Propylene/propane separation using N-methyl pyrrolidone/AgNO3 supported liquid membrane

The separation of propylene/propane gas mixtures using a supported liquid membrane was experimentally investigated. N-methyl-2-pyrrolidone (NMP) and silver nitrate were used as the solvent and carrier, respectively. Gas permeation tests were conducted at different salt concentrations (0, 1.8, 5.4 wt.%), feed pressures (1.2, 1.7, 2.2 bar), and propylene concentration (0.3, 0.5 and 0.7 mol/mol). The results showed that the permeation fluxes of both gases in pure NMP were high (i.e. 3.79 x 10(-4) mol/m(2)s), and the corresponding selectivity was around unity for different cases. Introduction of the silver salt into the solvent improved the permeation flux of propylene and its selectivity up to 8 x 10(-4) mol/m(2)s and 4.5, respectively and caused the propane permeation flux to decay to some extent. Moreover, the permeation flux of propylene increased as the three aforementioned variables increased. However, an increase of propylene concentration in the feed decreased the selectivity while an increase of salt concentration and feed pressure had the opposite effect. The system showed good stability against vaporization of the solvent and drying of the support. On the other hand, high permeation of both gases through the solvent dominated the silver ions performance and consequently high selectivity could not be achieved. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.