Reducing Emissions with Microwaves during a Cold Start

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According to the Swiss Federal Laboratories for Materials Science and Technology (Eidgenössische Materialprüfungs- und Forschungsanstalt, Empa) , 90 percent of all pollutants are produced in the first minute after the cold start of a modern petrol engine. Dimopoulos Eggenschwiler, an exhaust gas aftertreatment specialist at Empa’s engine laboratory, is researching a new type of preheating solution, so that the catalytic converter can work optimally from the very first turn of the engine. To achieve this, he intends to use the vehicle’s power supply to heat the catalytic converter to 300 degrees Celsius quickly and efficiently.

Empa’s researchers have developed a compact catalytic converter that conducts heat well, with an open-pore structure and a special coating, which can be heated up by a small microwave transmitter within ten seconds. The geometric lattice structure consisting of thin ceramic struts can efficiently purify the exhaust gas despite being coated with a low amount of precious metal. 

A catalytic converter from the printer

Using 3D printing, specialists at the University of Applied Sciences and Arts of Southern Switzerland (Scuola universitaria professionale della Svizzera italiana, SUPSI) in Lugano produced a prototype, which Empa researchers then coated with silicon carbide, zirconium oxide and aluminium oxide, as well as the active catalyst substances platinum, rhodium and palladium. The new catalytic converter successfully passed initial tests in the artificially generated exhaust gas stream of Empa’s model gas reactor. The researchers now want to install a full-scale 3D catalytic converter in a test vehicle and trial the catalytic converter both on the dynamometer and under real traffic conditions.

When integrating the microwave heating, one to two kilowatts of power for 10 to 20 seconds should be sufficient. "It’s important that we don’t heat up the entire ceramic structure", explains Dimopoulos Eggenschwiler: "We want to heat up just some segments of the catalytic converter by the microwaves that are generated by using precious battery power. As soon as the chemical reactions start, all the other parts will heat up themselves." EngiCer, based in Ticino, Switzerland, is to produce a small series of the new catalytic converter. Hybrid models could also benefit from this new development since the catalytic converter cools down when the vehicle switches to electrical operation and emits many pollutants when the engine is restarted.