Liquid-Phase Behavior during the Cracking of Asphaltenes

Abstract

Asphaltenic material from Athabasca bitumen, with and without fine solids, was reacted at 430 °C under a nitrogen environment in the liquid phase, mixed with either 1-methyl naphthalene or maltene fractions from Athabasca. Phase behavior during coke formation was investigated by examining the coke produced from selected reactions by scanning electron microscopy (SEM). Both fine solids and solvents were found to assist the dispersion of liquid coke spheres in an oil medium. Phase inversion, to an oil-in-coke structure, was observed in some sections of coke produced from pure asphaltenes. The thermodynamic feasibility of phase inversion was confirmed by calculating the entropy difference for a set of representative conditions. Qualitatively, as the volume fraction of coke increases, the probability of a phase inversion is increased. This result agrees with the behavior of polymer blends, where phase inversion occurs at high concentration.

Insights in mechanisms of carbonaceous microparticles formation from black liquor hydrothermal conversion

“…As the spherules grew, the coalescence of mesophase spherules resulted in the formation of a continuous mesophase matrix. Furthermore, the spheres or agglomerated spheres of carbonaceous particles suggested that this material was liquid or plastic at operating conditions [43]. These latter suggestions could explain that the coalescence was limited between 4 h and 6 h due to a high viscosity of the plastic mesophase.…”

“…At the operating conditions (350 • C, 16.5 MPa), the salts are prone to precipitate, and their participation cannot be excluded as a carrier of the solid formation, as shown by Rahmani et al [43]. Indeed, ICP analyses performed on liquid phase showed that 10 wt.…”

A review of upgrading heavy oils with supercritical fluids

“…[77][78][79][80][81][82][83] Rahmani et al found that the yield of coke was strongly inuenced by the hydrogen offering ability of the solvent and the hydrogen capturing ability of the asphaltenes. 84 In order to clarify the mechanism of coke formation in SCFs, Watanabe et al observed the coke formed during asphaltene pyrolysis in the absence and presence of SCW through scanning electron microscopy (SEM). 13 The major part of the coke formed in the absence of SCW had a coalescent structure that was made of small coke particles, while that formed in the presence of SCW had a porous structure, as shown in Fig.…”

Scanning Electron Microscopy Method as a Tool for the Evaluation of Selected Materials Microstructure

“…But the research of asphaltenes structure might help to explain the bitumen rheological properties. Scanning electron microscopy and environmental scanning electron microscopy (ESEM) have both been used successfully to image the asphaltene structure (Baginska et al, 2004;Bearsley et al, 2004;Loeber et al, 1996), because they offer a three-dimensional image that can be analyzed more easily than a two-dimensional one, usually obtained from optic techniques and transmission electron microscopy (TEM) (Rahmani et al, 2003). Electron microscopy has contributed considerably to the development of theories concerning the structure, composition, and properties of components of these blends and to the interpretation of their optical microscopy and applied research results (Wilson et al, 2000).…”

“…There are several techniques of oil phase (maltenes) elimination described in ČSN 65 6073 (Czech National Standard) and some additional ones mentioned in Baginska et al, 2004;Bearsley et al, 2004;Bragado et al, 2001;Rahmani et al, 2003: The procedure based on ČSN 65 6073: dissolution of 1 g of sample in 40 ml of n-heptane, kept in the dark over night, 1 hour of boiling under the reflux condenser, 2 hours of keeping in dark, filtration through the filter paper, 1 hour of washing the filter paper in a Soxhlet extraction apparatus with n-heptane, 1 hour of washing the filter paper in a Soxhlet extraction apparatus with toluene, pouring the solution into a glass bowl, toluene evaporation above the water bath, 1 hour of drying in 110° C, measuring, repeating to the constant weight. Procedure A: dissolution of 1 g of sample in 40 ml of n-heptane, 1 hour of boiling under the reflux condenser, 2 hours of keeping in the dark, filtration through the filter paper, 1 hour of washing the filter paper in a Soxhlet extraction apparatus, drying.…”