This study aims to identify and characterize compounds refractory to hydrodenitrogenation (HDN). The efficiency of a vacuum hydrocracking unit in removing nitrogen-containing compounds to produce a low-nitrogen-content effluent is examined. Molecular, structural, and compositional knowledge is a requisite for the optimization development of the hydrotreatment step processing unit because changes in the chemical composition of petroleum have a direct impact on physical properties and, thus, overall vacuum gas oil (VGO) upgrading processes. Two samples, a VGO and a effluent obtained after the HDN process containing 10 wppm of N, were analyzed by negative-mode electrospray ionization ultra-high-resolution tandem mass spectrometry (ESI–FT-ICR) and ion mobility spectrometry–mass spectrometry (IMS–MS). FT-ICR mass spectrometry provides ultrahigh mass resolving power to separate and characterize compounds in the highly complex petroleum samples. The fragments generated by MS/MS of selected N₁ refractory compounds were used for structural elucidation. Species with a double bond equivalent of 10 and 13, which proved to be highly refractory, were analyzed in more detail. On the other hand, the TWIMS–TOF MS measurements enabled the entire ion mobility analysis of refractory species to hydrotreatment processes. The MS/MS spectra revealed a specific pattern allowing for the identification of the molecular nucleus. Furthermore, it allowed for the understanding of the fragmentation pathways: loss of alkyl chains in the first step and opening and rearrangement of the nuclei after that. Ion mobility separation, in combination with MS/MS, allowed for the identification of the different conformations and the revealment of the typical fragments of these molecular nuclei. In particular, the ion mobility peak width indicates isomeric diversity and collision cross section (CCS) determination and provides structural information. The IMS analysis of the identified refractory precursor shows the evolution of its compounds at different processing stages and indicates that some families and structural conformations of N₁ species are more resistant to hydrotreatment. Isomers presenting low CCS values in negative mode are more resistant to HDN processes. The combination of TWIMS–TOF MS and ultra-high-resolution mass spectrometry opens exciting and promising prospects for structural determination of complex mixtures, in particular, problematic compounds in petroleum refining processes.

中文翻译：

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高分辨率串联质谱和离子淌度质谱法分析重油馏分加氢脱氮过程中难降解的中性氮化合物的结构

这项研究旨在鉴定和表征难于加氢脱氮（HDN）的化合物。检验了真空加氢裂化装置去除含氮化合物以产生低氮含量废水的效率。分子，结构和组成知识对于加氢处理步骤处理单元的优化开发是必不可少的，因为石油化学成分的变化会直接影响物理性能，进而直接影响整个真空粗柴油（VGO）的升级过程。通过负模式电喷雾电离超高分辨率串联质谱（ESI–FT-ICR）和离子迁移谱–质谱分析了H​​DN处理后获得的两个样品，即VGO和含有10 wppm N的废水。 IMS-MS）。FT-ICR质谱仪提供超高的质量分辨能力，可分离和表征高度复杂的石油样品中的化合物。选定N的MS / MS生成的片段_1个难熔化合物用于结构阐明。进一步分析了双键当量为10和13的物种，这些物种被证明具有很高的耐火性。另一方面，TWIMS-TOF MS测量可以对耐火物质加氢处理过程进行整个离子迁移率分析。MS / MS光谱揭示了一种特定的模式，可以识别分子核。此外，它还有助于理解断裂途径：第一步是烷基链的丢失，然后是核的开放和重排。离子淌度分离与MS / MS结合使用，可以鉴定不同的构象，并揭示这些分子核的典型片段。尤其是，离子迁移率峰宽指示异构体多样性和碰撞截面（CCS）确定，并提供结构信息。所鉴定的耐火材料前体的IMS分析显示了其化合物在不同加工阶段的演变，并表明了N的某些族和结构构象₁种对加氢处理更具抵抗力。在负模模式下呈现低CCS值的异构体更能抵抗HDN过程。TWIMS-TOF MS与超高分辨率质谱仪的结合为复杂混合物的结构测定（特别是石油精炼过程中有问题的化合物）的结构测定提供了令人兴奋且充满希望的前景。