Conversion of heavy oil with different chemical compositions under

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Conversion of heavy oil with different chemical compositions under catalytic aquathermolysis with an amphiphilic Fe-Co-Cu catalyst and kaolin Alexey V. Vakhin, Galina P. Kayukova, Anastasia M. Mikhailova, Dmitriy A. Feoktistov, and Igor P. Kosachev Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.8b00347 • Publication Date (Web): 08 May 2018 Downloaded from http://pubs.acs.org on May 9, 2018

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Conversion of heavy oil with different chemical compositions under catalytic aquathermolysis with an amphiphilic Fe-Co-Cu catalyst and kaolin G.P. Kayukova1,2, A.M. Mikhailova1, I. P. Kosachev1, D.A. Feoktistov1,2, A.V. Vakhin2* 1

A.E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific

Centre of RAS, 420088 Kazan, Russia, 2

Kazan (Volga Region) Federal University, Kazan 420000, Russia

Abstract: The physical simulation of heavy oil catalytic aquathermolysis with different chemical compositions from deposits located in the Tatarstan Republic, Russia (Ekaterinovsky oil, B2 type and Olimpiadovsky oil, A1 type) were designed. The catalytic aquathermolysis processes were conducted at a temperature of 300 °C in the presence of rock-forming additive - kaolin (the content of montmorillonite was 44%) and catalysts composed of transition metal (Fe, Co and Cu) carboxylates. The environment of the processes was a mixture of carbon dioxide and water vapor. The distinctive features of hydrothermal-catalytic conversion of various oil types are evaluated by fractional, structural-group, microelement compositions and H:C ratio changes. These variations are due to initial properties of crude oils and the activation degree of destruction reactions on C-C, C-N, C-O and C-S bonds leading to different levels of increase of saturated fractions content and decrease of resins and asphaltenes content in the products of experiments. By the thermal analysis method, the assessment of potential content of the oil on a solid sorbent before and after experiments was carried out. The high-molecular weight components of the naphthene-aromatic B2 type oil revealed greater adsorption

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capacity to the rocks, in comparison with the oil of the A1 type. Therefore, the adsorption of catalyst components on rocks is also greater. Keywords: heavy oil, composition, properties, aquathermolysis, oil-soluble catalyst, rock-forming mineral.

1. INTRODUCTION Heavy crude oil reservoirs are an important part of raw materials source. However, the development of such hydrocarbon resources is complicated by inability to process the produced heavy crude oil in already operating refineries. These factories are designed for the process of crudes with lower viscosity, sulfur content, resins and asphaltenes and higher content of distillates. Therefore, scientific researches that study partial upgrading of heavy oil compositions already in reservoirs are very relevant. Recently, in order to increase the efficiency of the SAGD technologies, special investigations on decreasing viscosity of heavy oil are conducted in many companies and scientific centers. These include viscosity reduction directly in oil fields whether by downstream or upstream processes. The main task of which is the conversion of high molecular weight components into the low boiling hydrocarbons [1-5]. This goal can be achieved with the use of various conversion catalysts [6], supercritical fluids and solvents [7] that reduce an interfacial tension on the "heavy oil – water" interfaces, and various steam-gas mixtures [8]. Technological impacts of different parameters on heavy oil lead to change the oil disperse structure that can affect its technological properties both positively and negatively. In early 1987, Japanese scientists discussed conversion of Kuwait heavy oil residue in lab-scale models [3]. The experiments were carried out in flow reactor under the temperature of 420°С and a pressure of 50-75 kg/cm2 in the presence of catalysts such as cobalt, nickel and molybdenum. The processes were in a CO and H2O environment. The formation of hydrogen during the reaction processes was affirmed. This hydrogen was further applied in hydrogenation of heavy oil residue. 2 ACS Paragon Plus Environment

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Because of thermal cracking and the presence of catalyst, a selectivity of light fraction yield increases, while the selectivity of gas and coke decreases. It is important to note the studies [9-12] of researchers from China, which reported the results of industrial applications of aquathermolysis in the presence of catalysts. The decrease in viscosity of produced oil, as well as sulfur content and high-molecular compounds was observed. Hence, the oil recovery factor increased. A large number of researches were performed in order to study the conversion processes of heavy oil compositions from Ashal’cha Field (Tatarstan) in various conditions of experimental models [13]. The article [14] provides the results of experiments regarding both catalytic and non-catalytic aquathermolysis of heavy oil from Ashal’cha Field in the presence of oil soluble compositions like nickel-, cobalt-based catalysts, hydrogen donor and rock minerals. The distinguishing features of hydrocarbon components, group compositions, rheological characteristics of oil and the average molecular mass of asphaltenes are revealed. After catalytic aquathermolysis the significant increase in light fractions of 70-250°С (23 wt %), n-alkyl benzenes, as well as the sum of saturate and aromatics by 1.3 times is observed. Moreover, the decrease in relative viscosity by 98% and the content of resins by 1.7 times. The article [15] describes the influences of temperatures (250, 300 and 350°С) on group and hydrocarbon compositions of Ashal’cha heavy oil in the presence of oil soluble iron carboxylate, hydrogen donor – tetralin and rock mineral – kaolin. As temperature increased up to 300 and 350°С, the content of saturate fractions also increased 1.5-1.75 times, correspondingly. In addition, the resin content decreased twice. The content of n-alkanes, lighter homologues of alkyl cyclohexane and tri-methyl alkyl benzenes in saturate fractions raised. This is explained by destruction of preferentially high-molecular resins due to cracking processes. The increase in asphaltene content at temperature of 350°С attests to the fact of not only intensive cracking processes in the given condition, but also condensing process followed by coke formation. 3 ACS Paragon Plus Environment

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The article [16] reports that injection of steam into reservoir rocks composed of natural catalyst – hematites (containing iron oxide) at temperatures of 210, 250, 300ºС activates the destruction processes of high-molecular components of Ashal’cha heavy oil. The new formed light fractions have a reflection in the changes of component, hydrocarbon, fractional and structural group compositions, as well as in structural parameters of asphaltenes. As the temperature increases and water content decreases in system, the yield of new-formed hydrocarbon decreases, while the content of asphaltenes and cokes increase. The general increasing tendency for aromaticity factor of asphaltene associates is revealed. The distance between aromatic layers and polymethylene chain fragments increases, while the size of associate itself and the number of aromatic layers in it reduces. The formation of coke is due to compounds, which are insoluble in toluene like carbene and carboid types. In case of achieving the specific concentration in oil disperse system, they precipitate together with cokes. In literature [17] the results of investigations concerning the changes in elemental, physical, chemical, rheological and group composition characteristics of heavy oil in catalytic and non-catalytic aquathermolysis are summarized. The chemistry of conversion processes for the given hydrocarbons and heteroatom compounds in water environment at high temperature, including sub-, supercritical conditions is considered. The problems and perspectives of industrial applications of catalytic aquathermolysis processes for upgrading compositions of heavy oil and natural bitumen are discussed. These investigations indicate the perspectives of search for possible intensification of aquathermolysis process and study the mechanism of conversion of heavy oil components under catalytic and non-catalytic in situ applications. However, there are several reasons why the problem of their full-field development becomes significantly complicated. Firstly, oil reservoirs in Permian deposits (on the territory of Tatarstan) are small and have a complex geological structure. Secondly, oil saturated formations are heterogeneous, as well as 4 ACS Paragon Plus Environment

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composition of fluids which are located in those rocks [17-22]. In recent years only the Ashalcha heavy oil field has been actively developing. Since the beginning of 2006, experimental and technological processes on extraction of heavy oil with the use of Steam-Assisted Gravity Drainage (SAGD) have been performing there [18, 19, 21]. The successful operating experience of horizontal wells at extraction of heavy oil is a big achievement of the PJSC TATNEFT Company, where various technological operation modes for these wells are developed. However, application of horizontal wells is still at the stage of exploration and arrangement. Because a successful oil recovery needs consideration of many factors connected with a geological structure of the field, the mode of exploitation and properties of the extracted oil. The oil-bearing section of Permian deposits consists of terrigenous reservoir rocks, which are dividing into sulphatic layers [21, 22]. These deposits lie at a small depth of average 50 - 250 m from the land surface. All found reservoirs belong to four-way closure traps with a complex structure, which are limited by water and non-permeable formations. These reservoirs by the sizes and stocks belong to small ones. For increasing the sweep efficiency in heavy oil reservoirs, their development is foreseen by the combined system. Therefore, areas with oilsaturated thickness more than 10-12 m are drilled by the pair of horizontal wells placed in pay zones one after another. In turn, places with oil-saturated thickness less than 10 m are drilled by horizontal wells for cyclic steam simulation techniques [18]. Heavy oil and natural bitumen of the Permian system differ in considerable fluctuations of viscosity, the increased content of asphaltenes, resins and aggressive components, such as heavy metals and sulphur [22]. Therefore, production and refinery of such a hydrocarbon crude is not effective and feasible today. Therefore, for the improvement of the applied technologies and development of new ways of utilizing horizontal wells, profound fundamental knowledge about the chemical nature of initial crude oil and conversions of its compositions, in both natural and technogenic processes considering specifics of geological conditions of certain fields and reservoirs is necessary. 5 ACS Paragon Plus Environment

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The purpose of this work is the identification of transformational behaviors of high-molecular components of heavy oil (various chemical types) during the physical simulation of catalytic aquathermolysis, the purpose of which is internal treatment of heavy oil in the presence of water steam.

2. OBJECTS AND METHODS The objects of this research were two oils of different chemical types from the Permian deposits of the territory of Tatarstan [2, 3]. First is heavy highsulphurous (4.86 %) oil of the Ekaterinovsky deposit of the naphthene-aromatic B1 type with 1.012 g/cm3 density and low paraffin (1.40 %) content. Second is less sulphurous (2.56 %), heavy oil of the Olimpiadovsky deposit of the A1 type with 0.951 g/cm3 density, with extremely high content of paraffin (22.15 %). Experiments on hydrothermal-catalytic conversion of heavy oil were made in the autoclave at 300 °C temperature in the environment of a steam-gas mixture: carbon dioxide with water vapor during 5 h. Initial content of water in the reaction system was 30 %, initial pressure was 1.5 MPa. In the course of experiments pressure raised up to 9 MPa. Kaolin was used as the rock-forming material. Among all minerals montmorillonite prevails – 44%, the quartz share is 29%, muscovite24% and kaolinite-3%. Conducting experiments in the presence of rocks is reasoned firstly by catalytic effects of some minerals during aquathermolysis processes [23], secondly – possible sorption of high molecular components of oil or metals [6]. The content of oil, which saturated rock sample was 20 wt%. Carboxylates of transition metals (iron, cobalt, and copper) received by the exchange reaction of sodium salts of tall oil and inorganic salts of the corresponding metals was used as composition for catalyst precursors [23]. The concentration of catalyst precursors injected into oil bulk including rock samples were 0.3 wt % by metal. Additionally, a propanol (5 %wt) was introduced to the reaction system as a modifying additive. The catalyst was selected based on the previous results of conducted experiments [24]. For instance, the influences of metals and modifying additives 6 ACS Paragon Plus Environment

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(tetrallin and propanol) on structural changes of heavy oil in hydrothermalcatalytic systems are studied from article [24]. In laboratory model experiments, the conversion characteristics of high molecular components of Ashal’cha heavy oil depending on nature of metals and experimental conditions are revealed. The processes are carried out at temperature of 300°С at inert and CO2 environment in the presence of oil soluble catalysts – carboxylates containing metals like Ni, Fe, Co and Cu. For the catalysts a specific characteristics – mixture of two catalysts can provide significant influence on reaction rate in contrast with a single metal. Besides investigating the influences of metals on heavy oil, the composition of metals consisting of Fe-Co and Fe-Co-Cu carboxylates are studied. The latter composition of catalyst precursors provide enough efficiency in reduction of heavy oil (Ashal’cha) viscosity by adding propanol at CO2 environment. This is achieved due to increase of saturate and aromatic hydrocarbon group compositions and decrease in resin content. Consequently, it was interesting to study the application of given catalyst compositions in other types of oils. While selecting propanol as a modifying additive, it was believed that solvent within metal carboxylates would have high polarity. Hence, it would reduce the viscosity due to interaction of OH-groups and polar groups of resins and asphaltenes, preventing them from associative formations [24]. Beyond that, propanol belongs to protic solvents and like tetrallin considered to be a proton donor as well [25]. After the reactor, the oil saturated rock samples were further extracted in the Soxhlet apparatus by the mix of next solvents: chloroform, benzene, and benzenealcohol taken in equal ratios. Extracts from rock samples were investigated by the set of physical and chemical methods. The analysis of rock samples on the content of organic matter (OM) and the existence of thermal effects was proceeded by the thermal analysis method [26] on the STA 443 F3 Jupiter (Netzsch, Germany) synchronous thermal analysis instrument. Conditions of measurements were as follows: in dynamic argon environment, 20-1000 °C temperature range and the heating rate was 10 °C/min. 7 ACS Paragon Plus Environment

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Processing of TG-DTA curves was carried out with the help of the Netzsch Proteus Thermal Analysis standard software. Determination of group composition was carried out according to GOST 32269-2013 standard, which is an analogue of the "SARA" analysis [27]. Extracts from rocks and products of experiments were divided into four fractions: asphaltenes, saturated hydrocarbons, aromatic compounds and polar aromatic compounds, i.e. resins. Asphaltenes were precipitated from the initial products in 40-fold amount of aliphatic solvent (hexane). Maltenes were divided by the liquidsolid chromatography on aluminum oxide previously calcinated at 420 °C into saturated hydrocarbons by hexane, aromatic compounds by toluene, and resins by the mix of benzene and isopropyl alcohol solvents taken in equal ratios. The structural-group composition of initial extracts and products of experiments were investigated by the IR Fourier spectroscopy method [28, 29]. IR spectra were taken by IR Fourier spectrophotometer Vector-22 (Bruker) in the 4000-400 cm-1 range with the 4 cm-1 resolution. For the comparative correlation of data, spectral coefficients characterizing the structural-group composition of the products C1 = D1600/D720 (aromaticity index); C2 = D1710/D1465 (state of oxidation); C3 = D1380/D1465 (branching degree); C4 = (D720+D1380)/D1600 (wax content); C5 = D1030/D1465 (sulfuring degree) were used. The hydrocarbon composition of the aquathermolysis products were investigated by the chromatography–mass spectrometry (GC-MS). The analysis was made on the DFS Thermo Electron Corporation device (Germany) in the Institute of organic and physical chemistry KazNC RAS. An ionization method is an energy of the ionizing electrons equals to 70 eV. Capillary column with the motionless phase ID-BP5X (DB-5MS analogue) 50 m long and 0.32 mm diameter was used. Helium was utilized as a carrier with a bulk rate of 2 ml/min. The temperature of an injector was 250 °C, the mode of temperature was from 60 (an isotherm within 1 min) up to 280 °C with a step of 10 °C/min, duration at final temperature was 20 min. Samples of the interest were diluted in CCl4 with ≈10–3 g/µL concentration before introduction into the device. Processing of mass and 8 ACS Paragon Plus Environment

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spectral data was carried out with the help of the Xcalibur program. Massfragmentograms on the total ionic current TIC with their subsequent reconstruction and interpretation on ions of m/z 85 (alkanes), m/z 83 (alkylcyclohexanes), m/z 91 (alkylbenzenes), and m/z 133 and 134 (alkylthreemethylbenzenes) were recorded. EPR-spectra of asphaltenes were taken on the SE/X-2544 (RadioPAN) EPRspectrometer. Signals of two types: a single symmetric signal of free stable radicals R* (g = 2.003), and a multicomponent ultrathin structure (UTS) corresponding to V4+ ions being part of the structure of vanadyl-porphyrin complexes [30-32] were recorded. The received intensity values of corresponding lines in EPR-spectra were normalized on the sample weight obtaining the R* and V4+ content in arbitrary units (a.u.). The elemental analysis of kaolin was measured by X-ray fluorescence method (M4 Tornado “Bruker”).

3. RESULTS AND DISCUSSION The results of thermal analysis show (Figure 1) that the initial rock samples independent from oil saturation are characterized by various weight losses in the temperature range from 20 to 1000 °C. This indicates to different thermal stability of investigated oil components and group compositions [34]. The thermal analysis allows to observe the content of organic matter (OM) in the rock and to estimate its thermal stability [33]. The content of OM was estimated from weight losses of rocks in the 200-600 °С temperature range. Weight losses in the 200-400 °С (∆m1) temperature range stands for the content of free hydrocarbons in rocks, whereas mass losses in the 400-600 °С (∆m2) temperature range corresponds to a highmolecular part of OM that destructs by thermal influences. At temperatures from 20 to 200 °C the adsorbed water is removed and volatile hydrocarbons from rocks are evaporated, while losses above 650 °C are due to crystallization water which is contained in kaolin. One of the distinctive features, reflecting the OM content, is a fractional composition parameter, FOM=∆m1(200-400°С)/∆m2(200-600°С), representing the 9 ACS Paragon Plus Environment

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relation of weight loss of OM in the mentioned temperature intervals [34,35]. According to the given parameters, oil from Olimpiadovsky field has more light components. After experiments the content of Ekaterinovsky oil in the rock sample decreases by 4 times, while Olimpiadovsky oil – by 6 times. Moreover, the content of light hydrocarbons decreases in all experiments. The high adsorption ability of high-molecular weight components of Ekaterinovsky heavy oil to rock-forming mineral is revealed. That is confirmed by the residual content of OM in rock samples after experiments and extraction. Another distinctive feature for conversion of both oils after experiments are also reflected in their group composition (Table 1). In experiment products, the content of saturated hydrocarbons of Ekaterinovsky oil increases from 25.91 up to 33.34 %, and the content of aromatic compounds rises from 22.59 up to 28.47 %. Amount of resins decreases from 35.10 to 23.61 %, and the content of asphaltenes slightly dropping away (from 16.40 to 14.58 %) as well. Olimpiadovsky oil differs from the Ekaterinovsky one by the higher content of saturated hydrocarbons and by smaller quantities of resins and asphaltenes. In experiment products, the content of saturated hydrocarbons increases (from 44.98 to 58.77 %), due to destruction of resins mainly, the content of which sharply decreases more than three times (from 28.16 to 7.61%). In the article [14], we have discussed the oil conversion in model systems in the presence of rock mineral – kaolin and catalyst – composition of nickel/cobalt carboxylates and proton donor. The main difference of such conversion is in activating destruction reactions in C-C, C-N, C–O, and C–S bonds. Moreover, preventing polymerization reaction and hence decreasing coke formation. According to some authors [36], the influence of metal carboxylates on destruction processes of heavy oil depends on interaction of metals with hydrogen sulfide and sulfuric compounds, which forms catalytically active metal sulfides. The latter weakens the C-S bonds in sulfur-containing compounds, resulting to destruction of molecules. The selected rock mineral kaolin, as well as montmorillonite exhibits acidic properties that sustains conduction of both condensation and cracking 10 ACS Paragon Plus Environment

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reactions. The former results to formation of asphaltenes in case of hydrogen source deficiency in reaction system [14, 15]. The catalyst promotes the reaction of hydrogen transfer from naphtene-aromatic components of oil, which have hydrogen donor properties, to free radicals. Thus providing their saturation and prevention from recombination [17]. In addition, the hydrogenolysis reaction of carbon-heteroatom, hydrogenation of aromatic rings and particular destruction of C-C bonds in resins and asphaltenes are intensified. According to IR spectroscopy, Ekaterinovsky oil and asphaltenes after experiments (Table 2, Figures 2, 3) are characterized by more aromatic structure, which is defined by the increase in the intensity spectra of absorption bands of aromatic bonds at 1600 cm-1 and increasing intensity of a triplet in the 880-730 cm1

range. The latter is a characteristic of aromatic structures what confirms by the

increase of the aromaticity coefficient, C1 from 2.71 to 3.10 for oil, and from 5.77 to 8.91 for asphaltenes. Olimpiadovsky Oil after hydrothermal-catalytic transformations becomes more paraffinic. That is revealed by a very low value of the aromaticity coefficient and noticeable increase in aliphaticity value in comparison with initial parameters (Table 2). Spectral data are in agreement with the group composition data showing increase in the content of saturated hydrocarbons. In addition, degree of aromaticity of asphaltenes of both oils increases. The thermal conversion of asphaltenes at various temperatures were conducted by a group of researchers [16]. They claim that at high temperatures, (300-350°С) dealkylation of asphaltenes occur and hence the degree of aromaticity increases. Besides, the asphaltenes with short aliphatic chains, undergo the internal reaction of cycling, as a result of which high carbon structures are formed. These are precursors of coke. In the investigated products of experiments, insoluble cokes were not detected. At the same time, an organic matter, which was not extracted by organic solvents, up to 3% remained in clays. This indicates that coke products can remain in rocks. 11 ACS Paragon Plus Environment

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According to GC-MS analysis, oils from the explored deposits are also essentially differ in individual hydrocarbon composition (Figure 4). As it has been written above, Ekaterinovsky oil belongs to B2 naphthene-aromatic oil by chemical type [22, 37]. Chromatogram of this oil (Figure 4a) represents the high naphthenic background indicating the presence of a large amount of isomeric naphthenic and aromatic hydrocarbons in its composition. Among individual hydrocarbons only peaks of the isoprenoid alkanes with obvious prevalence of a phytane (C20) are revealed. In the products of the catalytic aquathermolysis of this oil (Figure 4c) some decrease in a naphthenic background is observed along with the appearance of n-alkanes whose presence in initial oil was less noticeable. After aquathermolysis, the presence of new-formed n-alkanes in the composition of Ekaterinovskoe oil are clearly observed by mass-fragmentgram of m/z =85 (Figure 4c). Moreover, the increase in the products of experiments by new-formed light alkyl-tri-methyl-benzol content, among which arilizoprenoids are well identified on m/z = 133 is detected (Figure 5c). According to the data presented in article [38], the hydrocarbons containing long alkyl substitutes of isoprenoid structures look like isoprenoid alkanes with normal structures. The changes in molecular composition of these hydrocarbons reflect in the values of aryl isoprenoid index (AIR) [38], which is defined as a ratio of total aryl isoprenoid (C13-C17) content to the sum of their high molecular homologues (C18-C22) content. For Ekaterinovskoe oil the value of given parameter increases almost by 4 times: from 0.17 to 0.69. This is due to formation of more light homologues of C13-C17 compositions as in case of n-alkanes, which were almost not detected in initial oil. It is believed that catalytic aquathermolysis of given oil results to intensive destruction of high molecular aromatic and naphtene-aromatic compounds, which are related with the origin of initial organic matter. Olimpiadovsky oil of the paraffinic A1 type, unlike Ekaterinovsky oil, contains a wide homological series of n-alkanes with C12-C35 compositions. Only the absence of light fractions brings it into a class of heavy oils, while by a genotype this oil is similar with the light oils of Tatarstan’s depth horizons [22]. In 12 ACS Paragon Plus Environment

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products of experiments of this oil it is possible to note an increase in relative content of solid n-alkanes. Such an increase can be due to destruction of the long alkyl chains from asphaltenes and resins, as well as their detachment from asphaltene surfaces or solvation shells of resins and asphaltenes, where they could exist in occlude condition, from which they are released under hydrothermal influences [37]. The presence of newly-formed n-alkanes in the composition of the Ekaterinovsky oil after the catalytic aquathermolysis is more visible from the mass-fragmentograms at m/z 85 given in Figure 5c. In addition, an increase of content of newly-formed light alkyl trimethyl benzenes in the products of experiments is pronounced. Among them aryl-isoprenoids at m/z 133 are well identified (Figure 6c). According to the work [38], these are hydrocarbons containing long alkyl substituent of an isoprenoid structure similar to isoprenoid alkanes of a regular structure. Changes in the molecular composition of the abovementioned hydrocarbons reflect the values of the aryl-isoprenoid index (AIR) [37], which represents the ratio of the sum of aryl-isoprenoids of C13-C17 compositions to the sum of their high-molecular homologs of C18-C22 structure. The value of this indicator for aryl-isoprenoid increases almost by 4 times, from 0.17 to 0.69 in the products of experiments of Ekaterinovsky oil. This is because of the formation of lighter homologs of C13-C17 structure, which were practically absent in the initial oil as well as n-alkanes. It is believed that catalytic aquathermolysis of the given oil results to the destruction of high-molecular aromatic and the naphthene-aromatic compounds connected by the origin with an initial OM [34]. The considerable prevalence of light aryl-isoprenoid of C13-C17 compositions over their high-molecular homologs in the initial paraffinic Olimpiadovsky oil, (Figure 6b) what is confirmed by the AIR index (2.82), is very attractive. It indicates that this oil suffered high-temperature processes in its geological history. The hydrothermal-catalytic influences on the given oil in the laboratory conditions leads to an increase in its high-molecular aryl-isoprenoid of C22 (and more) 13 ACS Paragon Plus Environment

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composition, what in turn the AIR index decreases (Figure 6d) to the quantity of 1.02. It shows a detachment of aromatic fragments with long aliphatic isoprenoid chains in the conditions of this process. According to EPR analysis asphaltenes - products of a catalytic aquathermolysis of heavy oils, irrespective of their initial type, are characterized by the high content of paramagnetic centers (Figure 7).This is confirmed by the conduction of destruction processes, as a result of which free radicals are formed. In addition, redistribution of hydrogen protons among the components of reaction systems and rock minerals are able to hydrogenate unsaturated bonds. The authors of article [3] indicate that in the same conditions a hydrogen evolves, which participates in hydrogenation of heavy oil. In asphaltenes of Ekaterinovsky oil the relative concentration of free radicals (R*) increases after experiments by 1.3 times (1297 against 710 a.u.) while decreasing tetravalent vanadium (V4+) concentration (from 179 to 151 a.u.), which is a part of the vanadyl-porphyrin complexes. It leads to the increase in value of an R*/V4+ from 3.97 to 8.59. Asphaltenes of Olimpiadovsky oil differ in smaller concentration of V4+ and higher concentration of R*. After experiments, higher concentration of R* is observed, as well as in asphaltenes of Ekaterinovsky oil and the value of an R*/V4+ increases from 10.55 to 17.01. According to the results of X-ray fluorescence analysis the solid sorbent – clay rocks contain several microelements: Ti, Cr, Mn, Ni, Rb, Sr, Zr, Ba, La, Ce, Nd and Fe (Table 3). However, the composition of rocks after catalytic processes of heavy oil and its extraction from rocks revealed the significant concentration of microelements like Fe, Co and Cu, which were not observed in initial clays. This justifies the adsorption of catalyst metals on rock surfaces. As it was previously mentioned [14], the adsorption of metals on rocks provides to reduce the catalyst concentration and to realize the conception of heterogeneous catalysis in reservoirs. This approach is applied in CAPRI technology without introduction of heterogeneous catalysts around production wells. 14 ACS Paragon Plus Environment

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4. CONCLUSION In this study, the model experiments on the conversion of different oil types in the presence of catalyst and rock minerals were conducted. The temperature of treatment was 300°С, and the reactions were carried out in CO2 environment. The results of experiments revealed the increase in saturate fraction content and decrease in resin and asphaltene ones. The main difference in conversion of various types of oils is in distinct activation degree of destruction reactions in C-C, C–N, C–O, C–S bonds. The destruction of high molecular components provides particular compositions of experimental products. This reflected the group and structural composition, as well as mass distribution of n-alkanes and arylisoprenoids. In the aquathermolysis of the heaviest B1 type of oil (Ekaterinovskoye reservoir) the detachments of more short alkyl substituents were observed. As a result, the low molecular n-alkanes and arylisoprenoids were formed. In contrast, in case of paraffinic oil of A1 type (Olympiadovskoye reservoir), the same experimental conditions provided the detachment of long alkyl chains. Thus, the high molecular n-alkanes were formed. Overall, catalytic aquathermolysis could be a perspective process for the conversion of heavy oil in productive reservoirs. However, the development and application of new steam assisted gravity drainage technologies should consider the specific compositional characteristics of various types of oil and possible products of their conversion in case of catalytic aquathermolysis.

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Notes The authors declare no competing financial interest.


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ACKNOWLEDGMENT. The work is performed according to the Russian Government Program of Competitive Growth of Kazan Federal University.

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Figure 1. Diagram of the mass loss of the rock samples: rock samples before (brown) and after hydrothermal experiment (russet); after hydrothermal experiment and extraction (green)


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a)

b)

c)

d)

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Figure 2. IR spectra of Initial oils and Experimental products: Ekaterinovsky oil before (а) and after (c) thermal-catalytic treatment; Olimpiadovsky oil before (b) and after (d) thermal-catalytic treatment


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a)

b)

c)

d)

Figure 3. IR spectra of Initial oil Asphaltenes and Experimental products Asphaltenes: Ekaterinovsky oil before (а) and after (c) thermal-catalytic treatment; Olimpiadovsky oil before (b) and after (d) thermal-catalytic treatment


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a)

b)

c)

d)

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Figure 4. GC-MS chromatograms (TIC = total ion chromatography) of saturated hydrocarbon fraction of Initial oil and Experimental products: Ekaterinovsky oil before (а) and after (c) thermal-catalytic treatment; Olimpiadovsky oil before (b) and after (d) thermal-catalytic treatment. С10-С30 – n-alkanes, Pr – pristane and Ph – phytane


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а)

b)

c)

d)

Figure 5. GC-MS chromatograms (m/z 85 = n-alkanes and hopanes) of saturated hydrocarbon fraction of Initial oil and Experimental products: Ekaterinovsky oil before (а) and after (c) thermal-catalytic treatment; Olimpiadovsky oil before (b) and after (d) thermal-catalytic treatment. С10-С30 – n-alkanes, Pr – pristane and Ph – phytane


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a)

b)

c)

d)

Figure 6. GC-MS chromatograms (m/z 133 = aryl isoprenoids) of saturated hydrocarbon fraction of Initial oil and Experimental products: Ekaterinovsky oil before (а) and after (c) thermal-catalytic treatment; Olimpiadovsky oil before (b) and after (d) thermal-catalytic treatment


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а)

b)

Figure 7. EPR spectra Ekaterinovsky asphaltene (a) and Olimpiadovsky asphaltene (b) before (1) and after (2) thermal-catalytic treatment


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Table 1. SARA analysis of the Oil before and after Experiments №

* group composition, wt %

Objects

S

A

R

Asp

Ekaterinovsky oil, Type B2 1

Initial

25.91

22.59

35.10

16.40

2

After experiment

33.34

28.47

23.61

14.58

Olimpiadovsky oil, Type А1 1

Initial

44.98

21.52

28.16

5.34

2

After experiment

58.77

27.96

7.61

5.66

*S – saturated hydrocarbons; A – aromatic hydrocarbons; R - resins; Аsp – asphaltenes.

Table 2. IR-analysis of the Oils and Asphaltenes №

Optical density at wavenumber (λmax), sm-1 1740 1710 1600 1465 1380 1030 720

1 2

0.004 0.110

0.041 0.350

0.198 0.308

1.996 2.000

0.886 0.947

1 2

0.171 0.179

0.460 0.757

0.528 0.329

1.992 1.996

1.030 1.000

С1

Spectral coefficients С2 С3 С4

С5

Ekaterinovsky oil 0.658 0.141

0.167 0.278

2,71 3.10

0.02 0.17

0.44 0.47

4.90 3.42

0.33 0.07

1.46 0.66

0.23 0.38

0.52 0.50

2.63 4.55

0.08 0.22

0.08 0.15

0.38 0.55

1.63 1.23

0.42 0.10

0.36 0.41

0.53 0.47

1.12 1.03

0.23 0.48

Olimpiadovsky oil 0.163 0,437

0.361 0.498

Ekaterinovsky asphaltene 1 2

0.106 0.084

0.160 0.304

0.521 0.989

1.996 2.000

0.760 1.103

0.836 0.201

0.160 0.479

5.77 8,91

Olimpiadovsky asphaltene 1 2

0.285 0.791

0.722 0.817

1.201 1.114

1.996 2.000

1.065 0.947

0.464 0.962

0.278 0.198

4.32 5.63


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Table 3. Elemental Composition of Kaolin before and after Experiments Content elements, wt % Kaolin after steam Kaolin after steam treatment in the treatment in the Elements presence of presence of Initial kaolin catalyst with catalyst with Ekaterinovsky oil Olimpiadovsky oil Ti 0.3010 0.3427 0.4053 Cr 0.0615 0.0110 0.0208 Mn 0.0322 0.0166 0.0151 Ni 0.0053 0.0114 0.0480 Rb 0.0063 0.0071 0.0092 Sr 0.2113 0.2382 Y 0.0037 0.0036 Zr 0.0081 0.0123 0.0130 Ba 0.0256 0.0216 0.0283 La 0.0037 0.0037 Ce 0.0093 0.0071 0.0101 Nd 0.0043 0.0040 Fe* 2.8627 4.9167 4.0949 Co* 0.0376 0.0537 Cu* 0.0714 0.0180 *The elements presented in both initial kaolin and catalyst


Conversion of heavy oil with different chemical compositions under

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