Heavy Crude Oil Fractions Research Articles

Qualitative and Quantitative Evaluation of Sulfur-Containing Compound Types in Heavy Crude Oil and Its Fractions

Detailed molecular analysis of complex mixtures such as crude oil and its fractions has been successfully covered by a number of groups during the past two decades. On the other side, the most glaring need is some type of method that allows quantitative analysis of a single class, compound species, or even individual compounds. Here, the problem is being complicated by the complexity of the sample and the need for individual response factors necessary for the analysis of single compounds in almost all analytical methods. This can be circumvented by using a method with uniform response like inductively coupled plasma-mass spectrometry. Sulfur is one of the most important heteroelements present in crude oil and its products due to stringent regulations. Quantification of sulfur by means of mass spectrometry has always been a challenging task. Here, we present the combination of a sulfur-selective chromatographic separation of crude oil and its fractions on a Pd-coated stationary phase with two-dimensional detection. Qualitative analysis by ultrahigh-resolution Orbitrap mass spectrometry allows a detailed understanding of individual compositions after chromatographic separation, while the quantitative data from inductively coupled plasma tandem mass spectrometry details the quantities of each part of the chromatogram. The combination of the results from both methods allows assigning three different types of sulfur species and their quantitative determination in extremely complex heavy crude oil fractions.

Vanadium and nickel distributions in Pentane, In-between C5-C7 Asphaltenes, and heptane asphaltenes of heavy crude oils

After selective solvent extraction, the volatile and non-volatile vanadium and nickel distributions for two Venezuelan heavy crude oils and the NIST Standard Reference Material SRM 8505 were determined for the Entrained n-pentane (C5) maltenes, In-between C5-C7 asphaltenes, and n-heptane asphaltenes. The fractions were analyzed via the asphaltene solubility profile, size exclusion chromatography (SEC), High-Temperature Gas Chromatography coupled with Inductively Coupled Plasma Mass Spectrometry (HTGC-ICP-MS), and atmospheric pressure photoionization Fourier-transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS). Results showed that petroleum elution is strongly correlated to high hydrogen deficiency and increased heteroatom levels. The solubility decreased in the following order: Entrained C5 Maltenes, In-between C5-C7 asphaltenes, and C7 asphaltenes. Qualitative HTGC-ICP-MS shows that 51V traces of the first two asphaltene fractions showed a bimodal (Venezuelan crude oil 1 and NIST SRM 8505) or a multimodal distribution (Venezuelan crude oil 2). On the other hand, the 51V signal intensities for C7 asphaltenes were the lowest among all samples studied. FT-ICR MS revealed that the chemistry of vanadyl and nickel porphyrins is multimodal in terms of DBE. N4O1V1 and N4O2V1 classes exhibited abundant homologous series with DBE values of ≤22; when sulfur was incorporated, e.g., N4O1S1V1 class, the DBE increased by 4–6 units. Ni-containing porphyrins showed two major homologous series, pointing toward a bimodal chemical nature. We hypothesized that this compositional feature could be why the bimodal and multimodal distributions of boiling points were found in the studied heavy crude oil fractions.

Construction and practical application of a novel zeolite catalyst for hierarchically cracking of heavy oil

The conversion of the heavy fractions of crude oil into transportation fuels and chemical feedstocks is still a severe challenge for fluid catalytic cracking (FCC) technology, in which geometrical parameters of the catalyst are of key importance to the accessibility for reactant and product molecules to travel through the pore space. Here a new core-shell zeolite catalyst with hierarchical pore network from macro- via meso- to micropores is developed by controlling overgrowth of another zeolite shell on the surface of a commercial Y-zeolite. The zeolite shell is a distinctive nano ZSM-5 crystals. The core-shell zeolite catalyst has a high thermal and hydrothermal stability because of high crystallinity, which can meet the industrial requirements. More importantly, the heavy oil can be cracked by the designed zeolite catalyst step-by-step into the required products. The meso- and macroporous shell facilitates pre-cracking the large molecules in heavy oil into moderate ones which can directly diffuse into the micropores of the Y-zeolite to be cracked selectively into the desired products. Both the pore structure network and acid sites distribution of the core-shell zeolite catalyst in the FCC processing are completely harmonious. As a practical example, the catalytic cracking of VGO heavy oil is actualized over the new catalyst. The results showed that the conversion of heavy oil and the yield of gasoline increased by 1.8 wt% and 8.9 wt% respectively, LPG decreased by 6.9 wt%, iso-paraffins and olefins in gasoline fraction increased by 5.21 wt% and 6.31 wt% respectively, aromatics decreased by 11.55 wt%, because of the graduated cracking in core-shell zeolite and returned isomerization in nano ZSM-5, compared with commercially industrial FCC catalyst.

Impact of H-Bonds and Porphyrins on Asphaltene Aggregation As Revealed by Molecular Dynamics Simulations

The presence of metalloporphyrins alongside asphaltenes in heavy fractions of crude oil is a key issue in petroleum exploration and upgrading. These compounds are also expected to display interfacial activity in water/toluene mixtures, but the origin of this phenomenon remains uncertain. In this work, we use molecular dynamics simulations to investigate complex asphaltene mixtures constituted of 10 different molecules, under also multifaceted solvation conditions (toluene/n-heptane/water). We add nickel and vanadium (under the form of vanadyl) porphyrins with occasionally grafted polar lateral chains, in these mixtures. The aggregation behavior and interaction with water molecules (as a model to have insights from the interfacial activity of such molecules) are intimately linked to the type of porphyrin and to the molecular properties of the asphaltenes (mainly the presence of polar lateral chains). Vanadium porphyrins, even without polar lateral chains, can form H-bonds that might contribute to their pre...

Vanadium and nickel deposition on FCC catalyst: Influence of residual catalyst acidity on catalytic products

Abstract The alteration of catalytic activity and selectivity of the cracking catalyst by porphyrinic metallic elements present in heavy crude oil fractions is a subject that requires serious attention. In this study, the effects of the two most deleterious of the metals (vanadium and nickel) and how they shift the product selectivity of the catalytic cracking are discussed, with a key focus on the catalytic behavior of the residual acidity consequent upon metal deactivation. Increasing loadings of vanadium and nickel were deposited on the FCC catalyst and subjected to a simulated FCC regeneration unit conditions. It is found that at loadings greater than 0.3 wt%, vanadium is 4–5 times as destructive as nickel on the crystalline structure of the catalyst. Catalytic evaluation results revealed correlations between residual surface acidity, catalyst activity and amount of coke formed on the catalyst at a constant catalyst-to-oil ratio (CTO). This result is in slight contrast with the widely reported enhanced coking activity of vanadium on FCC catalyst consequent upon dehydrogenation reaction. An alternative coke formation pathway based on the residual catalyst acidity is advanced for the observed coking behavior of high vanadium laden catalyst. In addition, a vanadium control measure relying on the acid-base chemistry and hydrothermal stability of a mixed-metal oxide is demonstrated as an effective method to limit the mobility of vanadium into the framework of the catalyst, the action that initiates vanadium deleterious effects. This study is expected to renew interest in the research on the coking behavior of metal poison catalysts.

Structural Changes in Deactivated Fluid Catalytic Cracking Catalysts Determined by Electron Microscopy

Fluid catalytic cracking, an important process in the chemical industry, uses porous composite particles to convert the heavy fractions of crude oil into transportation fuels and chemical feedstocks. The employed particles, a spherical composite of zeolite and clay, decrease in catalytic activity during long-term operation, which demands their continuous replacement. To extend the lifetime of these catalysts, it is essential to understand the structural changes that cause the observed decrease in activity. By using a range of electron microscopy and elemental mapping techniques, the structural and chemical makeup of pristine and progressively deactivated catalyst particles were characterized from the micro- to the nanometer scale. Independent of the deactivation degree, the catalyst particles are found to maintain a porous interior structure similar to that of the pristine catalyst. An increasingly dense amorphous silica–alumina envelope enwrapping individual catalyst particles is formed during operation....

A comprehensive investigation of refinery preheaters foulant samples originated by heavy crude oil fractions as heating fluids

A deep understanding of the mechanisms responsible for fouling from both crude oils and their fractions is paramount to ensure efficient energy recovery in heat exchangers of crude preheat trains. In this work, seven samples of fouling deposits, carefully collected from a number of refinery heat exchangers processing vacuum gas oil (VGO) and vacuum bottom (VB) streams in an atmospheric crude preheat train were investigated using a range of characterization techniques with the aim of identifying the underlying mechanisms that led to deposition. Characterization of the deposits included morphological and physical examination, fractionating solubility test, Scanning Electron Microscopy-Energy Dispersive X-ray, Combustion Analysis and X-ray Diffraction. In all samples examined, more than 75 wt% of the deposits were identified as inorganic, with about 50 wt% being FeS. At 270–300 °C, FeO(OH) was also identified to be deposited on the tube surfaces made in Cr steel alloy, where more fouling and less corrosion were evident compared to carbon steel (CS). These observations were found in agreement with recent laboratory studies aimed at identifying the role of temperature and tube material in petroleum corrosion. Furthermore, sulphur crystals were found in several VGO fouling samples. Based on the experimental results obtained, a mechanism was proposed to explain the corrosion fouling phenomenon, considered to be the underlying mechanism affecting the refinery. The mechanism involves naphthenic acid attack to the tubes’ metal surface, decomposition of iron naphthenate, disproportion of iron oxide and sulphidation reactions. The results highlighted the importance of studying deposits formed under industrial conditions, timescales and variation of the deposition process, evidenced by the deposit characteristics, along extensive heat exchanger networks.

Evaluation of PC-SAFT model and Support Vector Regression (SVR) approach in prediction of asphaltene precipitation using the titration data

Asphaltene deposition in porous media, wellbore and surface facilities has been a severe problem in petroleum industry which causes considerable remediation costs annually. Asphaltenes are heavy and polydisperse fractions of crude oil which are insoluble in n-alkanes such as n-heptane. In this work, three Iranian crude oils were prepared for titration experiments with n-pentane, n-heptane and n-dodecane at different solvent ratios and constant temperature. The experimental data were correlated by perturbed chain form of statistical associating fluid theory (PC-SAFT). The association of asphaltene molecules has been considered in this model with adjusting the uncertain parameters (such as association energy and association volume of asphaltene pseudo component) to match the experimental data. PC-SAFT parameters for other non-associating pseudo components have been calculated using the correlations proposed in literature. The present study also evaluated the performance of SVR method as a supervised learning approach in prediction of asphaltene precipitation. Deviation of proposed models has been validated using the statistical evaluation criteria and graphical analysis. The results show that the proposed models have AAD values less than 0.073 and a high potential in prediction of asphaltene precipitation.

Localization and Speciation of Iron Impurities within a Fluid Catalytic Cracking Catalyst.

Fluid catalytic cracking is a chemical conversion process of industrial scale. This process, utilizing porous catalysts composed of clay and zeolite, converts heavy crude-oil fractions into transportation fuel and petrochemical feedstocks. Among other factors iron-rich reactor and feedstream impurities cause these catalyst particles to permanently deactivate. Herein, we report tomographic X-ray absorption spectroscopy measurements that reveal the presence of dissimilar iron impurities of specific localization within a single deactivated particle. Whereas the iron natural to clay in the composite seems to be unaffected by operation, exterior-facing and feedstream-introduced iron was found in two forms. Those being minute quantities of ferrous oxide, located near regions of increased porosity, and impurities rich in Fe3+ , preferentially located in the outer dense part of the particle and suggested to contribute to the formation of an isolating amorphous silica alumina envelope.

Direct Observation of Asphaltene Nanoparticles on Model Mineral Substrates.

The propensity for adherence to solid surfaces of asphaltenes, a complex solubility class of heteropolycyclic aromatic compounds from the heavy fraction of crude oil, has long been the root cause of scale deposition and remains an intractable problem in the petroleum industry. Although the adhesion is essential to understanding the process of asphaltene deposition, the relationship between the conformation of asphaltene molecules on mineral substrates and its impact on adhesion and mechanical properties of the deposits is not completely understood. To rationalize the primary processes in the process of organic scale deposition, here we use atomic force microscopy (AFM) to visualize the morphology of petroleum asphaltenes deposited on model mineral substrates. High imaging contrast was achieved by the differential adhesion of the tip between asphaltenes and the mineral substrate. While asphaltenes form smooth continuous films on all substrates at higher concentrations, they deposit as individual nanoparticles at lower concentrations. The size, shape, and spatial distribution of the nanoaggregates are strongly affected by the nature of the substrate; while uniformly distributed spherical particles are formed on highly polar and hydrophilic substrates (mica), irregular islands and thicker patches are observed with substrates of lower polarity (silica and calcite). Asphaltene nanoparticles flatten when adsorbed on highly oriented pyrolytic graphite due to π-π interactions with the polycyclic core. Force-distance profiles provide direct evidence of the conformational changes of asphaltene molecules on hydrophilic/hydrophobic substrates that result in dramatic changes in adhesion and mechanical properties of asphaltene deposits. Such an understanding of the nature of adhesion and mechanical properties tuned by surface properties, on the level of asphaltene nanoaggregates, would contribute to the design of efficient asphaltene inhibitors for preventing asphaltene fouling on targeted surfaces. Unlike flat surfaces, the AFM phase contrast images of defected calcite surfaces show that asphaltenes form continuous deposits to fill the recesses, and this process could trigger the onset for asphaltene deposition.

Degradation of asphaltenes by two Pseudomonas aeruginosa strains and their effects on physicochemical properties of crude oil

Microbes can enhance oil recovery through the degradation of some heavy fractions of crude oil. Two Pseudomonas aeruginosa strains (Gx and Fx) using crude oil as the carbon source were isolated from oil-contaminated soils. The potential of Gx and Fx for oil displacement was assessed by testing their ability to degrade pure asphalt and crude oil asphaltenes. Approximately ∼10% of pure asphalt and 59–72% of crude oil asphaltenes were degraded using cell-containing fermentation broths. The content of lighter fractions (saturates and aromatics, maximum 11%) increased and the content of heavier fractions (resins and others, maximum 75%) decreased in the degraded oil compared with the controls. The relative quantity of vaporizable fractions (230 °C) increased after treatment, 10% by Gx and 19% by Fx. The oil viscosity (35 °C) was reduced by nearly half from 76.5 m Pa∙s, and ∼90% of oil adsorbed on filter paper was removed after treatment. Gx and Fx produced surfactants with crude oil as the sole carbon source, and the oil-spreading diameter ranged from 15 to 17 cm. In conclusion, biosurfactant-producing P. aeruginosa strains Gx and Fx could efficiently degrade recalcitrant asphaltenes in crude oil and are therefore candidate strains for microbial enhanced oil recovery.

Bioremediation of Heavy Crude Oil Contamination

Crude oil contamination is one of the major environmental concerns and it has drawn interest from researchers and industries. Heavy oils contain 24-64% saturates and aromatics, 14-39% resins and 11-45% asphaltene. Resins and asphaltenes mainly consist of naphthenic aromatic hydrocarbons with alicyclic chains which are the hardest to degrade. Crude oil biodegradation process, with its minimal energy need and environmentally friendly approach, presents an opportunity for bioremediation and as well for enhanced oil recovery to utilize heavy oil resources in an efficient manner. Biodegradation entails crude oil utilization as a carbon source for microorganisms that in turn change the physical properties of heavy crude oil by oxidizing aromatic rings, chelating metals and severing internal bonds/chains between molecules. Biodegradation does not necessarily lower quality of crude oil as there are cases where quality was improved. This paper provides information on heavy crude oil chemistry, bioremediation concept, biodegradation enzymes, cases of Microbial Enhanced heavy crude Oil Recovery (MEOR) and screening criteria towards a better understanding of the biodegradation application. Through the utilization of single microorganisms and consortia, researchers were able to biodegrade single pure hydrocarbon components, transform heavy crude oil fractions to lighter fractions, remove heavy metals and reduce viscosity of crude oil.

Effect of exposure time and crude oil composition on low-salinity water flooding

Rational and systematic approaches to the application of low-salinity water flooding have been slow to develop, due in part to a lack of understanding of the physics concerning oil/brine/rock interactions and uncertainty in assessments of wetting behavior of the rock. This paper provides insight into some of the factors controlling rock wettability during low-salinity water injection. A series of core flood experiments were performed on three crude oil samples with different resin and asphaltene concentrations. Three brine salinities of 122,000, 10,000, and 500ppm were tested. Oil recovery, upstream pressure, and effluent pH were continuously monitored during the experiments. This study confirms that wettability alteration, during low-salinity water flooding, is sensitive to the heavy fractions of crude oil. Crude oils with a lower concentration of heavy ends are less responsive to low-salinity water injection. Additionally, this study indicates that the desorption of polar components is a time-dependent process, and sufficient exposure time between invaded low-salinity water and an in-situ oil/brine/rock system is required to ensure the complete transition from one wetting state to the next.These results add new experimental evidence to the literature that will assist in understanding the complex mechanism of wettability alteration in low-salinity water flooding.

Mechanism of High Stability of Water-in-Oil Emulsions at High Temperature

Thermal flooding by steam injection was a traditional method for exploiting heavy oil. The produced liquid was a highly stable water-in-oil or oil-in-water emulsion in several oilfields. In this work, we focused on studying the effect of high temperature on the stability of an emulsion system involving two typical crude oils (heavy crude oil and light crude oil) and brine. It was impossible to directly measure the interfacial viscoelastic modulus because of the high viscosity of the heavy oil. In order to solve this problem and analyze the contribution of those fractions to the formation of stable emulsions, the heavy crude oil was divided into three cuts: remaining fraction, resin, and asphaltene. The model oils were prepared from the mixture of several heavy crude oil fractions with kerosene:xylene (1:1 v/v) to investigate the high-temperature behaviors of their emulsions. The stability was evaluated through a high-temperature–high-pressure (HTHP) visual pressure–volume–temperature cell, and a temperatu...

Editorial: Microbiotechnology Based Surfactants and Their Applications.

This editorial is an annotation on the exciting research topic “Microbiotechnology based surfactants and their applications” that covers a compilation of original research articles, reviews and mini-reviews submitted by researchers enthusiastically working in the field of biosurfactants.

GM Crops: Safe or Not – the Fear must be Allayed

Microbial conversion of petroleum resins existing in a heavy fraction of crude oil was investigated by native isolated consortia. The heavy oil fraction was taken from an end cut of distillation tower of Abadan refinery in Iran. Several Soil samples were taken from different oil contaminated sites of Abadan oil refinery in Khuzestan province. Seven bacterial consortia were then prepared by enrichment method and were examined for their ability to convert resins. Amongst them, consortium AB6 reduced 37.3% of resins while, aliphatic and aromatic compounds increased by 86.8% and 6.7%, respectively. Three pure cultures were isolated from consortium AB6 which were identified as Serratia sp., Raoultella sp. and Ochrobactrum sp.

Bioconversion of Heavy Hydrocarbon Cuts Containing High Amounts of Resins by Microbial Consortia

Microbial conversion of petroleum resins existing in a heavy fraction of crude oil was investigated by native isolated consortia. The heavy oil fraction was taken from an end cut of distillation tower of Abadan refinery in Iran. Several Soil samples were taken from different oil contaminated sites of Abadan oil refinery in Khuzestan province. Seven bacterial consortia were then prepared by enrichment method and were examined for their ability to convert resins. Amongst them, consortium AB6 reduced 37.3% of resins while, aliphatic and aromatic compounds increased by 86.8% and 6.7%, respectively. Three pure cultures were isolated from consortium AB6 which were identified as Serratia sp., Raoultella sp. and Ochrobactrum sp.

Soil Microbial Degradation of Vacuum Residue

The effect of microbial consortia on the alteration of petroleum residual structure and portions was studied, which can propose an alternative or complementary method for stringent upgrading heavy crude oil methods, which consist of heavy and complex hydrocarbons. Biological processing of petroleum heavy fractions and residua may provide an alternative or complementary process in refining heavy crudes—the dominant refinery feed in the future—with less severe process conditions and higher selectivity to upgrade heavy fractions of crude oil. The primary objective was to observe the ability of an indigenous bacterial consortium taken from a soil bellow the vacuum column contaminated with vacuum residue (VR) for several decades from the Tehran refinery distillation unit, in degradation of residua components. Enrichment with VR, as sole source of carbon and energy, is the selected biosurfactant-producing microbial consortium. The biodegradation of net VR using indigenous consortia from this specific ecosystem was studied. The considered period of biodegradation of these heavy hydrocarbons was remarkably shorter than usual studies. Bacterial growth and VR biodegradation ability of this consortium analyzed with SARA test in 20 days. Studying the inoculum size and aeration effect revealed the significance of oxygen for this consortia activity and the similarity of 7% and 5% inoculation on alteration percentage of alkane, aromatic, and asphaltene and resin in VR. Results study revealed a 30.4%, 6.9%, and 9.4% decrease in the asphaltene, aromatics, and saturated aliphatic contents of VR, respectively, in only 20 days in 30°C at 150 rpm.

Characterization of Saturates, Aromatics, Resins, and Asphaltenes Heavy Crude Oil Fractions by Atmospheric Pressure Laser Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

In this study, a heavy crude oil sample was separated on the basis of solubility and polarity, resulting in saturates, aromatics, resins, and asphaltenes (SARA) fractions. The fractions were analyzed by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled to atmospheric pressure laser ionization (APLI). On the basis of the APLI–FT-ICR MS results, the molecular formulas and their corresponding aromaticity were compared to the bulk crude oil. The maltenes showed almost identical compound class distribution to the bulk sample, while the subfractions of the maltenes denoted unique distributions in compound classes and aromaticity. The aromaticity distributions of the fractions were in good agreement with expectations; however, the resins fraction showed higher aromaticity than the aromatics fraction. The potential of the SARA fractionation method as a sample-simplification tool that allows for a reduction of components present during the measurements was also demonstrated using APLI...

Evaluation of growth, carbazole biodegradation and anthranilic acid production by Pseudomonas stutzeri

The proportion of nitrogenated compounds such as carbazole in heavy fractions of crude oil is higher in Brazil than in other parts of the world. The degradation of this compound by microorganisms has already been described for bacteria such as Pseudomonas stutzeri ATCC 31258. Assays were undertaken to assess the influence of different carbazole concentrations on cell growth, carbazole degradation and the formation of anthranilic acid (an intermediate in the carbazole degradation pathway). The results indicated that there was an accumulation of anthranilic acid in the medium with the higher concentration of substrate (10 g/L), which could be related to the inhibition of Pseudomonas stutzeri growth in an excess of carbazole. With 1 g/L of carbazole, growth was found to be ten times greater (0.37 g dry cell weight/L) and there was no accumulation of anthranilic acid (formation of around 7 mg/L), with complete carbazole degradation after three days.