Producing syngas and hydrogen from biofuels is a promising technology in the modern energy. In this work results of authors’ research aimed at design of supported membranes for oxygen and hydrogen separation are reviewed. Nanocomposites were deposited as thin layers on Ni–Al foam substrates. Oxygen separation membranes were tested in CH4 selective oxidation/oxi-dry reforming. The hydrogen separation membranes were tested in C2H5OH steam reforming. High oxygen/hydrogen fluxes were demonstrated. For oxygen separation membranes syngas yield and methane conversion increase with temperature and contact time. For reactor with hydrogen separation membrane a good performance in ethanol steam reforming was obtained. Hydrogen permeation increases with ethanol inlet concentration, then a slight decrease is observed. The results of tests demonstrated the oxygen/hydrogen permeability promising for the practical application, high catalytic performance and a good thermochemical stability.

In the field of modern hydrogen energy, obtaining pure hydrogen and syngas and then being able to use them for green energy production are significant problems. Developing solid oxide fuel cells (SOFC) and catalytic membranes for oxygen separation as well as materials for these devices is one of the most likely ways to solve these problems. In this work, the authors’ recent studies in this field are reviewed; the fundamentals of developing materials for SOFC cathodes and oxygen separation membranes’ permselective layers based on research of their oxygen mobility and surface reactivity are presented. Ruddlesden – Popper phases Ln2–xCaxNiO4+δ (LnCNO) and perovskite-fluorite nanocomposites PrNi0.5Co0.5O3–δ–Ce0.9Y0.1O2–δ (PNC–YDC) were studied by isotope exchange of oxygen with C18O2 and 18O2 in flow and closed reactors. For LnCNO a high oxygen mobility was shown (D* ~ 10–7 cm2/s at 700 °C), being provided by the cooperative mechanism of oxygen migration involving both regular and highly-mobile interstitial oxygen. For PNC–YDC dominated a wide fast diffusion channel via fluorite phase and interphases due to features of the redistribution of cations resulting in superior oxygen mobility (D* ~ 10–8 cm2/s at 700 °C). After optimization of composition and nanodomain structure of these materials, as cathodes of SOFC they provided a high power density, while for asymmetric supported oxygen separation membranes – a high oxygen permeability.

Design of oxygen and hydrogen separation membranes is the point of current interest in producing syngas from biofuels. Nanocomposites with a high mixed ionic-electronic conductivity are known to be promising materials for these applications. This work aims at studying performance of oxygen and hydrogen separation membranes based on nanocomposites PrNi0.5Co0.5O3-delta + Ce0.9Y0.1O2-delta and Nd(5.5)WO1(1.25-delta) + NiCu alloy, respectively. A high and stable performance promising for the practical application was demonstrated for these membranes. For oxygen separation membrane CH4 conversion is up to 50% with H-2 content in the outlet feed being up to 25% at 900 degrees C. For reactor with hydrogen separation membrane complete EtOH conversion was achieved at T similar to 700 degrees C even at the highest flow rate, and a high hydrogen permeation (>= 1 ml H-2 cm(-2) min(-1)) was revealed. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Mechanism of ethanol partial oxidation into syngas over catalysts based on mesoporous MgAl2O4 spinel loaded with fluorite PrCeZrO or spinel MnCr2O4 oxides and promoted by Ru + Ni was studied by in situ FTIRS and 18O SSITKA. Surface species (ethoxy, adsorbed ethanol, acetaldehyde, acetate, etc.) were identified and their thermal stability and reactivity were estimated. Analysis of kinetics of the 18O transfer into reaction products (CO, CO2, CH3CHO) allowed to estimate the rates of steps and present a scheme of the reaction mechanism including (1) fast CH3CHO formation on mixed metal oxide sites; (2) rate-limiting stage of surface oxygen species incorporation into acetaldehyde or ethoxy species with C–C bond rupture yielding CO and CO2 along with H2 and H2O; (3) water gas shift reaction by redox mechanism affecting CO/CO2 ratio and their oxygen isotope fraction. Strong interaction of PrCeZrO or MnCr2O4 oxides with MgAl2O4 support results in decreasing constants of main reaction steps in comparison with those for catalysts based on bulk fluorite and spinel oxides, correlating with a higher surface oxygen bonding strength and its low coverage revealed by pulse microcalorimetry. DFT analysis confirmed a low energy barrier of the step of Ru–O oxygen incorporation into C–C bond of ethoxy species with its rupture explaining a higher syngas selectivity for Ru-doped catalysts.

Design of materials for solid oxide fuel cells cathodes and oxygen separation membranes and studying their oxygen transport characteristics are important problems of modern hydrogen energy. In the current work, fundamentals of such materials design based on characterization of their oxygen mobility by oxygen isotope exchange with C18O2 and 18O2 in flow and closed reactors for samples of Ruddlesden – Popper-type oxides Ln2-xCaxNiO4+δ, perovskite-fluorite nanocomposites PrNi0.5Co0.5O3-δ – Ce0.9Y0.1O2-δ, etc. are presented. Fast oxygen transport was demonstrated for PNC – YDC (DO ~10-8 cm2/s at 700°C) nanocomposites due to domination of the fast diffusion channel involving oxygen of the fluorite phase with incorporated Pr cations and developed perovskite-fluorite interfaces. For LnCNO materials a high oxygen mobility (DO ~10-7 cm2/s at 700°C) provided by the cooperative mechanism of its migration was demonstrated. Depending on Ca dopant content and Ln cation nature, in some cases 1–2 additional channels of the slow diffusion appear due to decreasing the interstitial oxygen content and increasing the energy barrier for oxygen jumps due to cationic size effect. Optimized by the chemical composition and nanodomain structure materials of these types demonstrated a high performance as SOFC cathodes and functional layers in asymmetric supported oxygen separation membranes.

Novel and stable to carbonization nanocomposite materials based upon Pr2−xNiO4+δ, Pr1−xSmxNi1−yCoyO3−δ and YDC were synthesized via Pechini route and ultrasonic dispersion, and were sintered using conventional and advanced (microwave, e-beam) techniques. Their real/nano structure and transport properties were characterized by sophisticated methods. Nanocomposites have high oxygen mobility due to cooperative mechanism of migration for Pr2−xNiO4+δ and fast channel of diffusion for nanocomposites due to Pr cations' incorporation into YDC. Power density values of single SOFCs were up to 0.5 W/cm2 at 700 °C, being comparable with that for state-of-the-art cathodes. For oxygen separation membranes, high and stable performance was demonstrated.

This chapter reviews recent advances in developing intermediate-temperature solid oxide fuel cells; oxygen and hydrogen separation membranes; and methods for obtaining advanced oxide, nanocomposite, and nanostructured materials for such devices. All the materials were synthesized by novel methods and characterized by sophisticated techniques. High ionic conductivity and improved oxygen/protonic mobility and surface reactivity were demonstrated. A new approach to building the functional layers was developed. A high-power density of single-button fuel cells in the intermediate-temperature range was reached. Oxygen and hydrogen separation membranes demonstrated promising and stable performance due to fast ionic transport and high catalytic activity of the materials concerned.

For structured catalysts of biofuels transformation into syngas inexpensive and stable to sintering active components based upon Mg-doped gamma-alumina with supported LaNi0.9Ru0.1O3 perovskite or MnCr2O4 spinel promoted by Ru + Ni were developed. Characterization of the surface features, reactivity, catalytic activity and routes of ethanol transformation on these catalysts demonstrated that suppression of support acidity, strong interaction of Ru-Ni alloy nanoparticles with manganese chromite layers on support and a high redox ability provide a high yield of syngas and stability to coking. The most promising active component (2 wt% Ni + 2 wt% Ru)/MnCr2O4/10 wt% MgO gamma-Al2O3 supported on microchannel heat-conducting CrAlO cermet plates demonstrated a high performance and stability to coking in the autothermal reforming of such reactive fuels as glycerol, anisol and turpentine, oil.

Vladislav Sadykov, Natalia Mezentseva, Galina Alikina, Rimma Bunina, Vladimir Pelipenko, Anton Lukashevich, Zakhar Vostrikov, Vladimir Rogov, Tamara Krieger, Arkady Ishchenko, Vladimir Zaikovsky, Lyudmila Bobrova, Julian Ross, Oleg Smorygo, Alevtina Smirnova, Bert Rietveld and Frans van Berkel, 1Boreskov Institute of Catalysis, Novosibirsk State University, 2University of Limerick, 3Powder Metallurgy Institute, 4Eastern Connecticut State University, 5Energy Research Center of the Netherlands, 1Russia 2Ireland 3Belarus 4USA 5Netherlands

Partial oxidation of methane into syngas at short contact times (5–15ms) was studied in both steady-state and transient modes at temperatures up to 850°C in realistic feeds (CH4 content up to 20%, CH4/O2=2) with a minimum impact of mass and heat transfer for structured catalysts carrying Pt/Ln0.3Ce0.35Zr0.35O2−y (Ln=La, Pr, Gd) as thin layers on walls of corundum channel substrates. Oxygen mobility and reactivity of the active phase were characterized by oxygen isotope heteroexchange, temperature-programmed O2 desorption and CH4 reduction, isothermal pulse reduction by methane with wide variation of CH4 concentrations and TAP pulse studies. Experimental data point towards a selective oxidation of methane into syngas via a direct route with oxygen-assisted methane activation. This mechanistic feature is related to the strong Pt-support interaction stabilizing highly dispersed oxidic Pt species less active in CH4 and syngas combustion than metallic Pt clusters. Support activates O2 molecules and supplies active oxygen species to Pt sites. A high rate of oxygen diffusion on the surface and in the bulk of the support and Pt-support oxygen spillover stabilizes Pt in a well dispersed partially oxidized state while preventing coking at high concentrations of CH4 in the feed.

Mixed ionic–electronic conducting nanocomposite La0.8Sr0.2Ni0.4Fe0.6O3 (LSNF)–Ce0.8Gd0.2O2– δ (GDC) was prepared via ultrasonic dispersion of nanocrystalline powders of perovskite and fluorite oxides in water with addition of surfactant, followed by drying and sintering up to 1300°C. Analysis of the real structure of nanocomposite (studied by XRD and TEM with EDX) and its surface composition (studied by XPS) revealed moderate redistribution of elements between phases favoring their epitaxy. Results of impedance spectroscopy, oxygen isotope exchange, O2 TPD and H2 TPR experiments revealed a positive effect of composite interfaces on the oxygen mobility and reactivity agreeing with the ambipolar transport behavior of MIEC composite. Preliminary testing of button-size cell with functionally graded LSNF–GDC cathode layer supported on thin YSZ layer covering Ni/YSZ cermet demonstrated high and stable performance, which is promising for its practical application.

Nanocomposite catalysts comprised Ni particles embedded into the complex oxide matrix comprised Y- or Sc-stabilized zirconia (YSZ, ScCeSZ) combined with doped ceria–zirconia oxides or La–Pr–Mn–Cr–O perovskite and promoted by Pt, Pd or Ru were synthesized via different routes (impregnation of YSZ or NiO/YSZ composites with different precursors, one-pot Pechini procedure). Both composition and preparation procedure determining degree of interaction between components of composites were found to strongly affect performance of nanocomposites in steam reforming of methane at short contact times as well as their stability to coking in stoichiometric feeds. Temperature-programmed reduction of composites by CH4 followed by temperature-programmed oxidation by H2O revealed more efficient dissociation of CH4 on promoted composites yielding loose surface CHx species more easily removed by water as compared with unpromoted composites. Best active components highly active and stable to coking were supported as thin layers on different substrates (Ni/YSZ anode platelets, refractory dense/porous metal alloys, cermet or corundum monolithic carriers). These structured catalysts demonstrated high efficiency and stability in the reactions of steam reforming of methane and oxygenates (ethanol, acetone) in pilot-scale reactors.

Ceria-zirconia samples doped with Gd, Pr, Sm, or La cations were prepared via Pechini route and promoted by Pt. Effect of their real structure and surface properties (characterized by neutronography, EXAFS, XPS, FTIRS of adsorbed CO) on the mobility and reactivity of the lattice oxygen (by oxygen isotope exchange and CH 4 TPR) was analyzed. For the reaction of CH 4 steam reforming (SR), catalytic performance is determined both by Pt dispersion and lattice oxygen mobility. Ni-YSZ anodes promoted by these catalysts possess a stable and efficient performance in CH 4 SR in the 600-800°C range in stoichiometric feeds without coking.

Nanocrystalline ceria-zirconia samples doped with rare-earth (Gd, Pr, Sm, La) cations were prepared via modified Pechini route. Effect of their real structure and surface composition characterized by a combination of sophisticated physical methods (XRD, TEM +EDX, EXAFS, WAXS, UV-Vis, XPS, SIMS) on the mobility and reactivity of the lattice oxygen estimated by oxygen isotope exchange, H 2 , CH 4 and CO TPR was analyzed. For the reaction of acetone autothermal reforming into syngas, catalytic activity correlates rather well with the oxygen mobility controlled by the type and content of a dopant

Effect of fluorite-like or perovskite-like complex oxide promoters, Pd and Cu on the performance of Ni/8YSZ and Ni/ScCeSZ anode materials in CH4 steam reforming (SR) or selective oxidation (SO) by O2 into syngas was studied. The spatial distribution of dopants in composites before and after contact with the reaction feed, features of components mutual interaction and forms of deposited coke were controlled by TEM combined with EDX analysis. The lattice oxygen mobility and reactivity were estimated by CH4 and H2 temperature-programmed reduction (TPR), and the amount of deposited carbon after operation in the feed with stoichiometric H2O/CH4 ratio was estimated by the temperature-programmed oxidation. Promoters decrease the amount of deposited coke, while doping by Pd or Cu ensures also a good and stable performance at moderate (∼550°C) temperatures required for the intermediate-temperature solid oxide fuel cells (IT SOFC) operation.

Nanocomposites comprised of fluorite-like (doped ceria) and perovskite- like (doped manganite) phases were prepared using a polymerized precursor (Pechini) route and two sources of lanthanides (Ln) - either pure Gd and Ce salts or an industrial ceria-rich mixture of Ln carbonates. Genesis of the structure of composites with annealing temperature has been studied by X-ray diffraction, Transmission Electron Microscopy and Raman. Up to 1300 o C, particle sizes of both fluorite and perovskite phases remain in the nano-range. Nanocomposites possess a high conductivity, lattice oxygen mobility and reactivity with respect to methane exceeding that of individual phases. They are also good catalysts for oxidation of decane by O2 without coking. Nanocomposite prepared from the industrial Ln source demonstrates better performance than that prepared from pure salts.

Effect of fluorite-like or perovskite-like complex oxide promoters and Pd on the performance of Ni/YSZ and Ni/ScSZ cermets in methane steam reforming or selective oxidation by O2 into syngas at short contact times was studied. Spatial uniformity of dopants distribution in composites was controlled by TEM combined with EDX, while the lattice oxygen mobility and reactivity was elucidated by CH4 and H2 TPR. Oxide promoters allow to operate even at stoichiometric H2O/CH4 ratio by suppressing coke deposition through modification of Ni surface, while doping by Pd ensures reasonable performance at moderate (~550 °C) temperatures required for Intermediate-Temperature Solid Oxide Fuel Cells (IT SOFC).

The activity of Pt/Ce1-xGdxO2-y samples in steam and dry reforming of methane at short contact times correlates with the lattice oxygen mobility. For the partial oxidation of methane (POM), the oxygen mobility should be optimized to prevent methane combustion.

For Pr-doped ceria Ce1-xPrxO2-y prepared by the Pechini route and promoted with Pt, the mobility and reactivity of lattice oxygen were found to depend on the Pr content, which seems to determine the density of surface and bulk anion vacancies and domain boundaries.

Nanopowders of LaGaO3- and LaMnO3-based complex perovskites (P) and ceria-based fluorites (F) were prepared by mechanosynthesis. Compatible nanocomposites F+P and P+P with mixed ion and electron conducting (MIEC) properties were prepared and sintered at moderate temperatures up to dense ceramics. The obtained materials were studied by means of XRD, SEM, TEM, electrical conductivity measurements, temperature programmed (TP) reduction/oxidation and preliminary estimations of permeability were obtained. A new strategy based on the advantages of the mechanochemical ceramic approach is proposed to design multilayer ceramic membranes for CMR. Casting technology and one-step sintering were used for the production of thin film membranes with MIEC properties on porous substrates. The coarse fraction of as-milled powders from agglomerates with density ∼70% was used for the porous substrate, and fine fractions of aggregates with sizes <1μm were used in preparation of composites for thin dense films. Ceria-based composites prepared by the Pechini route and/or mechanochemical method are proposed as materials for protecting thin films.