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The technology, which was developed by researchers at the University of Leeds, could work at lower temperatures and convert toxic emissions of carbon monoxide (CO) and nitrogen oxides (NOx) from diesel exhausts more effectively.
Vehicle fumes contribute to poor air quality in towns and cities. A recent report from Public Health England estimated that between 28,000 and 36,000 people a year die from long-term exposure to air pollution.
Catalytic converters are fitted to the exhaust pipes of most internal combustion engines, reducing the amount of toxic gases and pollutants by using a catalyst to facilitate chemical changes in exhaust fumes. In the case of diesel engines, which have been the subject of tightening legislation around the world, this includes conversion of CO and NOx to emissions such as carbon dioxide (CO2) and water.
There are limitations with the current technology, however. Many systems use costly platinum group metals, and the catalyst and converters do not become fully effective until the engine is very hot, above 150ºC – so they do not work as well when engines have just been started or vehicles are moving slowly or stationary, which is often the case in urban areas.
The researchers at Leeds demonstrated that their new technology is effective at much lower temperatures.
The team began work after investigating a fundamental question about the behaviour of CO2 in the atmosphere of Venus. Given proximity to the Sun, they were intrigued to know why CO2 levels in the atmosphere remained high. According to the principles of photochemistry, the CO2 should break down to CO and oxygen (O).
Project leader Dr Alexander James said there must be another process converting the CO and O back to CO2.
The team focused on the role played by a meteorite material found in the atmosphere of Venus, iron silicate. They concluded that the iron silicate must be acting as a catalyst, enabling the CO and O atoms to recombine – also one of the key features required of a catalytic converter.
The Leeds researchers aimed to create a synthetic material based on the chemistry of iron silicate, which could also act as a catalyst for converting nitrogen oxides into nitrogen and oxygen.
With funding from the Science and Technology Facilities Council, the scientists developed a synthetic compound as a proof of concept. They are now working on ways it could be manufactured at scale.
Dr James said: “We discovered that our synthetic material can effectively act as a catalyst for both the oxidation of carbon monoxide and the reduction of nitrogen oxides. There is a big need to change the technology used in catalytic converters, so they are better at reducing harmful emissions and cheaper to manufacture.
“Although the sale of new diesel vehicles is likely to cease in some countries by 2030, diesel engines will still be in use long beyond that. They are found in buses, trains and on ships, and are used as back-up for micro-grid electricity generation – so there is a need for efficient catalytic converter technology.”
Supervisor John Plane, professor of atmospheric chemistry at Leeds, said: “The funding from the Science and Technology Facilities Council’s Impact Acceleration Account has enabled us to make the crucial step from lab testing to preliminary engine trials. We are now in discussion with a company who manufacture catalytic converters to start full-vehicle trials.”
The university has applied for a patent to cover the synthetic compound, and the researchers are working with the university’s commercialisation team to develop the technology to a point where it can be licensed to industry.
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