Interfacial film properties of asphaltenes and resins

Interfacial film properties of asphaltenes and resins have been studied by interfacial shear viscosity measurements. The results show that the structure of the asphaltene film at the interface between oil and water is changed from two-dimensional to three-dimensional network as the concentration of the asphaltene at the interface increased. The film can be divided into three types namely expanded liquid film, condensed liquid film and solid-like three-dimensional network film. Furthermore, the structures of the interfacial films formed by asphaltene molecules and asphaltene particles are different and the strengths of these films are also different. The adsorption and migration processes of asphaltene molecules and migration process of asphaltene particles at the interface are different.     

Kinetic modeling of hydrocracking of heavy oil fractions: A review

An exhaustive review of the scientific literature on kinetic modeling of heavy petroleum fraction hydrocracking is reported in this paper. Kinetic models for hydrocracking of model compounds were not analyzed. The review includes models based on the lumping technique, continuous mixtures, structure oriented lumping, and single event models. Experimental data, reaction networks, main characteristics of kinetic approaches, and kinetic parameter values are also reported. In some cases when detailed experimental data were available, kinetic parameters were re-estimated and some differences were found in comparison with original reported values. One representative model of each kinetic approach was selected, and parameter estimation was done with reported experimental values in order to establish the capability and accuracy in the prediction of conversion and product yields. Advantages and disadvantages of the models are discussed in terms of their capability to predict detailed product composition, difficulty for parameter estimation, dependency of rate coefficient with feed properties, and required experimental data.     

Kinetics of asphaltenes conversion during hydrotreating of Maya crude

The kinetics of asphaltene conversion was studied during the hydrotreating of Maya heavy crude oil. Experimental tests were conducted in a pilot plant at the following reaction conditions: total pressure of 70–100 kg/cm², liquid hourly space-velocity (LHSV) of 0.33–1.5 h⁻¹, and reaction temperature of 380–420 °C at a constant hydrogen-to-oil ratio of 5000 ft³/bbl. A commercial NiMo/Al₂O₃ catalyst was used in all experiments. Asphaltenes were precipitated from Maya crude and from hydrotreated products in a Parr Batch Reactor at 25 kg/cm² and 60 °C with n-heptane as solvent. Asphaltene hydrocracking data were used to estimate reaction orders and activation energy using a power-law model, and the average absolute error between experimental and calculated concentrations of asphaltenes was found to be less than 5%.     

沥青质和胶质对辽河稠油乳状液破乳的影响

针对辽河曙光稠油乳状液粘度大、破乳难、破乳温度高等问题,以曙光稠油为研究对象,从中分离出沥青质和胶质,用傅里叶变换红外光谱法分析其主要官能团,考察沥青质和胶质对稠油乳状液粘度及破乳效果的影响。测定了不同含量胶质、沥青质对稠油油／水界面张力的影响。结果证实,沥青质比胶质含有羟基多,分子间氢键作用强烈,更容易造成原油粘稠。随着叫（胶质）、训（沥青质）升高,稠油乳状液脱水率降低,w（沥青质）超过2．1％,或w（胶质）超过32％时,稠油乳状液的破乳十分困难。w（胶质）、w（沥青质）的增高会使破乳剂水溶液与原油的界面张力增大,w（沥青质）增加0．7％比叫（胶质）增加7％原油的界面张力升高还要大,所以训（沥青质）的增加对油水界面张力影响更大。     

Kinetic modeling of the hydrotreatment of light cycle oil and heavy gas oil using the structural contributions approach

The kinetics of the hydrodesulfurization of light cycle oil (LCO) and heavy gas oil (HGO) over a CoMo/Al₂O₃ catalyst were investigated in a perfectly mixed flow reactor with stationary basket of the Robinson-Mahoney type at temperatures of 330, 310 and 290 °C, H₂/HC molar ratios of 2.8, 3.6 and 7.2 and a pressure of 65 bar. Hougen-Watson type rate equations were derived for the conversion of dibenzothiophene, substituted (di)benzothiophene and their products. To avoid having to deal with a huge number of model parameters, a methodology based upon structural contributions was applied. In the absence of own kinetic data on key components a number of kinetic and adsorption parameters were taken from published work on a very similar catalyst. For a given value of H₂/HC only a small number of experiments was required to determine the value of the very complex denominators DEN_σ and DEN_τ appearing in the rate equations for the hydrodesulfurization of LCO and of HGO and of their evolution with the conversion of the feedstock. With the rate equations constructed in this way the calculated total conversion of DBT, its conversion into biphenyl and into cyclohexylbenzene were in excellent agreement with the experimental values.     

Thermal cracking and combustion kinetics of asphaltenes derived from Fosterton oil

Thermal behavior of crude oil (Fosterton) asphaltenes mixed with reservoir sand was investigated using thermogravimetric analysis (TGA), in nitrogen and air atmospheres for different heating rates up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton asphaltenes and the coke derived from the asphaltenes. The parameters studied were heating rate (10, 15 and 20 °C min^− 1) and the type of purge gas (N₂ and air) employed for the process of thermal degradation of asphaltenes. Distributed activation energy model (DAEM) has been applied to study the asphaltene pyrolysis kinetics. It was observed that the activation energy was distributed from 46.16 to 72.17 kJ/mol, for the conversion range of 0.1 to 0.4. The general model for nth order reaction was used to obtain the kinetic parameters of coke oxidation reaction from the TGA data. From the model, the calculated activation energy, E, was 93.46 kJ/mol and the pre-exponential factor was 9.59 × 10⁵ min^− 1 for the coke combustion. The apparent order of combustion reaction gradually increased from 0.7 to 0.8 for different temperatures.     

Interfacial tension behavior and ESR properties of asphaltenes derived from heavy oil

Asphaltenes extracted from Lloydminster heavy oil (from Saskatchewan, Canada) were separated by sequential elution solvent chromatography (SESC) using ten different organic solvents. The fractions so obtained were dissolved in toluene and then examined for their interfacial tension (IFT) behavior against 0.1 wt.% sodium hydroxide solution. It was found that only about 40% (by weight) of the original asphaltenes contained species which were capable of lowering IFT against the alkaline solution. Multi-functional phenolic and other polar compounds were considered to be the components most likely responsible for the observed interfacial activity. Electron spin resonance measurements showed that the individual fractions contained varying concentrations of free radicals and VO²⁺ ions. However, no direct correlation between the content of either of these two species and the interfacial tension could be detected.     

The study on composition changes of heavy oils during steam stimulation processes

Using the heavy oils obtained from Liaohe oilfields in China, we have conducted the aquathermolysis reaction in laboratory at 240 °C. The results showed that Liaohe heavy oils have been undergoing visbreaking in the process of steam-drive and steam stimulation. After reaction with steam, the viscosity of the heavy oil was reduced by 28-42% and the amount of the saturated and aromatic hydrocarbons increased, while resin and asphaltene decreased. The gas partition chromatography showed that the accumulated amount of carbon numbers increased, after reaction, the accumulated amount of carbon numbers less than C₂₀ are 38.79-53.92%, and before reaction they are 13.30-20.92%. The results provided the basic data for heavy oil recovery by in situ catalytic method in production of heavy oil in oilfields.     

Recovery of heavy oil from contaminated sand by using exfoliated graphite

Heavy oil was recovered from contaminated sand through capillary suction into exfoliated graphite with differentpacked densities by using model sands, alumina powders, with different particle sizes. For efficient recovery it was important to have an appropriate combination of average size of sand particles and packed density of exfoliated graphite. Pumping of heavy oil into exfoliated graphite occurs as a balance in an attracting capillary force between exfoliated graphite and sand, the former being stronger than the latter because of the hydrophobic nature of the surface of graphite.     

Reburning and burnout simulations of natural gas for heavy oil combustion

Reburning and burnout simulations were carried out through PLUG code of CHEMKIN-III using a reduced mechanism, in order to determine preliminary experimental parameters for achieving maximum NO_x reduction to implement the reburning technology for heavy oil combustion in pilot scale equipments in Brazil. Gas compositions at the entrance of the reburning zone were estimated by the AComb program. Simulations were performed for eight conditions in the usual range of operational parameters for natural gas reburning. The maximum NO reduction (ca. 50%) was reached with 10 and 17.5% of power via natural gas and 1.5 and 3.0% O₂ excess, respectively, at 1273 K. The model predicts 250 ppm of NO, 50 ppm of CO and air mass flows in the range of about 50-130 kg/h for burnout.     

Behaviour of heavy metals in the partial oxidation of heavy fuel oil

The behaviour of heavy metals in the partial oxidation of heavy fuel oils under a pressure of up to 100 bar (10 MPa) has been investigated. The tests were carried out in a 5 MW HP POX (High Pressure Partial Oxidation) test plant, that is operated by the IEC (Department of Energy Process Engineering and Chemical Engineering, TU Bergakademie Freiberg) in cooperation with Lurgi GmbH. In several test campaigns preheated oil with a viscosity of up to 300 cSt (= 300 mm²/s) at the burner inlet has been gasified. The heavy metals nickel Ni, iron Fe and vanadium V occur in heavy residual oils in considerable concentration and may seriously impact the gasification itself and the synthesis gas conditioning and usage. While iron is largely recovered in the gasification residue, the recovery rates of nickel and vanadium depend on the process conditions. Volatile nickel compounds were detected in the raw synthesis gas. It was found that an incomplete carbon conversion enables the capture of nickel Ni and vanadium V in the solid residue phase and can thus mitigate the problem of volatile metal compounds in the raw synthesis gas.     

Precipitation, fractionation and characterization of asphaltenes from heavy and light crude oils

Asphaltenes of Maya and Isthmus crude oils were precipitated, fractionated and characterized in this work. Isolation of asphaltenes was performed by following the ASTM D3279 method, which uses n-heptane for solvent precipitation. Asphaltenes were separated into three fractions by Soxhlet extraction with a binary solvent system of toluene and n-heptane. C, H, O, N, S, and Ni and V contents were determined in asphaltenes and in their fractions by elemental analysis and atomic absorption, respectively. VPO aggregate weight and NMR measurements were also performed in all samples. Important differences in properties of unfractionated asphaltenes and asphaltenes fractions were observed. Some of these differences were attributed to impurities in the unfractionated asphaltenes.     

The use of coal liquefaction catalysts for coal/oil coprocessing and heavy oil upgrading

The catalytic hydrogenation of heavy oil and mixed coal-heavy oil (coprocessing) systems has been the focus of a recent study at the Federal Energy Technology Center (FETC). The intent of this effort was to extend the use of coal liquefaction technologies to heavy oil upgrading and coprocessing systems. Specifically, new dispersed molybdenum-based catalysts developed at FETC and a novel silica-doped hydrous titanium oxide (HTO : Si)-supported NiMo catalyst developed at Sandia National Laboratories (SNL) were tested in these systems. The results indicate the potential of coal liquefaction catalysts for use in coprocessing and heavy oil upgrading. High conversions of coal–oil mixtures were observed with dispersed catalyst loadings as low as 100 ppm Mo. Similar results were observed in heavy oil systems. Also, the novel NiMo/HTO : Si catalyst was at least as effective as commercially-available supported catalysts (e.g. Amocat 1C) for conversion of high boiling point material to distillable products and aromatics removal.     

Review of processes for downhole catalytic upgrading of heavy crude oil

Unlike conventional refinery processing, downhole upgrading involves implementing catalytic processes in oil-bearing geologic formations. In this way impurities contained in heavy crude oil can possibly be left in the ground or easily separated during oil production, providing an improved crude oil feed for refineries. Additionally, value or viability can be added to an otherwise uneconomic or remote heavy oil deposit. In order to successfully produce improved quality oil via a downhole upgrading project, several processing steps are anticipated: placement of catalysts into an appropriate downhole location, mobilization of reactants over the catalyst bed, and creation of processing conditions necessary to achieve a reasonable degree of catalytic upgrading. Each of these steps has been proven by past application; their combination into a unified below-ground process remains problematic. Downhole processing differs from surface processing in that brine, high steam partial pressures and low hydrogen partial pressures need to be accommodated in the downhole setting. There are no reports of significant downhole catalytic upgrading of crude oil, although examples of thermal upgrading are noted. However, available technology should be amenable to conducting a successful process. Upgrading of heavy crude oil at anticipated downhole processing conditions has been successfully proven in the laboratory. Recently published literature with immediate pertinence to the problems of downhole catalytic upgrading is reviewed with the goal of stimulating research and providing directions for future investigations.     

Liquid Chromatographic fractionation of oil-sand and crude oil asphaltenes

Asphaltenes extracted from Alberta oil sands (Athabasca, Cold Lake, and Peace River) and crude oils (Taber South and Fenn-Big Valley) were fractionated by sequential elution solvent chromatography (SESC) involving 10 organic solvents on a silica column. Athabasca asphaltenes and SESC fractions were further studied by elemental analysis, i.r., u.v., and n.m.r. spectroscopy. Incomplete extraction of maltenes from the oil-sand bitumens increased the yields of the first two SESC fractions, the saturates and aromatics, of oil-sand asphaltenes relative to the crude oil asphaltenes. About 55 wt% of the asphaltenes elute in fractions 3–5. Two distinct molecular types are present in the asphaltenes; namely, lower functionality species with lower heteroatom content and the higher functionality species with higher heteroatom content. Compounds eluting in fractions 3–10 are predominantly polynuclear aromatics with alkyl substituants and probably bridged by cycloalkanes. The extent of bridging as well as the location, number and type of heteroatoms determines the fraction in which each compound appears. Complexity of compounds eluting increases with time: earlier fractions are composed of smaller-size polynuclear aromatic centers and contain heteroatoms in predominantly ring locations, whereas later fractions contain a larger proportion of complex species and more functional heteroatom groups.     

Modification of a thermodynamic model and an equation of state for accurate calculation of asphaltene precipitation phase behavior

In this study, DPTG (Dashtizadeh-Pazuki-Taghikhani-Ghotbi) equation of state has been modified for calculation of phase behavior of fluids and solubility parameter. The accuracy of the modified EOS has been proved by estimation of the properties of some hydrocarbons such as densities of methane and condensate gases, vaporization enthalpy, sublimation pressure, compressibility factor and comparison of the obtained results with the results of the present equations of state such as NJ (Nasrifar-Jalali), ZMJL (Zhi-Meiren-Jun-Lee) and PR (Peng-Robinson). Then, the Flory-Huggins model has been modified and asphaltene precipitation phase behavior at different ratios of solvents in the crude oil has been predicted by the modified EOS and the developed Flory-Huggins model. Comparison of the obtained results with the experimental data of asphaltene precipitation and the calculated ones by the main Flory-Huggins model shows the accuracy of the developed model.     

Variation of physical properties during transesterification of sunflower oil to biodiesel as an approach to predict reaction progress

Biodiesel as a pure, non-toxic, biodegradable and renewable alternative for fossil diesel fuel has attracted much attention in recent decade. Thus, demands for researches in this field are growing up every day. In order to simplify the mentioned research a new method was introduced to determine progress and end point in transesterification of sunflower oil to biodiesel (methyl esters) by the use of physical property variation during reaction. This method can be replaced by expensive and time-consuming, quantitative analysis stage. In the present work first transesterification of sunflower oil at 65 °C with MeOH to oil molar ratio of 6:1 and 1 wt.% of KOH as catalyst under vigorous mixing at different durations was carried out to determine how conversion and physical properties change. It was concluded that this reaction proceeded over 90% in 5 min and most of the changes occurred in this short period. In the second step, to verify physical properties variation in all ranges, six blends of produced biodiesel and sunflower oil were prepared in different wt.%, as incomplete reaction mixture. Finally appropriate functions were fitted on the extracted data and were evaluated. Refractive index and specific gravity were selected as good physical properties to predict reaction progress.     

稠油化学降黏实验研究

以塔河某稠油为样,在优化条件下进行降黏实验研究。试油40g,降黏剂WWS质量分数0.4%,碳酸钠质量分数0.2%,加水量20mL(矿化度5 000mg/L),实验温度65℃,搅拌下反应80min,稠油的黏度从65℃时的5 620mPa.s降至180mPa.s,降黏率达到96%以上,改善了稠油的流动性。     

Hydrotreatment of heavy oil from a direct coal liquefaction process on sulfided Ni-W/SBA-15 catalysts

A series of Ni-W catalysts supported on SBA-15 with different pore sizes were prepared by incipient wetness impregnation method and characterized by N₂ adsorption-desorption and X-ray diffraction. The hydrogenation of heavy oil (distillation temperature: 320-340 °C) derived from the direct coal liquefaction process using Shengli coal in the presence of sulfided Ni-W/SBA-15 catalysts with different pore sizes were evaluated at 400 °C and initial H₂ pressure of 5.0 MPa. The results showed that the catalyst preparation method and the pore size of the support had a significant influence on the Ni/W crystallite size, hydrodenitrogenation (HDN) and hydrodearomatization (HDA) activities of coal-derived heavy oil. The larger pore could cause the Ni-W/SBA-15 to form larger Ni-W crystallite. The catalysts with largest pore in the range studied displayed highest HDN and HDA activities for upgrading of the coal-derived heavy oil.     

Effect of wax inhibitors on pour point and rheological properties of Iranian waxy crude oil

A variety of techniques have been employed in order to reduce problems caused by the crystallization of paraffin during the production and/or transportation of waxy crude oil. Flow improvers are used extensively to increase the mobility of crude oil. In this study, the influence of the ethylene-vinyl acetate copolymer (EVA), as flow improver, with different ranges of molecular weight on the viscosity and pour point of five Iranian waxy crude oils was evaluated. Five types of Iranian waxy crude oil were selected based on their similar wax (> 10%) but different asphaltene contents. Also, the effect of asphaltene content on the performance of this flow improver was studied. The rheological behavior of these crude oils, with middle range API gravity, in the absence/presence of flow improver was studied. The rheological data cover the temperature range of 5 to 40 °C. The results indicated that the performance of flow improver was dependent on the molecular weight and the asphaltene content. For crude oil with low asphaltene, higher molecular weight flow improvers are the best additive and lower molecular weight flow improvers showed good efficiency for crude oil with high asphaltene content. Addition of small quantities of asphaltene solvents such as xylene (1 wt.%), alone or in combination with flow improver, can improve viscosity of crude oil with high asphaltene content.