Studies of Radiation Mechanisms as Applied to the Potential Manufacturing Processes: Hydrazine from Ammonia, Nitrogen Fixation and Ozone from Oxygen

The slow progress of the past decade toward industrial utilization of radiation in chemical manufacturing is related, among other things, to the tendency to oversimplify or ignore the basic mechanisms and the essential complexity of the radiation chemical systems. The importance of the fundamental approach is illustrated by the radiation systems of hydrazine from ammonia, nitrogen fixation, and ozone from oxygen. Since the First Geneva Conference on the ''Peaceful Uses of Atomic Energy'', radiation production of hydrazine has been of interest because of its high traditional cost and its potential large scale use for rocketry. While considerable efforts had been made on the engineering aspects of such a system, little attention was paid to its radiation chemistry. We have examined this system theoretically and experimentally and have identified the basic mechanism by which yields of hydrazine are limited. On the basis of this mechanism we have proposed a method to increase yields, which has been confirmed by experimental studies. Coincidence mass spectrometry shows a major ionization reaction over a wide energy range forming hydrogen radicals and amino ions, NH2+. Workers.studying the photolysis of ammonia have shown that hydrogen radicals destroy hydrazine. Under radiolysis conditions that allow krypton or xenon to absorb nearly all of the radiation energy, the subsequent charge exchange reactions are unable to form hydrogen atoms directly, since the recombination energy of xenon and krypton are such that direct H formation is strongly endothermic: under these conditions we find a significant increase in the yield of hydrazine. By contrast, the charge exchange of ammonia with neon ions to form hydrogen radicals and the amino ion is strongly exothermic: under these conditions we find a large decrease in the hydrazine yield. For nitrogen fixation by irradiation, there is insufficient experimental data to allow confidence in theoretical predictions. Mass spectrometer experiments have shown that irradiation of N2 can yield the important ions N4+ and N3+ as well as N2+ and N+. There is evidence, however, that N4+ and N3+ whose reactions have hitherto been ignored, play an important role in nitrogen fixation. Finally, in the radiolysis of oxygen to form oxone, experimental results often are in apparent conflict. Our analysis of a likely mechanism leads to the conclusion that a low LET will favour ozone formation. Reported G-values for different types of radiation tend to support this conclusion. It is shown also that rare gas sensitization may be a useful technique for ozone formation in some systems. (author)