Pushpinder Singh Puri

Selective Permeation of Ammonia and Carbon Dioxide by Novel Membranes

Abstract Experimental results are presented on membranes of novel composition which selectively permeate ammonia and carbon dioxide from mixtures containing hydrogen. The CO2-selective membrane, which consists of a thin liquid film of the salt hydrate tetramethylammonium fluoride tetrahydrate, exhibits a CO2 permeance of 4-1 × 10−5 cm3/cm2·s·cmHg with selectivity, α(CO2/H2), ranging from 360-30. The NH3-selective membrane, poly(vinylammonium thiocyanate), displays a high NH3 permeance, 5−20 × 10−5 cm3/cm2·s·cmHg, with α(NH3/N2) as high as 3600 and α(NH3/H2) as high as 6000. Such membranes, which retain H2 at pressure in the feed stream, may offer new opportunities in the design of separation processes.

O2/N2 Selectivity improvement for polytrimethylsilypropyne membranes by UV-irradiation and further enhancement by subambient temperature operation

Abstract 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 × 104 barrer/cm when the membrane is cooled to −101°C. A process utilizing such a UV-treated PTMSP at subambient temperatures to separate N2 from air is described. Simultation of the process shows an attractive recovery and energy consumption with a modest liquid nitrogen requirement for refrigeration and reasonable equipment complexity.