Fractionation of Asphaltene by Adsorption onto Silica and Chemical Characterization by Atmospheric Pressure Photoionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, Fourier Transform Infrared Spectroscopy Coupled to Attenuated Total Reflectance, and Proton Nuclear Magnetic Resonance

Abstract

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.

Fractionation and Characterization of Petroleum Asphaltene: Focus on Metalopetroleomics

“…Petroleum, as the most important source of energy and raw chemical materials, is a complex but delicately balanced system that depends on the relationship of its constituent fractions to each other [1]. Hence, the disturbance of these interactions, such as recovery and refining, may cause sediment formation and asphaltene deposition [2,3], which brings about many negative effects to the petroleum industry, such as the deactivation of catalysts, blocked pipelines, and deposition on the internal surface of the reservoirs [4][5][6][7][8].…”

Thermodynamic Analysis and Modeling of Brazilian Crude Oil and Asphaltene Systems: An Experimental Measurement and a Pc-Saft Application

“…Other physicochemical properties of crude oil are described in Table 1. Maltenes were separated from asphaltenes using two different solvents (n-hexane and n-heptane), following a procedure described by Hannisdal, Hemmingsen and Sjöblom (2005) and also used by Nascimento et al (2016).…”

“…Dried asphaltenes were redissolved in toluene. This mixture containing asphaltenes from crude oil Source: (a) Petrobras R&D Centerand(b) Nascimento et al (2016). plus toluene was called "Model Oil" (Figure 2).…”

“…For a twocomponent mixture of asphaltene and toluene with four different mass fractions of asphaltene, the result of the PC-SAFT modeling is compared with the experimental data. The aromaticity value of asphaltene was set to 0.35 as reported by Tavakkoli et al (2014), the molecular weight of asphaltene is 466 g/mol according to Nascimento et al (2016) and the binary interaction parameter for asphaltene-toluene was set to 0.032. A where Y i is the actual value of n predictions and Ŷ i is the predicted or estimated value.…”

“…The removal of metals increases the rate of dissolution or, in other words, the metal content has a direct effect on asphaltene dissolution, being important in the self-association of asphaltenes (Kaminski, 2000). Asphaltene molecular weight ranges from 500 to 2000 g/mol (Nascimento et al, 2016) depending not only on the oil and its origin, but also depending on the nature of the solvent, the solution temperature, the preliminary treatment and the measurement method (Quintero, 2009).…”