Membrane separation is potential alternative technology for liquid amine scrubbing in CO2 capture at mass CO2 emission sources, such as coal-fired plants, due to the low-energy and cost effective process, and various membranes have been developed for effective CO2 capture. Among them, polymeric membranes would be promising because of versatile chemical approaches, synthetic feasibility, large-scale productivity, and good processability in comparison to inorganic membranes. In this research group, polymeric membranes have been investigated for pre-combustion CO2 capture, where CO2 is separated over H2. For preferential CO2 permeation over smaller H2, amines, such as poly(amidoamine)s (PAMAMs), are used to enhance CO2 solubility to the polymeric membrane. When PAMAMs are physically immobilized in cross-linked PEG or PVA to form polymeric membranes, the resulting membranes exhibit high CO2 separation properties over H2 especially under humidified conditions and lower CO2 partial pressure than 100 kPa [1-5]. The PAMAM membrane is waiting for demonstration test by Research Institute of Innovative Technology for the Earth (RITE, Japan).
The amine-containing polymeric membranes can be also applicable to on-site H2 refilling station to make the H2 production process carbon-free by capturing CO2 in the off-gas by the membranes as shown in Figure 1. The off-gas consists of H2 and CO2 at ambient pressure and temperature (CO2 partial pressure: 40-50 kPa). In comparison to mass CO2 emission sources, the amount of CO2 is smaller and thus the captured CO2 can be utilized for plant growth or even refrigerant. However, the CO2 permeability should be improved for implementation.
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