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Asphaltenes are defined as the petroleum fraction insoluble in n-alkanes and soluble in aromatic solvents, such as toluene. Such definition implies that asphaltenes are not a homogeneous material but a mixture of fractions. Asphaltenes represent one of the major contributors to several problematic issues for the petroleum industry. Destabilized asphaltenes can cause arterial clogging within pipelines and wellbores, corrosion and fouling of production equipment, reduction of catalyst activity in refining processes, and other problems. This work describes an investigation of the separation of asphaltenes into three different fractions by adsorption onto silica particles. These fractions (two adsorbed and one non-adsorbed onto silica) were characterized by elemental analysis (C, H, and N), Fourier transform infrared spectroscopy coupled to attenuated total reflectance (ATR−FTIR), proton nuclear magnetic resonance ( 1 H NMR) spectroscopy, and atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI−FT-ICR MS). APPI−FT-ICR MS and ATR−FTIR accessed chemical information on a molecular level [molecular formula, carbon number (CN) and double bond equivalent (DBE) distributions, and organic groups], whereas 1 H NMR and elemental analysis provided the aromaticity degree and C/H atomic ratio of the samples, respectively. The C/H atomic ratio decreases in the following the order: non-adsorbed > whole asphaltene > adsorbed > irreversibly adsorbed. The irreversible fraction adsorbed had the lowest percentage of aromatic hydrogen compared to other fractions by 1 H NMR. There was a good correlation between the results of NMR and elemental analysis. The efficiency of fractionation on silica particles was proven to be successful by the low concentration of polyaromatic hydrocabons observed for two samples adsorbed onto silica and the increasing of the aromaticity degree and C/H ratio for the non-adsorbed fraction. N 2 , N 2 O, and NO compound classes were selectively separated from whole asphaltene and concentrated in polar fractions (adsorbed fractions onto silica), with their CN and DBE distributions reported. Therefore, this work demonstrated the selectivity of the fractionation method onto silica to retain highly polar compounds and, moreover, extends to the study of the adsorbent surface and how the molecules of the asphaltenes will behave against this change.

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The magnetic resonance (MR) spectra of magnetitebased magnetic fluid are investigated in samples containing particle concentration in the range of 10 14 to 10 17 particle/cm 3 . A single layer of dodecanoic acid is used as the magnetite surface coating agent while hydrocarbon is the suspending medium. Features in the MR spectra are discussed in terms of particle-particle interaction and its dependence upon particle concentration in the sample.

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