Rate Constants of the Reactions of O(3P) Atoms with Ethene and Propene over the Temperature Range 230-900 K

Experimental Study of the Reaction of O(3P) with Carbonyl Sulfide between 220 and 960 K

The reaction of a ground-state O atom with carbonyl sulfide is of interest for atmospheric (stratosphere and hot near-source volcanic plume) and combustion chemistry. In the present work, we employed a discharge-flow system combined with a modulated molecular beam mass spectrometry technique to measure the rate constant and products of the O + OCS reaction. The overall rate constant was determined either from the kinetics of the reaction product, SO radical, formation or under pseudo-first-order conditions from the decays of OCS in an excess of oxygen atoms: k₁ = 1.92 × 10^-12 × (T/298)^2.08 exp(-1524/T) cm³ molecule^-1 s^-1 at T = 220-960 K, with conservative uncertainty of 20%. The yield of another reaction product, CO₂, was found to increase from 3.55% at T = 455 K to 14.2% at T = 960 K, resulting in the following Arrhenius expression for the rate constant of the minor (S + CO₂ forming) reaction channel: k_1b = 4.19 × 10^-11 exp(-4088/T) cm³ molecule^-1 s^-1 at T = 455-960 K (with an uncertainty of 25%). The kinetic and mechanistic data from the present work are discussed in comparison with previous experimental and computational studies.

Reaction of O(3P) with C3H6: Yield of the Reaction Products as a Function of Temperature

Reaction of oxygen atoms with propene is an important step in combustion processes particularly affecting the profiles of intermediate species and flame speed. The relative importance of different pathways of this multichannel reaction at different temperatures represents significant theoretical interest and is essential for modeling combustion systems. In the present work, we report the first experimental investigation of the products of the O(³P) + C₃H₆ reaction over an extended temperature range (298-905 K). By using a low pressure flow reactor combined with a quadrupole mass spectrometer, the yields of the five reaction products, H atom, CH₃, C₂H₅, CH₂O and OH were determined as a function of temperature between 298 and 905 K: 0.0064 × (T/298)^2.74 exp(765/T), 1.41 × (T/298)^-1.0 exp(-335/T), 0.92 × (T/298)^-1.41 exp(-381/T), 0.17 × (T/298)^0.165 exp(-36/T), and 0.0034 × (T/298)^2.34 exp(788/T), respectively (corresponding to the variation of the respective yields between 298 and 905 K in the ranges 0.08-0.31, 0.46-0.32, 0.26-0.12, 0.15-0.19, and 0.05-011), independent of pressure in the range 1-8 Torr of helium. For the yields of the minor reaction products, H₂ and CH₃CHO the upper limits were determined as 0.2 and 0.05, respectively. These results are compared with the experimental data and theoretical calculations available in the literature.