Durable poly(vinyl alcohol)/AgBF4/Al(NO3)3 complex membrane with high permeance for propylene/propane separation

A highly permeable and durable poly(vinyl alcohol) (PVA)/AgBF4/Al(NO3)3 complex membrane for propylene/propane separation was developed. The selectivity and permeance of the membrane were determined to be about 17 and 11 GPU, respectively, which represented improvement on previously developed membranes. The propylene/propane separation performance of the membrane was maintained for more than 145 h even though the Ag ions, which functioned as olefin carriers, were observed to be unstable during this period. This enhanced permeance and long-term stability was attributed to the incorporation of Al(NO3)3 into the permeable PVA matrix, which also contained AgBF4. The favorable interaction between the Al3+ ions and the BF4− ions of AgBF4 induced ready coordination between the NO3− and Ag+ ions, thereby affording the long-term stability. The complexation behavior of the PVA/AgBF4/Al(NO3)3 membrane was also investigated by thermogravimetric analysis, X-ray photoelectron spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and Fourier Transform Raman spectroscopy.