New technology to capture CO2 can reduce power plant greenhouse gases more efficiently


Metal-organic structures are highly porous, making them ideal for absorbing gases and liquids. This graphic shows the interior of a MOF based on the metal magnesium (green balls), and has added molecules – tetramine (blue and gray) – to the pores to more efficiently absorb carbon dioxide from power plant emissions. has gone. Credit: UC Berkeley Graphic by Eugene Kim

Tetraamine modified MOFs Remove 90% of CO2 more efficiently and inexpensively.

Major advances in carbon capture technology can provide an efficient and inexpensive way for natural gas power plants to remove carbon dioxide from their flu emissions, reducing greenhouse gas emissions to slow global warming and climate change Is a necessary step.

Developed by researchers University of California, Berkeley, Lawrence Berkeley National Laboratory and ExxonMobil, the new technique uses a highly porous material called a metal-organic framework, or MOF, modified with nitrogen-containing amine molecules to capture CO.2 And low-temperature steam to expel CO2 For other uses or to sequence it underground.

In experiments, the technique showed six times more capacity to remove CO2 Of flue gas compared to current amine-based technology, and was highly selective, occupying over 90% of the CO2 Emitted. The process uses low-temperature steam to regenerate MOFs for repeated use, meaning that carbon capture requires less energy.

“for2 Capture, steam stripping – where you use direct contact with steam to unload CO2 – There has been a kind of sacred grave for the area. This is seen as the cheapest way to do it properly, ”said senior researcher Jeffrey Long, UC Berkeley professor of chemistry and chemical and biochemical engineering and senior faculty scientist at Berkeley Lab. “These materials, at least from the experiments we have done so far, look very promising.”

Because there is little market for most of the captured COs2, Most of the power plants pump it back into the ground, or sequester it, where it would ideally turn into rock. In order to encourage CO, the cost of rubbing emissions must be facilitated by government policies, such as carbon trading or carbon tax.2 Some countries have already implemented capture and numbering.

The work was funded by ExxonMobil, which is working with both the Berkeley Group and Long Start-up, Mosaic Material Inc., to develop, scale and test to isolate CO.2 From emissions.

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

Atomic structure mof

The atomic structure of a single pore in MOFs shows how carbon dioxide molecules (gray and red shells) bind to tetramine (blue and white shells), forming a CO2 polymer that passes through the pore. Low-temperature steam can excrete carbon dioxide for cesestration, allowing MOFs to be reused to capture more carbon from power plant emissions. Credit: UC Berkeley Graphic by Eugene Kim

“We were able to make preliminary discoveries and, through research and testing, obtain a material that showed potential for CO not only in laboratory experiments.2 To do so under extreme conditions present in gas emissions from natural gas power plants, but with no loss in selectivity, “we co-authored Simon Weston, senior research associate and project lead at ExxonMobil Research and Engineering Company. Said shown that these new materials can be regenerated with low-grade steam for re-use, providing a route for a viable solution for carbon capture at scale. “

Carbon dioxide emissions in fossil fuel-burning vehicles, power generating plants and industry account for an estimated 65% of the greenhouse gases that drive climate change, raising the Earth’s average temperature by 1.8 degrees. Fahrenheit (1 degree Celcius) Since 19Th century. Without these emission reductions, climate scientists predict ever warmer temperatures, more erratic and violent storms, rising several feet of sea level and resulting droughts, floods, fires, famines and conflicts.

“In fact, the Intergovernmental Panel on Climate Change says what we need to do to control global warming, CO2 Possession is a very large part. “We don’t have access to most of the CO2 We need to stop emissions, but we have to do it.

to separate

Power Plant Strip CO2 By emitting flue gases through organic amines in water today, which bind and remove carbon dioxide. The liquid is then heated to 120–150 C (250–300 F) to release CO.2 Gas, after which the fluid is reused. The entire process consumes about 30% of the electricity generated. Caught interrogated CO2 The cost of the underground is an additional, though small, portion of that.

Power generation plant

Natural gas generating plant. A new technology can capture carbon dioxide from emissions from such plants so that it sequesters underground and reduces the greenhouse gases responsible for climate change. Courtesy: Courtesy of the International Energy Agency

Six years ago, Long and his group at UC Berkeley’s Center for Gas Separations, funded by the US Department of Energy, discovered a chemically modified MOF that would easily capture CO.2 Concentrated power plants can reduce capture costs by half, possibly from flu emissions. They added diamine molecules to a magnesium-based MOF to form polymer chains of CO.2 This can then be purified by flushing with a moist stream of carbon dioxide.

Because MOFs are very porous, in this case like a hive, the weight of a paper clip has an internal surface area equal to that of a football field, which is available to absorb all gases.

A major advantage of amine-applied MOFs is that amines can be tweaked to capture CO.2 At varying concentrations, from 12% to 15% typical of coal plant emissions, 4% typical of natural gas plants, or much lower concentrations in ambient air. The mosaic material, which was co-installed and directed for a long time, was made to make this technology widely available for power and industrial plants.

But 180 C stream of water and CO2 Caught CO needs to be flushed2 Diamine eventually turns off the molecules, shortening the life of the material. The new version uses four amine molecules – a tetramine – which is much more stable at high temperatures and in the presence of steam.

“Tetramine is so strongly bound within the MOF that we can use a very concentrated stream of water vapor with zero CO2, And if you tried that with previous adsorbents, steam would start destroying the material, ”said Long.

They showed that direct contact with steam at 110–120 C – slightly above the boiling point of water – works well to eject CO.2. At that temperature steam is readily available in natural gas power plants, while 180 C.O.2The previously modified MOF required a mixture of water to regenerate the required heating, which wastes energy.

When Long, Weston, and their colleagues first thought of replacing diamines with titeramine, it seemed like a long shot. But the crystal structures of the diamine-containing MOFs suggested that there might be ways to combine the two diamines to form tetramines while preserving the material’s ability to polymerize CO.2. When UC Berkeley graduate student Eugene Kim, the paper’s first author, created a chemically tetramine-appended MOF, it defeated the diamine-applied MOF in the first attempt.

Researchers later studied the structure of the modified MOF using Berkeley Lab’s advanced light source, revealing the CO2 Polymers that line the pores of the MOF are actually attached to tetramine, such as the ladder with tungramine. First-principles density functional theory calculations using the Corey supercomputer at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC), computing resources at Molecular Foundry and resources provided by the campus’s Berkeley Research Computing confirm this remarkable structure That Long’s team initially envisioned. .

Long said, “I’ve been researching Cal for 23 years, and this is one of those times where you sound like a crazy idea, and it’s working right now.”

Reference: Eugene J. Kim, Rebecca L. Siegelman, Henry ZH Jiang, Alexander C. Force, Jung-hee Lee, Jeffrey D. Martel, Philip 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

The co-authors of Long, Kim and Weston are Joseph Falkowski from ExxonMobil; Rebecca Siegelman, Henry Jiang, Alexander Force, Jeffrey Martel, Philip Milner, Jeffrey Reimer and Jeffrey Neaton from UC Berkeley; And Jung-hoon Lee from Berkeley Lab. Neaton and Reimer are also senior scientists on the faculty at Berkeley Lab.