Optical absorption spectroscopy of reactive oxygen and nitrogen species in a surface dielectric barrier discharge

Abstract

A twin surface dielectric barrier discharge (SDBD) ignited in a dry synthetic air gas stream is studied regarding the formation of reactive oxygen and nitrogen species (RONS) and their impact on the conversion of admixed n-butane. The discharge is driven by a damped sinusoidal voltage waveform at peak-topeak amplitudes of 8 kVpp to 13 kVpp and pulse repetition frequencies of 250 Hz to 4000 Hz. Absolute densities of O3, NO2, NO3, as well as estimates of the sum of the densities of N2O4 and N2O5 are determined temporally resolved by means of optical absorption spectroscopy using a laser driven broadband light source, suitable interference filters, and a photodiode detector. The measured densities are acquired across the center of the reactor chamber as well as at the outlet of the chamber. The temporal and spatial evolution of the species’ densities is correlated to the conversion of nbutane at concentrations of 50 ppm and 400 ppm, measured by means of flame ionization detectors. The n-butane is admixed either before or after the reactor chamber, in order to separate the impact of short- and long-lived reactive species on the conversion process. It is found that, despite the stationary conversion at the selected operating points, at higher voltages and repetition frequencies the densities of the measured species are not in steady state. Based on the produced results it is presumed that the presence of n-butane modifies the formation and consumption pathways of O3. At the same time, there is no significant impact on the formation of dinitrogen oxides (N2O4 and N2O5). Furthermore, a comparatively high conversion of n-butane, when admixed at the outlet of the reactor chamber is observed. These findings are discussed together with known rate coefficients for the reactions of n-butane with selected RONS.

A scalable twin surface dielectric barrier discharge system for pollution remediation at high gas flow rates

“…The behaviour is to be expected, as for higher energy densities (higher repetition frequencies in this case) more reactive species will be produced, which results in a higher conversion of the VOCs, 22 assuming the increasing temperature does not change the chemistry in a way that favours other species in the reactions. When reactive species are consumed in the oxidation of VOCs, their density decreases and so the probability for further oxidations decreases.…”

“…Additionally, Schücke et al 21 have studied the SDBD for the conversion of multiple VOCs with respect to power dissipation and gas chromatography-mass spectrometry measurements. In a further study Schücke et al 22 investigated the formation of reactive nitrogen and oxygen species by optical absorption spectroscopy (OAS) and their impact on conversion. Peters et al performed studies on the n -butane conversion, selectivity and carbon balance using the same electrode with complementary α-MnO 2 deposited as catalyst.…”

“…Additionally, the work of Schücke et al has indicated that O 3 has a limited direct effect on the oxidation of n -butane and possibly other VOCs. 22 Nevertheless, ozone is an important species to be monitored in any plasma-based conversion process, as it represents an important pollutant itself. Because of the risk to human health the permitted threshold for ozone is 50 ppb for 8 h of occupational exposure according to the World Health Organization.…”

Dynamics of NO, N2O, and ONOOH in atmospheric-pressure air dielectric barrier discharge: decoupling energy density and gas temperature effects varying with discharge voltage

“…Among the various methods for regulating RNS (e.g. electrical parameter control, device regulation, gas component control, discharge temperature control, and catalyst coordination) [23][24][25][26][27][28][29][30][31], discharge voltage regulation is a typically used and relatively simple approach [32][33][34][35]. For example, Liu et al [32] discovered no NO in plasma chemical products under a low discharge voltage and that NO was generated only when the discharge voltage exceeded 22 kV.…”

Investigation of flow characteristics in a twin-surface dielectric barrier discharge reactor by Schlieren imaging

“…Offerhaus et al [26] characterized the SDBD with respect to its plasma parameters, electrical parameters, chemical reactivity and performed preliminary Schlieren imaging. Schücke et al [27,28] and Peters et al [29] applied the SDBD in the plasma-only and plasma-catalytic oxidation of several VOCs and demonstrated its viability for such applications with a high performance. The plasma is limited to the surface of the SDBD electrode configuration with a radial expansion of approximately 100 µm and a lateral expansion of only a few millimeters.…”