Stanford Energy is brought to you by the Precourt Institute for Energy
Adapted from a UC–Berkeley press release
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 and possibly from vehicles.
The process for synthesizing the melamine material, published this week in the journal Science Advances, could potentially be scaled down to capture emissions from movable sources. CO2 from fossil fuel burning makes up about 75 percent of all greenhouse gases produced in the United States. 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.
The work is a collaboration among researchers at University of California–Berkeley, Stanford University, and Texas A&M University. The senior authors of the study are Yi Cui, director of Stanford’s Precourt Institute for Energy and professor of materials science, and Jeffrey Reimer, professor of chemical and biomolecular engineering at the UC–Berkeley. The two lead authors are Jing Tang, a postdoctoral fellow at Stanford and the SLAC National Accelerator Laboratory, Haiyan Mao, a UC–Berkeley postdoctoral fellow.
“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 Reimer.
The so-called melamine porous network captures CO2 with an efficiency comparable to early results for another relatively recent material for carbon capture, metal organic frameworks. MOFs have been show to efficiently remove CO2 from flue gases, such as those from a coal-fired power plant.
However, 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.
While eliminating fossil fuel burning is essential to halting climate change, a major interim strategy is to capture emissions of CO2 — the main greenhouse gas — and store the gas underground or turn CO2 into usable products. The U.S. Department of Energy has already announced projects totaling $3.18 billion to boost advanced and commercially scalable technologies for carbon capture, utilization and sequestration to reach an ambitious flue gas CO2 capture efficiency target of 90 percent. The ultimate U.S. goal is net zero carbon emissions by 2050.
But, carbon capture is far from commercially viable. The best technique today involves piping flue gases through liquid amines, which bind CO2. Much energy is used later to release the CO2 once it’s bound to the amines, so that it can be concentrated and stored underground. The amine mixture must be heated to between between 250 and 300 degrees Fahrenheit to release the CO2.
In contrast, the melamine porous network with diethylenetriamine (DETA) and cyanuric acid modification saves energy because it releases the CO2 at 176 degrees Fahrenheit.
In its research, the Berkeley/Stanford/Texas A&M 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.
Experiments confirmed that CO2 adhered somewhat to the formaldehyde-treated melamine, but adherence was much improved by adding another amine-containing chemical, DETA, to bind CO2. The researchers subsequently found that adding cyanuric acid during the polymerization reaction increased the pore size dramatically and radically improved CO2 capture efficiency: Nearly all the CO2 in a simulated flue gas mixture was absorbed within about three minutes.
The addition of cyanuric acid also allowed the material to be reused repeatedly.
The Cui and Reimer groups are continuing to tweak the pore size and amine groups to improve the carbon capture efficiency of melamine porous networks, while maintaining the energy efficiency. This involves using a technique called dynamic combinatorial chemistry to vary the proportions of ingredients to achieve effective, scalable, recyclable and high-capacity CO2 capture.
The two groups have also closely collaborated to synthesize other types of materials, including hierarchical nanoporous membranes — a class of nanocomposites combined with a carbon sphere and graphene oxide — and hierarchical nanoporous carbons made from pine wood, to capture CO2. Reimer developed solid-state NMR specifically to characterize the mechanism by which solid materials interact with CO2, in order to design better materials for carbon capture from the environment and energy storage. Cui developed a robust and sustainable solid-state platform and fabrication techniques for creating new materials to address climate change and energy storage.
This work was partly supported by the U.S. Department of Energy (DE-AC02-76SF00515).