Asphaltenes challenge nearly all analytical techniques because of their immense polydispersity in molecular composition and structure. This operationally defined fraction of crude oil, insoluble in n-alkanes but soluble in aromatic solvents, is known to concentrate in vacuum residues and islinked to fouling and deposition issues. However, presence and subsequent characterization of asphaltenes are seldom discussed in conventional/unconventional distillate fractions. Here, we isolate asphaltenes from conventional (<593 °C/1099 F) and unconventional (>593 °C) distillation cuts and provide molecular-level characterization by electrospray ionization and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry as a function of boiling point. Our results indicate that asphaltene molecular composition starts in the vacuum gas oil range and extends into vacuum residues. Moreover, we report that distillable asphaltene composition exists as both highly polar (heteroatom rich), aliphatic (atypical asphaltenes) species as well as condensed aromatic structures (classical asphaltenes). As a function of distillation temperature, asphaltene compounds exhibit structural trends consistent with thermal cracking that starts between 510 and 538 °C, increases between 538 and 593 °C, and is readily observed at temperatures up to 700 °C. Above 600 °C, low molecular weight compounds (expected to boil at much lower temperatures) that are n-heptane insoluble are detected across all heteroatom classes. Results herein suggest that these compounds are formed through structural rearrangement of archipelago asphaltenes because of thermal cracking reactions that occur during distillation and precipitate as asphaltenes. We report the isolation and mass spectral characterization of asphaltenes isolated from distillation cuts and propose that quantification of asphaltenes in distillates is critical to predict and prevent problems related to catalyst deactivation.

中文翻译：

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从馏分中分离出的沥青质的分子水平表征

沥青质由于其在分子组成和结构上的巨大多分散性，几乎挑战了所有分析技术。原油的这种可操作定义的馏分，不溶于n-烷烃但可溶于芳族溶剂，已知会浓缩在真空残留物中，并与结垢和沉积问题有关。然而，在常规/非常规馏分中很少讨论沥青质的存在和随后的表征。在这里，我们从常规（<593°C / 1099 F）和非常规（> 593°C）馏分中分离出沥青质，并通过电喷雾电离和大气压光电离提供傅里叶变换离子回旋共振质谱作为分子功能的分子水平表征。沸点。我们的结果表明，沥青质分子组成始于减压瓦斯油范围，并延伸至减压渣油中。此外，我们报告说，可蒸馏的沥青质成分以高极性（富含杂原子）形式存在，脂族（非典型沥青质）种类以及稠合的芳族结构（传统沥青质）。作为蒸馏温度的函数，沥青质化合物的结构趋势与热裂化相一致，热裂化在510和538°C之间开始，在538和593°C之间增加，并且在高达700°C的温度下容易观察到。高于600°C，低分子量化合物（预计会在更低的温度下沸腾）会在所有杂原子类别中均检测到正庚烷不溶物。本文的结果表明这些化合物是通过群岛沥青质的结构重排形成的，因为在蒸馏过程中会发生热裂化反应并以沥青质的形式沉淀出来。我们报道了从蒸馏馏分中分离出的沥青质的分离和质谱表征，并提出了馏出物中沥青质的定量对于预测和防止与催化剂失活有关的问题至关重要。