A Simple, Cheap Material for Carbon Capture, Perhaps from Tailpipes

by Robert Sanders (Berkeley News) ... Using an inexpensive polymer called melamine — the main component of Formica — chemists have created a cheap, easy and energy-efficient way to capture carbon dioxide from smokestacks, a key goal for the United States and other nations as they seek to reduce greenhouse gas emissions.

The process for synthesizing the melamine material, published this week 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 so-called 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. UC Berkeley chemists created the first such carbon-capture MOF in 2015, and subsequent versions have proved even more efficient at removing carbon dioxide from flue gases, such as those from a coal-fired power plant.

But 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.

The work is a collaboration among a group at UC Berkeley led by Reimer; a group at Stanford University led by Yi Cui, who is director of the Precourt Institute for Energy, the Somorjai Visiting Miller Professor at UC Berkeley, and a former UC Berkeley postdoctoral fellow; UC Berkeley Professor of the Graduate School Alexander Pines; and a group at Texas A&M University led by Hong-Cai Zhou. Jing Tang, a postdoctoral fellow at Stanford and the Stanford Linear Accelerator Center and a visiting scholar at UC Berkeley, is co-first author with Mao. Reimer is also a faculty scientist at Lawrence Berkeley National Laboratory.

In contrast, 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.

In its research, the Berkeley/Stanford/Texas team focused on the common polymer melamine, which is used not only in Formica but also inexpensive dinnerware and utensils, industrial coatings and other plastics. Treating melamine powder with formaldehyde — which the researchers did in kilogram quantities — creates nanoscale pores in the melamine that the researchers thought would absorb CO₂.

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 used over and over again.

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. READ MORE