A team of scientists from the University of California, Berkeley , Stanford and University of Texas have created a cheap, easy and energy-efficient way to capture carbon dioxide from smokestacks, using an inexpensive polymer called melamine.
The process for synthesising the melamine material, published in the journal Science Advances , could potentially be scaled down to capture emissions from vehicle exhaust or other movable sources of carbon dioxide. Carbon dioxide from fossil fuel burning makes up about 75% of all greenhouse gases produced in the U.S.
The new material is simple to make, requiring primarily off-the-shelf melamine powder — which today costs about $40 per ton — along with formaldehyde and cyanuric acid, a chemical that, among other uses, is added with chlorine to swimming pools.
“We wanted to think about a carbon capture material that was derived from sources that were really cheap and easy to get. And so, we decided to start with melamine,” said Jeffrey Reimer, Professor of the Graduate School in the Department of Chemical and Biomolecular Engineering at the University of California, Berkeley, and one of the corresponding authors of the paper.
The melamine porous network captures carbon dioxide with an efficiency comparable to early results for another relatively recent material for carbon capture, metal organic frameworks, or MOFs. Haiyan Mao, a UC Berkeley postdoctoral fellow who is first author of the paper, said that melamine-based materials use much cheaper ingredients, are easier to make and are more energy efficient than most MOFs. The low cost of porous melamine means that the material could be deployed widely.
“In this study, we focused on cheaper material design for capture and storage and elucidating the interaction mechanism between CO2 and the material,” Mao said. “This work creates a general industrialization method towards sustainable CO2 capture using porous networks. We hope we can design a future attachment for capturing car exhaust gas, or maybe an attachment to a building or even a coating on the surface of furniture.”
The melamine porous network with DETA and cyanuric acid modification captures CO2 at about 40 degrees Celsius, slightly above room temperature, and releases it at 80 degrees Celsius, below the boiling point of water. The energy savings come from not having to heat the substance to high temperatures.
Mao said that tests confirmed that formaldehyde-treated melamine adsorbed CO2 somewhat, but adsorption could be much improved by adding another amine-containing chemical, DETA (diethylenetriamine), to bind CO2. She and her colleagues subsequently found that adding cyanuric acid during the polymerization reaction increased the pore size dramatically and radically improved CO2 capture efficiency: Nearly all the carbon dioxide in a simulated flue gas mixture was absorbed within about 3 minutes. The addition of cyanuric acid also allowed the material to be reused numerous times.
Mao and her colleagues conducted solid-state nuclear magnetic resonance (NMR) studies to understand how cyanuric acid and DETA interacted to make carbon capture so efficient. The studies showed that cyanuric acid forms strong hydrogen bonds with the melamine network that helps stabilize DETA, preventing it from leaching out of the melamine pores during repeated cycles of carbon capture and regeneration.
“Utilizing solid-state nuclear magnetic resonance techniques, we systematically elucidated in unprecedented, atomic-level detail the mechanism of the reaction of the amorphous networks with CO2,” Mao said. “For the energy and environmental community, this work creates a high-performance, solid-state network family together with a thorough understanding of the mechanisms, but also encourages the evolution of porous materials research from trial-and-error methods to rational, step-by-step, atomic-level modulation.”
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