Nonthermal Plasma Chemical Processing of Bromomethane

ABSTRACT

Nonthermal plasma chemical decomposition of bromomethane (CH₃Br) was investigated with a coaxial type packed-bed plasma reactor. It has been demonstrated that plasma chemical processing is an effective approach to decompose CH₃Br in a wide concentration range. It has been shown that CH₃Br decomposition reactivity depends on reactor operating factors such as background gas, O₂ concentration, and humidification. Higher decomposition efficiencies can be obtained in dry N₂. However, organic byproducts such as BrCN are concurrently produced under deaerated conditions. Water suppresses CH₃Br decomposition and also affects the yields of CO_x (CO and CO₂) and organic byproducts due to the involvement of some active species generated from water. The presence of O₂ retards CH₃Br decomposition by quenching high-energy electrons, while it suppresses organic byproducts and improves CO_x yield. The reacted carbons in CH₃Br are recovered as CO_x almost quantitatively in air. Higher CO₂ selectivities cannot be achieved by increasing O₂ concentration. NO_x formation, which is accompanied by CH₃Br decomposition, can be effectively suppressed by decreasing O₂ concentration down to 2%. Furthermore, reaction mechanisms are discussed by comparing the reactivities of CH₃Br and its congeners.