Polyphosphazene membrane for desulfurization: Selecting poly[bis(trifluoroethoxy) phosphazene] for pervaporative removal of thiophene

Concerning the standstill state of pervaporation desulfurization, development of new pervaporation desulfurization membranes is vital. The polymer selection can be based on solubility parameter theory. Using group contribution method, the solubility parameter of poly[bis(trifluoroethoxy) phosphazene] (PTFEP) was calculated. The differences in solubility parameters between thiophene and polymers including PTFEP were calculated and investigated for their potential application as pervaporation desulfurization membranes. PTFEP had the most similar solubility parameter to thiophene among the polymers calculated in this work. The results indicated superior possibility for its application in pervaporation desulfurization. PTFEP was thus synthesized and characterized by DSC, GPC, XPS, 1H-NMR and 31P-NMR. The PTFEP composite membrane was fabricated and utilized in pervaporation removal of thiophene. A pretty high sulfur enrichment factor of 15.69 was obtained which confirmed the results suggested by the solubility parameter theory. Compared with literatures, we positively believe that an increase in solubility parameter differences causes a decrease in sulfur enrichment factor. Meanwhile, the swelling behavior and morphology of the membrane, the effect of feed temperature, and the effect of feed sulfur concentration were also investigated.

► Solubility parameter theory was used for selection of PV desulfurization membrane.
► Solubility parameters of 25 polymers were calculated using group contribution method.
► PTFEP was selected according to solubility parameter analysis.
► Separation factor of around 16 was obtained.