Rate Coefficients of the Reaction of OH with Allene and Propyne at High Temperatures

Et-Touhami Es-Sebbar; Fethi Khaled; Ahmed Elwardany; Aamir Farooq

doi:10.1021/acs.jpca.6b04387

Rate Coefficients of the Reaction of OH with Allene and Propyne at High Temperatures

J Phys Chem A. 2016 Oct 20;120(41):7998-8005. doi: 10.1021/acs.jpca.6b04387. Epub 2016 Oct 7.

Authors

Et-Touhami Es-Sebbar^{1

2}, Fethi Khaled¹, Ahmed Elwardany^{1

3}, Aamir Farooq¹

Affiliations

¹ Clean Combustion Research Centre, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia.
² Laboratory for Thermal Processes & Combustion, Paul Scherrer Institute (PSI) , CH-5232 Villigen PSI, Switzerland.
³ Mechanical Engineering Department, Faculty of Engineering, Alexandria University , Alexandria 21544, Egypt.

PMID: 27676243
DOI: 10.1021/acs.jpca.6b04387

Abstract

Allene (H₂C═C═CH₂; a-C₃H₄) and propyne (CH₃C≡CH; p-C₃H₄) are important species in various chemical environments. In combustion processes, the reactions of hydroxyl radicals with a-C₃H₄ and p-C₃H₄ are critical in the overall fuel oxidation system. In this work, rate coefficients of OH radicals with allene (OH + H₂C═C═CH₂ → products) and propyne (OH + CH₃C≡CH → products) were measured behind reflected shock waves over the temperature range of 843-1352 K and pressures near 1.5 atm. Hydroxyl radicals were generated by rapid thermal decomposition of tert-butyl hydroperoxide ((CH₃)₃-CO-OH), and monitored by narrow line width laser absorption of the well-characterized R₁(5) electronic transition of the OH A-X (0,0) electronic system near 306.7 nm. Results show that allene reacts faster with OH radicals than propyne over the temperature range of this study. Measured rate coefficients can be expressed in Arrhenius form as follows: k_allene+OH(T) = 8.51(±0.03) × 10^-22T^3.05 exp(2215(±3)/T), T = 843-1352 K; k_propyne+OH(T) = 1.30(±0.07) × 10^-21T^3.01 exp(1140(±6)/T), T = 846-1335 K.