FORMATION OF N-2 DURING CARBONIZATION OF POLYACRYLONITRILE USING IRONCATALYST

Iron-catalysed formation of N-2 during carbonization of polyacrylonitr ile was studied with a thermobalance. The chemical forms of nitrogen a s well as iron species were determined in detail during the reaction p ath by EXAFS, XRD and XPS techniques. The iron catalyst shows a very h igh activity for the formation of N-2. A solid-phase reaction mechanis m is predominant, in which the interaction between iron species and he terocyclic nitrogen structures results in the formation of iron nitrid es, and the latter subsequently decompose to form N-2. Iron nitrides a re first detected in the temperature range 500-600 degrees C. Pyridini c rather than pyrrolic nitrogen is preferentially converted to N-2. Th ere is counter-migration of iron and nitrogen between the surface and bulk, which favours their full contact and interaction and subsequent formation of N-2. Copyright (C) 1997 Elsevier Science Ltd.