Journal of Physical Chemistry A, Vol.119, No.28, 7792-7801, 2015
Rate Coefficient Determinations for H + NO2 -> OH plus NO from High Pressure Flow Reactor Measurements
Rate coefficients for the reaction H + NO2 -> OH + NO (R1) have been determined over the nominal temperature and pressure ranges of 737-882 K and 10-20 atm, respectively, from measurements in two different flow reactor facilities: one laminar and one turbulent. Considering the existing database of experimental k(1) measurements, the present conditions add measurements of k(1) at previously unconsidered temperatures between similar to 820-880 K, as well as at pressures that exceed existing measurements by over an order of magnitude. Experimental measurements of NOx-perturbed H-2 oxidation have been interpreted by a quasi-steady state NOx plateau (QSSP) method. At the QSSP conditions considered here, overall reactivity is sensitive only to the rates of R1 and H + O-2 + M -> HO2 + M (R2.M). Consequently, the ratio of k(1) to k(2.M) may be extracted as a simple algebraic function of measured NO2, O-2, and total gas concentrations with only minimal complication (within measurement uncertainty) due to treatment of overall gas composition M that differs slightly from pure bath gas B. Absolute values of k(1) have been determined with reference to the relatively well-known, pressure-dependent rate coefficients of R2.B for B = Ar and N-2. Rate coefficients for the title reaction determined from present experimental interpretation of both laminar and turbulent flow reactor results appear to be in very good agreement around a representative value of 1.05 x 10(14) cm(3) mol(-1) s(-1) (1.74 x 10(-10) cm(3) molecule(-1) s(-1)). Further, the results of this study agree both with existing low pressure flash photolysis k(1) determinations of Ko and Fontijn (J. Phys. Chem. 95 3984) near 760 K as well as a present fit to the theoretical expression of Su et al. (J. Phys. Chem. A 106 8261). These results indicate that, over the temperature range considered in this study and up to at least 20 atm, net chemistry due to stabilization of the H-NO2 reaction intermediate to form isomers of HNO2 may proceed at negligible rates compared to R1.