Abstract This paper incorporates a multi-scale approach to evaluate the contribution of nickel porphyrin to the aggregation and precipitation of asphaltenes in a medium of solvent/precipitator. This study provides an in-depth understanding of the role of metalloporphyrins in the complex matrix of petroleum/bitumen. Density functional theory (DFT) calculations and laboratory experiments were performed to examine the changes in physicochemical and rheological properties of a selected bituminous structure when doped with Ni octaethylporphyrin (NiOEP). Based on the DFT results, light and small assemblies of asphaltene-resin (in the limit of a single asphaltene molecule) are easily attracted to NiOEP. This in turn may help establish the role of a metal center as a nucleating agent promoting formation of small nanoaggregates in solution. Our experiment results using size-exclusion chromatography and rheological analysis of bitumen doped with NiOEP indicate an increased number of small-size nanoaggregates, as evidenced by a reduction in large molecular size (LMS) and a reduction in the polydispersity index. The latter is indicative of the formation of uniform particle size within the matrix after being doped with NiOEP. The modeling results further show that in larger nanoaggregates, asphaltene-asphaltene intermolecular interactions are too strong to allow an asphaltene core to be affected by NiOEP. In such cases, small resin molecules surrounding asphaltenes show preferential adsorption to NiOEP and take distance from the original nanoaggregates, reducing nanoaggregates’ overall size. This was in line with UV–Vis absorption spectroscopy of a NiOEP-doped solution of bitumen showing that at least 95% of the added NiOEP remained in the maltenes portion containing resin, while only a trace amount of NiOEP was found in the asphaltenes. Considering the role of resins in stabilizing asphaltene aggregates, their departure can promote precipitation of asphaltene nanoaggregates. The latter was also evidenced by TLC-FID chromatography measurement, showing a substantial increase in asphaltene extracts in NiOEP-doped specimens compared to a control sample.

中文翻译：

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镍卟啉对树脂的优先吸附增加沥青质沉淀

摘要 本文采用多尺度方法来评估镍卟啉在溶剂/沉淀剂介质中对沥青质聚集和沉淀的贡献。本研究深入了解金属卟啉在石油/沥青复杂基质中的作用。进行密度泛函理论 (DFT) 计算和实验室实验，以检查掺杂 Ni 八乙基卟啉 (NiOEP) 时所选沥青结构的物理化学和流变特性的变化。根据 DFT 结果，沥青质树脂的轻小组件（在单个沥青质分子的范围内）很容易被 NiOEP 吸引。这反过来可能有助于确立金属中心作为成核剂的作用，促进溶液中小纳米聚集体的形成。我们使用尺寸排阻色谱法和对掺有 NiOEP 的沥青进行流变分析的实验结果表明，小尺寸纳米聚集体的数量增加，大分子尺寸 (LMS) 的减小和多分散指数的降低证明了这一点。后者表明在掺入 NiOEP 后在基质内形成均匀的颗粒尺寸。建模结果进一步表明，在较大的纳米聚集体中，沥青质-沥青质分子间相互作用太强，以至于沥青质核不会受到 NiOEP 的影响。在这种情况下，沥青质周围的小树脂分子显示出对 NiOEP 的优先吸附，并与原始纳米聚集体保持距离，从而减小了纳米聚集体的整体尺寸。这与 NiOEP 掺杂的沥青溶液的紫外-可见吸收光谱一致，表明至少 95% 的添加 NiOEP 保留在含有树脂的麦芽烯部分中，而在沥青质中仅发现痕量的 NiOEP。考虑到树脂在稳定沥青质骨料中的作用，它们的离开会促进沥青质纳米骨料的沉淀。后者也通过 TLC-FID 色谱测量得到证实，与对照样品相比，NiOEP 掺杂样品中沥青质提取物显着增加。它们的离开可以促进沥青质纳米聚集体的沉淀。后者也通过 TLC-FID 色谱测量得到证实，与对照样品相比，NiOEP 掺杂样品中沥青质提取物显着增加。它们的离开可以促进沥青质纳米聚集体的沉淀。后者也通过 TLC-FID 色谱测量得到证实，与对照样品相比，NiOEP 掺杂样品中沥青质提取物显着增加。