The current strict environmental legislation demands advanced concepts to reduce the emission of harmful gasses by cars. Reducing the emission of nitrous oxides (NOx) emitted by diesel and lean-burn petrol engines is one of the challenges faced. These economical engines produce exhaust fumes that are particularly rich in oxygen and therefore the conventional three-way catalytic converter is not suitable for converting the generated NOx into nitrogen. The current trend is therefore to add specific components such as barium to the catalytic converter to store the NOx formed.
In this new type of NOx Storage Reduction (NSR) catalytic converter the diesel or petrol combustion in the engine takes place alternately over long oxygen-rich and short fuel-rich periods. During a long oxygen-rich period the generated NOx is stored in the barium component. When this component becomes saturated the catalyst is regenerated. This happens during the short fuel-rich period when an oxygen-poor emission gas is produced. The NOx stored is released and subsequently reduced to nitrogen over a precious metal such as platinum. Scholz investigated this NSR mechanism to gain a better understanding of how the storage component functions during the oxygen-rich and fuel-rich periods.
The researcher carried out experiments in a laboratory reactor containing the NSR catalyst. She studied the behaviour of the catalyst in detail, including analysis of the effect of the various forms in which barium occurs in the catalytic converter, the effect of the presence of carbon dioxide and water in the exhaust gas, and the effect of the various reducing agents, such as carbon monoxide, hydrogen, and ethylene on the NOx storage and reduction. The research has yielded important new insights with respect to the function of various components in the catalytic converter. Scholz has also produced a practical mathematical model that describes the various chemical reactions in the catalytic converter.
Knowledge for everyday practice
Using this reaction model, a regulatory system in the car can determine when the maximum NOx capacity of the catalyst has been reached, followed by the length of time extra fuel must be injected to regenerate the catalyst. The research was carried out in cooperation with the car manufacturers PSA Peugeot Citroen, Toyota and Ford, the car development company PD&E Automotive Solutions, catalytic converter manufacturer Engelhard De Meern (now BASF), and with TNO Automotive, Shell, E.P. Controls and IPCOS.
Dr Karen Scholz | alfa
The car of the future – sleeper cars and travelling offices too?
18.06.2018 | Fraunhofer-Institut für Arbeitswirtschaft und Organisation IAO
Self-driving cars for country roads
07.05.2018 | Massachusetts Institute of Technology, CSAIL
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
19.07.2018 | Materials Sciences