Degradation of n-hexane by the high-throughput double dielectric barrier discharge: Influencing factors, degradation mechanism and pathways

Abstract

The emission of volatile organic compounds (VOCs) is known to be a source of various environmental problems. N-hexane is a saturated aliphatic hydrocarbon that is a major precursor of ozone. For the decomposition of n-hexane, a novel double dielectric barrier discharge (DDBD) reactor design is developed and tested on a pilot scale. The factors influencing the plasma degradation of n-hexane have been thoroughly investigated. The degradation efficiency, carbon balance and nitrogen oxide concentration were measured and analysed. Through experiments, it was found that the maximum removal of n-hexane at an initial concentration of 2000 ppm and a flow rate of 5 L/min was 1544 ppm. The associated energy efficiency reached 67.71 ppm/J. The excited states of oxygen and nitrogen (O2+, O(3 s5S-3p5P), N2(C3Πu-B3Πg), N2+(B2Σu+-X2Σg+)) during n-hexane degradation were observed. Possible degradation pathways of n-hexane are proposed, and it is revealed that the active species play an important role in the formation of oxygen and nitrogen-containing volatile organic by-products. The results show that the pilot-scale design of the DDBD system provides a feasible way for the industrial treatment of n-hexane, and provides fundamental insights into the mechanism of plasma catalytic system operation.