Last year Professor Andrew Barron, Ser Cymru chair in engineering at Swansea University, who is also a chair at Rice University in Texas, found that buckyballs, discovered at Rice in the 1980s, gain the ability to sequester carbon dioxide when combined with a polymer known as polyethyleneimine (PEI).

Two critical questions – how and how well – are addressed in a new paper in the American Chemical Society journal Energy and Fuels, the lead author of which is Dr Enrico Andreoli, senior lecturer at Swansea University.

The amine-rich combination of C60 and PEI showed its potential in the previous study to capture emissions of carbon dioxide, a greenhouse gas, from such sources as industrial flue gases and natural-gas wells.

In the new study, the researchers found pyrolyzing the material – heating it in an oxygen-free environment – changes its chemical composition in ways that may in the future be used to tune what the scientists call PEI-C60 for specific carbon-capture applications.

Read the research paper

Picture: Dr Enrico Andreoli (left) and Prof Andrew Barron (right), from the College of Engineering at Swansea University

Professor Andrew Barron said:

"One of the things we wanted to see is at what point, chemically, it converts from being something that absorbed best at high temperature to something that absorbed best at low temperature. 

In other words, at what point does the chemistry change from one to the other?"

Lead author Enrico Andreoli pyrolyzed PEI-C60 in argon at various temperatures from 100 to 1,000 degrees Celsius (212 to 1,832 degrees Fahrenheit) and then evaluated each batch for carbon uptake.

He discovered the existence of a transition point at 200 C, a boundary between the material's ability to soak in carbon dioxide through chemical means as opposed to physical absorption.

The material that was pyrolyzed at low temperatures became gooey and failed at pulling in carbon from high-temperature sources by chemical means. The opposite was true for PEI-C60 pyrolyzed at high heat. The now-porous, brittle material became better in low-temperature environments, physically soaking up carbon dioxide molecules.

At 200 C, they found the heat treatment breaks the polymer's carbon-nitrogen bonds, leading to a drastic decrease in carbon capture by any means.

Andreoli found that at its peak, untreated PEI-C60 absorbed more than a 10th of its weight in carbon dioxide at high temperatures (0.13 grams per gram of material at 90 C). Pyrolyzed PEI-C60 did nearly as well at low temperatures (0.12 grams at 25 C).

Dr Enrico Andreoli explained:

"Amine-modified nanocarbons are a promising and exciting class of materials for carbon dioxide capture. This is true even after thermal treatment giving sorbents with enhanced CO2 sorption performance at room temperature."

Professor Andrew Barron said:

"One of the goals was to see if can we make this a little less gooey and still have chemical uptake, and the answer is, not really. It flips from one process to the other. But this does give us a nice continuum of how to get from one to the other."

The researchers, with an eye on potential environmental benefits, continue to refine their process.

‌Picture:  a Carbon-60 molecule, known as Buckminsterfullerene, or Buckyballs.

Enrico Andreoli is a former postdoctoral researcher at Rice University and a senior lecturer at Swansea University.

Andrew Barron is the Ser Cymru Chair of Low Carbon Energy and Environment at Swansea University, and Charles W. Duncan Jr.–Welch Professor of Chemistry and a professor of materials science and nanoengineering at Rice University. Texas.

The Welsh Government Ser Cymru Programme, Apache Corp., and the Robert A. Welch Foundation, supported the research.

Swansea University College of Engineering
 
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