The role of reactive oxygen and nitrogen species on the conversion of volatile organic compounds in a twin surface dielectric barrier discharge*

In consideration of the increasing consciousness for environmental protection, energy efficient processes for purification of exhaust gas streams, e.g. in industrial plants, are growing in demand. These gas streams can be contaminated with pollutants such as fine particles, volatile organic compounds (VOCs), and various microorganisms, depending on the industry and application.

A twin surface dielectric barrier discharge (SDBD), specially designed for the conversion of VOCs in synthetic air, has been studied regarding its fundamental plasma parameters, power efficiency, gas phase chemistry, gas dynamics, and conversion of frequently used hydrocarbons with and without catalyst [1-3]. However, the complex interaction of the different media and the underlying conversion mechanism is not yet fully understood.

Optical absorption spectroscopy (OAS) is used to measure absolute densities of selected reactive oxygen and nitrogen species (RONS) to further elucidate the conversion mechanism based on these radicals. The species composition is found to vary strongly based on a number of parameters. For example, at lower gas temperatures ozone exhibits the highest density of the considered species. For higher temperatures, however, the density of ozone declines and the concentrations of nitric oxides grow increasingly higher. A complementary zero dimensional chemistry model supports these observations. The possible influence on the conversion process will be discussed.