Scanning curves in wedge pore with the wide end closed: Effects of temperature

The desorption scanning curves within the hysteresis loop of argon adsorbed in a wedge-shaped pore with its wide end closed have been studied in the temperature range between 60 and 87 K, using grand canonical Monte Carlo simulation. The distinct features are: (1) adsorbate packing follows a sequence of commensurate regions (zones) and incommensurate regions (junctions); (2) the mechanism for evaporation switches from cavitation-like pore blocking to cavitation when the temperature is increased; as typically observed for ink-bottle pores. When cavitation is the operating mechanism, the descending scanning curve spans across the loop in two stages: a gradual decrease in density in a zone followed by a sharp evaporation from a junction, and then terminates at the lowest point on the vertical cavitation boundary. The adsorption scanning curve proceeds across the loop in two stages complementary to the desorption scanning-curve: a gradual change in density at a junction followed by a sharp change through a zone. Conversely, when cavitation-like pore blocking is operating, the descending curve leaves the adsorption boundary, spans across the hysteresis loop and returns to a different point on the same boundary, rather than to the desorption boundary or to the lower closure point. This feature does not seem to have been recognized in earlier literature and should be considered in the classification of scanning curves. (c) 2015 American Institute of Chemical Engineers AIChE J, 61: 3936-3943, 2015