The Chemistry of Dichloromethane Destruction in Atmospheric-Pressure Gas Streams by a Dielectric Packed-Bed Plasma Reactor

Abstract

The destruction of dichloromethane by a nonthermal plasma in atmospheric-pressure gas streams of nitrogen with variable amounts of added oxygen has been investigated. The identities and concentrations of the end products are determined by on-line FTIR spectroscopy, and the plasma chemistry is interpreted using a kinetic modeling scheme. Peak destructions of 20% are found for a deposited energy of 66 J L -1 . The maximum dissociation is found for a carrier gas that contains 1-3% O 2 , and the dissociation is greater in pure nitrogen than in an air stream. The major end products of the processing are HCN, Cl 2 , and HCl in pure nitrogen and CO, COCl 2 , HCl, and Cl 2 for gas streams containing oxygen. The plasma processing in streams containing oxygen also produces significant yields of nitrogen oxides. The mechanism of dichloromethane destruction in the plasma is predominantly oxidation initiated by atomic chlorine that is produced by collisions of dichloromethane with electronically excited nitrogen atoms and molecules. Because of low cross sections, electron attachment does not play a role in the destruction of dichloromethane. The addition of oxygen to the gas streams initially causes additional destruction from O and OH reactions, but further increase in the oxygen concentration causes inhibition of both the atomic chlorine cycle and the formation of NO x and a consequent reduction in dichloromethane destruction.

Microwave Plasma Conversion of Volatile Organic Compounds

“…Smaller flows are more conveniently treated by other nonthermal plasmas, such as the microwave plasma. Fitzsimmons et al 13 reported a 20% reduction in the concentration of dichloromethane in a packed dielectric bed plasma reactor with an energy input of approximately 66 J/L; some N 2 O and NO 2 formed as a result of the large energy density and heating of the flow. The formation of NO x is not an issue for the current system as a result of the exclusion of N from the system.…”

“…A microwave power of 800 W achieved almost total removal of the freon. Fitzsimmons et al 13 explored the use of a microwave plasma to destroy dichloromethane in an atmospheric pressure flow of air.…”

Removal of Elemental Mercury from a Gas Stream Facilitated by a Non-Thermal Plasma Device

“…These plasmas produce highly reactive ions and metastable species to achieve chemical and thermal conversions, with gas temperatures on the order of 100 °C (212 °F). Similar devices have also been demonstrated for destruction of low concentrations of volatile organic compounds such as dichloromethane, methyl chloride, carbon tetrachloride, trichloroethane, trichloroethene, and chlorobenzene (Fitzsimmons et al, 2000). A limited amount of research has also discussed volatile metals capture.…”

Destruction of Fluorinated Greenhouse Gases by Using Nonthermal Plasma Process

“…Although data are not shown, nitrous oxide (N 2 O) was also identified in the effluent gas stream. The formation of N 2 O is common in plasma processing of air-like gases containing both N 2 and O 2 (Fitzsimmons et al, 2000;Ricketts et al, 2004;Harling et al, 2005). Properly, the amounts of destruction products were more in the presence of alumina than zirconia, because of higher destruction efficiency.…”