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

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: kallene+OH(T) = 8.51(±0.03) × 10–22T3.05 exp(2215(±3)/T), T = 843–1352 K; kpropyne+OH(T) = 1.30(±0.07) × 10–21T3.01 exp(1140(±6)/T), T = 846–1335 K.丙二烯（Allene，H₂C=C=CH₂；a-C₃H₄）与丙炔（propyne，CH₃C≡CH；p-C₃H₄）是各类化学环境中的重要物种。在燃烧过程中，羟基自由基与a-C₃H₄、p-C₃H₄的反应是整体燃料氧化系统的关键环节。本研究在反射激波管后沿区域，于843–1352 K的温度范围以及近1.5 atm的压力条件下，测定了羟基自由基分别与丙二烯（OH + H₂C=C=CH₂ → 产物）、丙炔（OH + CH₃C≡CH → 产物）的反应速率系数。羟基自由基通过叔丁基过氧化氢（(CH₃)₃–CO–OH）的快速热分解生成，并借助306.7 nm附近OH A–X (0,0)电子系统的R1(5)电子跃迁的窄线宽激光吸收进行监测，该跃迁已被充分表征。实验结果表明，在本研究覆盖的温度区间内，丙二烯与羟基自由基的反应速率快于丙炔。测得的反应速率系数可表示为阿伦尼乌斯（Arrhenius）形式如下： k_allene+OH(T) = 8.51(±0.03) × 10⁻²²T³.05 exp(2215(±3)/T)，T = 843–1352 K； k_propyne+OH(T) = 1.30(±0.07) × 10⁻²¹T³.01 exp(1140(±6)/T)，T = 846–1335 K。