Membrane purification of Cl2 gas: I. Permeabilities as a function of temperature for Cl2, O2, N2, H2 in two types of PDMS membranes

Permeability (P) of Cl2, O2, N2 and H2 was measured in polydimethylsiloxane (PDMS) composite membranes with two different degrees of cross-linking. The permeability was measured in the low pressure range (1–3 bar absolute) over a fairly large temperature range 35–120°C. The functionalities of the membranes were compared on the basis of permeation rate and ability to separate the gases Cl2–O2. These results are part of an extensive survey where perfluorinated and carbon membranes are also included (not reported here). The purpose of the project is to develop an industrial membrane with high permselectivity for either O2 or Cl2 (depending on the type of membrane) at temperatures preferably above 70°C. Process conditions are set in an industrial project. The PDMS membranes are good candidates for this separation, having a high permeation rate for Cl2 and a selectivity of Cl2/O2 in the range of 8–25 depending on temperature. Durability of the PDMS membranes in this aggressive environment is found to be very dependent on process conditions and on how the material is polymerized and cured. For documentation of durability, various silicones were tested; these results are to be reported separately.