Preferential CO₂ separation over H₂ with poly(amidoamine) dendrimer-containing polymeric membrane

Development of effective CO₂ separation technologies is one of the most critical issues for implementation of CO₂ Capture & Storage (CCS) because CO₂ capturing covers about 60 % of the total CCS cost. CO₂ capturing with solution absorption technology has gained current acceptance, and the actual operations have been demonstrated in many countries. However, This technology requires certain amount of energy in recovering CO₂ from the CO₂-capturing solution, which results in developing alternative CO₂ capturing technologies. Because difference in partial pressure of the interest gas between feed and permeate side drives the separation, membrane separation does not need additional energy and can make CO₂ separation much more effective. In pre-combustion such as an integrated gasification combined cycle (IGCC) plant, CO₂/H₂ gas mixture after water-gas shift reaction has a pressure of 2.4 MPa, which would be preferable for membrane separation. Various membranes for CO₂ separation over H2 have been investigated, however, the membrane separation has not been implemented due to lack in CO₂ selectivity or permeability. In this paper, poly(amidoamine) (PAMAM) dendrimer is used to enhance affinity to CO₂ and incorporated in a polymer matrix. The resulting polymeric membrane expressed excellent CO₂ separation properties even under pressure. The CO₂ permeance is relatively lower than the requirement value and 1.0 × 10^-10 m³(STP)/(m² s Pa). However, the permeance can be enhanced by reducing membrane thickness.