Engineers at a company co-founded by a
University of Texas at Dallas professor have identified a material that can
reduce the pollution produced by vehicles that run on diesel fuel.
The material, from a family of minerals called
oxides, could replace platinum, a rare and expensive metal that is currently
used in diesel engines to try to control the amount of pollution released into
In a study published in Science,
researchers found that when a man-made version of the oxide mullite replaces
platinum, pollution is up to 45% lower than with platinum catalysts.
“Many pollution control and renewable-energy
applications require precious metals that are limited—there isn’t enough
platinum to supply the millions and millions of automobiles driven in the
world,” says Kyeongjae “K.J.” Cho, professor of materials science and
engineering and physics at UT Dallas and a senior author of study. “Mullite is
not only easier to produce than platinum, but also better at reducing pollution
in diesel engines.”
For the environmentally conscious, the higher
fuel efficiency of diesel engines makes an attractive alternative to engines
that run on gasoline. On the flip side, compared with gasoline engines, diesel
vehicles produce more nitric oxide and nitrogen dioxide, which are known as NOx
In June (2012), the World Health Organization
upgraded the classification of diesel engine exhaust as carcinogenic in humans,
putting it in the same category as cigarette smoke and asbestos. Countries
throughout the world have drafted guidelines to reduce diesel air pollution in
the next decade.
Platinum, because of its expense to mine and
limited supply, is considered a precious metal. Estimates suggest that for 10
tons of platinum ore mined, only about 1 ounce of usable platinum is produced.
In 2003, Cho became a co-founder and lead
scientist at Nanostellar, a company created to find catalysts through a
material design that would replace platinum in reducing diesel exhaust (carbon
monoxide and NOx pollutants). His company has designed and commercialized a
platinum-gold alloy catalyst that is a viable alternative to platinum alone,
but until this experiment with mullite, had not found a catalyst made of
materials that are less expensive to produce.
Cho, also a visiting professor at Seoul
National University in South Korea, and his team suspected that the
oxygen-based composition of mullite, originally found off the Isle of Mull in
Scotland, might prove to be a suitable alternative. His team synthesized
mullite and used advanced computer modeling techniques to analyze how different
forms of the mineral interacted with oxygen and NOx. After computer modeling
confirmed the efficiency of mullite to consume NOx, researchers used the oxide
catalyst to replace platinum in diesel engine experiments.
“Our goal to move completely away from
precious metals and replace them with oxides that can be seen commonly in the
environment has been achieved,” Cho says. “We’ve found new possibilities to
create renewable, clean energy technology by designing new functional materials
without being limited by the supply of precious metals.”
The mullite alternative is being
commercialized under the trademark name Noxicat. Cho and his team will also
explore other applications for mullite, such as fuel cells.
Source: University of Texas at Dallas