ACTIVATION-ENERGY FOR THERMAL-DECOMPOSITION OF NITRIC-OXIDE

Variation of the reaction mechanism for homogeneous thermal decomposit ion of NO into N-2 and O-2 in the temperature range between 1000 and 4 000 K is studied. The decomposition always proceeds through an atomic chain mechanism initiated by formation of oxygen atom. However the ste p of the oxygen atom initiation depends on the reaction condition, i.e ., collision between two NO molecules at low conversions (when P-O2/P- NO ratio << 1) and collision between NO and O-2 and/or unimolecular de composition of O-2 at high conversions (after substantial O-2 has been accumulated from the reaction). In this study, apparent activation en ergy (E(app)) of the decomposition reaction has been theoretically det ermined on the basis of our proposed mechanisms. The E(app) thus deter mined varies widely (from 254 to 401 kj mol(-1)) with the accepted ste p of initiation. This variation can account for the variations among e xperimental activation energies for the decomposition reaction in the literature. (C) 1996 John Wiley & Sons, Inc.