Shock-Tube Study of the Oxidation of Carbon Disulfide

The oxidation of carbon disulfide has been studied after shock heating the following mixtures: CS2: O2:Ar = 1:3:96, 1:6:93, 1:9:90, and 5:15:80. A range of initial pressures between 10 and 30 torr, combined with the change of mixture composition and use of reflected as well as incident shocks, resulted in a variation of CS2 and O2 concentrations equal to a factor of 20 in each case. Chemiluminescence accompanying the reaction was recorded at temperatures between 1600 and 2100°K. The assumption that the chemiluminescence is the SO+O recombination emission is consistent with experimental observations of the growth rates of emission intensity and SO absorption. These observations indicate that a direct proportionality exists between the concentrations of SO and O during the early stages of reaction. Induction period measurements and the exponential growth rates for emission are analyzed assuming the following branching-chain-reaction mechanism: CS2, O2→ lim k8SO, O, CS, CS2+O→ lim k9CS+SO, CS+O2→ lim k10aCO+SO, CS+O2→ lim k10bCOS+O, SO+O2→ lim k1SO2+O. The reaction seems to proceed through steps (8)–(10b) and (1), with the oxidation of SO being the single rate-determining step. On this basis a value for the rate constant k1 is given by the expression k1 = (9.7 ± 0.2) × 1013exp(− 29.0 ± 1.0 kcal mole−1/RT) cm3mole−1·sec−1. A few experiments were carried out with COS replacing CS2. The results showed that the oxidation is much slower than in the case of CS2 and goes by a different process. A reaction sequence analogous to that for CS2 can be used to interpret this behavior.