Chemical Engineering May 2023 - 6

without the use of conventional industrial
refrigerants. Instead, it uses a
temperature-active, magnetic metal
to cool a water mixture. In principle,
this technology can be used for any
type of cooling.
A pilot plant aimed at demonstrating
the magnetocaloric principle for more
efficient liquefaction of hydrogen is
being planned as part of the HyLICAL
project, funded under the E.U. Horizon
program. The goal is a prototype
with a capacity to produce 5 ton/d of
liquid H2. This will be done by first cooling
H2 to -196°C using liquid N2, and
then to -253°C using Magnotherm's
technology. The company estimates
that this process can reduce energy
consumption by 50% compared to
conventional technology.
MXENES
MXenes are compounds similar to
graphene and have " extraordinary "
electronic properties. These relatively
new materials have potential applications
in turbines, aerospace and
medical implants, but making MAX
phase powders (ternary transition
metal compounds) at the industrial
scale has not been possible before.
MXenes are one of the largest
families of 2-D materials. They are a
few-atom-thick sheets with the structures
of transition-metal carbides and
nitrides. Similar to graphene, their
distinctive properties, such as high
electrical conductivity, make them
potential candidates for applications
in energy storage and harvesting
(batteries and supercapacitors).
However, the production of MXenes
has been labor-intensive, requiring
several steps that include heating a
mixture to more than 1,500°C, followed
by selective etching with HF or
Lewis acidic molten salts.
Now, an alternative process that
is faster, simpler and generates less
toxic waste has been described by
researchers at the University of Chicago
(www.uchicago.edu) in a recent
(March 24) issue of Science. The onestep
process involves simply heating
mixtures of chemicals and the desired
metal at high temperature. For
example, the direct synthesis (milligram
scale) of Ti2CCl2 MXene was
performed by the reaction of titanium
metal, graphite and TiCl4. The mixture
was sealed in a quartz tube and
heated to 950°C for around 2 h.
'GREEN' CONCRETE
Carbonaide Oy (Joensuu, Finland;
www.carbonaide.com), a spin-out
company from VTT Technical Re(Continues
on p. 8)
6
Optimizing CIP for membrane filtration plants
M
embrane filtration plants
are often used in the food
and dairy industry to separate
or concentrate substances
without thermal stress. Until
now, cleaning-in-place (CIP) operations
for this equipment was energyand
water-intensive, requiring three
or four individual cleaning steps with
different chemical cleaning agents to
be pumped and circulated throughout
the equipment for a specified amount
of time before rinsing it out with water.
Now, water and power consumption
can be significantly reduced, thanks to
two digital tools - Smart Filtration CIP
and Smart Filtration Flush - developed
by GEA AG (Düsseldorf, Germany;
www.gea.com).
With Smart Filtration
Flush, sensors
constantly measure
the permeate
quality of the water
during the flushing
process,
and
stop
the process
as soon as the
necessary hygienic
level is reached,
thereby reducing
Bio-inspired synthesis leads to new
hydrogen-reaction mechanism
I
n synthesizing a new molecule that
mimics the nickel-iron (NiFe) hydrogenase
enzyme, a team of researchers
from University of Illinois UrbanaChampaign
(www.illinois.edu)
may
have
uncovered a promising alternative
to the platinum-based catalysts typically
used in the electrolysis of water to
produce hydrogen. With the new molecule,
the scientists have uncovered
a previously unreported mechanism in
the hydrogen evolution reaction (HER).
In work published in Nature Communications,
the team reports that they
have, for the first time, demonstrated
that both NiI and NiIII paramagnetic
states are accessed during catalytic
hydrogen evolution, which is believed
to be indicative of the specific chemistry
of NiFe hydrogenases.
While other nickel complexes have
been investigated for electrocatalytic
hydrogen production, their reaction
intermediates and activity did not support
an efficient reaction. The key to the
new catalyst's efficiency is the formation
of the paramagnetic intermediate
species at the nickel center. The intermediates'
unpaired electron and short
lifespan mean that the HER proceeds
more efficiently than with other nickelbased
catalysts. The molecule's unique
behavior when compared
to
other
catalysts is due in part to a carbonhydrogen
bond located near that nickel
center, which is cleaved and mended
during the reaction, helping to stabilize
the paramagnetic species. Furthermore,
the molecule was outfitted with
a specialized ligand based on 3,7-dithia-1(2,6)-pyridina-5(1,3)-benzenacyclooctaphane
that could support the
paramagnetic states and their seemingly
challenging behavior - a direct
mirror of the cysteine ligands found in
NiFe hydrogenases.
The new catalyst exhibited high turnover
frequencies for hydrogen production
in the presence of trifluoroacetic
acid. The team hopes that this work will
spur deeper research into bio-inspired
organometallic complexes.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM MAY 2023
the amount of water used, as well
as the amount of wastewater generated.
Depending on the type and size
of the plant and the water properties,
operators can reduce their freshwater
requirements by up to 50%, the company
says.
" A typical dairy-whey protein concentration
process needs two to four
filtration plants connected in a series.
This setup can require more than
100,000 L of water, per cleaning cycle, "
explains Nils Mørk, R&D Engineer for
membrane filtration at GEA. " Today,
we know from plant tests that we can
save well up to 50,000 L of water per
cleaning in such large plants and 500
to 700 L per CIP in small productions. "
GEA
http://www.gea.com http://www.illinois.edu http://www.uchicago.edu http://www.carbonaide.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering May 2023

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