Thin-Film Composite Cyclomatrix Poly(Phenoxy)Phosphazenes Membranes for Hot Hydrogen Separation

Abstract

An interfacial polymerization process is introduced for the fabrication ofthermally stable cyclomatrix poly(phenoxy)phosphazenes thin-film com-posite membranes that can sieve hydrogen from hot gas mixtures. Byreplacing the conventionally used aqueous phase with dimethyl sulfoxide/potassium hydroxide, a variety of biphenol molecules are deprotonated toaryloxide anions that react with hexachlorocyclotriphosphazene dissolvedin cyclohexane to form a thin film of a highly cross-linked polymer film. Thefilm membranes have persistent permselectivities for hydrogen over nitrogen(16–27) and methane (14–30) while maintaining hydrogen permeances in theorder of (10−8–10−7 mol m−2s−1Pa−1) at temperatures as high as 260 °C anddo not lose their performance after exposure to 450 °C. The unprecedentedthermal stability of these polymer membranes opens the potential for indus-trial membrane gas separations at elevated temperatures.