Polymer solution and lattice theory applications for modeling of asphaltene precipitation in petroleum mixtures

Dehghani, Seyed Ali Mousavi; Nematollahzadeh, Ali; Vafaie-Sefti, Mohsen

doi:10.1590/s0104-66322008000300010

Cited by 18 publications

(5 citation statements)

References 26 publications

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“…The Hildebrand solubility parameter, δ asp , of asphaltenes has been determined both experimentally and theoretically. The reported values in the open literature range from 19 to 22 MPa 1/2 . ,, Thus, for the petroleum asphaltenes precipitated by n -heptane, a value of 20 MPa 1/2 would be a satisfactory approximation and was used in this study. In the calculation of χ, Hildebrand solubility parameters of solvents were used: 18.3 MPa 1/2 for toluene and 15.3 MPa 1/2 for heptane .…”

Section: Discussionmentioning

confidence: 99%

Interaction Forces between Asphaltene Surfaces in Organic Solvents

Li²,

et al. 2009

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The colloidal interactions between asphaltene surfaces in heptol, a mixture of n-heptane and toluene, were studied for the first time by colloidal force measurements using an atomic force microscope (AFM). Asphaltenes were deposited on silica wafers and silica spheres using the Langmuir-Blodgett upstroke technique. The results showed that the ratio of toluene to heptane can significantly change solvent quality in terms of the ability to solubilize asphaltenes and hence the nature and the magnitude of the interaction forces between asphaltene surfaces. In pure toluene, there is a steric long-range repulsion which can be well fitted by the scaling theory of polymer brushes. As toluene volume fraction in heptol (Phi(T)) is gradually decreased from Phi(T) = 1 (pure toluene) to Phi(T) = 0 (pure n-heptane), the steric repulsion reduced and changed to weak attraction when Phi(T) < 0.2. The attraction in heptane can be fitted by van der Waals forces alone which are thus believed to promote asphaltene aggregation, leading to asphaltene precipitation. The results obtained in this study provide an insight into interactions that determine asphaltene behavior in an organic medium and hence in crude oils.

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Section: Discussionmentioning

confidence: 99%

Interaction Forces between Asphaltene Surfaces in Organic Solvents

Li²,

et al. 2009

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“… a δ asph : solubility parameter of asphaltene phase at the bubble-point pressure. b Estimated from eq . c Determined by oil titration. d Relative deposition (%) = 100× deposited asphaltene at bubblepoint pressure/estimated asphaltene in the feed oil e From ref . CO 2 was injected at its normal state.…”

Section: Resultsmentioning

confidence: 99%

“…Their thermodynamic properties are generally derived from the Flory–Huggins-type solution theory, using an energy interaction parameter estimated from Hildebrand’s solubility parameter. This theory, discussed extensively by Mousavi-Dehghani et al, has served as a basis of considerable work in the modeling of organic deposition. ,,− …”

Section: Thermodynamic Model Of Asphaltene Aggregation and Depositionmentioning

confidence: 99%

Asphaltene Aggregation in Crude Oils during Supercritical Gas Injection

et al. 2016

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This paper presents the aggregation of asphaltenic materials in three dead crude oils, including two heavy samples from Hokkaido (Japan) and an extra heavy sample from Canada. In this study, a modified ASTM D3279 method and PVT test were used to estimate the amount of precipitated asphaltene and the experimental bubble-point pressures of the samples, respectively. Upon which, a crude oil characterization was performed following pseudocomponent approach with the use of molecular weight and specific gravity of single carbon number from oil assay data as distribution variables. A simplified thermodynamic model, derived from the solubility model, was used to correlate the maximum asphaltene soluble with the aggregated amount. This study has highlighted that oil precipitation, during its titration, occurs as a function of both the molecular weight of the titrant and the carbon-to-hydrogen ratio in the asphaltene phase. Furthermore, the kinetics and the stability of intermolecular forces, developed during the miscibility process, are believed to alter oil polarity and gas solubility. More specifically, pressurization of the system [oil-supercritical gas] decreases the solubility parameters of the asphaltene fraction and increases the solvating strength of gas. Both effects were found to occur concurrently. This study has also demonstrated that asphaltenes are less soluble in impure gases compared to the pure one. At/near the bubble-point pressure, the supercritical gas, in contact with the oil, develops a potential as either a flocculant or coagulant. The increase in pseudo equilibrium temperature attained after gas injection was found also to alter asphaltene aggregation.

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“…If too few bits are used the effect of weight quantization will be significant, resulting in poor convergence. On the other hand, a large number of bits per weight will again lead to slow convergence because of a long chromosome string (19).…”

Section: Genetic Evolve Neural Networkmentioning

confidence: 99%

Optimization of Predicted Cell Voltage & Caustic Current Efficiency in a Chlor-Alkali Membrane Cell with Application of Genetic Algorithm

et al. 2010

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This paper presents the development of hybrid neural-genetic algorithm model for the prediction of cell voltage and caustic current efficiency (CCE) versus various operating parameters in a lab scale chlor-alkali membrane cell. Each of six process parameters including anolyte pH (2-5), operating temperature (25-90 oC), electrolyte velocity (1.3-5.9 cm/s), brine concentration (200-300 g/L), current density (1-4 kA/m2), and run time (up to 150 min) were thoroughly studied at four levels for low caustic concentrations (5 g/L). According to the obtained results, the predicted cell voltages and current efficiencies using GA modeling were found to be very close to the measured values with an average deviation of about 2.82% & 1.77% for test validation data, respectively. It was also found that the developed model is not only capable to predict the voltage and current efficiency but also to reflect the impacts of the other process parameters on the same functions.

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Polymer solution and lattice theory applications for modeling of asphaltene precipitation in petroleum mixtures

Cited by 18 publications

References 26 publications

Interaction Forces between Asphaltene Surfaces in Organic Solvents

Interaction Forces between Asphaltene Surfaces in Organic Solvents

Asphaltene Aggregation in Crude Oils during Supercritical Gas Injection

Optimization of Predicted Cell Voltage & Caustic Current Efficiency in a Chlor-Alkali Membrane Cell with Application of Genetic Algorithm

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