Solvent Swelling of Kukersite Oil Shale Macromolecular Organic Matter in Binary Mixtures: Impact of Specifically Interacting Solvents

Abstract

The present work deals with the volumetric solvent swelling of the cross-linked macromolecular organic matter (kerogen) of Estonian kukersite oil shale in binary solvent mixtures. A two-step solvent swelling procedure was used in which swelling was performed first in one solvent followed by the addition of a second solvent. The results confirm the important role of specific interactions in determining the swelling behavior of this kerogen. The kerogen swells more in strong electron donor solvents that are able to break specific kerogen-kerogen interaction such as hydrogen bonds. When comparing the maximum swelling achieved, the binary solvent mixtures did not perform any better than strong electron donor solvents, regardless of how the experiments were conducted.

Kerogen Swelling and Confinement: Its implication on Fluid Thermodynamic Properties in Shales

“…Further experiments were conducted on a binary mixture of kerogen and decane to investigate the change in the thermodynamic properties of the sorbed decane. Swollen kerogen samples were prepared by equilibrating kerogen and decane for 24 hours, after which no further swelling was observed, in agreement with previous swelling studies 3 – 11 . The swelling ratio (Q v ) is defined as the ratio between the volume of the swollen kerogen and the original volume of the kerogen.…”

“…1 ). Both type I and type II kerogens show swelling in the presence of hydrocarbon fluids based on several previous studies 3 – 11 . Evidence for the hypothesis that the thermodynamic properties of sorbed hydrocarbon liquids that swell kerogens are different has been provided in the paper.…”

Application of DSC to study the promoting effect of a small amount of high donor number solvent on the solvent swelling of kerogen with non-covalent cross-links in non-polar solvents

“…The cross-link density reduction and network relaxation effects caused by addition of a small amount of H-bonding solvent were previously shown by Larsen et al for coal [7,8]. Our qualitative screening tests, using a traditional test-tube swelling technique, have indicated similar trends occur for Kukersite oil shale kerogen swelling in non-polar solvents in the presence of a small amount of an H-bonding solvent [17]. In this study benzene, o-xylene and tetralin were used as non-specifically interacting solvents, or base solvents.…”

“…the ratio determined by DSC). Thus, the swelling ratio determined by the volumetric test-tube method can be corrected to obtain the real swelling ratio using the empirical correlation that was suggested in our previous paper [17] based on experimental data from reference [16]:…”

“…As a result, swellability of highly polar kerogen in non-specifically interacting solvents is determined by apparent cross-link density (covalent and non-covalent cross-links), while in the case of specifically interacting (hydrogen-bonding) solvents it is determined by the real (covalent) cross-link density because of the ability of such solvents to disrupt the kerogen's intramolecular hydrogen bonds. Consequently, solvent swelling experiments on these kerogens show increased swelling in hydrogen-bonding solvents with high electron donor numbers, such as pyridine, N-methyl-2-pyrrolidinone or propylamine [15][16][17].…”