Suitable Density Determination for Heavy Hydrocarbons by Solution Pycnometry: Virgin and Thermal Cracked Athabasca Vacuum Residue Fractions

Abstract

Density is an important parameter for understanding molecular packing, stability, and reactivity of petroleum fractions. The determination of density for extremely viscous residual fractions measured at high temperature (reduced viscosity) is difficult and prone to error if results are extrapolated to lower temperature ranges. This problem is addressed in the present study with fractions derived from virgin and visbroken Athabasca vacuum residua. Solution pycnometry (toluene solvent) was studied and demonstrated a feasible, fast, simple, and reliable technique, applicable to a wide variety of petroleum materials, including asphaltenes and vacuum residua. Reported densities were affected to the third decimal position [American Petroleum Institute (API) gravities found reliable to (0.15°API]. The density for mixtures of residual oil fractions was determined to be an additive property. Athabasca vacuum residue solvent deasphalting and thermal cracked fractions are studied. Thermal cracking was observed to increase asphaltene densities to values as high as those displayed by coals, suggesting that highly aromatic-condensed structures represent these species better. Further application of the methodology is illustrated by monitoring Athabasca bitumen upgrading at bench scale.

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

“… 7 Even the measurement of the density of the vacuum residues can report incorrect values if no dilution approach is undertaken. 8 − 10 One of the most explored ways to characterize the chemical nature of oils and vacuum residues is saturates, aromatics, resins, and asphaltenes (SARA) analysis. 11 − 27 The different techniques employed to measure the vacuum residue SARA composition, however, can report different values even for the same samples studied.…”

“…However, the characterization of the vacuum residue is not an easy task considering its low volatility, high viscosity, and high melting point . Even the measurement of the density of the vacuum residues can report incorrect values if no dilution approach is undertaken. − One of the most explored ways to characterize the chemical nature of oils and vacuum residues is saturates, aromatics, resins, and asphaltenes (SARA) analysis. − The different techniques employed to measure the vacuum residue SARA composition, however, can report different values even for the same samples studied . Youtcheff, for example, pointed out that thin-layer chromatography (TLC), also known as Iatroscan, is featured with a separation that has a large amount of error on repeat analysis.…”

Experimental and Numerical Simulation of Combined Enhanced Oil Recovery with In Situ Upgrading in a Naturally Fractured Reservoir

“…To get the densities by the pycnometer method, a methodology developed by Carbognani et al (L. Carbognani, 2011) was used. Basically, the method consists of dissolving between 0.7 to 1 grams of sample in toluene, then transfers it into a glass pycnometer of 10 ml capacity, and places it in a thermal bath at 15.6 C to stabilize the sample.…”

“…Regarding naphtha or light components, MTK has a highest composition with 8.67 % and MAN has the lowest composition of lighter components with 5.97 %.API gravity is a common way to represent crude oils densities. For the oil samples received from Mexico, API gravity was calculated indirectly by using a pycnometer and the methodology developed byCarbognani et al (L. Carbognani, 2011).Figure 4.12 shows the API gravity results for the Mexican oil samples.…”

Empirical Modeling of Viscosities and Softening Points of Straight-Run Vacuum Residues from Different Origins and of Hydrocracked Unconverted Vacuum Residues Obtained in Different Conversions

“…For that reason, sometimes strange values for a VR's physicochemical properties are reported [4,5]. The proper preparation of a VR sample before analyzing is important to reduce the probability of misinterpretation of the obtained results [5,6]. For example, the most complex compounds of a VR-the asphaltenes-were believed to consist predominantly of molecules with one polycyclic aromatic hydrocarbon (PAH) unit per molecule, with roughly 7 rings having a structure "like your hand" (palm), which has a small number of aliphatic chains (fingers) [7].…”