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.

Asphaltenes represent the heaviest fraction of crude oils, being recognized by their tendency to self-associate and precipitate. Asphaltene precipitation and subsequent deposition can cause problems in all stages of production. The objective of this paper is to model Brazilian crude oil and asphaltene systems using the PC-SAFT equation of state. Asphaltenes were extracted from crude oil through the addition of different n-alkanes. The PC-SAFT was capable of accurately predicting liquid density for toluene and asphaltenes and boiling point elevation for crude oil at different concentrations of toluene. Asphaltene precipitation from model oil allowed us to evaluate the influence of binary interaction parameters on modeling results. The influence of precipitant agent (n-hexane and n-heptane) on the asphaltene phase behavior was analyzed, showing that n-hexane was able to precipitate more asphaltenes than n-heptane, as expected. Furthermore, simulated results are in agreement with experimental observations: the average relative errors are 3.75 % and 10.25 % for the weight percentage of precipitated asphaltene using n-hexane and n-heptane as precipitant, respectively.

Microparticles (MPs) have been extensively researched as a potential drug delivery vehicle. Here, we investigated the fabrication of MPs with pH-responsive macropores and evaluated their potential applicability in developing solid oral drug formulations. Our previous study showed that macropored MPs, made of Eudragit L100-55, could encapsulate 100 nm, 1 µm, and 4 µm sized fluorescent beads-model drugs that are mimicking vaccines, bacteria, and cells. In the present study, closed-pored MPs after freeze-drying were coated with a gastric soluble Eudragit EPO layer to protect MPs in the simulated pregastric environment. Subsequently, drug encapsulated MPs maintained their intact closed-pored structure in the simulated gastric environment and exhibited a rapid release in the simulated intestine environment. Our MP system was found to provide a significantly higher level of protection to the encapsulated lactase enzyme compared to the control sample (i.e. without using MPs). Real-time fluorescence microscopy analysis showed that macropored MPs released encapsulated drugs in a burst-release pattern and in a size-independent manner. This work shows that our proposed EPO-coated MPs with pH-responsive macropores can meet the challenges posed by the multiple physiological environments of the digestive tract and be used in developing highly effective solid oral drug/vaccine formulations.