A discovery in molecular chemistry may help remove a barrier to widespread use of diesel and other fuel-efficient "lean burn" vehicle engines. Researchers at the Department of Energy's Pacific Northwest National Laboratory have recorded the first observations of how certain catalyst materials used in emission control devices are constructed.
The PNNL team observed how barium oxide attaches itself to the surface of gamma-alumina. Barium oxide is a compound that absorbs toxic nitrogen oxide, commonly referred to as NOx, from tail-pipe emissions. Gamma alumina is a form of aluminum oxide that is used as a support for catalyst materials, such as barium oxide, that are the active ingredients in exhaust systems.
"The discovery is encouraging because understanding catalysts in molecular and atomic detail can directly identify new ways to improve them," said PNNL researcher Janos Szanyi. The manner in which barium oxide anchors onto alumina suggests the exact site where catalytic materials begin to form - and where they can be available to absorb NOx emissions.
Lean burn engines deliver up to 35 percent better fuel economy because they mix more air with gasoline than standard internal combustion engines. But the more efficient engines can't meet strict emissions standards because current aftertreatment devices don't effectively reduce NOx emissions. New catalysts are essential before the economic and environmental benefits of lean burn engines can be realized.
Alumina is a common and relatively inexpensive catalyst support material. Its surface structure, formation and thermal stability have been the subjects of much research, but the alumina particles are too small and poorly crystalline for traditional surface analysis. Researchers used the world's first 900-MHz nuclear magnetic resonance spectrometer to reveal the anchoring behavior. The instrument is located at the William R. Wiley Environmental Molecular Sciences Laboratory, a DOE national scientific user facility at PNNL.
Scientists know that the aluminum ions in alumina coordinate, or bond, to either four or six oxygen ions. When water is present, 10 to 15 percent of the aluminum ions on the surface bond to six oxygen ions: one underneath to the bulk of the alumina, four in a square on the surface and one on top to an oxygen ion in the water molecule.
Removing the water by heating leaves the aluminum ion with only five oxygen bonds. In this "penta-coordinated" state, the aluminum is open for bonding to the barium oxide. Results from the NMR spectrometer showed that the catalyst filled every available penta-coordinated site, atom-for-atom.
The team is now examining the interaction of gamma-alumina with other metal and metal oxide particles to determine if penta-coordinated aluminum ions are suitable bonding locations for other catalytic materials.
DOE's Office of Basic Energy Sciences, Division of Chemical Sciences funded the research, which was facilitated by the laboratory's Institute for Interfacial Catalysis.
PNNL is a DOE Office of Science national laboratory that solves complex problems in energy, national security and the environment, and advances scientific frontiers in the chemical, biological, materials, environmental and computational sciences. PNNL employs 4,000 staff, has a $750 million annual budget, and has been managed by Ohio-based Battelle since the lab's inception in 1965.
A portion of this research was conducted at the William R. Wiley Environmental Molecular Sciences Laboratory in Richland, Wash. EMSL is a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.
Reference: Ja Hun Kwak, Jain Zhi Hu, Do Heui Kim, Janos Szanyi and Charles Peden. "Penta-coordinated Al3+ Ions as Preferential Nucleation Sites for BaO on ã-Al2O3." Journal of Catalysis 251(1):189-194. July 2007.
Contacts: Judith Graybeal, PNNL, (509) 375-4351
Judith Graybeal | EurekAlert!
New algorithm for optimized stability of planar-rod objects
11.08.2016 | Institute of Science and Technology Austria
Automated driving: Steering without limits
05.02.2016 | FZI Forschungszentrum Informatik am Karlsruher Institut für Technologie
Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.
This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...
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...
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...
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...
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...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
25.10.2016 | Earth Sciences
25.10.2016 | Power and Electrical Engineering
25.10.2016 | Process Engineering