Explosion of acetylene–chlorine mixture at room temperatures initiated by small additions of oxygen: Kinetic study and mechanism

Abstract

Oxygen added in amounts of O.Ol-O.l% was found to cause the explosion of an acetylene-chlorine mixture at temperatures as low as -78OC. Explosion occurrence and nature depend on the mode of mixing the reactants, the effect of oxygen being associated with concentration limits. The dependence of explosion-inducing oxygen amounts on temperature, pressure, concentrations of reactants, reactor surface type and area, additions of inert gases, and reaction products were investigated. The effect of light on the C2H2 + C12 + O2 was studied. The composition of gaseous products resulting from acetylenechlorine mixture explosion in the presence of minute amounts of oxygen, from a slow reaction inhibited and noninhibited by oxygen, and also from explosion at 400°C in the absence of oxygen, was determined. The results obtained point to the fact that any acetylene-chlorine mixture flash caused by small amounts of oxygen is a branched chain reaction involving activated particles, chain branching presumably being associated with the decomposition of radical CHCl=CHOO*+ CH + HCI + CO2.

Comparison between the shock wave and chemical initiation in detonation of acetylene—oxygen mixtures

“…The explosion of an acetylene-chlorine mixture at room temperature initiated by small addition of oxygen was studied in [16][17][18]. The dependence of explosioninducing amount of oxygen on temperature, pressure, and concentration of the reactants, the reactor surface type and area, and addition of inert gases was examined.…”

Mechanism of acetylene–chlorine mixture explosion initiated by small additions of oxygen

“…A radical-chain mechanism was suggested [2,3], which involves chain branching by decomposition of the chemically activated radical. This mechanism, however, postulated the absence of vibrational deactivation on the acetylene molecule and did not account for the inhibiting effect of oxygen below the explosion limit [3, Fig.…”

“…The assumption of the existence of elementary step (2) makes it possible to dispense with a rather questionable suggestion [3] that a vibrationally activated radical exerts no deactivation by collision with an acetylene molecule. Reactions (9)-(12) describe the inhibiting effect of oxygen in terms of the well-known formation of low-activity peroxy radicals.…”

“…The energy of the third bond in CZHZ is 62 kcal/mol. (The value of 65.5 kcal/mol in [3] is corrected for new data [lo] for AH;(C2H3) to 62 f 2 kcal/mol.) The C-0 bond energy of the vinyl group in vinyl formate equals 96.5 kcal/mol [lo], and that of the ethyl group in diethylperoxide is 70.0 kcal/mol [lo].…”

“…The characteristic features of this mechanism are the branching pathway via the formation of the C100 radical by a three-body reaction (1) reported in the literature [5], followed by C100 addition to the triple bond of acetylene, reaction (3), and an assumption that, in case the third body in reaction (1) is the molecule of acetylene, chemically activated radical formation occurs in a single elementary act (2) at an excitation energy which exceeds the excitation energy of the activated radical formed in reaction (3) by the enthalpy of reaction (l), namely, by 8 kcal/mol. The assumption of the existence of elementary step (2) makes it possible to dispense with a rather questionable suggestion [3] that a vibrationally activated radical exerts no deactivation by collision with an acetylene molecule. Reactions (9)-(12) describe the inhibiting effect of oxygen in terms of the well-known formation of low-activity peroxy radicals.…”