The Molecular Composition of Soot
The Molecular Composition of Soot
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DOI：
10.1002/anie.201914115
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发表时间：
2020-01-30
影响因子：
16.6
通讯作者：
Miller, J. Houston
中科院分区：
文献类型：
--
作者：
Jacobson, Rachelle S.;Korte, Andrew R.;Miller, J. Houston
碳烟（有时称为黑碳）是碳氢燃料燃烧时产生的。我们的假设是，多环芳烃（PAH）分子是烟尘的主要成分，与单个PAH分子形成有序的堆栈，聚集成初级颗粒（PP）。在这里，我们表明，多环芳烃组成的烟尘可以准确地确定和空间分辨低通量激光解吸电离，再加上高分辨率质谱成像。该分析表明，多环芳烃的239-838 Da，含有少量的含氧物质，包括在乙烯扩散火焰中观察到的烟灰。根据化学图形理论（CGT），在采样颗粒物中观察到的绝大多数物质可被描述为仅由稠合6元环组成的苯并噻吩。在该限度内，有明确的证据表明颗粒样品中存在自由基PAH。此外，对于苯型结构，所观察到的经验式将所观察到的异构体限制为对于给定芳环数具有高芳族共轭长度的接近圆形的那些异构体。这些结果与最近的报道相反，这些报道表明初级颗粒的脂肪族组成更高。
Soot (sometimes referred to as black carbon) is produced when hydrocarbon fuels are burned. Our hypothesis is that polynuclear aromatic hydrocarbon (PAH) molecules are the dominant component of soot, with individual PAH molecules forming ordered stacks that agglomerate into primary particles (PP). Here we show that the PAH composition of soot can be exactly determined and spatially resolved by low-fluence laser desorption ionization, coupled with high-resolution mass spectrometry imaging. This analysis revealed that PAHs of 239-838 Da, containing few oxygenated species, comprise the soot observed in an ethylene diffusion flame. As informed by chemical graph theory (CGT), the vast majority of species observed in the sampled particulate matter may be described as benzenoids, consisting of only fused 6-membered rings. Within that limit, there is clear evidence for the presence of radical PAH in the particulate samples. Further, for benzenoid structures the observed empirical formulae limit the observed isomers to those which are nearly circular with high aromatic conjugation lengths for a given aromatic ring count. These results stand in contrast to recent reports that suggest higher aliphatic composition of primary particles.