Carbonate-ceramic dual-phase membrane for carbon dioxide separation

A new carbonate-ceramic dual-phase membrane for high temperature CO₂ separation was synthesized from porous La_0.6Sr_0.4Co_0.8Fe_0.2O_3-δ (LSCF) supports infiltrated with a eutectic molten carbonate (Li₂CO₃/Na₂CO₃/K₂CO₃) mixture. Helium permeances of the LSCF support before and after infiltration of molten carbonate were found to be on the order of 10^-6 and less than 10^-10molm^-2s^-1Pa^-1 respectively. On average, supports were found to increase in weight by 33% after infiltration. High temperature CO₂ permeation experiments were carried out for several membranes of varying thickness under low oxygen partial pressure (PO2=10-4 atm). Maximum permeances of 2.01, 3.73, 4.63 and 4.77×10^-8molm^-2s^-1Pa^-1 were obtained at 900°C for dual-phase membranes with thicknesses of 3.0, 1.5, 0.75 and 0.375mm respectively. A CO₂/Ar separation factor of at least 225 was achieved at 900°C for the 0.375mm thick membrane. The activation energy for CO₂ permeation for these membranes was calculated to be 86.4-89.9kJmol^-1 depending on membrane thickness. Experimental CO₂ permeation data can be well predicted by a model that considers oxygen ionic conduction in the solid phase of LSCF support in conjunction with structure data for the molten carbonate and LSCF solid phases that was characterized by helium permeation and electrical conductivity measurements.