O2/N2 SELECTIVITY IMPROVEMENT FOR POLYTRIMETHYLSILYLPROPYNE MEMBRANES BY UV-IRRADIATION AND FURTHER ENHANCEMENT BY SUBAMBIENT TEMPERATURE OPERATION

Surface treatment of a polytrimethylsilylpropyne (PTMSP) membrane by UV irradiation significantly enhances its selectivity for O2 over N2. For example, the selectivity is increased from the intrinsic value of 1.4 to approximately 4 after treatment. The selectivity of such a surface-modified membrane can be further enhanced by operating in a subambient temperature environment whilst still retaining attractive values for O2 permeance. For example, the membrane exhibits an O2/N2 selectivity of about 12 and O2 permeance of 9.3 X 10(4) barrer/cm when the membrane is cooled to - 101-degrees-C. A process utilizing such a UV-treated PTMSP at subambient temperatures to separate N2 from air is described. Simulation of the process shows an attractive recovery and energy consumption with a modest liquid nitrogen requirement for refrigeration and reasonable equipment complexity.