A critical review of cyclic transient membrane gas separation processes: State of the art, opportunities and limitations

► A systematic analysis of the potential interest (increased selectivity or reverse selectivity) of transient membrane gas separations is reported for 2145 different gas pairs is reported. This target has been achieved based on theoretical solubility and diffusivity correlations (trade-off upper bound calculations). ► Four different case studies on the performances of unsteady vs. steady membrane separations in terms of selectivity and productivity, obtained through a rigorous optimization strategy are reported (helium recovery, rare gases separation, hydrogen purification, uranium isotope separation). ► The limited exhaustion ratio of short time scale cyclic transient membrane separations is demonstrated for the first time.