The Magic of Spiro‐Epoxy Moiety: An Easy Way to Improve CO₂‐Separation Performance of Polymer Membrane

Abstract

The development of polymers with high separation characteristics for the efficient removal of carbon dioxide from bio‐/natural gases is the key to reducing the environmental impact of CO2. In this work, preparation and gas‐separation properties of novel vinyl‐addition polynorbornenes containing oxirane‐moieties at spiro centers, which combine high CO2‐permeability with remarkable selectivities for separation of CO2 from its mixtures with nitrogen and methane are published. Gas permeability data of the epoxidized polymer based on 5‐ethylidene‐2‐norbornene exceed the Robeson upper bound of 2019 for the CO2/N2 system (CO2 permeability is 1000 Barrer, α(CO2/N2) = 67)). Separation experiments with mixtures of gases confirm the high separation performance of this polymer. In particular, the data for CO2/CH4 separation are above or close to the upper bound of 2018 for mixed gases. A similar effect of introducing oxirane moieties into spiro centers is also shown for another vinyl‐addition polymer derived from 5‐isopropylidene‐2‐norbornene and is not observed for a related polymer bearing oxirane moieties at the ends of side chains. A simple synthesis of the epoxidized polymer from available 5‐ethylidene‐2‐norbornene, combined with high CO2‐permeability and selectivities, may open a window for industrial applications of this polymer in important membrane processes, in particular, for natural/biogas upgrading.