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

The kinetics of the reactions of propane, n-pentane, and n-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, k(1)= 5.1x 10(-17)T(1.85)exp(-160/T)cm(3) molecule(-1) s(-1) (uncertainty of 20%), measured in a wide temperature range, 230-898K, 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 with n-pentane and n-heptane can be represented as three parameter expressions (incm(3) molecule(-1) s(-1), uncertainty of 20%): k(2)= 5.8x 10(-18)T(2.2)exp(260/T) at T= 248-900K and k(3)= 2.7x 10(-16)T(1.7)exp(138/T) at T= 248-896K, respectively. A combination of the present data with those from previous studies leads to the following expressions: k(1)= 2.64x 10(-17)T(1.93)exp(-114/T), k(2)= 9.0x 10(-17)T(1.8) exp(120/T), and k(3)= 3.75x 10(-16)T(1.65) exp(101/T)cm(3) molecule(-1) s(-1), which can be recommended for k(1), k(2), and k(3) (with uncertainty of 20%) in the temperature ranges 190-1300, 240-1300, and 220-1300K, respectively.