Eliminating nano-pollutants

UK catalyst specialist Johnson Matthey is developing a pollution control technology capable of trapping and destroying nano-sized exhaust particulate emissions.

The Gaspart system, developed in conjunction with Imperial College, can be used to prevent emissions of very fine carbon-rich particulates in any type of internal combustion engine running on any fuel – including petrol, diesel, biodiesel or natural gas.

The technology is capable of destroying more than 99 per cent of sub-100nm diameter particles in an exhaust gas, according to Dr. Stan Golunski, technology manager for gas-phase catalysis at Johnson Matthey.

The system is based on a thin wire fitted along the length of the exhaust pipe. An electric current is applied to the area between the pipe and wire which induces a charge on the particles being carried within the exhaust gas, immobilising them on the inside of the pipe.

If the particles were to remain in that position, however, they would begin to interfere with the trapping effect, so a catalyst is coated on to the inside of the pipe. As soon as the particles come into contact with the catalyst they begin to oxidise, turning into CO2 which is released into the atmosphere.

While CO2 is itself a pollutant, it is less directly harmful to human health than particulates, said Golunski. ‘In some cases, there are not that many of these particles around, so the difference in CO2 emissions will not be that great.’

But if left as particulates, they will hang around in the atmosphere for long periods of time, he said. The device is also likely to be used as part of a comprehensive emission-control package.

The system is being developed with funding from the DTI-backed Foresight Vehicle programme.

An initial 1m-long prototype has been successfully tested on exhaust from turbo-charged diesel and direct-injection petrol engines. The researchers are now designing and developing a working Gaspart unit, the same size and shape as a conventional catalytic converter.

The researchers are now designing and developing a working Gaspart unit, the same size and shape as a conventional catalytic converter.

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