The CO2/CH4 and CO2/H-2 permselectivity of poly(vinylbenzyltrimethylam
monium fluoride), PVBTAF polyelectrolyte membranes can be significantl
y improved by blending in certain fluoride-containing organic and inor
ganic salts. For example, the CO2 permeance of a PVBTAF-4CsF (4 mel Cs
F/mol repeat unit) composite membrane was more than four times that of
a simple PVBTAF composite membrane while CO2/CH4 and CO2/H-2 selectiv
ities were comparable. Surprisingly, the blends are at least macroscop
ically homogeneous even with as much a 6 mel salt/mol PVBTAF repeat un
it. The optimal salt loading appears to be approximately 4 mol CsF/mol
polyelectrolyte repeat unit. Membrane performance is strongly depende
nt on the relative humidity of the gas streams and is maximized in the
range of 30-50% relative humidity. Membranes containing choline fluor
ide exhibited improved membrane performance at relative humidities bel
ow 30%. Permselective data suggests that CO2 transport is kinetically
limited in 10 mu m thick films. The blends are stable in CO2/CH4/H-2 s
treams for more than 30 days of continuous operation, however, the mem
branes suffer an irreversible degradation due to reaction with trace l
evel sulfur-containing contaminants common to cylinder H2S.