Synthesis and Characterization of Thin Samarium Doped Ceria/ Carbonate Dual-Phase Membranes for High Temperature Carbon Dioxide Separation

Synthesis and Characterization of Thin Samarium doped Ceria/ Carbonate Dual-Phase Membranes for High Temperature Carbon Dioxide Separation
 
Bo Lu and Jerry Y.S. Lin*

School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287

*Correspondence author, email: jerry.lin@asu.edu

Abstract: Most CO₂ perm-selective membranes become CO₂ non-selective at high temperatures (>600^oC). Recently, we reported ceramic-carbonate dual-phase membranes which exhibit good CO₂ selectivity and high CO₂ permeance at high temperatures.  In particular, the samarium doped ceria (SDC) /carbonate membranes exhibit highest CO₂ permeance and good stability.  However, these membranes were generally quite thick.  CO₂ permeation through the dual-phase membrane is dominated by oxygen ionic transport in the metal oxide phase.  Thus reduction of membrane thickness could effectively improve membrane performance.  This approach was demonstrated in our previous work by making thin yttria-stabilized-zirconia/carbonate dual-phase membranes which exhibit higher CO₂ permeance than thick dual-phase membranes. The present paper reports synthesis and CO₂permeation properties of thin SDC-carbonate dual-phase membranes.

Thin SDC-carbonate membranes were prepared on macroporous base supports made of mixture of 60 vol% Bi_1.5Y_0.3Sm_0.2O_3-δ (BYS) and 40 vol% SDC powders.  BYS is non-wettable to carbonate, which prevents penetration of molten carbonate to the base support ensuring its porosity after infiltration of carbonate to the thin SDC top layer.  The addition of SDC in the base support is needed to ensure better sintering comparability with the thin SDC layer.  An asymmetric porous supports consisting of thick (~ 2 mm) BYS/SDC support sandwiched by two thin SDC layers (to balance sintering stress) were prepared by co-pressing method.  The thickness of the porous thin SDC layer was around 150-200 μm.  Carbonate was infiltrated to one side of thin porous SDC layer to obtain the asymmetric membranes consisting of the thick base BYS/SDC support and a thin, hermetic SDC-carbonate dual-phase membrane.  CO₂ permeation and separation tests were performed from 500 to 700^oC.  The thin SDC-carbonate membranes exhibit CO₂ permeance from 0.33 x10^-7 to 1.21x10^-7 mol/s.m².Pa in the temperature range of 500-700^oC, with an activation energy for CO₂ permeation of 60 kJ/mol.  The CO₂ permeance of the thin SDC-carbonate membranes is about 5 times that of the thick SDC-carbonate membrane of similar structure.  CO₂ permeance for the thin SDC-carbonate membranes increases with CO₂ partial pressure.   The thin SDC-carbonate dual-phase membranes show stable operation for at least 100 hrs.  These results show promise for using the thin membranes for industrial applications.