Nonthermal Plasma Chemical Processing of Bromomethane

Abstract

Nonthermal plasma chemical decomposition of bromomethane (CH 3 Br) was investigated with a coaxial type packed-bed plasma reactor. It has been demonstrated that plasma chemical processing is an effective approach to decompose CH 3 Br in a wide concentration range. It has been shown that CH 3 Br decomposition reactivity depends on reactor operating factors such as background gas, O 2 concentration, and humidification. Higher decomposition efficiencies can be obtained in dry N 2 . However, organic byproducts such as BrCN are concurrently produced under deaerated conditions. Water suppresses CH 3 Br decomposition and also affects the yields of CO x (CO and CO 2 ) and organic byproducts due to the involvement of some active species generated from water. The presence of O 2 retards CH 3 Br decomposition by quenching highenergy electrons, while it suppresses organic byproducts and improves CO x yield. The reacted carbons in CH 3 Br are recovered as CO x almost quantitatively in air. Higher CO 2 selectivities cannot be achieved by increasing O 2 concentration. NO x formation, which is accompanied by IMPLICATIONS Bromomethane (CH 3 Br) is commonly used as an excellent fumigant on fields and in quarantine facilities, but it threatens to cause stratospheric ozone depletion (ODP CH 3 Br = 0.74). It has been decided that the use of CH 3 Br will be continued as an essential use in quarantine facilities even after 2004, because no alternative compounds have yet been found due to its high sterilizing power and advantageous properties (i.e., a colorless and odorless gas). Up to 5000 parts per million of CH 3 Br is emitted from silo roofs in these facilities without any treatment, and its total consumption amounted to 2370 tons per year in Japan in 1995. In these facilities, nonthermal plasma chemical decomposition is considered to be a potential candidate to solve the problem. This paper summarizes the results from a laboratory-scale evaluation of CH 3 Br reactivity in nonthermal plasma and the effects of reaction parameters affecting byproduct distributions.CH 3 Br decomposition, can be effectively suppressed by decreasing O 2 concentration down to 2%. Furthermore, reaction mechanisms are discussed by comparing the reactivities of CH 3 Br and its congeners.

Synergistic effect of silent discharge plasma and catalysts on benzene decomposition

“…According to our previous data with SDR, no correlation was observed between the amount of O 3 formed from gaseous oxygen and the conversions of VOCs such as trichloroethylene (TCE) [13], benzene [14], and CH 3 Br [12] under aerated conditions. Interestingly, only the decomposition of TCE was promoted by gaseous oxygen without catalysts.…”

“…Nonthermal plasma has attracted much attention as an energy-saving method for VOCs control for this decade [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] due to its unique properties such as quick response at ambient temperature, achievement of high electron energies within short residence times, system compactness, and easy operations. This technique is especially effective in removing olefinic VOCs such as trichloroethylene, tetrachloroethylene, and ethylene at smaller energy consumptions [6].…”

Elimination of Carbon Monoxide in the Gas Streams by Dielectric Barrier Discharge Systems with Mn Catalyst

“…(5) Furthermore, the increase of background oxygen level cannot effectively reduce CO formation; for instance, the ratio of CO/(CO + CO 2 ) was around 70% in the effluent when the BaTiO 3 packed-bed DBD reactor was utilized to destruct CH 3 Br. (6) In addition, Malik and Jiang (7) found that the increase of inlet toluene and benzene concentrations led to more CO formation. The maximum ratios of CO/CO 2 observed in their study were 2.5 and 3.0 with respect to toluene and benzene.…”

Decomposition of Toluene and Acetone in Packed Dielectric Barrier Discharge Reactors

“…In particular, NTP was reported to be effective technology to decompose many volatile organic compounds (VOCs) including benzene, acetaldehyde, p-xylene, toluene, and bromomethane etc. (3)(4)(5)(6)(7) The NTP technology seems not widely applied to control contaminated gas streams currently because of its lower energetic efficiency, and the formation of harmful by-products. (8) Therefore, in order to solve these drawbacks, packed beds were applied in the NTP reactors.…”