CO₂ Separation Improvement Produced on a Ceramic-Carbonate Dense Membrane Superficially Modified with Au-Pd

Ceramic-carbonate membranes have been proposed for the selective separation of CO₂. In previous reports, membranes performance has been enhanced through the improvement of microstructural features and conductivity properties. Different to the aforesaid, this paper was focused on modifying the membrane surface by incorporating metallic particles to promote the involved surface reactions. First, a composite made of a Ce_0.85Sm_0.15O_2-δ and Sm_0.6Sr_0.4Al_0.3Fe_0.7O_3-δ was chemically synthesized. Then porous supports were obtained by pressing powders and sintering. Then, dense membranes were fabricated by infiltration of the supports with molten carbonates and the subsequent deposition of metallic Au-Pd particles on the membrane feed side surface. Obtained membranes were tested for CO₂ separation between 700 °C and 900 °C, using different feed gas mixtures. Membranes show excellent CO₂ permeance (1.72 × 10^-7 mol m^-2 s^-1 Pa^-1) operating at low CO₂ partial pressure in the feed side (PCO₂ = 0.115 atm), wherein about 24% of the total permeation values resulted from the surface modification approach. The permeation mechanism is discussed on the basis of these results.