On the preparation of supported nanoporous carbon membranes

New preparation techniques for synthesis of thin film supported nanoporous carbon membranes (SNPCM) using ultrasonic deposition (UD) have been examined. In contrast to other work we have published, in which membranes were prepared either by brush or spray coating of the polymer precursor onto the porous stainless steel support, the ultrasonic deposition method provides a greater degree of control over the deposition step. Permeation experiments on the UD-SNPCM with pure gases such as nitrogen (N2) and oxygen (O2) were used to benchmark properties and characteristics as a function of synthesis variables. The UD-SNPCM display ideal separation factors for O2/N2 ranging from 2 to 30 depending on synthesis conditions. With other gases ideal separation factors were as large as: H2/CH4=600, CO2/CH4=45, N2O/N2=17, and H2/CO2=14 at 295 K. Permeation rates ranged from 7.9×10−13 to 4.1×10−8 mol m−2 Pa−1 s−1 and were largely independent of pressure. Oxygen versus nitrogen selectivities were inversely proportional to oxygen flux.