Membrane purification of Cl-2 gas I. Permeabilities as a function of temperature for Cl-2, O-2, N-2, H-2 in two types of PDMS membranes

Permeability (P) of Cl-2, O-2, N-2 and H-2 was measured in polydimethylsilo xane (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 degrees C. The functionaliti es of the membranes were compared on the basis of permeation rate and abili ty to separate the gases Cl-2-O-2 These results are part of an extensive su rvey where perfluorinated and carbon membranes are also included (not repor ted here). The purpose of the project is to develop an industrial membrane with high permselectivity for either O-2 or Cl-2 (depending on the type of membrane) at temperatures preferably above 70 degrees C. Process conditions are set in an industrial project. The PDMS membranes are good candidates f or this separation, having a high permeation rate for Cl-2 and a selectivit y of Cl-2/O-2 in the range of 8-25 depending on temperature. Durability of the PDMS membranes in this aggressive environment is found to be very depen dent on process conditions aod on how the material is polymerized and cured . For documentation of durability, various silicones were tested; these res ults are to be reported separately. (C) 2000 Elsevier Science B.V. All righ ts reserved.