Tech Briefs Magazine - August 2024 - 31

This array of specialized cells could help produce more sustainable fuels using artificial photosynthesis.
(Image: Adapted from ACS Engineering Au, 2023, DOI: 10.1021/acsengineeringau.3c00034)
Previously, Kazunari Domen and colleagues
developed a system that used
sunlight to split water into hydrogen
and oxygen gas. Now, they wanted to
evolve the process to more fully mimic
photosynthesis, taking in CO2 to store
the sun's energy in methane instead,
while still using cost-effective and easily
scalable materials.
The team created a set of reaction
cells, similar to solar panels, that were
each coated with an aluminum-doped
strontium titanate (SrTiO3
) photocatalyst
to help power the reaction. These
coated cells were filled with water and
placed in the sun. Under those conditions,
the water split into hydrogen and
oxygen gas, which were separated, and
the purified hydrogen gas was fed into
the second part of the system. In the second
chamber, the hydrogen gas reacted
with CO2, forming methane and water,
the latter being recycled back into the
first step with the photoreactor.
Next, they created a 130-square-foot
array of the cells - about the size of a
small bedroom - that operated continuously
for three days in a variety of
weather conditions. Though promising,
the team recognizes that the efficiency
of artificial photosynthesis systems needs
to improve before these devices can become
viable options for large-scale power
generation.
According to the researchers, this
proof-of-concept system could be adapted
to help produce precursors for plastics
or other chemical feedstocks, as well
as scaled up to produce larger amounts
of sustainable biofuels.
For more information, contact Emily
Abbott at e_abbott@acs.org.
Advancing Chemical Recycling of Waste Plastics
New research proposes computational approach for predicting product distributions.
University of Pittsburgh, PA
U
nlike glass, which is infinitely recyclable,
plastic recycling is challenging
and expensive because of the material's
complex molecular structure designed
for specific needs. A new research from
the lab of Giannis Mpoumpakis, Associate
Professor of Chemical and Petroleum
Engineering at the University
of Pittsburgh, focuses on optimizing a
promising technology called pyrolysis,
which can chemically recycle waste plastics
into more valuable chemicals.
" Pyrolysis is relatively low in cost and
can generate high-value products, so it
presents an appealing, practical solution, "
said Mpourmpakis. " It has already
been developed on a commercial
scale. The main challenge now is finding
optimal operating conditions, given
the starting and final chemical products,
without needing to rely heavily on
trial-and-error experimentation. "
To optimize pyrolysis conditions and
produce desired products, researchers
typically use thermodynamic calculations
based on what's known as the
Tech Briefs, August 2024
Gibbs free energy minimization approach.
However, the lack of thermochemical
data can limit the accuracy of
these calculations.
While density functional theory
(DFT) calculations are commonly used
to obtain precise thermochemical data
for small molecules, their application
becomes challenging and computationally
expensive for the large, flexible
molecules that make up waste
plastics, especially at elevated temperatures
of pyrolysis.
In this study, Mpourmpakis and
former postdoc Hyunguk Kwon, who
is now a Professor at Seoul National
University of Science and Technology,
developed a computational framework
to accurately calculate the temperature-dependent
thermochemistry of
large and flexible molecules.
This framework combines conformational
search, DFT calculations,
thermochemical corrections, and
Boltzmann statistics; the resulting thermochemistry
data is used to predict the
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thermal decomposition profiles of octadecane,
a model compound representing
polyethylene.
The proposed computational analysis
based on first principles offers a significant
advancement in predicting temperature-dependent
product distributions
from plastic pyrolysis. It can guide
future experimental efforts in chemical
plastic recycling, enabling researchers
to optimize pyrolysis conditions and increase
the efficiency of converting waste
plastics into valuable chemicals.
" The production of plastics is expected
to keep increasing, so it's essential that we
find and perfect ways to recycle and reuse
plastics without harming the environment, "
said Mpourmpakis. " This work,
which has been funded by the National
Science Foundation, contributes to the
development of sustainable waste management
strategies and the reduction of
plastic pollution, offering potential benefits
for both the environment and society.
For more information, contact Maggie
Lindenberg at mlindenberg@pitt.edu.
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Tech Briefs Magazine - August 2024

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