Treated plastic waste good at grabbing carbon dioxide
Turning hard-to-process trash into carbon-capture master
Date:
April 5, 2022
Source:
Rice University
Summary:
Rice University chemists treat waste plastic to absorb carbon
dioxide from flue gas streams more efficiently than current
processes.
FULL STORY ========================================================================== Here's another thing to do with that mountain of used plastic: make it
soak up excess carbon dioxide.
==========================================================================
What seems like a win-win for a pair of pressing environmental problems describes a Rice University lab's newly discovered chemical technique
to turn waste plastic into an effective carbon dioxide (CO2) sorbent
for industry.
Rice chemist James Tour and co-lead authors Rice alumnus Wala Algozeeb, graduate student Paul Savas and postdoctoral researcher Zhe Yuan reported
in the American Chemical Society journal ACS Nanothat heating plastic
waste in the presence of potassium acetate produced particles with nanometer-scale pores that trap carbon dioxide molecules.
These particles can be used to remove CO2 from flue gas streams,
they reported.
"Point sources of CO2 emissions like power plant exhaust stacks can
be fitted with this waste-plastic-derived material to remove enormous
amounts of CO2 that would normally fill the atmosphere," Tour said. "It is
a great way to have one problem, plastic waste, address another problem,
CO2 emissions." A current process to pyrolyze plastic known as chemical recycling produces oils, gases and waxes, but the carbon byproduct is
nearly useless, he said.
However, pyrolyzing plastic in the presence of potassium acetate produces porous particles able to hold up to 18% of their own weight in CO2 at
room temperature.
==========================================================================
In addition, while typical chemical recycling doesn't work for polymer
wastes with low fixed carbon content in order to generate CO2 sorbent, including polypropylene and high- and low-density polyethylene, the
main constituents in municipal waste, those plastics work especially
well for capturing CO2 when treated with potassium acetate.
The lab estimates the cost of carbon dioxide capture from a point source
like post-combustion flue gas would be $21 a ton, far less expensive
than the energy-intensive, amine-based process in common use to pull
carbon dioxide from natural gas feeds, which costs $80-$160 a ton.
Like amine-based materials, the sorbent can be reused. Heating it to
about 75 degrees Celsius (167 degrees Fahrenheit) releases trapped
carbon dioxide from the pores, regenerating about 90% of the material's
binding sites.
Because it cycles at 75 degrees Celsius, polyvinyl chloride vessels
are sufficient to replace the expensive metal vessels that are normally required.
The researchers noted the sorbent is expected to have a longer lifetime
than liquid amines, cutting downtime due to corrosion and sludge
formation.
To make the material, waste plastic is turned into powder, mixed with
potassium acetate and heated at 600 C (1,112 F) for 45 minutes to
optimize the pores, most of which are about 0.7 nanometers wide. Higher temperatures led to wider pores. The process also produces a wax byproduct
that can be recycled into detergents or lubricants, the researchers said.
Co-authors of the paper are Rice alumnus Zhe Wang and research scientist
Carter Kittrell, and graduate student Jacklyn Hall and Praveen Bollini,
an assistant professor of chemical and biomolecular engineering, both
of the University of Houston. Tour is the T.T. and W.F. Chao Chair in
Chemistry as well as a professor of materials science and nanoengineering.
The Department of Energy (DE-F0031794) and Saudi Aramco supported the
research.
========================================================================== Story Source: Materials provided by Rice_University. Original written
by Mike Williams. Note: Content may be edited for style and length.
========================================================================== Journal Reference:
1. Wala A. Algozeeb, Paul E. Savas, Zhe Yuan, Zhe Wang, Carter
Kittrell,
Jacklyn N. Hall, Weiyin Chen, Praveen Bollini, James
M. Tour. Plastic Waste Product Captures Carbon Dioxide in Nanometer
Pores. ACS Nano, 2022; DOI: 10.1021/acsnano.2c00955 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220405143537.htm
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