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A combination of analytical methods (including CHNS-O elemental analysis, X-ray diffraction, 1H and 13C NMR spectroscopy, MALDI-TOF and ICP mass spectrometry) was used to determine the elemental composition and average molecular and structural parameters of asphaltenes isolated from a heavy oil sample from the Ashalchinskoye field and vacuum residue samples from two different Russian oil refineries. The study identified differences in the nano-aggregate size of asphaltenes in heavy oil and vacuum residues, and evaluated the effects of the composition and molecular structure of asphaltenes on the composition and properties of the heavy petroleum feedstock samples.

This article demonstrates possible separation of Pd(II), Pt(IV), and Rh(III) ions from chloride solutions by solvent extraction in rotating coiled columns (RCC). The most common reagents used for extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributyl phosphate (TBP), and relatively new reagent—N,N,N',N'-tetra-n-octyldiglycolamide (TODGA). The completeness of extraction of platinum metals from individual and mixed hydrochloric acid and chloride solutions has been analyzed as a function of the essence and concentration of extractant, acidity of the analyzed solutions, and other factors. Optimum conditions of quantitative extraction of the metals from model hydrochloric acid and chloride solutions into the extractant phase have been determined, including subsequent selective separation at the re-extraction stage. A flowchart has been proposed for multistage extraction of Pd(II), Pt(IV), and Rh(III) using 0.05 M MTAA solution in toluene as a stationary phase in RCC. The flowchart includes extraction of Pd(II) and Pt(IV) ions from the solution (0.1 M HCl + 30 g/L Cl–) into the organic phase upon simultaneous separation of Rh(III) remaining in the aqueous phase and consecutive re-extraction of Pd(II) and Pt(IV) from the organic phase using 0.01 M solution of thiourea in 0.1 M HCl and 1 M solution of thiourea in 0.5 M HCl, respectively. The flowchart has been verified for separation of platinum metals in the production process of preset composition. The degree of metal extraction after processing by 0.05 M solution of MTAA in in toluene and consecutive re-extraction by solutions of thiourea is 99.5% for rhodium(III), 99.9% for palladium(II), and 97.4% for platinum(IV). The extracted aqueous phases of rhodium and platinum after output from the column did not contain impurities of other platinum metals. In the aqueous fraction of palladium, the platinum content was 0.5%.

The characterization of the feedstock is an important analytical task in the modeling and development of processes for upgrading of petroleum residues. This work presents the results of fractionati...

Transmission electron microscopy (TEM) was used to study the structure of particles of CO2-asphaltenes precipitated from a goudron vacuum residue sample in the gas anti-solvent (GAS) process using heptane, toluene, and their mixture (heptol) as diluents. It was shown that CO2-asphaltenes, despite lower aromaticity and polarity compared to C7-asphaltenes, have a similar irregular layered internal structure, as well as a close distribution of the aromatic layers and similar distance between the layers in the packed crystallites.. The type of the diluent used affects not only the yield and composition of the precipitated CO2-asphaltenes, but also the degree of order and the size of layers of aromatic fragments of the molecules forming their structure. In this respect, toluene as a diluent ensures the formation of CO2 asphaltenes that are comparable to C7-asphaltene particles in their molecular structure and structural parameters.

A study was carried out on the precipitation of heavy fractions and the isolation of asphaltenes from a petroleum sample using supercritical carbon dioxide (SC-CO2) as the antisolvent. The experiments were carried out in a laboratory supercritical fluid extraction device using a GAS (gas antisolvent) procedure at from 50 to 140°C and pressure from 10 to 30 MPa. We determined the effects of temperature and pressure as well as of the addition of a hydrocarbon diluent on the yields of the isolated fractions. The elemental and microelement composition was determined as well as the structural properties of the components isolated in the SC-CO2 medium at various temperatures. An increase in temperature at pressures above 20 MPa as well as the addition of small amounts of toluene to the starting petroleum sample gave greater isolation selectivity, greater concentration of asphaltenes in the precipitated fractions, and drier solid particles. In contrast to C7-asphaltenes, CO2-asphaltenes have lower aromaticity, polarity, and metal content. The proposed analytical method permits the isolation of asphaltenes in only a few hours, does not require large volumes of organic solvents, and yields asphaltenes in amounts sufficient for subsequent detailed study of their composition and properties.

We demonstrate that the method based on supercritical fluid extraction (SFE) using supercritical carbon dioxide (SC-CO2) as a basis of a solvent can be used, in principle, to fractionate a sample of heavy oil into narrow fractions. Studies are conducted using heavy oil of the Ashalchinskoye field as an example. The composition and yield of the fractions extracted from heavy oil depend on the concentration of the organic modifier (toluene) added to SC-CO2. Supercritical fluid extraction was carried out in a semiperiodic mode at 50°C and a pressure of 100 bar with a gradual increase in the concentration of toluene from 0 to 40 wt %. This resulted in nine fractions extracted with a total extract yield of 83.4 wt %. The use of SFE can significantly decrease the amount of the residue after the fractionation of heavy oil. The composition and properties of narrow fractions extracted from heavy oil are determined. The distribution of group hydrocarbon components, metals, sulfur, and Conradson carbon residue (CCR) between the extract fractions and the residue is found.

The capabilities of countercurrent chromatography (CCC) in the elemental analysis of samples with different chemical and phase compositions are demonstrated. The combination of the characteristic features of extraction chromatography and multistage extraction with separation and preconcentration processes performed in a closed system (a Teflon coiled column) opens up prospects for applying this method to the analysis of a wide range of materials from high-purity substances to oil and rocks. The use of CCC at the stage of sample preparation makes it possible to decrease the detection limits of impurity elements in high-purity materials to a pg/g level, i.e., by two or three orders of magnitude, as compared with those in the direct determination by inductively coupled plasma mass spectrometry. In the analysis of oil samples, CCC allows one to determine their complete trace element composition (including platinum group, rare, and rare earth elements) due to the concentration of trace elements in a small volume of a stationary aqueous phase retained in the column.

Highly dispersed materials Fe3O4@TEOS and Fe3O4@PVP for asphaltenes extraction from organic media have been synthesized via modifications of nanosized magnetite with tetraethoxysilane and N-polyvinylpyrrolidone. Using model compounds simulating the main functional groups of asphaltenes and some natural asphaltenes isolated from crude oil, the sorption capacity was estimated for Fe3O4@TEOS. It was found that the extraction degree of asphaltenes from a toluene solution at 45 °C reached 65–70%, and the sorption capacity was 28 mg g–1.

The development and use of instrumental methods for the determination of a wide range of trace elements in oil is considered. Special attention is paid to methods of the direct introduction of samples into spectrometers. It is shown that preliminary sample preparation is in certain cases necessary for the determination of trace elements in oil. The main methods of sample preparation of oils, including methods of extraction of a series of trace elements from crude oil (extraction, membrane, sorption, etc.), are described.

A comprehensive approach to the determination of the elemental composition of oils (including those with a viscosity of 5000 mm2/s) is proposed. It ensures the determination of the most elements present in oils using two versions of sample preparation, autoclave decomposition of oil samples and extraction preconcentration of elements from oil into an aqueous solution on rotating coiled columns (RCCs). The application of RCCs in the elemental analysis of oil ensures the preconcentration of a number of trace elements from oil (including rare-earth elements) and the determination of their concentrations at a level of ng/kg. The preconcentration factor of trace elements from oil using an RCC depends on the volume of oil sample pumped through a constant volume of the stationary phase (acid solution) retained in the column and on the speciation of elements in the oil.

Solvent deasphalting of vacuum residue using carbon dioxide-toluene mixture was studied to assess the effect of the process parameters and mixture composition on the yield and composition of deasphalted oil (DAO) produced. An insignificant effect of the toluene content in the mixture on the DAO yield was found at a concentration above 30 wt.%, which was attributed to effective anti-solvent properties of carbon dioxide. At relatively low-pressure region, an increase in temperature and the transition of the mixture to the supercritical state led to a rapid decrease in the solvent density and the DAO yield. At the same time, at pressures providing a mixture density in the region above ∼0.6 g/mL, an increase in temperature above the mixture critical value was accompanied by increasing the DAO yield, even despite a noticeable decrease in the solvent density. However, conducting the extraction at temperatures near and beyond the mixture critical temperature reduces the separation selectivity at close the extraction yields due to increased solubility of metal-containing polar compounds. A proposed mixture in the single-phase liquid state can provide high DAO quality with metal and CCR removal efficiency of more than 90 and 80 wt.%, respectively.

The effect of magnetic field on the composition and physicochemical properties of oil and petroleum products is described. Experimental data are presented, illustrating that the structure of heavy oil residues (HORs) of different origin can be changed upon exposure to a magnetic field. The effect of exposure time and power of magnetic field on changes in the composition of HOR solutions in various solvents (toluene, n-hexane, dichloromethane, and isopentane) is studied. The use of magnetic field at the stage of sample preparation of solutions is proposed in the identification of heavy oil residues and the elucidation of their origin based on gas chromatography with a mass-selective detector (GC–MS).

This is an Open Access Article. It is published by International Union of Pure and Applied Chemistry (IUPAC) under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence (CC BY-NC-ND). Full details of this licence are available at: http://creativecommons.org/licenses/by-nc-nd/4.0/