Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Insights into catalytic converters


X-ray methods reveal interactions of active metals with gas molecules -- publication in Chemical Communications

Modern catalytic converters for the treatment of exhaust gases in vehicles with a combustion engine have largely contributed to reducing of pollutant emissions. By oxidation or reduction, i.e. the donation or acceptance of electrons, the catalysts convert combustion pollutants, such as carbon monoxide, nitrogen oxides and hydrocarbons, into carbon dioxide, water, and nitrogen.

With the help of X-rays, reactions in catalytic converters can be observed under close-to-reality conditions.


Increasingly strict emission regulations call for a further reduction of fuel consumption and for an efficient use of the exhaust gas aftertreatment system. When adding the reduction agent ammonia formed by e.g. decomposition of urea, nitrogen oxides are converted into harmless nitrogen and water vapor over the catalytic converter. For this purpose, typically an urea solution (AdBlue®) is injected into the exhaust gas section upstream of the catalytic converter. (DOI: 10.1039/C5CC01758K)

To improve catalytic converters, it is required to precisely understand their function and the individual reaction steps. "Reliable findings relating to the reactions taking place may only be obtained under close-to-reality conditions," Professor Jan-Dierk Grunwaldt, Holder of the Chair for Chemical Technology and Catalysis of KIT, says. "This means that we have to watch the catalytic converters at work.

Synchrotron radiation sources are perfectly suited for this purpose." Synchrotron radiation is electromagnetic radiation (from infrared to hard X-rays) of several hundreds or even a million electron-volts in energy. Using hard X-rays, the properties of the active metal centers in the catalytic converter and their interactions with the gas molecules can be observed.

Two methods may be applied: (i) X-ray absorption spectroscopy (XAS) allows the determination of oxidation state and coordination number, i.e. the number of nearest neighbors of an atom; (ii) X-ray emission spectroscopy (XES) which can be used to distinguish between different molecules adsorbed on the catalytic converter. On this basis, it can be concluded which molecules cause reduction, when competing adsorption takes place, i.e. if several substances compete for adsorption on catalytic converters, and how individual molecules coordinate on the metal atom.

A group of researchers headed by Professor Jan-Dierk Grunwaldt, Professor Christoph R. Jacob, who recently moved from KIT to TU Braunschweig, and Dr. Pieter Glatzel at the European Synchrotron Radiation Facility (ESRF) in Grenoble / France now for the first time have combined the above methods to study under close-to-reality conditions reactions on two catalytically active materials applied in vehicles, namely Fe-ZSM-5 and Cu-SSZ-13. Both are based on zeolites, i.e. special minerals of porous structure. The results of the study are presented in the journal Chemical Communications.

With the help of the X-ray methods, the researchers studied and compared the interactions of the pollutant molecule nitrogen monoxide and the reducing agent ammonia with the iron and copper centers. "Although the reaction is the same in summary, we observed different reaction paths for the two catalytic converter materials," Tobias Günter, doctoral student at the Chair for Chemical Technology and Catalysis, reports.

The scientists found that the reaction on Fe-ZSM-5 is based on adsorption of nitrogen monoxide via a positively charged oxygen atom. The Cu-SSZ-13 catalytic converter, by contrast, did not exhibit this behavior. As no direct coordination via the nitrogen atom took place, the researchers assume a reaction from the gas phase with a potential activation on the ammonia molecule. "This also explains why ammonia inhibited the reaction on Fe-ZSM-5 contrary to Cu-SSZ-13," Tobias Günter explains.

The findings of the team headed by Jan-Dierk Grunwaldt provide valuable information for models to better predict the behavior of catalytic converters in operation. "Our approach based on the two X-ray methods cannot only be used for the materials mentioned, but may be transferred to many other materials and reactions," Professor Grunwaldt says. In the future, this approach will push the further development and improvement of catalytic converters.


Tobias Günter, Hudson W. P. Carvalho, Dmitry E. Doronkin, Thomas Sheppard, Pieter Glatzel, Andrew J. Atkins, Julian Rudolph, Christoph R. Jacob, Maria Casapu and Jan-Dierk Grunwaldt: Structural snapshots of the SCR reaction mechanism on Cu-SSZ-13. Chemical Communications, 2015, 51, 9227-9230. DOI: 10.1039/C5CC01758K.

Karlsruhe Institute of Technology (KIT) is a public corporation pursuing the tasks of a Baden-Wuerttemberg state university and of a national research center of the Helmholtz Association. The KIT mission combines the three core tasks of research, higher education, and innovation. With about 9,400 employees and 24,500 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe.

Since 2010, the KIT has been certified as a family-friendly university.

Media Contact

Monika Landgraf


Monika Landgraf | EurekAlert!

More articles from Life Sciences:

nachricht ‘Farming’ bacteria to boost growth in the oceans
24.10.2016 | Max-Planck-Institut für marine Mikrobiologie

nachricht Calcium Induces Chronic Lung Infections
24.10.2016 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Oasis of life in the ice-covered central Arctic

24.10.2016 | Earth Sciences

‘Farming’ bacteria to boost growth in the oceans

24.10.2016 | Life Sciences

Light-driven atomic rotations excite magnetic waves

24.10.2016 | Physics and Astronomy

More VideoLinks >>>