Temperature Dependence of Solvent Swelling and Diffusion Processes in Coals

Abstract

The rates of solvent swelling of the Argonne Premium Sample coals have been measured in various organic solvents at various temperatures. The results show that the extents of swelling, when experiments are carried out in liquid solvents, are independent of the temperature, within the temperature range studied here (10−60 °C). Thermodynamically, this requires that equilibrium swelling should occur with a near-zero enthalpy, as generally required for absence of a temperature effect on equilibrium. This conclusion is consistent with a number of other recently published results. The rates of swelling of the coals do not correlate with rank. The nature of the swelling process varies from relaxation controlled to Fickian diffusion controlled. The activation energies for the kinetics of swelling are consistent with other recently published values, but again, a correlation with rank could not be substantiated. The activation energies all fall in the range from 20 to 60 kJ/mol, suggesting that the activation barrier may be associated with the breakage of internal electron donor−acceptor (e.g., hydrogen bonding) interactions. Thermal pretreatment of some of the coals to 350 °C had significant effects on their swelling behaviors. The effect was generally to increase the rate of swelling, and in some cases, the extent of swelling. The activation energies for swelling were, however, unaffected. This is interpreted as consistent with the hypothesis that the activation energy barrier is determined by donor−acceptor interactions which are unaffected by pretreatment but that other thermally dissociable coal−coal interactions may serve to stiffen its structure.

Swelling Measurements of a Low Rank Coal in Supercritical CO<sub>2</sub>

“…Based on these results, the maximum volumetric swelling ratio measured is very similar to ones reported by [5,6,[15][16][17], who used blocks and crushed coal samples. The maximum swelling from [6] with Ro 0.89% was ~2.6% at around 8 MPa and 40˚C.…”

“…Otake and Suuberg [17] reported that the packing density of particles could affect swelling measurements and introduce significant artifacts. To solve this problem, we used small particle sizes (200 -250 μm) and sample columns were centrifuged to ensure that the particles packed into the interstitial spaces and were distributed evenly.…”

Kinetics of oil group-type generation and expulsion: An integrated application to Dongying Depression, Bohai Bay Basin, China

“…It has been shown that coals are macromolecular systems which can be studied by techniques developed in polymer science (Takanohashi et al, 1996(Takanohashi et al, , 2000Cody and Painter, 1997;Otake and Suuberg, 1997) and their application to primary migration (Sandvik et al, 1992) and kerogen (Larsen and Li, 1997a,b) has been attempted. One object of this study was to apply the swelling theory to predict retention and expulsion of petroleum and its fractions.…”

Diffusion of alcohols and aromatics in a mesoporous MCM-41 material

“…For an infinite plane sheet, the values would be 0.5 and 1.0 for Fickian and pure Case II, respectively. In addition, in the case of an infinite cylinder, these values would be 0.45 and 0.89, respectively [60]. The diffusion exponents of methanol, ethanol, n-propanol, i-propanol and n-butanol in natural zeolite systems measured by Sakintuna et al [44] were between 0.96-1.00 indicating an anomalous diffusion mechanism.…”