Estimation of SARA Fraction Properties With the SRK EOS

Abstract

One approach to modelling asphaltene solubility is regular solution theory. The key parameters for this approach are the molar volume and solubility parameters of each constituent. However, these parameters are largely unknown for crude oils. Some authors have used cubic equations of state (CEOS) to estimate the solubility parameters and molar volumes of solvents and C 7 + fractions, but CEOS have yet to be applied in this way to asphaltenes due to their high molar mass and unknown critical properties.In this work, a modified Soave-Redlich-Kwong EOS with the Peneloux correction is used to estimate the molar volumes and solubility parameter of the four solubility classes (saturates, aromatics, resins, and asphaltenes) of bitumens. The EOS is modified for the asphaltenes, which are assumed to be polymeric-like compounds consisting of aggregates of monodisperse asphaltene monomers. Correlations are developed for the critical properties and acentric factor of each solubility class. The EOS-predicted properties are tested against density measurements of SARA fractions from several bitumens. The predicted parameters are used to determine the onset of asphaltene precipitation from bitumen upon the addition of heptane and the predictions are compared with measured onsets.

Commercial Investigation of the Ebullated-Bed Vacuum Residue Hydrocracking in the Conversion Range of 55–93%

“…This interval was defined by the values for the density of different SARA fractions reported in previous studies. 16 , 64 − 66 The function f i approximates data x i (density), y i (aromatic structure content) from Data i , i , I = 1, 2, 3 (mentioned above).…”

“…The value of 0.881 g/cm 3 corresponding to zero aromatic structure content in the VR oils is in good agreement with the density of the saturate components of VR oils reported in the literature. 16 , 64 − 66 We consider that it is reasonable to assume that the three curves, described by eqs 5 – 7 , should have the same zero content of aromatic structures at the same density because in the LNB SARA method, 28 the saturate compounds are deemed to be the components that have refractive index n d 20 ≤ 1.49. By the use of eq 6a from the work of Yarranton et al., 10 for n d 20 = 1.49, ρ 20 of 0.882 g/cm 3 is obtained.…”

Predicting Asphaltene Precipitation from Heavy Oils Diluted by n-Heptane Using a Four-Parameter EOS

“…In this study, theHildebrand and Scott [48,49] regular solution theory is applied to model asphaltene precipitation diluted by adding n-heptane into four different Canadian bitumens with same properties as mentioned by Greaves et al [50]. Each bitumen is divided into four main pseudo components corresponding to SARA fractions.…”

“…As it is known, asphaltenes tend to self-associate and the aggregates can be analogous to polymer-like compounds. It has been shown that asphaltene association can be modeled same as linear polymerization [43,44,46,50,54,55]. Since the structure of asphaltene monomers is repeated throughout the structure of asphaltene aggregates, the asphaltene monomers can be considered as a group, for which the Van der Waals forces are involved in the association mechanism instead of chemical bonding.…”

Modelling of Bitumen-and-Solvent-Mixture Viscosity Data Using Thermodynamic Perturbation Theory

“…Mehrotra and Svrcek (1987) tested several types of correlations to find the best match to regenerate the experimental viscosity data of Cold Lake bitumen. Physical properties of Cold Lake bitumen obtained from Mehrotra and Svrcek (1987) and Greaves et al (2004) are given in Table 2.…”