Structural and transport properties of E-beam sintered materials for catalytic membranes with selective hydrogen permeability
BESPALKO Y. 1, KHARINA S. 1, EREMEEV N. 1, MIKHAILENKO M. 2, KOROBEYNIKOV M. 3, ULIHIN A. 2, SADYKOV V. 1
1 Boreskov Institute of Catalysis, Novosibirsk, Russian Federation; 2 Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk, Russian Federation; 3 Budker Institute of Nuclear Physics, Novosibirsk, Russian Federation
Last decade proton conducting mixed oxides have been extensively studied as application in the different electrochemical devices (fuel cells, separators, etc.). Proton conducting membranes based on them can also be used to remove hydrogen from products of catalytic reactions, for example, ethanol steam reforming, which increases efficiency of reactors. Ceramic-metal composites with high mixed proton-electron conductivity have a great potential for use in catalytic membrane reactors, since they meet requirements of high thermal and mechanical strength along with chemical stability in the working media. The metal phase increases the electronic conductivity and reactivity in the surface processes of hydrogen exchange, while ceramic phase, in addition to ionic conductivity, contributes to the mechanical strength of the composite. Lanthanide orthoniobates, tungstates and scandates are promising materials for hydrogen separation membranes due to their high protonic conductivity.
Nanocomposites were prepared by treating in the high-power planetary ball mill AGO-2 a mixture of mixed oxides (Nd5.5(Mo,W)O11.25-δ, La0,96Sr0,04ScO3 ? LaNb0,8Mo0,2O4) calcined at 700ºC and NiCu alloy with addition of isopropanol. The powders were pressed into pellets and then sintered using conventional thermal sintering as well as radiation -thermal sintering using e-beams at 1100-1300 °C.
The influence of the structure of nanocomposites and sintering conditions on the transport properties of obtained materials was investigated. According to XRD, in nanocomposites the main phases of scheelite LaNb0.8Mo0.2O4, perovskite La0.96Sr0.04ScO3 and fluorite Nd5.5(Mo,W)O11.25 were observed. The phases of Ni and Cu oxides disappeared after treatment in hydrogen and formed a new phase of NiCu alloy. No chemical interaction between alloy and mixed oxide nanoparticles was observed. The oxygen mobility studies by temperature-programmed heteroexchange with C18O2 revealed two types of bulk oxygen migration channels related to two phases in samples. Asymmetric membranes comprised of these nanocomposites supported as thin layers on Ni-Al foam substrates with spatial gradient porosity demonstrated a high hydrogen permeability, selectivity and stability in hydrogen separation from syngas produced by steam reforming of ethanol.
The work was supported by the Russian Science Foundation (Project 23-73-00045).