Effects of membrane thickness and structural type on the hydrogen separation performance of oxygen-permeable membrane reactors.

Abstract Membrane thickness and structural type, which are closely related to the species diffusion in the membrane bulk and reactions at the gas-solid interfaces, have important influences on the performance of a dense ceramic membrane. Recently, oxygen-permeable dense ceramic membrane reactors have been suggested for hydrogen purification at elevated temperatures. Mixed conducting composite with composition of 75 wt% Ce 0.85 Sm 0.15 O 2-δ -25 wt% Sm 0.6 Sr 0.4 Al 0.3 Fe 0.7 O 3-δ (SDC-SSAF) was fabricated into oxygen-permeable membranes with different thicknesses and structural types. The effects of membrane thickness and structural type on the hydrogen separation performance were tested under different hydrogen concentrations and flow rates on side I, different flow rates of steam/He mixed gas on side II as well as different temperatures. The effect of concentration polarization on hydrogen separation rate and the rate determining steps were discussed by comparing the performances of the symmetric membranes and the asymmetric membranes. The apparent activation energies of the membrane reactors for hydrogen separation were analyzed. This study will give some constructive guides to the subsequent work on how to effectively improve the hydrogen separation performance. Graphical abstract Three oxygen-permeable ceramic membranes with different thicknesses and structural types were designed, prepared and tested to explore the effects of membrane thickness and structural type on the hydrogen separation performance. fx1 Highlights • Membranes with different thicknesses and structural types were prepared and tested. • Concentration polarization has weak effect on hydrogen separation process for asymmetric membranes. • Reducing the membrane thickness is effective to improve the hydrogen separation rate at high temperature. • Developing high activity catalysts is the key to enhance performance at low temperature. [ABSTRACT FROM AUTHOR]