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New Technique to Catch CO2 More Effectively Can Reduce Power Plant Greenhouse Gases



Emissions of Metal Frame Organic Power Plants

Organic metal frames are highly porous, making them ideal for the absorption of gases and liquids. This graph shows the interior of a MOF based on metal magnesium (green balls), and added molecules ̵

1; tetraamines (blue and gray) – added to the pores to more efficiently absorb carbon dioxide. carbon from power plant emissions. Credit: UC Berkeley graphics by Eugene Kim

Modified with tetraamine MOFs remove 90% of CO2 more efficiently and cheaply.

A major advancement in carbon capture technology could provide an efficient and inexpensive way for natural gas power plants to remove carbon dioxide from chimney emissions, a necessary step in reducing emissions. greenhouse gas emissions to reduce global warming and climate change.

Developed by researchers in University of California, Berkeley, Lawrence Berkeley National Laboratory and ExxonMobil, the new technique uses a highly porous material called an organic metal frame, or MOF, modified with nitrogen-containing amine molecules to capture CO2 and low-temperature steam to rinse CO2 for other uses or to be seized underground.

In the experiments, the technique showed six times greater ability to remove CO2 from flue gas from current amine-based technology, and was highly selective, captured more than 90% of CO2 to come out. The process uses low-temperature steam to regenerate the MOF for repeated use, meaning less energy is needed to capture carbon.

“For CO2 capture, steam stripping – where you use direct contact with steam to take in CO2 It was a kind of holy grail for the field. It’s rightly considered the cheapest way to do it, ”said senior researcher Jeffrey Long, a UC Berkeley chemistry professor and chemical and biomolecular engineering and senior faculty scientist at the Berkeley Lab. “These materials, at least from the experiments we’ve done so far, look promising.”

Because there is little market for most of the trapped CO2, power plants are likely to pump most of it back into the ground, or be trapped, where they ideally turn into a rock. The cost of washing emissions will have to be facilitated by government policies, such as carbon trading or carbon tax, to incentivize CO2 seizure and seizure, something that many countries have already implemented.

The work was funded by ExxonMobil, which is working with both the Berkeley group and long-term startup, Mosaic Materials Inc., to develop, grow and test CO-stripping processes.2 from emissions.

Long is the senior author of a paper describing the new technique that was published in the July 24, 2020 issue of the journal. Science.

MOF Atomic Structure

The atomic structure of a single pore in an MF shows how carbon dioxide molecules (gray and red spheres) bind to tetraamines (blue and white spheres), and build a CO2 polymer that passes through the pores. Low-temperature steam can remove carbon dioxide to capture, allowing the MOF to be reused to capture more carbon from the power plant’s emissions. Credit: UC Berkeley graphics by Eugene Kim

“We were able to take the initial discovery and, through research and testing, start material that in laboratory experiments has shown the potential to not only capture CO2 under the present extreme conditions in flue gas emissions from natural gas power plants, but to do so without any loss in selectivity, “said co-author Simon Weston, a senior associate at research and leading project at ExxonMobil Research and Engineering Co. ” We have shown that these new materials can then be regenerated with low-grade steam for repeated use, and provide a pathway to a viable solution for large-scale carbon capture. “

Carbon dioxide emissions from fossil fuel burning vehicles, power plants and industry account for about 65% of the greenhouse gases that drive climate change, which has already increased the the average temperature of the Earth by 1.8 degrees Fahrenheit (1 degree Celsius) since 19th century. Without a reduction in these emissions, climate scientists predict increasingly hotter temperatures, more erratic and violent storms, several feet above sea level rising and resulting in leaks, floods, fires, famine and conflict. .

“In reality, from the kinds of things the Intergovernmental Panel on Climate Change says we need to do to control global warming, CO2 catching is a huge part, ”Long said. “We don’t have a use for most of the CO2 that we need to stop throwing away, but we have to do it. “

Peeling

CO strip power plants2 from flue gas emissions today by igniting flue gases through organic amines in water, which bind and extract carbon dioxide. The liquid is then heated to 120 to 150 C (250-300 F) to release CO2 gas, after which the liquids are reused. The whole process consumes about 30% of the power generated. The seizure of the captured CO2 The underground cost costs an additional fraction, albeit a small one.

Electricity generating plant

Natural gas-fired power plant. A new technique could capture carbon dioxide from emissions from such plants in order to spread underground and reduce greenhouse gases responsible for climate change. Credit: Courtesy of the International Energy Agency

Six years ago, Long and his group at the UC Berkeley Gas Separation Center, which is funded by the U.S. Department of Energy, discovered a chemically modified, highly flammable MOF. -CO2 from flue emissions of a concentrated power plant, potentially halving the catch price. They added diamine molecules to magnesium-based MOF to catalyze the formation of polymer CO chains.2 which can then be cleaned by rinsing with a damp stream of carbon dioxide.

Because MOFs are very porous, in this case like a honeycomb, an amount of the weight of a paper clip has an internal surface area equal to that of a football field, all available for absorbing gases.

A major advantage of MOFs attached to the amine is that the amines can be adjusted to capture CO2 in different concentrations, ranging from the typical 12% to 15% of coal plant emissions to the typical 4% of natural gas plants, or even much lower concentrations in ambient air. Mosaic Materials, which he co-founded in the long run and directs, was created to make this technique widely available to power plants and industry.

But the water of 180 C and CO2 required to discard trapped CO2 eventually removing the diamine molecules, shortening the life of the material. The new version uses four amine molecules – tetraamine – which is much more stable at high temperatures and in the presence of steam.

“Tetraamines are strongly bound in the MOF that we can use a highly concentrated water flow with 0 CO2, and if I tried that with the previous absorbents, the steam would start to destroy the material, ”Long said.

They have shown that direct contact with steam at 110-120 C – just above the boiling point of water – works well to release CO2. Steam at that temperature is readily available in natural gas power plants, while 180 C CO2the water mixture needed to regenerate the previously modified MOF that required heating, wasting energy.

When Long, Weston and their colleagues first thought about replacing diamonds with tougher tetraamines, it looked like a long shot. But the crystal structures of the diamond-containing MOFs suggested that there may be ways of connecting two diamonds to form tetraamine while maintaining the ability of the material to polymerize CO.2. When UC Berkeley college student Eugene Kim, the paper’s first author, chemically created the tetraamine-attached MOF, he surpassed the diamine-attached MOF in the first trial.

The researchers subsequently studied the structure of the modified MOF using the Berkeley Lab Advanced Light Source, which showed that CO2 MOF pore-lining polymers are effectively bound to tetraamines, such as a ladder with tetraamines as the rungs. Calculations of the functional density theory of the first principles using the Cori supercomputer at the Berkeley Lab’s Center for Scientific Research on Energy Research (NERSC), computing resources in the Molecular foundation and resources provided by the Berkeley Research Computing program of the campus confirmed this remarkable structure that Long’s team was initially intended for. .

“I’ve been doing research in Cal for 23 years now, and this is one of those times where you have what seemed like a crazy idea, and I worked right away,” Long said.

Reference: “Carbon capture and cooperative steam regeneration with organic metal frames attached to tetraamine” by Eugene J. Kim, Rebecca L. Siegelman, Henry ZH Jiang, Alexander C. Forse, Jung -Hoon Lee, Jeffrey D. Martell, Phillip J Milner, Joseph M. Falkowski, Jeffrey B. Neaton, Jeffrey A. Reimer, Simon C. Weston and Jeffrey R. Long, 24 July 2020, Science.
DOI: 10.1126 / science.abb3976

Co-authors with Long, Kim and Weston are Joseph Falkowski from ExxonMobil; Rebecca Siegelman, Henry Jiang, Alexander Forse, Jeffrey Martell, Phillip Milner, Jeffrey Reimer and Jeffrey Neaton from UC Berkeley; and Jung-Hoon Lee from Berkeley Lab. Neaton and Reimer are also senior faculty scientists at the Berkeley Lab.




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