KINETICS AND MODELING OF THE H-2-O-2-NOX, SYSTEM

The addition of NO (0 to 400 ppm) to mixtures of H-2 (ca. 1%) and O-2 (0.7 to 22%) has been studied over the temperature range 700 to 825 K, in a flow reactor at atmospheric pressure. The overall effect of NO i s to promote the oxidation of H-2 but high concentrations of O-2 actua lly inhibit the NO-promoted oxidation of H-2. A detailed kinetic mecha nism has been constructed and found to describe the experimental obser vations. The promotion of the oxidation of Hz arises through the catal ytic cycle R.5 H + O-2 + M double left right arrow HO2 + M R.34 NO + H O2 double left right arrow NO2 +OH R.35 NO2 +H double left right arrow NO + OH R.2 H-2 + OH double left right arrow H2O + H The ability of R .34 to reactivate chains normally terminated by the formation of HO2 i s a key feature of this system. The predictions are highly sensitive t o the rate of the reaction R.5 and the rate constants for this reactio n is the only adjustable parameter required in the model. The value of k(5,N2) found to describe all the results k(5,N2) = 2.60 X 10(15) exp (+1350 cal.mol(-1)/RT) cm(6).mol(-2).s(-1) has an absolute uncertainty <35%. The uncertainty relative to other important rate constants in t he H-2-O-2 system is less than 10%. (C) 1995 John Wiley & Sons, Inc.