Rate Coefficient Determinations for H + NO2 ? OH + NO from High Pressure Flow Reactor Measurements.

The journal of physical chemistry. A

PubMedID: 25867548

Haas FM, Dryer FL. Rate Coefficient Determinations for H + NO2 ? OH + NO from High Pressure Flow Reactor Measurements. J Phys Chem A. 2015;.
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 k1 measurements, the present conditions add measurements of k1 at previously unconsidered temperatures between ~820-880 K, as well as at pressures that exceed existing measurements by over an order of magnitude. Experimental measurements of NOx-perturbed H2 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 + O2 + M ? HO2 + M (R2. M). Consequently, the ratio of k1 to k2,M may be extracted as a simple algebraic function of measured NO2, O2, 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 k1 have been determined with reference to the relatively well known, pressure-dependent rate coefficients of R2. B for B = Ar and N2. 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 × 1014 cm3/mol/s (1. 74 × 10-10 cm3/molecule/s). Further, the results of this study agree both with existing low pressure flash photolysis k1 determinations of Ko & 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.