Gas-phase chain reaction

Dichlorine shortens the induction period of autoxidation of paraffin wax [187] and accelerates the oxidation of hydrocarbons [109]. Difluorine is known as very active initiator of gas-phase chain reactions, for example, chlorination [188,189]. 

An unusual phenomenon was reported in the Arctic in the mid-1980s. Ozone measured at ground level was observed to decrease rapidly to small concentrations, at times near zero (Bottenheim et al., 1986 Oltmans and Komhyr, 1986). As seen in Fig. 6.37, an increase in bromide ion collected on filters (f-Br) was inversely correlated with the 03 decrease (Barrie et al., 1988 Oltmans et al., 1989 Sturges et al., 1993 Lehrer et al., 1997) this could reflect either particle bromide or a sticky gas such as HBr that could be collected on the filter simultaneously. This correlation suggested that the loss of ozone was due to gas-phase chain reactions... 

If reaction by this pathway proceeds at a rate significant with respect to the uncatalysed rate such that the total rate is increased, X is a catalyst. In this sense, a catalytic reaction is a closed sequence of elementary steps similar to the propagation steps of a gas-phase chain reaction. 

Some gas phase chain reactions have rates which are affected by the surface of the reaction vessel. Heterogeneous catalysis occurs when a surface increases the rate of the reaction. 

Lastly, some gas-phase chain reactions, among them the hydrogen-oxygen reaction, can be triggered by an electric discharge. 

Hoebink JHBJ, Couwenberg PM, Marin GB. Fixed bed reactor design for gas phase chain reactions catalysed by solids The oxidative coupling of methane. Chemical Engineering Science 1994 49 5453-5463. 

G.B. (1996) Kinetics of a gas-phase chain reaction catalyzed by a solid the oxidative coupling of methane over Li/MgO-based catalysts. Ind. Eng. Chem. Res.,... 

Gas Phase Chain Reactions and Ozone Depletion by CFCs. . . 407... 

For such a gas phase chain reaction, radical-radical reactions (7.84, 7.86-7.88) predominate when the mixing ratios of halogen radicals (XO) exceed e.g. 3 pptv. However, as their mixing ratios decrease, the formation of HOX by the reaction of XO with HO2,... 

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