Ion-conducting dual-phase membrane for high temperature CO 2 separation Hang Qi, Alan Thursfield, Evangelos Papaioannou and Ian S. Metcalfe Merz Court, NE1 7RU, Newcastle-upon-Tyne, United Kingdom The concept of a dual-phase carbonate-electroceramic membrane based on the idea of the molten carbonate fuel cell (MCFC) has been demonstrated recently [1, 2]. The dual-phase system consists of a porous oxygen anion O 2- conducting ceramic substrate hosting a guest molten carbonate phase (usually a Li/Na/K carbonate eutectic mixture) infiltrated within the pore network. Carbon dioxide from the feed gas reacts with oxygen ions supplied by the ionic conducting host membrane to form a carbonate (CO 3 2- ) anion in the molten carbonate phase. The CO 3 2- anion is transported through the molten phase carbonate at high temperatures under a chemical potential gradient and released as gasous CO 2 on the permeate side. The O 2- anion is transported back to the feed side membrane by the substrate [1, 2]. A schematic is presented in Figure 2. In this project, the dual phase membrane was fabricated by yttria stabilized zirconia (8 mol% Y 2 O 3 ) powder which was mechanically mixed with up to 33 wt% corn starch as a pore former and sintered at 1450 °C. The sintered porous membrane was then infiltrated with a known quantity of a eutectic mixture of; Li 2 CO 3, Na 2 CO 3 and K 2 CO 3 in the molar ratio 51:16:33. Experimental setup YSZ-carbonate membrane Gas outlet tube in permeate side of membrane Alumina tube support for membrane Gas inlet tube in permeate side of membrane Thermal couple helium CO 2 /N 2 1:1 To mass spectrometer for analysis References 1.Jennifer L. Wade, C.L., Alan C. West, Klaus S. Lackner, Composite electrolyte membranes for high temperature CO2 separation. Journal of Membrane Science, (2011): p Matthew Anderson, Y.S.L., Carbonate–ceramic dual- phase membrane for carbon dioxide separation. Journal of Membrane Science, (2010): p Conceptual schematic of the ion conducting, dual-phase membrane. 50% CO 2 and 50% N 2 was provided in feed side of membrane; helium was carrier gas in permeate side of membrane. Silver paste pre-seal the membrane to the alumina tube. Glass based sealant at edge of the membrane Clean surface of the dual-phase membrane. Membrane sealing Conclusion The CO 2 permeability of a dual-phase YSZ-carbonate membrane was investigated by long term CO 2 permeation at 800 °C, mol of CO 2 was permeated during 50 hours; while mol carbonate ions were infiltrated which indicated that CO 2 permeation had occurred. The CO 2 permeability at 850 °C was 7× mol m -1 s -1 Pa -1, while at 800 °C it decreased to 4 mol m -1 s -1 Pa -1 and 2 mol m -1 s -1 Pa -1 at 780°C. The sealing method gives a ratio of permeated CO 2 to leak N 2 of 15:1 at 850 °C. Selected Results The CO 2 permeated over 50 hours was estimated to be mol; while the carbonate that was infiltrated into the membrane is 0.28 gram which contains mol of carbonate ions. The average leak-subtracted CO 2 permeability at 850°C was 7× mol m -1 s -1 Pa -1, while at 780°C it decreased to 2× mol m -1 s -1 Pa -1. The average selectivity of CO 2 over N 2 at 850°C is 15:1 and initially 17:1 at 780°C. It decreases to 2:1 after a further one hour as the N 2 leak increases. CO 2 permeability dependence on temperature. It can be seen that permeability decreases on a decrease of temperature. This decrease is reversible on returning the membrane temperature to the original value. Group of Applied Catalysis Introduction Figure 2. Figure 1. Membrane reactor setup Figure 3. The membrane is 2.4mm thick and diameter is 14mm. The porosity of the host membrane was measured by mercury porosimetry which indicated that 33 wt% of corn starch pore former creates about 47% porosity with an average pore size of around 700 nm. For a 1.5 g porous YSZ host membrane with about 40% porosity, 0.28 gram carbonate (2.2g cm -3 ) was infiltrated, as one would expect if all of the pore volume was occupied by carbonate. Figure 4. (a) Flux of CO 2 and leak N 2 ; (b) Leak-subtracted CO 2 permeability. At 1bar