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D2.5 Optimum membranes and ILs for CO2 capture and concentration including scale-up strategy - Executive Summary

IL modified polysulfone membranes were prepared by two different methods: chemical modification and soaking in IL solutions. Obtained membranes were characterized physico-chemically and finally their CO2 capture abilities were studied. Although modified polysulfone in the membranes could not be detected by elemental analysis nor ATR-IR, a change in the membrane internal morphology after its incorporation by ESEM analysis was detected. The introduction of the modified polysulfone resulted in an amorphous morphology in comparison to the porous structure of the reference membrane. During the CO2 permeability studies the best results were obtained with SL20 material thus further enhancement of the membrane structure were done.

On the other hand, when poly-ionic liquids were introduced to the membrane structure, we were able to detect it by means of elemental analysisand ATR-IR analysis. The membranes produced were tested for the CO2 diffusion and nitrogen diffusion using microbalance. The data clearly shows that the presence of ILs increases the solubility of CO2 in the membrane itself, and the best representative is the one containing octyl imidazole, having a good balance between the permeability of carbon dioxide (thus velocity of the CO2 capture) and the selectivity of nitrogen.

Four of the best performing membranes obtained by soaking were further used to perform permeability test. The quantitative values of CO2 and N2 permeability were obtained only for the blank polysulfone membranes and not for the modified ones. Thus, we can conclude that the membranes are capable to adsorb CO2 but not to transport it through. It looks like the ILs in the pores created an impermeable barrier for gases. For the scale-up of the membranes: 5 flat sheets in dimensions of 15x21 cm2 are needed. This is not so far from the obtained membranes and 28.65g/membrane of polymeric solution will be needed to cast membrane of size 15x21 cm2. It can be easily prepared with the use of equipment currently available at EUT.

The ionic liquids needed for the membranes were selected and the strategies for their scale up were analyzed. The best possible scale up approach in terms of the production cost, yields, workup and availability of the starting materials was selected. The two chemical absorbing ILs, BMIM OAc and BMIM oTf were scaled up to 5kg, whereas the IL needed for the membranes (BMIM Succ) only to a scale of 500g, which is more than enough for the needs of the TPER reactor.