Influence of the Distribution General Shape of n-Alkane Molar Concentrations on the Structural State of Multi-Alkane Mixtures

Chevallier, Virginie; Briard, Anne-Julie; Petitjean, D.; Hubert, Nathalie; Bouroukba, M.; Dirand, M.

doi:10.1080/10587250008025250

Cited by 19 publications

(30 citation statements)

References 16 publications

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“…Strong evidence today shows that the alkyl chains in the wax lead to an orthorhombic structure (Chevallier et al, 2001) even if some isoalkanes or alkyl aromatic compounds are present (Dorset, 2000). The thermophysical properties, when the solid phase is poorly defined, are usually fitted to a set of experimental data and the values adopted, usually to a large extent far from the pure compounds data, actually compensate for weaknesses in the non-ideality description; thereby, are of limited applicability for systems other than those used in the development of the correlation.…”

Section: Thermodynamic Models For Petroleum Waxmentioning

confidence: 99%

Cloud Points: Can We Measure or Model Them?

Hammami¹,

Ratulowski²,

Coutinho³

2003

Petroleum Science and Technology

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The terminology "cloud point" has been traditionaly adopted by the American Society for Testing and Materials (ASTM) D2500 to refer to the temperature at which "cloudiness" of a relatively transparent petroleum fluid is observed upon cooling. The cloudiness forms as a "finite and detectable" amount of wax and/or paraffins precipitates from the test fluid contained in a 1½-in (~ 30 mm) diameter glass tube. Nowadays, more sophisticated techniques of differing measurement principles and varying degrees of sensitivity have been developed to measure cloud points of petroleum fluids including opaque hydrocarbon systems (dark oils). Alternative terminologies like wax appearance temperature (WAT) and wax precipitation temperature (WPT), amongst a few others, have also emerged and are used interchangeably. Meanwhile, numerous characterization and modeling efforts have been made to simulate "measured" cloud points of petroleum fluids. The goals of this paper are to provide an objective review of the concept of "cloud point" and to illucidate the adequacy and limitations of the measurement techniques and modeling approaches.

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Section: Thermodynamic Models For Petroleum Waxmentioning

confidence: 99%

Cloud Points: Can We Measure or Model Them?

Hammami¹,

Ratulowski²,

Coutinho³

2003

Petroleum Science and Technology

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“…has been proposed, where n RX stands for the mean carbon atom number chain incorporated into crystals. 35,38,47 For the crude oil, at 20 °C, n RX is 50, while for the model oil, at the same temperature, n RX is 27. These results highlight the differences in the n-paraffin distribution of the two oils.…”

Section: Resultsmentioning

confidence: 99%

“…The n -paraffin distribution is characterized by its mean number of carbon atoms n̅ and the standard deviation σ. These parameters were calculated from relationships , described in Supporting Information Sd.…”

Section: Methodsmentioning

confidence: 99%

Probing Multiscale Structure and Dynamics of Waxy Crude Oil by Low-Field NMR, X-ray Scattering, and Optical Microscopy

et al. 2020

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Wax deposition is one of the major concerns for waxy crude oil production and transportation. A better understanding and prediction of fluid properties related to this issue require knowledge of the medium structuration at scales ranging from nanometers (molecules) to a few micrometers (crystals). For this purpose, the behavior of a waxy crude oil in the bulk was compared to that of a model oil over a wide range of temperatures above and below the wax appearance temperature. The combined use of cross-polarized microscopy (CPM) and the implementation of innovative techniques for the field such as small-and wideangle X-ray scattering and low-field nuclear magnetic resonance has provided a more precise idea of the structure of these two types of fluids. If the nature of the orthorhombic crystals and their lamellar shape are identical for both fluids, a very appreciable difference is highlighted in their chain axis dimensions. The n-paraffin crystal size is larger than 120 nm in the model oil. In crude oil, it is only about 1−10 nm with a long-range order in the directions perpendicular to the chain axis and a monomolecular thickness in the chain axis. Moreover, from the model oil CPM images, we observed aggregates of lamellar shape crystals. Because the model oil does not contain asphaltenes and resins, the crystals are larger and the branches divide significantly less than in crude oil, which results in a trapped liquid proton population unobservable in the model oil. All these observations give a vision of the structure of n-paraffin crystals. It is made of aggregates of relatively dense lamellae in the center and more aerated lamellae at the periphery, which split into several branches.

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“… 20 The alkyl chains in the wax lead to an orthorhombic structure creation. 22 , 39 , 40 As a result, the coordination number, Z , is set to 6 for n -alkanes in the orthorhombic phase. 20 The sublimation enthalpy of pure n -alkanes is estimated by summing the component latent heats of the solid–solid transition (Δ H tr ), melting (Δ H f ), and vaporization (Δ H vap ) 19 The correlation of Morgan and Kobayashi to calculate the enthalpy of vaporization is given as follows 41 In eq 36 , T c represents the critical temperature.…”

Section: Activity Coefficient Modelsmentioning

confidence: 99%

Experimental Measurement and Thermodynamic Modeling of the Wax Disappearance Temperature (WDT) for a Quaternary System of Normal Paraffins

et al. 2022

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Normal paraffin ( N -alkane)-based wax is well known as a severe problem in petroleum production, transportation, and processing. Implementing suitable solutions for wax-related problems requires vast technical knowledge and investigation of the wax disappearance temperature (WDT) of multicomponent systems in petroleum-dominated systems. In this study, the WDTs of a quaternary system comprising different mixtures of n -undecane + n -tetradecane + n -hexadecane + n -octadecane were measured using a visual-based diagnosis apparatus under atmospheric pressure. On the other hand, the WDTs of the studied systems are predicted by applying a solid solution model without any adjustable parameter. Two approaches namely γ–φ and γ–γ are assessed. In the (γ–φ) approach, perturbed-chain statistical associating fluid theory (PC-SAFT) is applied for liquid phase modeling, while the solid phase is described using different activity coefficient models. In the (γ–γ) approach, nonidealities of both the liquid and solid phases are investigated using different combinations of activity coefficient models such as ideal solution, regular solution theory, predictive Wilson, predictive UNIQUAC, and UNIFAC. Comparison of experimental data and thermodynamic modeling results indicates that applying the predictive UNIQUAC model for describing the nonideality of the solid phase and the regular solution model for the liquid phase is the best combination for the aforementioned system with the average absolute deviation (AAD) of 0.8 K.

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Influence of the Distribution General Shape of n-Alkane Molar Concentrations on the Structural State of Multi-Alkane Mixtures

Cited by 19 publications

References 16 publications

Cloud Points: Can We Measure or Model Them?

Cloud Points: Can We Measure or Model Them?

Probing Multiscale Structure and Dynamics of Waxy Crude Oil by Low-Field NMR, X-ray Scattering, and Optical Microscopy

Experimental Measurement and Thermodynamic Modeling of the Wax Disappearance Temperature (WDT) for a Quaternary System of Normal Paraffins

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