Six coals with carbon contents ranging from 69 to 80 wt % dry ash-free (daf) were rapidly pyrolyzed at 1300 degrees C under a stream of high purity He in a free fall-type graphite reactor incorporating a graphite filter to control the residence time of coal particles. In this manner, the effects of both residence time and inherent mineral contents on N-2 formation from char-N following devolatilization were examined. At a residence time of zero, 20-30% of the coal-N was released as volatile-N species, such as tar-N, HCN and NH3, while <15% was transitioned to N-2 and the remainder (60-80%) was retained in the char. When the residence time was increased to 120 s, the yields of tar-N, HCN and NH3 were almost unchanged, irrespective of the coal type, although the N-2 yield increased and the char-N decreased with increasing residence times, with the changes in yields of both species being roughly equal. When an Indonesian char sample already devolatilized at 1000 degrees C was pyrolyzed again by applying a slow heating rate of 10 degrees C/min to 1300 degrees C, the nitrogen in the 1000 degrees C char was converted almost exclusively to N-2. These observations demonstrate that char-N and/or its precursors are the main source of the N-2 in pyrolysis products. The enhancement in N-2 yield observed on increasing the residence time from zero to 120 s increased with increasing inherent Ca or Fe contents in the range of <= 0.3 wt % (dry), although the data were somewhat scattered. Thus, small amounts of naturally occurring Ca and Fe appear to promote N-2 formation from the devolatilized char-N. It appears likely that Ca- or Fe-containing minerals in the coal are partly transformed into CaO or alpha-Fe, respectively, under the present rapid pyrolysis conditions, both of which enhance the conversion of char-N to N-2 as well as the transition of amorphous carbon to crystallized carbon with turbostratic structures. A linear relationship was observed between the N-2 yield and the proportion of crystallized carbon formed, which may indicate that the yield of one may be predicted from the yield of the other. The catalysis of N-2 formation from char-N without volatile materials through the presence of mineral-derived CaO or a-Fe is discussed herein in terms of solid solid reactions of these metal particles with heterocyclic nitrogen species in the char.