Emissions of gaseous impurities into atmosphere may be prevented with the help of membrane purifying modules, which capture certain gases and let out others. In such modules carbon dioxide does not get into the ambient air, but goes through a layer, which selectively lets it out. The better is the passage of gas through the membrane, the less selectivity of capturing is observed. And vice versa, if the capturing is over-selective, very small amounts of it pass through the polymer, and filtration is not efficient enough. That is why scientists are trying to create membranes allowing for the balance between selectivity and permeability for carbon dioxide.
Scientists from the Petroleum-Chemical Synthesis Institute of RAS proposed their solution to this issue. They synthesised polymeric material allowing for capturing carbon dioxide from gas mixes with high level of selectivity. This polymeric material is based on norbornene – an organic compound capable of forming polymers with different spatial network depending on the type of catalyst used in the synthesis process. However, not all norbornene-based polymers have the required features. To improve their gas permeability, the scientists introduced epoxy materials into their structure, which allow for selective passing-through of carbon dioxide.
As a rule, norbornene synthesised in that way quickly decays when used for a long time. The researchers were able to resolve this problem using palladium containing catalysts allowing for receiving stable polymers with high thermal and chemical endurance. The authors of the study compared the levels of efficiency of polymers with and without epoxy materials when separating the mixes of carbon dioxide with nitrogen, oxygen or methane. It turned out that after adding epoxy the permeability for methane and oxygen went down by 56% and 37% respectively, and for carbon dioxide the permeability grew 2.5 times. At the same time the selectivity (separation) rate of the new polymer grew 1.9-3.4 times versus the substances for which epoxy materials were not used.
“As a rule, polymers for gas-separating membranes feature a balance between permeability for certain type of gas and selectivity of its separation versus other gases in the mix. The higher permeability, the lower selectivity. The most efficient polymers in this segment have a certain limit of their performance associated with this compromise between permeability and selectivity. New research and development activities result in creating new polymers, so this limit is moved up gradually. Our polymer is outstanding as it is beyond the currently existing limit being 2–3 times more efficient than its analogues”, Russian Science Foundation is citing Alyona Voznyak, one of the researchers.
