Abstract This contribution investigates the propensity of low-temperature ignition of sulfur, a hazardous substance because of its facile ignition. We applied the coupled thermogravimetric analyser and differential scanning calorimeter (TGA-DSC), in conjunction with a vertically-entrained reactor, to study the ignition behaviour of sulfur powder. The thermogravimetric measurements capture the ignition temperature of sulfur powder that transforms itself to partly polymerised S8 phase (Sγ) prior to ignition, revealing a temperature as low as 480 K. Likewise, experiments performed in a vertically-entrained reactor, coupled with an online Fourier-transform infrared (FTIR) spectrometry confirm the ignition temperature of Sγ of between 473 K and 483 K, as well as the full conversion of S into SO2 at 503 K. The density-functional-theory calculations for the S + O2 reaction identify the formation of SO + O as the initiation step, with a shallow activation barrier of 24.6 kJ mol−1. Further oxidation of SO + O2 → SO2 + O proceeds slower with a relatively high activation barrier at 34.0 kJ mol−1, acting as the bottleneck step of oxidation of elementary S, in analogy to the DSC profile of ignition of Sγ.

中文翻译：

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硫磺粉的易燃性 - 一种极其危险的化学品

摘要 本文研究了硫的低温引燃倾向，硫是一种危险物质，因为它易于引燃。我们应用耦合热重分析仪和差示扫描量热仪 (TGA-DSC)，结合垂直夹带反应器，研究硫粉的点火行为。热重测量捕获硫粉的着火温度，硫粉在点火前自身转化为部分聚合的 S8 相 (Sγ)，显示温度低至 480 K。同样，在垂直夹带反应器中进行的实验，加上在线傅立叶变换红外 (FTIR) 光谱法证实 Sγ 的着火温度在 473 K 和 483 K 之间，以及 S 在 503 K 时完全转化为 SO2。S + O2 反应的密度泛函理论计算将 SO + O 的形成确定为起始步骤，具有 24.6 kJ mol-1 的浅活化势垒。SO + O2 → SO2 + O 的进一步氧化进行得更慢，在 34.0 kJ mol-1 处具有相对较高的活化势垒，作为元素 S 氧化的瓶颈步骤，类似于 Sγ 点火的 DSC 曲线。