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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Mechanism of the Reaction C_2H_5 + O_2 from 298 To 680 K
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Mechanism of the Reaction C_2H_5 + O_2 from 298 To 680 K

机译：C_2H_5 + O_2从298到680 K反应的机理

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摘要

The reaction C_2H_5 + O_2 has been studied by steady-state photolysis of mixtures containing Cl_2, C_2H_6, and O_2 over the temperature range 298-680 K at a constant density of 6.8 * 10~(18) molecules cm~(-3). Limited experiments were also performed as a function of a pressure (200 - 1300 Torr) at four temperatures. After UV irradiation, the mixture were analyzed by GC/MS to determine the product yields. The yields of C_2H_4 increases slowly between 298 and 450 K (E_a ～ 1 kcal mol~(-1)) and then increase sharply (E_a ～ 25 kcal mol~(-1)) reaching a yield of 100(±10)% of the O_2 reaction channel by 630 K. For T < 450 K, the C_2H_4 yield depends on the inverse of the pressure, indicating that the ethylene is formed via a chemically activated (C_3H_5O_2~*) radical as has been observed previously. Above 500 K, the C_2H_4 yield is independent of pressure indicating that a new channel has opened. This is confirmed by the observation that the ratio β (= C_2H_4/C_2H_5Cl) increases sharply (from 0.8 to 3.5) between 450 and 500 K. If the C_2H_5 radical remained the sole source C_2H_4 (via C_2H_5O_2) throughout the entire temperature range, no sharp break in β would occur. The very small yield of ethylene oxide (2.5% at 660 K) and the excellent carbon balance between C_2H_6 consumed and products formed above 530 K support the formation of C_2H_4 at elevated temperature via both the thermally activated, concerted path (C_2H_5O_2 → C_2H_4 + HO_2) proposed recently and the chemically activated (C_2H_5O_2) path. The former reaction occurs from a stabilized ethylperoxy radical without passing through a stable hydroperoxyethyl radical. Phenomenological rate constants at the experimental density are presented for the chemically and thermally activated paths to C_2H_4 formation. The data also indicate that the formation of C_2H_4 by direct H-atom abstraction is negligible under the conditions of these experiments [k_(abs)(700 K) < 1 * 10~(-13) cm~3 molecule~(-1) s~(-1)].
机译：通过在298-680 K的温度范围内以6.8 * 10〜（18）分子cm〜（-3）的恒定密度对含Cl_2，C_2H_6和O_2的混合物进行稳态光解研究了C_2H_5 + O_2反应。还根据四个温度下的压力（200-1300托）进行了有限的实验。紫外线照射后，通过GC / MS分析混合物，以确定产物收率。 C_2H_4的产率在298和450 K之间缓慢增加（E_a〜1 kcal mol〜（-1）），然后急剧增加（E_a〜25 kcal mol〜（-1）），达到100％（±10）％的产率。 O_2反应通道的反应温度为630K。对于T <450 K，C_2H_4的产率取决于压力的倒数，这表明乙烯是通过化学活化的（C_3H_5O_2〜*）自由基形成的。高于500 K时，C_2H_4的产量与压力无关，表明已打开新通道。这可以通过观察得到证实，比率β（= C_2H_4 / C_2H_5Cl）在450和500 K之间急剧增加（从0.8到3.5）。如果C_2H_5自由基在整个温度范围内仍然是唯一的来源C_2H_4（通过C_2H_5O_2），则没有β会急剧断裂。环氧乙烷的收率非常低（在660 K时为2.5％）以及消耗的C_2H_6与530 K以上形成的产物之间极好的碳平衡，支持在高温下通过热活化的一致路径（C_2H_5O_2→C_2H_4 + HO_2）形成C_2H_4。 ）和最近提出的化学活化（C_2H_5O_2）路径。前一反应由稳定的乙基过氧自由基发生，而不经过稳定的氢过氧乙基。给出了化学和热活化途径形成C_2H_4的现象密度在实验密度下的现象学速率常数。数据还表明，在这些实验条件下[k_（abs）（700 K）<1 * 10〜（-13）cm〜3分子〜（-1），通过直接H原子抽象形成C_2H_4可以忽略不计。 s〜（-1）]。

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