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Characterization of Petroleum Compounds Adsorbed on Solids by Infrared Spectroscopy and Mass Spectrometry

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journal contribution
posted on 2020-03-25, 18:45 authored by Santiago Villabona-Estupiñan, Fernando A. Rojas-Ruiz, Jose L. Pinto-Camargo, Eduardo J. Manrique, Jorge A. Orrego-Ruiz
A better understanding of the nature of crude oil compounds that preferentially interact with certain types of solids is essential to visualize solutions to challenges in oil fields, such as enhancing the oil recovery factor, via wettability alteration, and remediating emulsions stabilized by fines, among others. The simplistic assumption that the organic matter linked to hydrophilic solids corresponds to polar fractions (i.e., asphaltenes) needs more compositional detail. In an attempt to elucidate this important issue, in the present work, the organic species from an oil adsorbed on silica, alumina (synthetic solids), bentonite, and kaolinite (clays) were isolated and subsequently identified by infrared spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry in atmospheric pressure photoionization positive mode. The solids were characterized by X-ray powder diffraction and point of zero charge. Interestingly, the nature of adsorbed compounds depends upon either the surficial charge of the solids or the acidic character of the functional groups. Through both infrared spectroscopy and mass spectrometry, consistent and complementary results were achieved. The preferential adsorption of nitrogen basic compounds on bentonite and kaolinite was evidenced, promoted by the presence of metal–OH groups on the clay surface. Furthermore, that compounds adsorbed on all of the materials had slightly lower aromaticity than asphaltene-type compounds but an important contribution of oxygen compounds, which included sulfone-type compounds not detected in the asphaltene fraction. Highly conjugated aromatic oxygenated species were identified in the adsorbed organic matter by alumina, while oxygenated acidic compounds (carbonyl derivatives) were identified in the extracts recovered from silica, kaolinite, and bentonite.

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