Asphaltene Aggregation from Crude Oils and Model Systems Studied by High-Pressure NIR Spectroscopy

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• 作者：Narve Aske ; Harald Kallevik ; Einar Eng Johnsen ; and Johan Sj&ouml ; blom
• 刊名：Energy & Fuels
• 出版年：2002
• 出版时间：September 2002
• 年：2002
• 卷：16
• 期：5
• 页码：1287 - 1295
• 全文大小：187K
• 年卷期：v.16,no.5(September 2002)
• ISSN：1520-5029

文摘

The aggregation of asphaltenes by pressure depletion both in a live crude oil and model systemsof asphaltenes in toluene/pentane solvents is studied. Near-infrared spectroscopy utilizing a high-pressure NIR cell with a maximum operating pressure of 325 bar is used to study the onset ofasphaltene aggregation. The NIR spectra are subject to a principal component analysis (PCA) inorder to detect the asphaltene aggregation onset pressure. The effect of fluid compressibility onthe NIR spectra is also demonstrated. The aggregation behavior of asphaltenes in model systemsis shown to resemble the aggregation behavior for the crude oil. However, while the asphalteneaggregation in the crude oil is more or less completely reversible with repressurization, indicationsof only a partial redissolution are seen in the model systems. The kinetics of the redissolution isquite slow. A time of 72 h to equilibrate at the original pressure of 300 bar was required toredissolve the asphaltene aggregates formed within the crude oil by depressurization of thesample. Near-infrared spectroscopy in combination with principal component analysis is shownto be an efficient tool in detecting both bubble points and asphaltene aggregation onset pressuresin high-pressure systems.