Thermal decomposition of carbon tetrachloride
- Argonne National Lab., IL (United States)
- Univ. of Illinois, Chicago (United States)
The first rate measurements of the thermal dissociation of CCl[sub 4] are reported. Three detection techniques were used in monitoring the reaction rate for various dilutions over a wide temperature range: (i) ARAS of product Cl atoms in reflected shock waves using 3.2--6.4 ppM of CCl[sub 4] in Ar over 1084--1705 K and 150--908 Torr, (ii) decay of CCl[sub 4] by molecular absorption of O-atom resonance radiation in reflected shock waves using 48--173 ppM of CCl[sub 4] in Ar over 1192--1733 K and 219--855 Torr, and (iii) laser schlieren density gradients in incident shock waves using 0.5 and 2% CCl[sub 4] in Kr over 1470--2186 K and 90--660 Torr. The second-order rates from ARAS and molecular absorption measurements for the bond fission reaction CCl[sub 4] [yields] CCl[sub 3] + Cl are in complete agreement with the laser schlieren results where they overlap. The temperature and pressure dependence of these rates is well characterized by Gorin model RRKM calculations using current [Delta]H[degrees][sub 0] = 67.71 kcal/mol for E[sub 0], derived from [Delta][sub f]H[degrees][sub 298] = 17.0 kcal/mol for for CCl[sub 3]. The low-pressure rate constant (k[sub 0]) derived from this RRKM fit is log k[sub 0] (cm[sup 3]/(mol s)) = 54.980 [minus] 10.624 log T [minus] 74.796 (kcal/mol)/2.303RT. These low-pressure rates require unusually large [beta][sub c] corresponding to a [l angle][Delta]E[r angle][sub down] = 1200 cm[sup [minus]1]. This may be a general feature of chlorocarbon dissociations. The ARAS data indicate that two Cl atoms are ultimately produced for each CCl[sub 4] that dissociates, with the second Cl atom forming slower than the first. Here all the measurements are consistent with a further dissociation of CCl[sub 3], CCl[sub 3] [yields] CCl[sub 2] + Cl, as the dominant source of secondary Cl-atom at a rate about 0.1 that of the primary fission. 31 refs., 9 figs., 2 tabs.
- DOE Contract Number:
- W-31109-ENG-38; FG02-85ER13384
- OSTI ID:
- 6232254
- Journal Information:
- Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:9; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201 -- Chemical & Physicochemical Properties
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
ARGON
CARBON TETRACHLORIDE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
DECOMPOSITION
ELEMENTS
FLUIDS
GASES
HALOGENATED ALIPHATIC HYDROCARBONS
HELIUM
KINETICS
LASERS
MANAGEMENT
NONMETALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PYROLYSIS
RARE GASES
REACTION KINETICS
SHOCK WAVES
SPECTROSCOPY
TEMPERATURE DEPENDENCE
THERMOCHEMICAL PROCESSES
WASTE DISPOSAL
WASTE MANAGEMENT