Experimental Study and Modeling of the Reaction H + O2 + M yields HO2 + M (M= Ar, N2, H2O) at Elevated Pressures and Temperatures Between 1050-1250K.

摘要

The H + O2 + M yields HO2 + M reaction was investigated at temperatures between 1050-1250 K and pressures from 7 to 152 bar behind reflected shock waves in gas mixtures of H2, 02, NO, and bath gases of Ar, N2, and H2O. Narrow linewidth laser absorption of NO2 at 472.7 nm was used to measure quasi-steady NO2 concentration plateaus in experiments designed to be sensitive only to the H + 02 + M yields HO2 + M and the relatively well-known H + NO2 yields NO + OH and H + 02 yields OH + 0 reaction rates. The pressure dependence of the reaction was studied by measuring the fall-off of the reaction for M = Ar over a 10-152 bar pressure range. A simple modified Hindered-Gorin model of the transition state is used in an RRKM analysis of the results to facilitate comparisons of this work with measurements from other researchers at lower pressures. The RRKM calculations can also be described, using the simple functional form suggested by Troe, with the following: k(sub infinity)/cu cm molecule(exp -1)s(exp -1) = 4.7x10(exp -11)(T/300)(exp .02); k(sub 0)(Ar)/cm(exp 6) molecule(exp -2)s(exp -1) = 2.0x10(exp -32)(T/300)(exp -1.2); k(sub 0)(N2)/ cm(exp 6) molecule(exp -2)s(exp -1) = 4.4 x 10(exp -32)(T/300)(exp -1.3); k(sub 0)(H2O)/cm(exp 6) molecule(exp -2)s(exp-1) = 3.4 x 10(exp -31)(T/300)(exp -1.0); F(sub c) = 0.7 for Ar and N2 and 0.8 for H20. Measured values of the reaction rate for M = Ar in the highest pressure experiments fall below both simple RRKM analysis and the more sophisticated treatment of Troe using an ab initio potential energy surface. Collision efficiencies of N2 and H20 relative to Ar at 1200K are 3.3 and 20 respectively.