Thermal decomposition of CH2Cl2

Abstract

The thermal decomposition of CH 2 Cl 2 has been investigated in reflected shock wave experiments at temperatures between 1400 and 2300 K and at three different loading pressures with various initial CH 2 Cl 2 concentrations. The resulting product Cl atoms are monitored by the atomic resonance absorption spectrometric (ARAS) technique. A reaction mechanism is used to numerically simulate the measured Cl-atom profiles in order to obtain rate constants for the two primary dissociation reactions: (1) CH 2 Cl 2 →CHCl+HCl, and (2) CH 2 Cl 2 →CH 2 Cl+Cl. The experimental second-order Arrhenius expressions for the two reactions are k 1 /[Kr]=2.26×10 −8 exp(−29,007 K/T ) cm 3 molecule −1 s −1 and k 2 /[Kr]=6.64×10 −9 exp(−28,404 K/T ) cm 3 molecule −1 s −1 , with standard deviations of ±43 and 40%, respectively. The results are compared to theoretical calculations using the semiempirical Troe formalism. The best fits to the experimental data are obtained with threshold energy and collisional energy transfer parameters of E 1 o =73.0 kcal mole −1 and Δ E 1down =630 cm −1 . Similar values for reaction (2) are E 2 o =Δ H 2 o (OK)=78.25 kcal mole −1 and Δ E 2down =394 cm −1 .