Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chemistry for Greenhouse Gases

16.12.2010
If fossil fuels burn completely, the end products are carbon dioxide and water. Today, the carbon dioxide is a waste product, one that goes into the air — adding to global warming; or the oceans — acidifying them; or underground — with as yet unknown consequences.

But it’s not impossible, says Liviu M. Mirica, PhD, assistant professor of chemistry in Arts & Sciences at Washington University in St. Louis, to drive things the other way, turning carbon dioxide into fuels such as methanol or hydrocarbons.

Until now, reversing combustion has been a loser’s game because making carbon dioxide into a fuel uses up more energy than combustion releases and produces more carbon dioxide than it reclaims.

But Mirica thinks catalysts might change everything. Catalysts might provide alternative reaction pathways with lower energy barriers. The reactants then could be bumped over those lower barriers with carbonless energy sources such as sunlight.

Instead of being a polluting one-way street, hydrocarbon chemistry could circle back on itself and become a clean carbon-neutral cycle, although one that still consumed energy.

In the Journal of the American Chemical Society, Mirica describes a new metal complex that can combine methyl groups (CH3) in the presence of oxygen to produce ethane (CH3-CH3).

This is the second step in the conversation of methane (CH4), the main component of natural gas, into a longer-chain hydrocarbon, or liquid fuel.

Mirica’s team is currently tweaking the complex so that it will perform the first step in the methane-to-ethane conversion as well.

The energy problem

Fossil fuels are useful because they pack energy in their chemical bonds and release that energy when they are burned. So they’re essentially convenient little energy suitcases.

Reactions that release energy, however, are reluctant to reverse themselves and the more energy they release, the more reluctant they are to back up.

There’s no way around this problem; if a reaction released energy both going forward and going backward, it could fuel a perpetual motion machine, which, of course, is an impossibility.

Still, it is possible to make hydrocarbon combustion reactions run backward — either by brute force or by finesse.

The brute force way is to pump in energy. That’s how the Nazis turned coal into oil during World War II. Saddled with an abundance of coal but short on oil, Germany solved the problem by transmuting coal to oil by chemical means.

But Nazi synthetic oil plants worked only at high temperatures and pressures and much more energy was used to drive the reactions than was ultimately stored in synthetic oil they produced. (See caption in Image 2: The brute force method.)

The finesse is to devise a chemical compound, a catalyst, that takes the reactants up an alternative, lower energy pathway to the reaction products. In effect, instead of going straight up the energy hill, the reaction takes a more manageable — ideally the minimal-energy — series of switchbacks to the top.

Like a ball in a glove

Last year, Mirica’s group was working with a palladium compound that they hoped could catalyze the splitting of water. “The catalyst we made for that reaction worked,” Mirica says. “But not as well as we hoped. But we noticed it was easily oxidized, even by the oxygen in air.

“This was our first hint that this might be an interesting system. So then we asked, what else could we use it for?

“One of our ideas was to use it to turn methane into ethane,” Mirica says. Methane, the main component of natural gas, is released in large amounts when an oil well is tapped. Currently the methane from the oil fields is wasted; it is flared off on site, releasing even more carbon dioxide into the atmosphere.

Turning methane to ethane, Mirica says, could be the first step in a process of building longer-chain hydrocarbons such as butane and octane, which would be liquid at normal temperatures and pressures and so could easily be transported to distant users.

Mirica’s metal complex solves half the problem of methane-to-ethane conversion. It takes two methyl groups (CH3) and, in the presence of oxygen and light, binds the carbon atoms to one another to form ethane.

The complex consists of an organic molecule that binds a central palladium atom through four nitrogen atoms, holding it like a ball in a glove.

The organic molecule is key to the metal complex’s function, because it stabilizes it in the unusual “+3” oxidation state (it has given up three electrons), which is responsible for its unprecedented chemical activity.

Once in the glove, the palladium atom still has two docking spots that can be occupied by chemical species whose reaction it might catalyze.

In the reported work, these sites are occupied by methyl groups, which the palladium atom joins to produce ethane. But, Mirica emphasizes, the sites could easily be occupied by other chemical species. What’s more, the reactions could be reducing ones (where electrons are donated to reactants) rather than the oxidizing ones (where electrons are removed from reactants) like the methyl-to-ethane conversion.

In short, the complex opens up a whole new area of palladium chemistry.

The to-do list

Mirica’s lab is currently trying to tweak the metal complex so that it can perform the entire methane-to-ethane reaction.

The first part of that reaction is pulling methyl groups off methane molecules. That’s a bit tricky, says Mirica, because it is hard to break one C-H bond of the methane molecule, which has four C-H bonds, without breaking all four.

“The reaction wants to run straight down the energy hill all the way to the bottom (CO2),” Mirica says. “Our goal is to design a catalyst that stops the reaction part of the way down the hill (when only one hydrogen has been removed).

His lab also is testing the metal complex’s ability to perform a reduction reaction, the conversion of CO2 into methanol (CH3OH).

“Carbon dioxide is an exceptionally stable molecule, so anything you do with it is going to require energy,” Mirica says. “We’re just trying to use the metal complex to minimize the energy input.”

Both the ethane and methanol reactions take greenhouse gases and transform them to liquid or easily liquefied compounds that could then be reused as fuels. If the energy penalty turns out to be low enough, the carbon could be recycled in this way many times.

Chemistry for the greenhouse

Ultimately, Mirica’s goal is a recycling carbon chemistry that requires so little energy that it can run off sunlight.

“If we’re going to keep using these carbon-containing fuels that make CO2, we should be trying to make combustion carbon-neutral by using catalysts and the sun’s energy to convert CO2 back into fuel,” he says.

Diana Lutz | Newswise Science News
Further information:
http://www.wustl.edu

More articles from Life Sciences:

nachricht A Map of the Cell’s Power Station
18.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

nachricht On the way to developing a new active ingredient against chronic infections
18.08.2017 | Deutsches Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>