POLYELECTROLYTE-SALT BLEND MEMBRANES FOR ACID GAS SEPARATIONS

Citation
R. Quinn et al., POLYELECTROLYTE-SALT BLEND MEMBRANES FOR ACID GAS SEPARATIONS, Journal of membrane science, 131(1-2), 1997, pp. 61-69
Citations number
17
Categorie Soggetti
Engineering, Chemical","Polymer Sciences
Journal title
ISSN journal
03767388
Volume
131
Issue
1-2
Year of publication
1997
Pages
61 - 69
Database
ISI
SICI code
0376-7388(1997)131:1-2<61:PBMFAG>2.0.ZU;2-R
Abstract
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.