Perovskite-based hydrogen membranes

In addition to the challenges mentioned above, the thermochemical stability of the perovskite membranes in syngas environment is a major hurdle that needs to be overcome for successful implementation of membrane technology for hydrogen separation. Both SrCeOs and BaCe03 based compositions are shown to be unstable in the presence of CO2 and H2O [16-18]. It was shown that replacing a fraction of Ce in the perovskite with Zr also provided improved stability [19]. However this... 

Concerning non-porous membranes, these are categorized as dense ceramic electrolytes such as yttria-stabilized zirconia (YSZ) and perovskite membranes [16], which allow only the permeation of ionic oxygen. Permeation through metal membranes such as palladium and a palladium alloy is based on the selective dissolution of hydrogen and diffusion through the metal membrane. 

Packed bed membrane reactors have two main limitations (i) the difficult heat management that can be very detrimental for highly exothermic reactions like in perovskite membrane reactors and (ii) the extent of bed-to-wall mass transfer limitations that are more important for extractor-type reactors like Pd-based membrane reactors (due to the high permeation fluxes of membranes). In fact, the bed-to-wall mass transfer limitations would decrease the partial pressure of hydrogen close to the membrane surface and thus decrease the membrane flux. 

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