Shock initiated ignition in COSO₂Ar mixtures

Abstract

The ignition of COS + 0 2 mixtures diluted in argon was studied behind reflected shocks in a single-pulse shock tube over the temperature range of 1100-1 700°K. Ignition delay times and the distribution of reaction products before and after ignition were determined experimentally. From a total of 63 tests run at varying initial conditions, the following correlation for the induction times was derived:where Using a reaction scheme of 14 steps, the following values were obtained by a computer modeling of the induction times: = f0.22, 8 2 = -1.55, and E = 17.3 kcal/mole. The calculations showed that the reaction COS + S -+ CO f SZ caused the inhibiting effect of the COS. The reaction COS -+ 0 -+ COZ + S has a very strong accelerating effect, whereas the parallel channel COS + 0 ---f CO + SO shows the opposite effect. It was also shown that the reaction 0 f S2 -+ SO + 0 is very slow and does not contribute to the overall oxidation reaction. It is suggested that the rate constant given to the four-center reaction COS + SO --f COz -+ Sz, that is, 10" cm3/mole.sec at 300°K is incorrect. This constant is not much higher than lo8 cm3/mole .set at 1300°K.= +0.30, 0 2 = -1.12, and E = 16.9 kcal/mole.

Kinetics and Mechanisms of the Oxidation of Gaseous Sulfur Compounds

“…The mechanism was used to interpret a number of experimental studies, with approximate agreement to the data being found in all cases. The experiments included a room-temperature, 1.4 Torr flow system study of a CS 2 -O-atom flame reported by Slagle et al (1974); a stirred-reactor study of CS2-02 mixtures of variable composition at 573 K and 3 Torr reported by Kondratiev (1940); another stirred-reactor study of CS2-02 mixtures at 623 K and 3 Torr reported by Sarkisyan et al (1968), in which O-atom and SO-concentrations were measured; a flow reactor study of S02 reduction by CO at 1215 K and 50 Torr reported by Arutyunov et al (1990); ignition delays in an 8% COS, 12% 02 mixture in argon investigated by Lifshitz et al (1975); and an O-atom profile in a 1615 K, 1 atm reflected shock wave experiment reported by Saito et al (1986). Basevich et al (1994) later used this mechanism to model the CS2-air flames studied by Egerton and Sen (1953), obtaining reasonable agreement with the flame speeds but flame thicknesses about half of the experimental values.…”

Oxidation of cyanogen. II. The mechanism of the oxidation

“…Although the initiation is an essential step in the beginning of the reaction, it very soon loses its significance owing to the establishment of much faster channels through which free radicals are being added to the system [reaction (91. This phenomenon is expected and has already been observed in other systems [5].…”

“…It is interesting to note that a similar discussion was presented in the analysis of the mechanism of the COS oxidation by oxygen behind reflected shocks [5]. There, however, the situation is exactly the opposite.…”

“…The most important conclusion that can be reached from the calculations just described is that the overall behavior of the oxidation of cyanogen is characterized by the thermal chains (3) and (4). The addition of oxygen atoms to the chain by reaction (5) [and (6)] is an important factor which increases its propagation rate continuously. The temperature dependence of the induction period is determined to a great extent by the activation energy of reaction (5).…”

“…The addition of oxygen atoms to the chain by reaction (5) [and (6)] is an important factor which increases its propagation rate continuously. The temperature dependence of the induction period is determined to a great extent by the activation energy of reaction (5).…”