Sour mixed-gas upper bounds of glassy polymeric membranes

Abstract

Polymeric membranes prepared from glassy polymers suffer from a permeability-selectivity trade-off relationship. When their permeability is increased, their selectivity decreases, and vice versa. The performance of membranes during pure-gas permeation is assessed by plotting their permeability and selectivity data on a corresponding pure-gas upper bound graph reported in literature. For potential use in industrial applications, it is recommended to assess the performance of membranes through their mixed-gas separation performance, as the use of pure-gas upper bounds could be misleading. As a result of this, theoretical (2015) and experimental (2018) CO2/CH4 sweet mixed-gas upper bounds have been proposed. Sour mixed-gas separation is even more complex, due to the presence of hydrogen sulfide (H2S) in the gas stream. Several H2S/CH4 trade-off lines were reported in literature based on the performance of specific materials prepared, however, in each case, the empirical parameters were drastically different. In this paper, we revisited the 2018 CO2/CH4 mixed-gas upper bound by including data measured in our laboratory and the latest sweet mixed-gas permeation data reported to date. Moreover, we propose new H2S/CH4, CO2/CH4, and combined acid gas sour mixed-gas upper bounds based on all of the sour mixed-gas permeation data reported by our research group and those available in literature. These upper bounds will serve as unique qualitative standards to design and assess new polymeric membranes developed in the future with potential use in industrial applications.