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Discovery may yield cheaper alternative to platinum catalysts

17 August 2012

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 diesel powered vehicles.

Dr Kyeongjae Cho

Diesel engines produce higher levels of oxides of nitrogen (NOx) pollutants than petrol fuelled engines. In June, 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.

Automotive exhaust pollutants are reduced using catalytic converters, which use platinum catalysts. Dr Kyeongjae Cho, professor of materials science and engineering and physics at UT Dallas and a senior member of the research team, said precious metals are limited and there just isn’t enough platinum to supply the many millions of automobiles that are in use throughout the world today.

Now, his research team has found that a manmade version of the oxide mullite achieves up to 45 percent lower diesel exhaust pollution than platinum catalysts. “Mullite is not only easier to produce than platinum, but also better at reducing pollution in diesel engines,” days Dr Cho.

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 commercialised 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 synthesised mullite and used advanced computer modelling techniques to analyse how different forms of the mineral interacted with oxygen and NOx. After computer modelling confirmed the efficiency of mullite to consume NOx, researchers used the oxide catalyst to replace platinum in diesel engine experiments.

The mullite alternative is being commercialised under the trademark name 'Noxicat'. Dr Cho and his team will also explore other applications for mullite, such as fuel cells.

A report on this work is published in the August 17 issue of Science


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