Water sorption on composites "LiBr in a porous carbon"

Water sorption equilibrium of LiBr confined to pores of a mesoporous synthetic carbon Sibunit and a macroporous expanded graphite (samples SWS-2C and SWS-2EG, respectively) was studied. Isobars of water sorption on these composites are measured at vapor pressure 6-81 mbar and temperature 30-145 degreesC. The type of sorption equilibrium for the two composites appears to be quite different. The isobars for SWS-2EG have a plateau corresponding to one molecule of H2O adsorbed by one molecule of LiBr, which indicates the formation of crystalline hydrate LiBr.H2O inside pores with a monovariant type of equilibrium. At lower temperatures, the equilibrium becomes divariant that is typical for LiBr-water solutions. On the contrary, the water sorption equilibrium for SWS-2C is divariant over the whole temperature and pressure range which means that no crystalline hydrates are formed inside Sibunit pores. In our opinion, this distinction results from differences in a pore structure of the host carbons. The composite sorption capacity can reach 0.6-1.1 g H2O per I g of the dry sorbent at relative humidity 70%. The advanced sorption capacity makes the sorbents promising for gas drying, thermal storage of energy and other applications. (C) 2002 Elsevier Science B.V. All rights reserved.