Experimental Study of the Reactions of OH Radicals with Propane,n‐Pentane, andn‐Heptane over a Wide Temperature Range

Abstract

ABSTRACTThe kinetics of the reactions of propane,n‐pentane, andn‐heptane with OH radicals has been studied using a low‐pressure flow tube reactor (P = 1 Torr) coupled with a quadrupole mass spectrometer. The rate constants of the title reactions were determined under pseudo–first‐order conditions, monitoring the kinetics of OH radical consumption in excess of the alkanes. A newly developed high‐temperature flow reactor was validated by the study of the OH + propane reaction, where the reaction rate constant,k1 = 5.1 × 10−17T1.85exp(–160/T) cm3molecule−1s−1(uncertainty of 20%), measured in a wide temperature range, 230–898 K, was found to be in excellent agreement with previous studies and current recommendations. The experimental data for the rate constants of the reactions of OH withn‐pentane andn‐heptane can be represented as three parameter expressions (in cm3molecule−1s−1, uncertainty of 20%):k2 = 5.8 × 10−18T2.2exp(260/T) atT= 248–900 K andk3 = 2.7 × 10−16T1.7exp(138/T) atT= 248–896 K, respectively. A combination of the present data with those from previous studies leads to the following expressions:k1 = 2.64 × 10−17T1.93exp(–114/T),k2 = 9.0 × 10−17T1.8exp(120/T), andk3 = 3.75 × 10−16T1.65exp(101/T) cm3molecule−1s−1, which can be recommended fork1,k2, andk3(with uncertainty of 20%) in the temperature ranges 190–1300, 240–1300, and 220–1300 K, respectively.