THERMO-OSMOSIS OF SORBABLE GASES IN POROUS-MEDIA .3. SINGLE GASES

The theoretical basis of non-isothermal transport of a sorbable gas through a porous membrane has been further developed. At the thermo-osmotic steady-state, two integral heats of transport QBAR and Q(dagger), can be involved according to the experimental measurements made. The theoretical relation between these heats has been investigated and in our experiments the difference has been shown to be small. Measurements of isobaric steady-state fluxes and of the thermo-osmotic steady-state pressures on entry and exit sides of the membrane have been made utilising, in the main, two carbon compacts fabricated, respectively, from the contrasting carbon powder adsorbents Carbolac I and Graphon. Some (limited) additional results have been obtained using a second Carbolac carbon membrane. Isobaric fluxes J(N), isobaric permeabilities, B/P and heats of transport, QBAR, for He, CO2, CH4, C2H6, C3H8, n-C4H10, iso-C4H10, n-C5H12, iso-C5H12, neo-C5H12 and n-C6H14, have been determined as functions of initial pressure, P. Characteristic differences in the functional dependencies of J(N), B/P and QBAR between the Carbolac and Graphon membranes have been found and have been discussed in terms of energetic non-uniformity of the carbon surfaces and of amounts sorbed. For the Graphon membrane there is a correlation between Q(max)/DELTAE and DELTAE, where DELTAE denotes the energy of sorption determined at low coverage.