OCR Text |
Show that the effluents that we see are not due to failure in the oxidative mechanism, but rather due to packets of gases for which a pyrolytic mechanism is controlling. To account for observations it is therefore necessary to consider pyrolytic processes where hydrogen atom pay a principal role. c: Hydrogen atom attack: Hydrogen atom attack represent an important channel for the destruction of organic molecules under pyrolytic conditions. Actually in an oxidative environment, hydrogen atom concentrations are in fact quite high and except for OH is quite important in its own right. Table II contains some data on hydrogen atom reactions with aromatics and other organic compounds. Due to the unfavorable thermochemistry, rate constants for the abstraction of a ring hydrogen by hydrogen atoms is extremely slow. Benzene is thus extremely stable under pyrolytic conditions. This is in contrast to the situation under oxidative conditions. Indeed comparison of the data in Tables I and II show many such cases. Thus the setting up of a meaningful scale of incinerability is an extremely difficult task. Note that under pyrolytic conditions the end product is graphite and thus for the chlorinated aromatics under pyrolysis all that can be achieved is the removal of the chlorine from the aromatic ring. Displacement represents the simplest and probably the most important mode for dechlorination under pyrolytic conditions and in our experimental work we have concentrated on this type of reaction. It is interesting to note that the direct abstraction of chlorine, although also an exothermic process does not apparently occur to any great extent. Actually for our purposes the ultimate consequences are similar, that is the removal of a chlorine atom from the ring. We have determined much of the data on hydrogen atom attack on 10 |