Study of capillary condensation of butane in a Vycor glass membrane

Abstract

Two basic types of experiments were made to study the transport mechanisms of butane as a condensable gas through a Vycor glass membrane, measurements of (a) gas fluxes using a steady state permeation arrangement and (b) liquid fluxes. Steady state experiments enable to study butane transport for different concentration profiles in the pores. Measurements of liquid fluxes are indispensable for the evaluation of the presence of condensate in pores during gas permeation. Differences between the gas flux (at both sides of the membrane the butane is in the gas phase) and the liquid butane flux (on the high pressure side of the membrane is liquid, on the opposite side is gas) were observed for the same pressure gradients across the membrane. The differences between these fluxes decrease with decreasing pressure gradients. For a pressure gradient higher than 2 bar the flux of the liquid butane is approximately two times higher, for a pressure gradient of 1.3 bar the ratio of liquid and gas fluxes decreases to 1.7. No difference between liquid and gas fluxes was registered for the lowest pressure gradient investigated (pressures on the two sides of the membrane: 2.22 and 1.91 bar). From the results obtained it can be concluded that the condensation of butane in pores occurs at high pressures on both sides if simultaneously the pressure difference is small.