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 Complete skin regeneration system of fish unraveled
24.04.2018 | Tokyo Institute of Technology

nachricht Scientists generate an atlas of the human genome using stem cells
24.04.2018 | The Hebrew University of Jerusalem

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Complete skin regeneration system of fish unraveled

24.04.2018 | Life Sciences

Scientists create innovative new 'green' concrete using graphene

24.04.2018 | Materials Sciences

BAM@Hannover Messe: innovative 3D printing method for space flight

24.04.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>