Transportation Research Highlights
September 01, 2005
RICHLAND, Wash. –
Researchers from the Department of Energy's Pacific Northwest National Laboratory presented the following results at the 230th national meeting of the American Chemical Society, Aug. 28 through Sept. 1 in Washington, D.C.
Pacific Northwest National Laboratory researcher Maciej Gutowski presented his results Monday, Aug. 29.
Researchers examine potential for 'refilling' hydrogen storage material
Performing quantum calculations on a supercomputer, scientists at Pacific Northwest National Laboratory have characterized a material that might allow on-board refueling of hydrogen powered vehicles.
Researchers, led by Maciej Gutowski, looked at different crystalline structures of a compound made up of nitrogen, boron and hydrogen - NBH6 - and found one that might be more stable compared to ammonia borane, a molecular crystal built of NH3BH3 molecules. Ammonia borane can hold a lot of hydrogen but isn't easily reversible – or able to be refilled with hydrogen. Ammonia borane, as a storage material, would likely have to be removed from the vehicle and be sent to some sort of processing plant and undergo a reaction to be refilled.
The more stable compound, diammoniate of diborane or DADB, holds more promise for reversibility. Initial thermodynamic properties for the compound indicate that it might spontaneously uptake hydrogen fuel.
This work is performed under the Grand Challenge Project "Computational studies of materials to hydrogen storage" in the Molecular Sciences Computing Facility at PNNL. Researchers plan to perform additional calculations, synthesize the diammoniate of diborane compound and test their theories on the material in the coming year
Pacific Northwest National Laboratory researcher Tom Autrey presented his results Monday, Aug. 29.
'Operando' methods for understanding catalysis in hydrogen storage
As researchers at Pacific Northwest National Laboratory investigated the hydrogen storage capabilities of amine borane compounds, they knew that a rhodium catalyst readily releases hydrogen from the compound at room temperature. But they weren’t sure how it worked. Aside from the scientific quest for knowledge, understanding the mechanism at work with rhodium may help with the development of a more cost-effective catalyst to enable hydrogen storage.
PNNL scientists used a type of x-ray spectroscopy available at the Advanced Photon Source synchrotron at Argonne National Laboratory to look at the reaction as it was occurring. They found the active site of the catalyst centered around a cluster of about four rhodium atoms. They also found that the catalyst structure during the reaction was different than the structure before and after the reaction, thus highlighting the importance of measuring the catalyst structure during the reaction conditions.
By combining these results with subsequent in situ nuclear magnetic resonance and infrared spectroscopy, researchers were able to "see" what happens to the boron compound as the hydrogen is released. The results show the mechanism of how the amine borane compound binds to the active catalyst and then how the hydrogen molecule is released as a gas.
The research demonstrates the importance of "operando" methods – or observation of the fundamental molecular level measurements of the catalyst, the reactants and the products – under practical conditions. The PNNL group is using this approach to investigate other chemical reactions where little is known about the key catalytic processes.
Pacific Northwest National Laboratory researcher Liyu Li presented his results Wednesday, Aug. 31.
Inexpensive oxidation catalyst could reduce diesel emissions
It’s not a new material, but a new application of silver hollandite could make a big impact in diesel emissions control. Researchers at Pacific Northwest National Laboratory have developed an inexpensive method of synthesizing nano-sized silver hollandite and have found the material has unique catalytic properties that can completely oxidize nitrogens of oxide, carbon monoxide and hydrocarbons. These chemical reactions caused by the silver hollandite are key to reducing pollutants in diesel engine emissions.
PNNL researchers have also discovered that silver hollandite is an excellent low-temperature sulfur oxides absorbent. Unlike most oxidation catalysts, which can be easily poisoned by sulfur oxides, silver hollandite maintains its catalytic activity even while it ages by absorbing sulfur oxides.
Pacific Northwest National Laboratory researcher Liyu Li presented his results Thursday, Sept. 1.
Super sulfur soaker material may help control diesel emissions
The mineral cryptomelane holds promise to absorb the toxic sulfur oxides that can degrade the emission control systems on diesel vehicles. Pacific Northwest National Laboratory researchers have identified the potential for using cryptomelane to trap sulfur dioxide and sulfur trioxide from diesel engine emissions on monolith supports – sturdy honeycombed structures composed of small parallel channels.
Cryptomelane has a very high capacity for absorbing sulfur dioxide – more than 10 times as high as those of standard metal oxide-based absorbents. Finding a way to capture sulfur is important since most fuels have a sulfur content that is harmful to the environment, clogs emissions control devices or damages fuel cells.
PNNL researchers tested cryptomelane under diesel engine conditions that are being proposed to trap nitrogen oxides – the most dangerous component of diesel exhaust. Under those conditions, including high temperatures, the cryptomelane maintains its very high sulfur dioxide capacity. These studies indicate that cryptomelane can be used to protect the nitrogen oxides traps from the sulfur oxide that degrades them under these conditions.
Finding cryptomelane to be an excellent catalyst for oxidizing sulfur dioxide, PNNL researchers have filed for a patent on this application. They believe the catalyst may degrade additional undesirable material and are looking for research partners to demonstrate the usefulness of cryptomelane.
Tags: Energy, Environment, Fundamental Science, Computational Science, Emissions, Fuel Cells, Catalysis, Supercomputer