Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

In Chemical Reactions, Water Adds Speed Without Heat

18.05.2012
An international team of researchers has discovered how adding trace amounts of water can tremendously speed up chemical reactions—such as hydrogenation and hydrogenolysis—in which hydrogen is one of the reactants, or starting materials.

Led by Manos Mavrikakis, the Paul A. Elfers professor of chemical and biological engineering at the University of Wisconsin-Madison, and Flemming Besenbacher, a professor of physics and astronomy at the University of Aarhus, Denmark, the team published its findings in the May 18 issue of the journal Science.

Hydrogenation and hydrogenolysis reactions have huge applications in many key industrial sectors, including the petrochemical, pharmaceutical, food and agricultural industries. "In the petrochemical industry, for example, upgrading of oil to gasoline, and in making various biomass-derived products, you need to hydrogenate molecules—to add hydrogen—and all this happens through catalytic transformations," says Mavrikakis, who is among the top-100 chemists of the 2000-10 decade, according to Thomson Reuters.

A chemical reaction transforms a set of molecules (the reactants) into another set of molecules (the products), and a catalyst is a substance that accelerates that chemical reaction, while not itself being consumed in the process.

In industrial applications, the speed of catalytic transformations is important, says Mavrikakis. "The rate at which the hydrogen atoms diffuse on the surfaces of the catalyst determines, to a large extent, the rate of the chemical reaction—the rate at which we produce the products we want to produce," he says.

While many researchers have observed that water can accelerate chemical reactions in which hydrogen is a reactant or a product, until now, they lacked a fundamental grasp of how that effect was taking place, says Mavrikakis. "Nobody had appreciated the importance of water, even at the parts per million level," he says.

In their research, Mavrikakis and Besenbacher drew on their respective theoretical and experimental expertise to study metal oxides, a class of materials often used as catalysts or catalyst supports. They found that the presence of even the most minute amounts of water—on the order of those in an outer-space vacuum—can accelerate the diffusion of hydrogen atoms on iron oxide by 16 orders of magnitude at room temperature. In other words, water makes hydrogen diffuse 10,000 trillion times faster on metal oxides than it would have diffused in the absence of water. Without water, heat is needed to speed up that motion.

Besenbacher and his colleagues have one of the world's fastest scanning tunneling microscopes, which has atomic-scale resolution. With it, they could see how quickly hydrogen atoms diffused across iron oxide in the presence of water.

To explain the fundamental mechanisms of how that happened, Mavrikakis and his team used quantum mechanics, a branch of physics that explains the behavior of matter on the atomic scale; and massively parallel computing. Essentially, when water is present, hydrogen diffuses via a proton transfer, or proton "hopping," mechanism, in which hydrogen atoms from the oxide surface jump onto nearby water molecules and make hydronium ions, which then deliver their extra proton to the oxide surface and liberate a water molecule. That repeated process leads to rapid hydrogen atom diffusion on the oxide surface.

It's a process that doesn't happen willy-nilly, either. The researchers also showed that when they roll out the proverbial red carpet—a nanoscale "path" templated with hydrogen atoms—on iron oxide, the water will find that path, stay on it, and keep moving. The discovery could be relevant in nanoscale precision applications mediated by water, such as nanofluidics, nanotube sensors, and transfer across biological membranes, among others.

The U.S. Department of Energy Office of Basic Energy Sciences funded the UW-Madison research. Other UW-Madison authors on the Science paper include chemical and biological engineering research scientist Guowen Peng, PhD student Carrie Farberow, and PhD alumnus Lars Grabow (now an assistant professor at the University of Houston). Other authors include Lindsay Merte, Ralf Bechstein, Felix Rieboldt, Wilhelmine Kudernatsch, Stefan Wendt and Erik Laegsgaard of Aarhus University.

Manos Mavrikakis | Newswise Science News
Further information:
http://www.wisc.edu

More articles from Life Sciences:

nachricht More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>