory (ORNL; Oak
Ridge, Tenn.; www.ornl.gov), Holocene developed
a process with two distinct chemical
loops (diagram): in the first, an amino acid
solution is used to absorb CO2 from the air
with an apparatus that is similar to the air-liquid
contactor in a cooling tower. In a second
step, guanidine compounds are added to
the CO2-rich solution,
forming an insoluble
carbonate salt. The
much lower solubility
of the guanidine carbonate
salt, compared
to its guanidine precursor,
drives the process
and results in a
solid, CO2-containing
Ambient
air
Air-liquid contactor
CO2-lean
air
CO2-loaded amino
acid solution
Loop #1
Solid-liquid
separation
D
iscovering new catalysts and materials
for specific applications can
be a tedious and time-consuming
process involving labor-intensive
tests and expensive samples. Technology
developed by Mattiq (Skokie, Ill.; www.
mattiq.com) enables the " printing " of tens
of thousands of tiny material samples
onto a single chip for comparison against
a reference material. " We can screen the
materials for their electrochemical activity
very quickly, but we can also take the chip
and subject the entire chip to accelerated
stress testing because one parameter we
really care about is durability. In just a few
hours, we can determine which materials
might degrade under certain conditions, "
explains Andrey Ivankin, chief technology
officer and co-founder of Mattiq. Currently,
the technology is being used to investigate
potential alternatives to the costly iridiumbased
catalysts used in proton-exchange
membrane (PEM) electrolysis. " We can
precipitate. The solid material is filtered and
heated (110°C) to release the CO2, which is
then sent on for further use or sequestration.
" Having two distinct loops increases the
robustness of our process and lowers the
energy requirements, " explains Holocene
co-founder Keeton Ross. " We can keep
the amino acids away from heat, where
they would degrade. Also, we are able
to heat only the solid to regenerate CO2,
rather than wasting energy heating a large
volume of water. "
The amino-acid markets are mature, and
Holocene is focused on scaling up production
and optimizing the performance of their
guanidine derivatives.
Holocene has working bench-scale versions
of all DAC unit operations, and is
currently building its first integrated facility
- with capacity of around 10 ton/yr CO2
- for planned commissioning at the end of
2023. This will be followed by the design of
larger, commercially available facilities.
CO2-loaded amino
acid solution
Crystallizer
(precipitate)
CO2
stream
Loop #2
CO2 regeneration
Sent off
for drying,
compression,
and
sequestration
CO2-loaded guanidine
carbonate
Holocene
'Printing' new catalyst candidates onto a chip
quickly go through two- or three-element
species and compare them side by side
with the reference material on the chip. If
we find promising candidates, we can scale
them up to milligram and gram scales, and
we can integrate them into onsite PEM
electrolyzers for further testing. We have
built the electrolyzer infrastructure in house
to prove that the material works as we observed
on the chip, " says Ivankin.
What sets Mattiq's methods for material
discovery apart is the combination of scale
and complexity of materials that can be
synthesized onto the chip. " We can create
10,000 discrete materials in ten minutes.
Many other methods rely on thin films instead
of discrete materials, but that isn't
how those materials are used in electrolyzers
and reactors, and the properties can differ
once they are in the application, " says
Ivankin. " We've really created an end-toend
pipeline for materials simulation, synthesis,
exploration and testing, " he adds.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
SEPTEMBER 2023
CO2-lean guanidine
derivative (free base)
Edited by:
Gerald Ondrey
STEAM REFORMING
Honeywell International
Inc. (Charlotte, N.C.; www.
honeywell.com) and ZoneFlow
Reactor Technologies,
LLC (ZFRT; Windsor,
Conn.; www.zoneflowtech.
com) have successfully
conducted pilot-plant testing
of the ZoneFlow Reactor
in ZFRT's
pilot
plant at
large-scale
Université
Catholique de Louvain in
Louvain-la-Neuve, Belgium.
The near-commercial-level
testing validated increased
steam-methane-reforming
(SMR) capacity by at least
15% in terms of feed flow
compared to conventional
state-of-the-art pellets, with
no higher methane slip and
without increasing the maximum
tube-skin temperature
or pressure drop. This
increased production of H2
allows for the reformer to
convert hydrocarbon feeds,
such as natural gas or naphtha,
and steam into synthesis
gas (syngas).
In 2021, the two companies
signed a joint development
agreement to grow
and commercialize the
ZoneFlow Reactor technology.
This technology can
provide a significant improvement
in the productivity
and cost-effectiveness of
SMR for H2 and syngas production
(see Chem. Eng.,
December 2021, p. 5).
NEW MEMBRANE
Wastewater from foodprocessing,
tanneries, textile
processing, paper mills,
pharmaceuticals and other
industries often contain a
mixture of salts and organic
material - often nutrients
and other valuable byproducts
- that cannot be
separated and recovered
by conventional treatment
methods, such as reverse
osmosis. Although conventional
nanofiltration and electrodialysis
can be used for
desalinating the organic-rich
wastewater, the combination
has separation efficien(Continues
on p. 6)
5
http://www.honeywell.com http://www.honeywell.com http://www.zoneflowtech.com http://www.zoneflowtech.com http://www.theholocene.co http://www.theholocene.co http://www.ornl.gov http://www.mattiq.com http://www.mattiq.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering September 2023

Table of Contents for the Digital Edition of Chemical Engineering September 2023
