A combination of methods, including scanning electron microscopy, X-ray diffraction analysis, Fourier transform infrared spectroscopy, and structural group analysis was used to trace the evolution of the molecular and supramolecular organization of asphaltenes in light and heavy crude oils during their thermal conversion in supercritical n-hexane. It has been shown that thermolysis of asphaltense under supercritical conditions is accompanied by the disintegration of the initial nanoaggregate and formation of smaller particles. Moreover, the asphaltenes of light crude oil undergo more extensive degradation. It was found out that the cracking of saturated fragments and the condensation of aromatic nuclei in the molecules of the resulted high-molecular components under conversion conditions occur simultaneously. This is evidenced by an increase in the size of quasi-crystallites in the structure of 'secondary' asphaltenes, an increase in the degree of aromaticity, and a decrease in the content of naphthenic rings in the structure of 'secondary' asphaltenes and the resulted resins. The resulted oil components are enriched in long-chain n-alkanes and depleted in heteroatoms. They are characterized by similar molecular composition. The compounds identified in the oils are n-alkanes, alpha-olefins, naphthenes, mono-and polycyclic aromatic hydrocarbons, including naphthene-aromatic and sulfur-containing structures. It was found out that oil components resulted from the conversion of light crude oil asphaltenes contain alkyl derivatives of policyclic aromatic hydrocarbons of higher molecular weight than those obtained by converting heavy crude asphaltenes. The data obtained indicate similarities in the thermal transformations of light and heavy crude oil asphaltenes. Differences in the macromolecular architecture of the original asphaltenes manifest themselves in the composition of the degradation products. This finding mayAbe useful for molecular characterization of the oils and prediction of the behavior of their resin-asphaltene components during thermal processing.

The products of oxidative destruction of asphaltenes of heavy Paleozoic oils from the Ashalcha and Nurlat oilfields differing in the age of host sediments have been studied. It is shown that oxidation of the asphaltenes of both oils by hydrogen peroxide in the presence of acetic acid results in the release of occluded compounds. The compounds identified in their composition include n-alkanes, steranes, hopanes and methyl esters of n-alkane acids. A peculiarity of the asphaltenes of Nurlat oil occurring in the Devonian sediments is the presence of n-alkenes in the composition of occluded compounds. The presence of occluded compounds in the structure of asphaltenes is confirmed by the results of X-ray diffraction analysis.

Compounds occluded by asphaltenes of methanonaphthenic oil from the Krapivinskoye field and naphthenoaromatic oil from the Usinskoye field are investigated using the hydrogen peroxide- acetic acid system. The study has found that their composition contains normal and branched alkanes, nalkylcyclohexanes, n-alk-1-enes, steranes, terpanes and nalkanoic acids which are similar in structure. The presence of alkyl- substituted benzenes and alkylnaphthalenes in the composition of captured compounds is a distinguishing feature of naphthenoaromatic oil asphaltenes.

Relevance. The need to obtain information about the chemical nature of the resin-asphaltene and oil components of atmospheric residue from distillation of crude oil produced at the Krapivinskoe field in order to select optimal technologies for its rational utilization. Aim. To study the structures of asphaltene macromolecules and resin substances and the molecular composition of the oil components of atmospheric residue from distillation of crude oil produced at the Krapivinskoe field. Methods. Transmission electron microscopy, X-ray phase analysis, IR spectroscopy, 1H NMR spectroscopy, structural group analysis, chemical destruction, gas chromatography-mass spectrometry. Results. The structure of resin-asphaltene substances and the molecular composition of atmospheric residue obtained in the course of atmospheric distillation of oil from the Krapivinskoe field in laboratory conditions have been characterized using a complex of physicochemical research methods. It was found out that asphaltenes of atmospheric residue have a predominantly amorphous structure because of the presence of a developed alkyl chain configuration in their macromolecules. Mean asphaltene molecules consist of three structural blocks, which basis is triarene cores condensed with four to five naphthenic rings. These naphthenoaromatic systems neighbor upon methyl substituents only. The mean molecules of atmospheric residue resins are predominantly single-block. Their structural blocks are more compact due to the smaller number of aromatic and naphthenic rings in the naphthenoaromatic system. A feature of mean resin molecules is also the presence of relatively long alkyl substituents in the blocks. It was established that the structure of asphaltenes and atmospheric residue resins contains fragments linked to each other or to the naphthenoaromatic core of their macromolecules through sulfide and ether bridges. In both types of ‘linked’ fragments, n-alkanes, n-alkylcyclohexanes and hopanes were identified. Among the fragments linked through sulfide bridges, n-alkylbenzenes, n-alkylmethylbenzenes and n-alkanoic acids were additionally identified, while ethyl esters of n-alkanoic acids were identified among fragments linked through ether bridges. A structural feature of the atmospheric residue resins is the presence of phenylalkanes with different positions of the phenyl substituent in both types of bridge-linked compounds. Steranes and phenanthrenes are present in the composition of compounds linked through sulfide bridges. The oil components of atmospheric residue contain n-alkanes, n-alkylcyclohexanes, hopanes, steranes, n-alkylbenzenes, n-alkylmethylbenzenes, alkylnaphthalenes and alkylphenanthrenes.

Resins extracted from heavy high-viscous oil of the Nurlat oilfield were investigated. The composition of fragments bound through sulphide and ether bridges in the molecules of initial resins and the liquid products of their conversion at 450 °C under the conditions of laboratory experiment was studied using a set of physicochemical methods (IR spectroscopy, UV spectroscopy, gas chromatography - mass spectrometry, chemical destruction). It is shown that the fragments undergoing destruction are mainly those bound in the structure of the initial sample through the least thermally stable functional groups of esters and aliphatic sulphides. Sulphur- and ether-bound compounds in the structure of both resin samples are represented by n-alkanes, n-alkylcyclopentanes, n-alkylcyclohexanes and hopanes. The presence of nickel porphyrins was established among the sulphur-bound compounds. It is the molecular composition of bound n-alkanes that changes most noticeably during thermolysis. Ether bond cleavage in the molecules of secondary resins leads to the formation of products containing mono- and dibromides of alkyl biphenyls. This fact provides evidence that these aromatic compounds are present in resins in the form of fragments bound with other structural fragments through one and two ether bridges.

Relevance. Conditioned by the need to expand the amount of data on composition and structure of the asphaltene constituents of heavy oils. The data are important for creation of new and modernization of existing technologies for processing unconventional hydrocarbon raw materials. Aim. To study the composition of structural fragments in macromolecules of asphaltenes of bituminous oils from the Ashalchinskoe, Usinskoe, and Nurlatskoe oilfields using the ruthenium ion-catalyzed oxidation. Object. Fractions of high-molecular asphaltenes, which make up the bulk of the asphaltene constituents of the Ashalchinskoe, Usinskoe, and Nurlatskoe oils (94.1; 92.1 and 95.0 rel. %). Methods. Elemental analysis, cryoscopy in benzene, selective chemical destruction of Car–C bonds using a ruthenium ion-catalyzed oxidation, gas chromatography–mass spectrometry. Results. It has been established that the structure of high-molecular asphaltenes of bituminous oils from the Ashalchinskoe, Usinskoe, and Nurlatskoe oilfields contains fragments bound to the core of their molecules through Car.–C bridges and compounds trapped in the hollow cells of macromolecular entities of asphaltenes during kerogen cracking. It follows from the analysis of the oxidation products that the covalently bonded fragments are represented by C8–C32 n-alkanes, branched C9–C30 alkanes (2-methylalkanes and C15, C19, C20 isoprenoids), C22–C24 cheilanthanes, C27, C29–C33 hopanes and long chain alkyl bridges (C9–C30) connecting aromatic blocks. Most of the fragments linked by Car.–C bridges are linear paraffin chains. Typical biological markers, i. e. n-alkanes and hopanes were identified among the occluded compounds.

Comparative characteristics of resins, asphaltenes, andlow polarcomponents of heavy oils from the Ashalchinskoye (I) and Nurlatskoye(II) oil fields (Republic of Tatarstan, Russia) are given. These oilsdiffer in the age of host rocks (Permian and Devonian, respectively)and the content of their components and heteroatoms. An X-ray phaseanalysis and scanning and transmission electron microscopy revealthat, in contrast to smooth surface asphaltenes of oil I, asphaltenesof oil II are characterized by a loose and porous surface and smallersizes of nanoaggregates. Nanoaggregates form a disorderly tangledstructure because of the alkyl side-chain configuration, which makesit difficult to stack aromatic sheets. The crystallites of nanoaggregatesof asphaltenes of oil II are smaller than the crystallites of nanoaggregatesof asphaltenes of oil I. The application of the method of structural-groupanalysis based on the use of the measured indicators of the elementalcomposition, average molecular weights, and the results of H-1 NMR spectroscopy made it possible to establish that overall sizesof mean molecules of resins and asphaltenes of heavy oil I are largerdue to the increased content of aromatic and naphthenic cycles inthe naphthenoaromatic system. A feature of the structure of the resin-asphaltenecomponents of oil II is a greater number of alkyl substituents inthe side chains. According to gas chromatography-mass spectrometry(GC-MS) analysis, the low polar components under study arecharacterized by a similar set of saturated hydrocarbons (n-alkanes, mono-, and polycycloalkanes) but differ in thecomposition of identified aromatic hydrocarbons and heteroorganiccompounds. A feature of the low polar components of oil II is thepresence of a wider range of n-alkyl- and phenylalkyl-substitutedbenzenes and nitrogen- and oxygen-organic compounds in their composition.

Data on the composition and structure of aliphatic and aromatic fragments bound through oxygen in the molecules of resinous-asphaltene and oil components of bitumoid from the sample of Dmitrievskoe oil shale have been obtained.

An effect of biogenic oxidation of heavy high-viscosity oil from the Ashalchinskoye oilfield by native soil microflora (laboratory experiment) on the composition and structure of its resin components is investigated by using a complex of physicochemical research methods (elemental analysis, IR spectroscopy, selective chemical cleavage of sulfide and ether bonds, gas chromatography-mass spectrometry). It has been found out that the share of alkyl fragments decreases, while the conventional content of aromatic fragments and oxygen-containing structures increases in the structure of resin heavy high-viscosity oil substances in the course of biodegradation. The biodegradation of resins heavy oil is accompanied by changes in the qualitative and molecular compositions of the compounds bound in their structure through sulfide and ether bridges. The share of aromatic hydrocarbons is lower, while the relative content of heteroorganic compounds is higher in the compounds identified in the products of chemical destruction of biodegraded oil resins. The predominance of saturated hydrocarbons remains stable. The molecular composition of bound n-alkanes, n-alkylbenzenes, and naphthalenes changes most noticeably in the course of biodegradation. The relative content of linear hydrocarbons is lower in the alkanes determined in the products of chemical degradation of resins of the biodegraded oil. The share of macromolecular compounds and homologues with an even number of carbon atoms is higher in linear hydrocarbons. In naphthalenes, the relative content of the least resistant to microbial oxidation naphthalene and its C-1 and C-2 homologues is lower, while the share of C-3 and C-4 homologues is higher. Monoalkylbenzenes of resins are subject to biooxidation in the entire range of the number of carbon atoms. The obtained information allows a more detailed assessment of the influence of the biodegradation process on the composition and structure of heavy high-viscosity oil resins.

Structural group analysis and gas chromatography–mass spectrometry were used to characterize high- and low-molecular-weight nitrogen-containing bases of bituminous oils from various oil and gas provinces of Russia. It was found that the high-molecular-weight bases were similar in their structural organization: their averaged molecules were almost not different in the numbers of structural blocks and aromatic and naphthenic rings contained in them, and the numbers of carbon atoms in paraffin fragments. It was shown that the low-molecular-weight bases of all oils contained similar sets of alkyl-substituted quinolines, benzoquinolines, azapyrenes, and thiopheno- and benzothiophenoquinolines.

The relevance. The need to obtain information on heat treatment effect on composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe field (Republic of Tatarstan) to solve the problems associated with their negative impact on oil refining. The aim. To characterize the composition of nitrogenous organic bases, isolated from the resins of bituminous oil of the Nurlatskoe field, and the products of their thermal cracking. Methods. Complex formation, extraction, liquid adsorption chromatography, potentiometric titration, 1H NMR spectroscopy, structural group analysis, combined gas chromatography-mass spectrometry. Results. Based on a comparative study of the composition and structure of nitrogenous bases of the initial and thermally treated resins of the bituminous oil from the Nurlatskoe field, the authors found out that they both contain high- and low-molecular nitrogenous bases with predominance of high-molecular compounds precipitated by hydrogen chloride. As a result of thermal exposure, the number of such bases increases due to an increase in the proportion of compounds with shorter alkyl substituents in their composition. The method of structural group analysis was used to show that the main directions of thermal transformations of high- and low-molecular bases of resins in Nurlatskoe oil are destruction of alkyl substituents and cyclization of shortened alkyl chains with formation of naphthenic rings. Among the lowest molecular weight bases of the initial resins and thermolysate the authors have identified alkyl-substituted quinolines, benzoquinolines, azapyrenes, thiophenoquinolines, and benzothiophenoquinolines with similar molecular weight distributions. During the thermolysis of resins, the relative content of low molecular weight homologues in the identified nitrogenous bases increases. The share of structures with reduced chromatographic mobility caused by a decrease in the degree of spatial screening of a nitrogen atom increases among similar homologues.

An effect of biogenic oxidation of high-viscosity oil from the Ashalchinskoye oilfield by native soil microflora (laboratory experiment) on the composition of structural fragments bound through sulfide and ether bridges in the macromolecules of its asphaltene components is investigated by using the method of selective chemical destruction. Chemolysis of ether and sulfide bonds in asphaltene macromolecules was carried out using boron tribromide and nickel boride, respectively. Composition of structural fragments linked through sulfide and ether bridges was revealed by GC-MS analysis using a DFS instrument "TERMO-scientific". It has been found out that the biodegradation of asphaltenes is accompanied by changes in the qualitative and molecular composition of sulfur- and ether-bound compounds. The share of aromatic hydrocarbons is lower, while the relative content of heteroorganic compounds is higher in the compounds identified in the products of chemical destruction of asphaltenes of biodegraded oil. This is most noticeable in structures bound through sulfur. However, the prevalence of saturated hydrocarbons, which in biooxidized asphaltenes are predominantly bound through oxygen, remains stable. This is the molecular composition of bound alkanes of both types represented by n-alkanes and isoalkanes in the samples under study, which changes most noticeably in the course of biodegradation. The relative content of linear hydrocarbons, where the share of macromolecular compounds and homologues with an even number of carbon atoms increases, is lower in the ether- and sulfur-bound alkanes identified in the products of chemical destruction of biomodified asphaltenes. The content of pristane and phytane in the ester-bound isoalkanes is noticeably decreased, which suggests the participation of isoprenoids in the process of microbial oxidation. The information obtained allows a more detailed assessment of the influence of the biodegradation process on the composition and structure of asphaltenes.

It was shown that the averaged asphaltene molecules of bituminous oils include no more than four structural blocks, the skeletons of which differ in the numbers of aromatic and naphthenic rings and the numbers of carbon atoms in alkyl substituents. The crystalline part of the macromolecules of the test asphaltenes had a layered structure. In terms of the number of layers of a packed structure, the thickness and the average diameter of its packing, and the number of aromatic rings in a layer, the test asphaltenes differed insignificantly.

The composition of fragments linked by ester, ether, and sulfide bridges in heavy oil asphaltenes and in asphaltene components recovered from liquid products of their conversion at 300 and 450°C was studied by methods of selective chemical degradation and gas chromatography–mass spectrometry. The composition of “bound” fragments in molecules of secondary asphaltenes differs from that of products formed by cleavage of bridging bonds in molecules of the initial asphaltene samples and depends on the thermolysis temperature. At the initial thermolysis temperature, the mainly degrading fragments are those bound in the initial sample through the least thermally stable ester functional groups. An increase in the cracking temperature leads to the decomposition of bridges that link with each other structural fragments of macromolecules and separate aromatic clusters of the naphthene–aromatic system. Such bridges involve more thermally stable ether functional groups and С–S bonds in saturated and aromatic rings. The specific features of the distribution of “bound” fragments in the structure of the products of thermal degradation of the initial asphaltenes indicate that the asphaltene components of heavy oils contain molecules differing in the nature and position of sulfide, ether, and ester bridging bonds. The identified ether/ester-bound high-molecular-mass n- alkanes not only are covalently bound fragments but can also be occluded compounds that are released upon degradation of aromatic cores of asphaltene aggregates.

The relevance. Accumulation of data on the structure of asphaltenes of methane-naphthenic oil of the Krapivinskoe oil field from the Upper Jurassic deposits in the territory of the Tomsk region is one of the conditions necessary for solving problems associated with its production, transportation, and processing. The purpose of the work is to study the composition of asphaltenes in oil from the Krapivinskoe oil field using the oxidation reaction catalyzed by ruthenium ions. The object of investigation is the fraction of high molecular weight asphaltenes that make up the bulk of asphaltene components of the Krapivinskoe oil (87,9 % rel.). Methods: selective chemical destruction of Car-C bonds using the oxidation reaction catalyzed by ruthenium ions and gas chromatography-mass spectrometry. Results. It was found out that the composition of high-molecular-weight asphaltenes of methane-naphthene oil contains fragments bound to the cores of their molecules through the C-ar-C bridges and occluded compounds. Covalently bound fragments are represented by C-5-C-18 n-alkanes, aromatic structures of the biphenyl type, and naphthalenes located at the periphery of asphaltene molecules. Among the occluded compounds n-alkanes, alkylcycloalkanes, steranes, terpanes, alkylbenzenes, naphthalenes, phenanthrenes, fluorenes, pyrene, chrysene, fluoranthene, biphenyls, phenylnaphthalenes, dibenzothiophenes, benzonaphthothiophenes, indole, carbazol, quinoline, benzoquinolines, phenols, dibenzofurans, and benznaphtofurans were identified. Saturated hydrocarbons are typical biological markers; they are trapped in hollow cells of macromolecular formations of asphaltenes during kerogen cracking. Aromatic hydrocarbons and heteroorganic compounds are products of thermal destruction of parent asphaltenes; they are blocked by geomacromolecules at later stages of the formation of their macrostructure. The information obtained expands the understanding of the structure of asphaltenes in oil dispersed systems, so it may be used to construct a hypothetical model of their molecules.

Selective chemical decomposition, IR spectroscopy, and high-resolution mass spectrometry were used to study the composition of structural fragments linked through sulfur bridges in the asphaltene components of heavy fuel oil as well as the products of its thermal and thermocatalytic cracking. Pyrolysis in the presence of initiators derived from fly ash ferrospheres leads to more extensive changes in the structure of the asphaltene components.

Ruthenium ion-catalyzed oxidation of methanonaphthene oil (Krapivinskoye oilfield) revealed that its high molecular asphaltenes contain aromatic–aliphatic bridges and non- covalently bound (occluded) compounds. Covalently bound fragments are represented by C 5 –C 18 n -alkanes, aromatic biphenyl-type structures, and naphthalenes located in the peripheral part of asphaltene molecules. Typical biological markers, i.e . terpanes, steranes, and n -alkanes have been identified among the occluded compounds.

An oxidation reaction catalyzed by ruthenium ions has revealed that high-molecular asphaltenes of methano-naphthene oil from the Krapivinskoye oilfield contains structural fragments linked by means of Car-C bridges and non-covalently bound (occluded) compounds. It was found that covalently bound fragments in the composition of high mo-lecular weight asphaltenes of Krapivinskaya oil are represented by alkanes of normal structure, aromatic structures of biphenyl type and naphthalenes located in the periphery of the molecule. Typical hydrocarbon biomarkers such as n-alkanes, steranes, and terpanes are present among the occluded compounds.

The relevance of the work is caused by the need to expand the amount of data on resin-asphaltene substances and oil components of heavy oils, which share in the volume of the extracted and processed hydrocarbon raw materials is steadily growing. The refining of oils with high content of asphaltenes, resins, and heteroatomic compounds using existing basic technologies is hard and costly. Hence. information on the composition and structure of the heavy oil components is of great importance for the development of innovative technical solutions of their rational use. This is due. first of all, to the fact that resins and asphaltenes are considered the important reserve for the advanced processing of crude oil while oil components are considered the basis for the production of commercial petroleum products. The purpose of the work is to study the structural-group composition of asphaltene and resin macromolecules and the molecular composition of oil components of heavy oils sampled in various oil and gas provinces and differing in the age of the enclosing deposits and the content of resin-asphaltene and oil components. Methods: liquid adsorption chromatography, elemental analysis, cryoscopy in benzene, H-1 NMR spectroscopy, structural group analysis, combined gas chromatography mass-spectrometry. Results. A comparative description of the composition and structure of macromolecules of resin-asphaltene substances and the molecular composition of oil components of heavy oils from the Ashalchinskoe (I), Usinskoe (II) and Nurlatskoe (III) fields is given. These oils differ in the content of these components and heteroatoms and in the age of the enclosing deposits (Permian. Permian-Carboniferous, and Devonian). It has been found out that the content of asphaltenes and resins increases in the series of heavy oils I-II-III. At the same time, their average molecular weight decreases and the overall sizes of their mean molecules become smaller. This is due to a decrease in the number of structural blocks. which become more compact because of decreasing total number of rings in the naphthenoaromatic system, mainly naphthenic ones. In this case. the number of carbon atoms in the paraffin fragments of the structural blocks of mean molecules increases. The observable changes in the structural parameters of molecules are most pronounced for the resin-asphaltene components of oil from Devonian deposits. It is shown that oil components of heavy oils are characterized by a similar set of saturated hydrocarbons. but differ in the composition of identified aromatic hydrocarbons and heteroorganic compounds. A feature of oil components in the oil III is a wider range of mono- and bicyclic arenes and oxygen-containing structures.

Using the methods of selective chemical destruction, IR spectroscopy and chromatography - mass spectrometry, a comparative study of the composition of structural fragments connected through sulfide bridges in the molecules of asphaltene components of heavy oil fuel oil and products of its thermal and thermocatalytic cracking was carried out. It is shown that the effect of temperature in the presence of initiating additives based on ferrospheres of energy ash leads to deeper changes in the structure of asphaltene components.