Hydrocarbon disappearance, rates

It is interesting to note that the chlorinated ethylenes do not appear to follow this trend of increasing rates with increasing chlorination. (Lowry and Reinhard 1999 Schreier 1996) This may be due in part to the extremely fast rates of these reactions, which increase the relative importance of mass transfer limitations. For very fast reactions, mass transfer of compounds to the catalyst surface, rather than the intrinsic catalytic reaction rate, may determine the rate of disappearance of hydrocarbons and the resulting apparent rate constants. 

Oxidation rate constant k, for gas-phase second order rate constants, koH for reaction with OH radical, kNQ3 with N03 radical and kQ3 with 03 or as indicated, data at other temperatures see reference photooxidation t,/2 > 9.9 d for the gas-phase reaction with OH radical in air, based on the rate of disappearance of hydrocarbon due to reaction with hydroxyl radical (Darnall et al. 1976) koe = 2.77 x 10 11 cm3-molecules-1-s-1 at 299 K (Atkinson et al. 1977 quoted, Carlier et al. 1986) photooxidation t,/5 = 321 d in water, based on a rate constant k = 2.5 x 109 L-mol -s 1 for the aqueous-phase reaction with photochemically produced OH radical of 1 x 10 17 mol-I, 1 (Mill et al. 1980 Giiesten et al. 1981 quoted, Howard 1990)... 

Air t,/5 > 9.9 d for the gas-phase reaction with hydroxyl radical in air, based on the rate of disappearance of hydrocarbon due to reaction with hydroxyl radical (Darnall et al. 1976) ... 

In these experiments, we use multiphoton dissociation at 193 nm to generate C2 radicals. C2 concentrations are subsequently monitored using laser induced fluorescence. Disappearance rates of both Cj X3 g and a3IIu are reported at ambient temperature with hydrocarbons (CH , C2H2, CjH, and C2H6), hydrogen, oxygen, and carbon dioxide. 

Air photooxidation t,/, = 0.24-2.4 h in air for the gas-phase reaction with hydroxyl radical, based on the rate of disappearance of hydrocarbon due to reaction with hydroxyl radical (Darnall et al. 1976) photooxidation t,/, = 6.2-72 h, based on measured rate constant for the reaction with hydroxyl radical in air (Atkinson 1985, 1987 quoted, Howard 1990 selected, Howard et al. 1991). 

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