Synthesis and characterization of thin ceramic-carbonate dual-phase membranes for carbon dioxide separation

Ceramic-carbonate dual-phase membranes are perm-selective to carbon dioxide at high temperatures. This paper reports a strategy to prepare thin ceramic-carbonate dual-phase membranes with improved carbon dioxide permeance. Two-layer asymmetric supports consisting of a large pore base support and a thin small pore ionic conducting ceramic top-layer were prepared for the thin dual-phase membranes. A dense thin ceramic-carbonate dual-phase membrane was successfully prepared on the asymmetric support containing carbonate non-wettable base with adequate mechanical bonding between the top-layer and base. The thin dual-phase membrane was constructed with a thin, small pore yttria-stabilized zirconia (YSZ) layer on a large pore Bi_1.5Y_0.3Sm_0.2O_3-δ (BYS) support. Li/Na/K molten carbonate mixture was infiltrated into the top YSZ layer via a direct infiltration method. Carbonate non-wettable BYS support stopped the penetration of carbonate and maintained its porous structure. By this way, a thin, dense ceramic-carbonate dual-phase membrane was prepared on a porous support after infiltration. High temperature CO₂ permeation test was carried out for the membrane. CO₂ permeance through the thin dual-phase membrane increased with temperature (500-650°C). At 650°C, maximum CO₂ flux was 3.9×10^-3molm^-2s^-1. The CO₂ permeation activation energy is 106kJmol^-1. The thin YSZ-carbonate dual-phase membrane offers much higher CO₂ permeance than the reported thick dual-phase membranes. Reduction of the thickness hence lessening resistance and strengthening ionic transport should be the major reason.