Berkeley universities

Cheap material could effectively capture carbon from exhaust gas

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 fireplaces, a key goal for the United States and others countries as they seek to reduce greenhouse gas emissions. .

The process for synthesizing the material melamine, published this week in the journal Science Advances, could potentially be scaled down to capture emissions from vehicle exhaust or other mobile sources of carbon dioxide. Carbon dioxide from burning fossil fuels accounts for about 75% of all greenhouse gases produced in the United States.

The new material is simple to manufacture, requiring mostly standard melamine powder – which today costs around $40 a ton – as well as formaldehyde and cyanuric acid, a chemical which, among other uses, is added chlorine in swimming pools.

“We wanted to think about a carbon capture material derived from really cheap and easy to get sources. And so, we decided to start with melamine,” said Jeffrey Reimer, a professor in the Graduate School of the Department of Chemical and Biomolecular Engineering at the University of California, Berkeley and one of the paper’s corresponding authors.

The so-called melamine porous network captures carbon dioxide with an efficiency comparable to the first results of another relatively new material for carbon capture, organometallic frames or MOFs. UC Berkeley chemists created the first-of-its-kind carbon capture MOF in 2015, and later versions have proven even more effective at removing carbon dioxide from flue gases, such as those from a power plant. coal-fired electric.

But Haiyan Mao, a UC Berkeley postdoctoral fellow who is the paper’s first author, said melamine materials use much cheaper ingredients, are easier to manufacture, and are more energy efficient than most MOFs. The low cost of porous melamine means the material could be widely deployed.

“In this study, we focused on designing cheaper materials 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 to design a future accessory to capture car exhaust, or perhaps an accessory to a building or even a coating on the surface of furniture.

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

Carbon neutrality by 2050

While eliminating the burning of fossil fuels is essential to stemming climate change, a major interim strategy is to capture emissions of carbon dioxide – the primary greenhouse gas – and store the gas underground or transform CO2 into usable products. The U.S. Department of Energy has already announced projects totaling $3.18 billion to boost advanced and commercially scalable carbon capture, utilization, and sequestration (CCUS) technologies to achieve an ambitious goal of 90% CO2 capture efficiency in flue gases. The ultimate goal for the United States is net zero carbon emissions by 2050.

But carbon capture is far from commercially viable. The best technique today is to channel the combustion gases through liquid amines, which fix the CO2. But it requires large amounts of energy to release the carbon dioxide once it’s bound to the amines, so it can be concentrated and stored underground. The amine mixture must be heated to between 120 and 150 degrees Celsius (250-300 degrees Fahrenheit) to regenerate the CO2.

In contrast, the porous network of melamine with DETA modification and cyanuric acid captures CO2 at around 40 degrees Celsius, slightly above room temperature, and releases it at 80 degrees Celsius, below the boiling point of the water. The energy savings come from not having to heat the substance to high temperatures.

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

Mao said tests confirmed that formaldehyde-treated melamine adsorbs CO2 somewhat, but adsorption could be greatly improved by adding another amine-containing chemical, DETA (diethylenetriamine), to bind CO2. She and her colleagues then discovered that adding cyanuric acid during the polymerization reaction dramatically increased pore size and drastically improved the capture efficiency of CO2: almost all the carbon dioxide in a flue gas mixture simulated was absorbed in about 3 minutes.

The addition of cyanuric acid also allowed the material to be used again and again.

A new family of porous networks

Mao and his colleagues conducted solid-state nuclear magnetic resonance (NMR) studies to understand how cyanuric acid and DETA interact to make carbon capture so efficient. Studies have shown that cyanuric acid forms strong hydrogen bonds with the melamine network which helps stabilize DETA, preventing it from leaking out of the melamine pores during repeated cycles of carbon capture and regeneration.

“What Haiyan and his colleagues were able to show with these elegant techniques is exactly how these groups intertwine, exactly how CO2 reacts with them, and that in the presence of this pore-opening cyanuric acid, it is able to turn CO2 on and off many times with a capacity that’s really, really good,” Reimer said. “And the rate at which CO2 adsorbs is actually quite fast, compared to some other materials. So all of the lab-scale practicalities of this material for CO2 capture have been met, and it’s just incredibly cheap and easy to manufacture.”

“Using solid-state nuclear magnetic resonance techniques, we have systematically elucidated in unprecedented detail at the atomic level the mechanism of the reaction of amorphous lattices with CO2,” Mao said. “For the energy and environmental community, this work creates a family of high-performance semiconductor networks as well as a deep understanding of the mechanisms, but also encourages the evolution of porous materials research from trial and error methods towards rational, stepwise methods – stepwise modulation, at the atomic level.

The Reimer and Cui groups continue to fine-tune pore size and amine groups to improve the carbon capture efficiency of porous melamine networks, while maintaining energy efficiency. This involves using a technique called dynamic combinatorial chemistry to vary the proportions of ingredients to achieve efficient, scalable, recyclable and high-capacity CO2 capture.

Reimer and Mao have also worked closely with Stanford’s Cui group to synthesize other types of materials, including hierarchical nanoporous membranes – a class of nanocomposites combined with a carbon sphere and graphene oxide – and nanoporous carbons hierarchical made from pine wood, to adsorb carbon dioxide. Reimer developed solid-state NMR specifically to characterize the mechanism by which solid materials interact with carbon dioxide, in order to design better materials for capturing carbon from the environment and storing energy. Cui has developed a robust and durable semiconductor platform and manufacturing techniques to create new materials to address climate change and energy storage.

Reference: Mao H, Tang J, Day GS, et al. A scalable solid-state nanoporous network with an atomic-level interaction design for carbon dioxide capture. Science Adv. 2022;8(31):eabo6849. do I:10.1126/sciadv.abo6849

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