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CO2/H2 separation by membranes

This activity aims to develop and characterize different types of polymeric membranes to separate pure gas or mixes of gases similar to syngas.

In the pre-combustion-capture (applied in integrated gasification combined cycle – IGCC – plants), CO2 is separated from the syngas before combustion: primary fuel is converted into a syngas that can be processed for the CO2 capture; after the water-gas shift reaction, syngas is mainly composed by CO2 and H2. The target of the activity is to develop selective membranes to separate CO2 from H2 before syngas utilization in the gas turbine. In particular, the use of polymeric membranes are promising for this purpose because of their specific properties.

Unfortunately, such membranes show a trade-off relationship between selectivity and permeability: a solution to this problem can be given from the combination of polymeric materials and inorganic fillers, with so-called mixed matrix membranes (MMMs), thus combining the superior transport properties of fillers without giving up the processability and mechanical properties of polymers. The research activity, developed with the Department of Civil, Chemical, Environmental and Materials Engineering of the University of Bologna, has made it possible to verify the feasibility of MMMs based on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) for H2/CO2 separation in the purification of syngas obtained from coal gasification processes. PPO is a glassy polymer suitable for industrial applications, which shows a very high permeability but a moderate selectivity for combined H2/CO2 at room temperature. In order to perform H2 purification and carbon capture at the same time, the research aims to improve H2-selective behaviour by incorporating different types of filler such as zeolites and metal organic frameworks (MOFs).

The work involves the preparation and preliminary characterization of membranes with specific selectivity and diffusivity; membranes, prepared at the University of Bologna, will be tested soon in a permeometer at the Sotacarbo laboratories.