Effect of Fixed Charge Groups and Counter Ions on the Transport Phenomena of Paraffin and Olefin across Anhydrous Negatively Charged Membranes

Abstract

Permeability coefficients, apparent diffusion coefficients, and apparent solubility coefficients ofn-butane and 1-butene gases across anhydrous sulfonated and carboxylated polyperfluorocarbon-type cation exchange membranes which have different counterions of Na+, Ag+, Co2+, and Ni2+were investigated at 25°C. Prior to then-butane and 1-butene gas permeability measurements, O2gas permeabilities were measured. From the results, it was shown that those membranes appeared to dense membranes. In each membrane, the permeability of 1-butene was higher than that ofn-butane. In comparison with the same counterion membranes, the sulfonated membrane had higher permeability than the carboxylated membrane for both gases. The Ag+-form sulfonated membrane exhibited the highest permeability coefficient for 1-butene and the ideal separation factor of 1-butene/n-butane was 10.3. This is caused by the high solubility of 1-butene gas. From the calculated result using the MO method, it was shown that the interaction between the olefin and metal ions was weakened by the influence of a charged group. Therefore, the affinity between the olefin and Co2+or Ni2+did not function in the membrane as expected because of the divalent ions. This is the reason why the solubility coefficients of Co2+- and Ni2+-form membranes were smaller than those of the Ag+-form membrane.