Catalyst for change
17 Mar 2005
The new catalyst, still in the early stages of testing, uses a combination of iron, aluminium and other metals to harvest hydrogen from carbon monoxide and water, explained Umit Ozkan, professor of chemical and biomolecular engineering at
Around the world, researchers are working to develop fuel cells - devices which would use chemical reactions to produce electricity. Cars are a prime target for this technology, and experts believe that the type of fuel cell that is best suited to cars is one that runs on hydrogen.
“Hydrogen is the ultimate fuel,” Ozkan said. “At the same time, we have very large coal reserves. If we could somehow go from coal to hydrogen, we could put those reserves to use in a new way.”
That’s why the Ohio Coal Development Office and the Ohio Department of Development are funding Ozkan’s research.
The first step for making hydrogen from coal is a process called gasification, which converts coal to a carbon monoxide-rich stream. But the next step - retrieving hydrogen from a reaction between carbon monoxide and water - only works within a narrow range of low temperatures. New catalysts are needed to boost the reaction, especially for large-scale coal gasification, she said.
Until now, the most popular commercial catalyst has been one made from iron and the toxic metal chromium. During hydrogen production, the catalyst can release chromium as a byproduct. When the catalyst material has passed its useful lifetime, it requires expensive disposal methods.
Because researchers don’t fully understand why the iron-chromium catalyst works as well as it does, coming up with a more environmentally friendly alternative hasn’t been easy.
“We didn’t just want to make a better catalyst, but also understand why it’s better, and what we can do to make it work even better,” Ozkan said.
She and her team suspected that the chromium helps maintain the pore structure of iron during the reaction, so they looked for a metal with a similar chemical structure. That led them to aluminium, and to other complementary metals that greatly increased hydrogen production.
“What is important is not only which metals are used, but how these metal molecules fit together. We believe the specific way we prepare the catalyst is a key factor in its superior performance,” she said. “This performance was maintained when we tested the catalyst using a feed mixture similar to what is produced from coal gasification,” she added.
The next thing Ozkan and her colleagues want to do is test whether their catalyst works in the presence of sulphur, since coal from Ohio and much of the American northeast is sulphur-rich.
The coal gasification process typically removes sulphur, she pointed out. “The amount that’s left behind - our catalyst may be able to handle that,” she said.
