Physicochemical and Gas-Transport Properties of Membranes Based on Ultem and Siltem Polyetherimides for Hydrogen Recovery in Ammonia Industry Systems

The physicochemical and transport properties of polymer films based on polyetherimides Ultem-1000 and Siltem-1700 are presented. Using the gravimetric method, the sorption, diffusion, and permeability coefficients for a number of model gases (N2, CH4, O2, CO2) were determined, and ideal selectivities for key gas pairs (O2/N2, CO2/CH4) were calculated. It was found that membranes based on Siltem demonstrate significantly higher permeability for all gases studied, but are inferior to Ultem in selectivity. The transport of water (H2O) and ammonia (NH3) vapors through continuous polymer films was also investigated. The water vapor permeability coefficient was 2570 Barrer for Siltem and 1720 Barrer for Ultem; for NH3 these values were 29 and 10 Barrer, respectively. The influence of the composition of the casting solution on the transport characteristics of Ultem membranes was studied: the highest permeability values were achieved using N‑methylpyrrolidone (NMP) as a solvent. The obtained data can be used in the design of membrane systems for the separation of hydrogen-containing gas mixtures, including ammonia recovery and hydrogen purification processes within the framework of low-carbon energy.