The rates of solvent swelling of the Argonne Premium Sample coals have
been measured in various organic solvents at various temperatures. Th
e results show that the extents of swelling, when experiments are carr
ied out in liquid solvents, are independent of the temperature, within
the temperature range studied here (10-60 degrees C). Thermodynamical
ly, this requires that equilibrium swelling should occur with a near-z
ero enthalpy, as generally required for absence of a temperature effec
t 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 r
elaxation controlled to Fickian diffusion controlled. The activation e
nergies for the kinetics of swelling are consistent with other recentl
y published values, but again, a correlation with rank could not be su
bstantiated. The activation energies all fall in the range from 20 to
60 kJ/mol, suggesting that the activation barrier may be associated wi
th the breakage of internal electron donor-acceptor (e.g., hydrogen bo
nding) interactions. Thermal pretreatment of some of the coals to 350
degrees C had significant effects on their swelling behaviors. The eff
ect was generally to increase the rate of swelling, and in some cases,
the extent of swelling. The activation energies for swelling were, ho
wever, unaffected. This is interpreted as consistent with the hypothes
is that the activation energy barrier is determined by donor-acceptor
interactions which are unaffected by pretreatment but that other therm
ally dissociable coal-coal interactions may serve to stiffen its struc
ture.