The mechanism of thermal dehydrochlorination. Pyrolysis of 1‐Chloro‐1‐fluoroethane and 1‐chloro‐1, 1‐difluoroethane

Abstract

The thermal decompositions of I-chloro-1-fluoroethane and 1-chloro-1,l-difluorethane at atmospheric pressure have been studied in the temperature range 500-6OO0C in a flow system. The dehydrochlorinations are homogenous in a carbonaceous reactor and unimolecular. The rate constants are given by The criteria for molecular or chain processes in thermal dehydrochlorinations are discussed.

Pyrolysis of 1-chloro-1,1-difluoroethane: Considerations about its molecular nature

“…Various reasons for the absence of a radical chain pyrolysis are suggested in literature: (i) the radical reaction is too slow because of too slow initiation and propagation steps [4]; (ii) the radical reaction is inhibited by inert ⅐ CF 2 CH 3 radicals formed in the initiation [2]. These unreactive radicals can stop the chain reaction by recombination with the Cl chain carriers; and (iii) the radical reaction is inhibited by the formation of CF 3 CH 3 [1].…”

Kinetics and mechanism of the pyrolysis of 1-chloro-1,1-difluoroethane in the presence of additives

“…A simplified reaction mechanism consisting of 7 elementary reaction steps has been proposed which leads to initial reaction rates in good agreement with the experimental data [3]. The purpose of this article is to present a more elaborated model that is able to describe new experimental results on the evolution with time of the dehydrochlorination in the presence of small amounts of catalysts (CCl 4 and C 2 Cl 6 ) and inhibitors (CF 3 CH 3 and CF 2 " CH 2 ). C 2 Cl 6 is a by-product when CCl 4 is added as catalyst and CF 3 CH 3 is formed in the pyrolysis of pure CF 2 ClCH 3 [3].…”

“…This included points for the pyrolyses of mixtures of CF 2 ClCH 3 and CCl 4 or C 2 Cl 6 , and of mixtures of CF 2 ClCH 3 , CCl 4 , and HCl or CF 3 CH 3 , for conversions up to about 20%. Some of the points and the optimized ⌬p** vs. time curves are shown in the figures given below.…”

“…The comprehensive kinetic reaction model started from, involves 30 species and 81 homogeneous and heterogeneous molecular and radical elementary reactions for mixtures of CF 2 ClCH 3 , CCl 4 , C 2 Cl 6 , CF 2 " CH 2 , HCl, and CF 3 CH 3 . The radical reactions are the decompositions of the reagents and the radicals and the reactions of the atoms and radicals with the reagents, the products, the atoms, the radicals, and the reactor wall.…”

“…In a conditioned reactor, this pyrolysis appears to be a homogeneous molecular first-order process [3 -5]. In the presence of CCl 4 or mixtures of CCl 4 and HCl, reaction (1) is markedly accelerated [3]. It then proceeds through a radical-chain mechanism.…”