Shock-Tube Study of the Oxidation of Carbon Disulfide

Abstract

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: $${\mathrm{CS}}_2,{\mathrm{O}}_2\to {\displaystyle {lim}^{k_8}}\mathrm{SO},\mathrm{O},\mathrm{CS},$$ $${\mathrm{CS}}_2+\mathrm{O}\to {\displaystyle {lim}^{k_9}}\mathrm{CS}+\mathrm{SO},$$ $$\mathrm{CS}+{\mathrm{O}}_2\to {\displaystyle {lim}^{k_{\text{10a}}}}\mathrm{CO}+\mathrm{SO},$$ $$\mathrm{CS}+{\mathrm{O}}_2\to {\displaystyle {lim}^{k_{\text{10b}}}}\mathrm{COS}+\mathrm{O},$$ $$\mathrm{SO}+{\mathrm{O}}_2\to {\displaystyle {lim}^{k_1}}{\mathrm{SO}}_2+\mathrm{O}.$$ 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 $k_1$ is given by the expression $k_1{\text{\hspace{0.17em}=\hspace{0.17em}(9.7\hspace{0.17em}±\hspace{0.17em}0.2)\hspace{0.17em}×\hspace{0.17em}10}}^{13}\exp \text{(−\hspace{0.17em}29.0\hspace{0.17em}±\hspace{0.17em}1.0}{\mathrm{kcal\; mole}}^{\text{−1}}\mathrm{/RT)}{\mathrm{cm}}^3{\mathrm{mole}}^{\text{−1}}·{\sec }^{\text{−1}}$ . 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.