Optimizing the synthesis of composite polyvinylidene dichloride-based selective surface flow carbon membranes for gas separation

Selective surface flow (SSF) carbon membranes were fabricated by pyrolysis of polyvinylidene dichloride (PVDC) layer deposited on macroporous ceramic supports. The pore properties of PVDC carbons were examined by physical adsorption of nitrogen and subsequent micropore analysis. The measured average pore sizes range from 1.23 to 1.42 nm for PVDC carbons with the pyrolysis temperature range of 873–1273 K respectively. The advantage of PVDC-based SSF carbon membranes is their low transport resistance with typical gas permeances of 10−6–10−7 mol/m2 s Pa, 2–4 orders of magnitude higher than those of carbon molecular sieve membranes. They are suitable for separation of feed streams containing strongly adsorbing species such as hydrocarbons from non/weakly adsorbing components. In this study, gas molecules of similar kinetic diameter but disparate adsorption ability like ethane and nitrogen were chosen to evaluate the membrane separation performance and the reverse-selectivity characteristic of SSF carbon membranes. Commercial PVDC solutions were used and the preparation factors like concentration of polymer precursor, carbonization temperature and coating conditions were taken into account to optimize the SSF carbon membranes performance for hydrocarbons–nitrogen separations.