Mullite reduces the pollution produced by diesel vehicles

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Engineers have identified a material that can reduce the pollution produced by vehicles that run on diesel.

In a study published in the 17 August issue of Science, researchers found that pollution is up to 45 per cent lower when a man-made version of the oxide mullite replaces platinum in diesel catalytic converters.

‘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,’ said Dr Kyeongjae ‘KJ’ Cho, professor of materials science and engineering and physics at the University of Texas at 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.’

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.

According to a statement, his company 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 were less expensive to produce.

Cho and his team suspected that the oxygen-based composition of mullite 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 nitrogen oxide (NOx).

After computer modelling 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 said. ‘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 commercialised under the trademark name Noxicat. Cho and his team will also explore other applications for mullite, such as fuel cells.

Researchers from Kentucky University and the Huazhong University of Science and Technology in China were also involved in this work.