NORECS / Videos / ProboStat Fixed bed reactor Search FAQ Order and Enquiry Contact Language
ProboStat webinar: Fixed bed reactor

Introduces the Fixed Bed Reactor accessory for ProboStat. Exchangeable glass or quartz frit tubes for plain catalytic activity testing, thermocouple inside the catalyst bed, plus the possibility to add electrodes to study effects of electrical fields, currents, or plasma.

These articles refer to ProboStat or other NORECS products, filtered with keywords: 'catalytic, catalyst, fixed bed reactor'  
ID=604

Tuning the RWGS Reaction via EPOC and In Situ Electro-oxidation of Cobalt Nanoparticles

Authors Dimitrios Zagoraios Dimitrios Zagoraios Department of Chemical Engineering, University oDimitrios Zagoraios, Sotirios Tsatsos, Stella Kennou, Constantinos G. Vayenas, Georgios Kyriakou, and Alexandros Katsaounis
Source
ACS Catal.
Volume: 10, Issue: 24, Pages: 14916–14927
Time of Publication: 2020
Abstract The electrochemical promotion of catalytic activity by non-noble transition metals is rarely reported in the literature. Here, Co nanoparticles were utilized for the electrochemical activation of CO2 hydrogenation under atmospheric pressure conditions. A range of transient kinetic experiments in conjunction with X-ray photoelectron spectroscopy and imaging techniques were employed to correlate the observed catalytic activity with the electronic and morphological characteristics of the cobalt catalyst surface. Our results show that migrating ions from the solid electrolyte to the catalyst surface has a dual effect, which has an impact on the observed catalytic behavior. First, they lead to an electrochemically formed double layer on the catalyst surface, which effectively modifies the catalyst work function and consequently alters the observed catalytic rate. Second, they have a profound effect on the oxidation state of cobalt and therefore on the structure of the cobalt oxide particles formed. The presence of Co oxide phases upon anodic polarization shows up to a 5-fold increase in the catalytic rate of the reverse water gas shift (RWGS) reaction. The enhancement of the catalytic activity observed in this work, with a relatively inexpensive cobalt oxide film, is comparable to that obtained with noble metal catalysts in classical EPOC studies. The present study also demonstrates that the formation of different oxide phases can be controlled accurately by electrochemical means and used to tune the catalytic activity and selectivity of cobalt. The reported results could guide the design and operation of more selective and active catalytic processes for the RWGS reaction.
Keywords electrochemical promotion, cobalt oxide, CO2 hydrogenation, XPS, RWGS
Remark Link
ID=578

In-situ Ni exsolution from NiTiO3 as potential anode for solid oxide fuel cells

Authors Lucía M.Toscani, Florencia Volpe Giangiordano, Nora Nichio, Francisco Pompeo, Susana A. Larrondo
Source
International Journal of Hydrogen Energy
Volume: 45, Issue: 43 Time of Publication: 2020
Abstract Sample NiTiO3 (NTO) is prepared by the molten salts synthesis route as a potential anode material for solid oxide fuel cell (SOFC) applications. An additional sample impregnated with 5 mol%Ni (N-NTO) is also presented. Structural characterization reveal a pure NiTiO3 phase upon calcination at 850 °C and 1000 °C. Redox characterization by temperature programmed reduction tests indicate the transition from NiTiO3 to Ni/TiO2 at ca. 700 °C. Ni nanoparticles (ca. 26 nm) are exsolved in-situ from the structure after a reducing treatment at 850 °C. Catalytic activity tests for partial oxidation of methane performed in a fixed bed reactor reveal excellent values of activity and selectivity due to the highly dispersed Ni nanoparticles in the support surface. Time-on-stream behavior during 100 h operation in reaction conditions for sample N-NTO yield a stable CH4 conversion. Electrolyte supported symmetrical cells are prepared with both materials achieving excellent polarization resistance of 0.023 Ω cm2 in 7%H2/N2 atmosphere at 750 °C with sample N-NTO. The maximum power density achieved is of 273 mW cm−2 at 800 °C with a commercial Pt ink used as a reference cathode, indicating further improvement of the system can be achieved and positioning the N-NTO material as a promising SOFC anode material.
Remark Link
ID=577

Support effects on catalysis of low temperature methane steam reforming

Authors Maki Torimoto, Shuhei Ogo, Yudai Hisai, Naoya Nakano, Ayako Takahashi, Quanbao Ma, Jeong Gil Seo, Hideaki Tsuneki, Truls Norby and Yasushi Sekine
Source
RSC Adv.
Volume: 10, Pages: 26418-26424
Time of Publication: 2020
Abstract Low temperature (<500 K) methane steam reforming in an electric field was investigated over various catalysts. To elucidate the factors governing catalytic activity, activity tests and various characterization methods were conducted over various oxides including CeO2, Nb2O5, and Ta2O5 as supports. Activities of Pd catalysts loaded on these oxides showed the order of CeO2 > Nb2O5 > Ta2O5. Surface proton conductivity has a key role for the activation of methane in an electric field. Proton hopping ability on the oxide surface was estimated using electrochemical impedance measurements. Proton transport ability on the oxide surface at 473 K was in the order of CeO2 > Nb2O5 > Ta2O5. The OH group amounts on the oxide surface were evaluated by measuring pyridine adsorption with and without H2O pretreatment. Results indicate that the surface OH group concentrations on the oxide surface were in the order of CeO2 > Nb2O5 > Ta2O5. These results demonstrate that the surface concentrations of OH groups are related to the proton hopping ability on the oxide surface. The concentrations reflect the catalytic activity of low-temperature methane steam reforming in the electric field.
Remark Link
ID=557

Activation of C−H Bond of Propane by Strong Basic Sites Generated by Bulk Proton Conduction on V‐Modified Hydroxyapatites for the Formation of Propene

Authors Sarah Petit, Cyril Thomas, Yannick Millot, Jean‐Marc Krafft, Christel Laberty‐Robert, Guylène Costentin
Source
ChemCatChem
Volume: 12, Issue: 9, Pages: 2506-2521
Time of Publication: 2020
Abstract Insights into the catalytic transformation of propane to propene on V‐apatite catalysts are provided based on structure‐reactivity relationships. Substitution of phosphates by vanadates in the hydroxyapatite structure leads to the formation of Ca10(PO4)6‐x(VO4)x(OH)2‐yOy V‐oxy‐hydroxy‐apatite solid solutions (x=0→6). Bulk vanadium incorporation promotes (i) calcium rich terminations (XPS, CO adsorption), (ii) proton deficiency inside the OH− channels (1H NMR) giving rise to O2− native species, (iii) the thermally‐activated formation of additional O2− species along the OH− channels resulting in H‐bonding interaction (in situ DRIFT) and (iv) the proton conduction process that eventually results in the surface exposure of O2− species (in situ impedance spectroscopy). The exposure of Ca2+−O2− surface acid‐base pairs allows the dissociation of hydrogen, emphasizing the strong basicity of the related O2− species. Whereas an increasing vanadium content is beneficial to propene selectivity, it scarcely impacts propane conversion. The reaction proceeds mainly upon oxidative dehydrogenation, even if the minor dehydrogenation route is also observed. Surface O2− generated thanks to proton mobility are involved in the C−H bond activation, as shown by the synergistic effect between the oxidative dehydrogenation of propane reaction and the bulk proton conduction measured under operando conditions. This puts emphasis on the key role of strong basic sites for propane activation.
Remark https://doi.org/10.1002/cctc.201902181
Link
ID=544

Mn-rich SmBaCo0.5Mn1.5O5+δ double perovskite cathode material for SOFCs

Authors Anna Olszewska, Yang Zhang, Zhihong Du, Mateusz Marzec, Konrad &#346;wierczek, Hailei Zhao, Bogdan Dabrowski
Source
International Journal of Hydrogen Energy
Volume: 44, Issue: 50 Time of Publication: 2019
Abstract SmBaCo0.5Mn1.5O5+δ oxide with Sm-Ba cation-ordered perovskite-type structure is synthesized and examined in relation to whole RBaCo0.5Mn1.5O5+δ series (R: selected rare earth elements). Presence of Sm and 3:1 ratio of Mn to Co allows to balance physicochemical properties of the composition, with moderate thermal expansion coefficient value of 18.70(1)·10−6 K−1 in 300–900 °C range, high concentration of disordered oxygen vacancies in 600–900 °C range (δ = 0.16 at 900 °C), and good transport properties with electrical conductivity reaching 33 S cm−1 at 900 °C in air. Consequently, the compound enables to manufacture catalytically-active cathode, with good electrochemical performance measured for the electrolyte-supported laboratory-scale solid oxide fuel cell with Ni-Gd1.9Ce0.1O2-δ|La0.4Ce0.6O2-δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ configuration, for which 1060 mW cm−2 power density is observed at 900 °C. Furthermore, the tested symmetrical SmBaCo0.5Mn1.5O5+δ|La0.8Sr0.2Ga0.8Mg0.2O3-δ|SmBaCo0.5Mn1.5O5+δ cell delivers 377 mW cm−2 power density at 850 °C, which is a promising result.
Keywords Mn-rich layered perovskites; Physicochemical properties; Cathode materials; SOFC; Symmetrical SOFC
Remark https://doi.org/10.1016/j.ijhydene.2019.08.254
Link
ID=530

Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO3

Authors Bu&#287;ra Kayaalp, Kurt Klauke, Mattia Biesuz, Alessandro Iannaci, Vincenzo M. Sglavo, Massimiliano D&#8217;Arienzo, Heshmat Noei, Siwon Lee, WooChul Jung, Simone Mascotto
Source
J. Phys. Chem. C
Volume: 123, Issue: 27, Pages: 16883-16892
Time of Publication: 2019
Abstract In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La0.1Sr0.9TiO3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material’s surface. In addition, a high concentration of O– defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics.
Remark Link
ID=513

Template-free mesoporous La0.3Sr0.7Ti1-xFexO3±δ for CH4 and CO oxidation catalysis

Authors Bu&#287;ra Kayaalp, Siwon Lee, Kurt Klauke, Jongsu Seo, Luca Nodaric, Andreas Kornowski, WooChul Jung, Simone Mascotto
Source
Applied catalysis B: Enviromental
Volume: 245, Pages: 536-545
Time of Publication: 2019
Abstract The design of perovskite oxides with improved textural properties in combination with tunable composition variations is a forward-looking strategy for the preparation of next generation catalytic converter. In the present work we report the template-free synthesis of mesoporous solid solutions of La0.3Sr0.7Ti1-xFexO3±δ (0 ≤ x ≤ 0.5) and the study of their catalytic performance towards CH4 and CO oxidation. Using an innovative polymer complex route, phase pure perovskite solid solutions with specific surface area of 65 m2 g−1 and average pore size of 15 nm were prepared. The iron concentration increase led to a progressive enhancement of not only both concentration and transport of the charge carriers but also reducibility and oxygen desorption capability on the catalyst. As a result, we observed almost complete conversion of CH4 and CO at 600 °C and 300 °C, respectively. Kinetic studies on methane oxidation showed that competing suprafacial and intrafacial reaction mechanisms coexist, and that the concentration of 30% of Fe maximizes the suprafacial contribution. Under reducing conditions at 600 °C the materials retained their structural and morphological integrity, showing superior stability. Finally, the reaction rate of CH4 and CO conversion evidenced that our systems are by a maximum of 90 times more performing than other bulk and nanoporous Fe-based perovskites in literature (e.g. La0.66Sr0.34Co0.2Fe0.8O3-δ), as a result their large surface area, intimate gas-solid contact and short intragrain oxygen diffusion pathways induced by the mesoporous structure.
Remark Link
ID=490

Wide bandgap oxides for low-temperature single-layered nanocomposite fuel cell

Authors
Source
Nano Energy
Volume: 53, Pages: 391-397
Time of Publication: 2018
Abstract A composite of wide bandgap lithium-nickel-zinc-oxide (LNZ) and gadolinium-doped-cerium-oxide (GDC) was systematically analyzed for a low-temperature nanocomposite fuel cell in a so-called single-component configuration in which the electrodes and electrolyte form a homogenous mixture. We found that the operational principle of a single-layer fuel cell can be explained by electronic blocking by the oxide mixture with almost insulator-like properties in the operating voltage regime of the fuel cell, which will prevent short-circuiting, and by its catalytic properties that drive the fuel cell HOR and ORR reactions. The resistance to charge transport and leakage currents are dominant performance limiting factors of the single-component fuel cell. A test cell with Au as current collector reached a power density of 357 mWcm−2 at 550 °C. Changing the current collector to a Ni0.8Co0.15Al0.05LiO2 (NCAL) coated Ni foam produced 801 mWcm−2, explained by better catalytic properties. However, utilizing NCAL coated Ni foam may actually turn the 1-layer fuel cell device into a traditional 3-layer (anode-electrolyte-cathode) structure. This work will help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device important to further develop this potential energy technology.
Keywords Bandgap; Ceramic; Fuel cell; Ionic conductivity; Nanocomposite; Single-component
Remark https://doi.org/10.1016/j.nanoen.2018.08.070
Link
ID=485

A novel anode for solid oxide fuel cells prepared from phase conversion of La0.3Sr0.7Fe0.7Cr0.3O3-δ perovskite under humid hydrogen

Authors Min Chen, Yang Hu, Dongchu Chen, Huawen Hu, Qing Xu
Source
Electrochimica Acta
Volume: 284, Pages: 303-313
Time of Publication: 2018
Abstract A novel anode for solid oxide fuel cells (SOFCs), consisting of a Ruddlesden-Popper compound, La0.6Sr1.4Fe0.4Cr0.6O3.8, with in situ exsolved α-Fe nanoparticles (RP-LSF + Fe), is prepared from the phase conversion of the La0.3Sr0.7Fe0.7Cr0.3O3-δ (LSFCr-3) perovskite under humid H2 at 800 °C. On the surface of the RP-LSF + Fe anode, Fe cations are presented to be a mixture of Fe2+ and Fe3+, of which the average valence is lower than that in the bulk (Fe3+). The coverage of atomic hydrogen on the RP-LSF + Fe anode is over 0.8 in the pH2 range of 0.017–0.27 atm, implying a significant effect of these small amount (∼8 mol% on the surface) of exsolved Fe nanoparticles (∼200–300 nm) on promoting the dissociative absorption of H2. The charge transfer resistance is found to be closely related to the concentration of surface oxygen vacancies of the oxide matrix. The addition of catalytic amount of Ni (1–3 wt.%) greatly improves the fuel flexibility of the RP-LSF + Fe anode. Furthermore, it contributes to acceleration the phase conversion of the LSFCr-3 perovskite and reduced time for in situ preparation of the RP-LSF + Fe anode. The RP-LSF + Fe anode with 2.7 wt.% Ni exhibits a stable cell performance under 2.7%H2O+1:1-(H2:CO) and 2.7%H2O + CH4 for ∼30 h. It costs shortest time (30 h) to reach a stable cell voltage of 0.76 V at a galvanostatic current density of 0.25 A/cm2 under humid H2, which is clearly an active and stable anode material for SOFCs.
Keywords Solid oxide fuel cell, Oxide anode, Phase conversion, Electrodics, Fuel flexibility
Remark https://doi.org/10.1016/j.electacta.2018.07.132
Link
ID=467

Electrochemical promotion of nanodispersed Ru-Co catalysts for the hydrogenation of CO2

Authors A. Kotsirasa, I. Kalaitzidoua, D. Grigorioua, A. Symillidisa, M. Makria, A. Katsaounisa, C.G. Vayenas
Source
Applied Catalysis B: Environmental
Volume: 232, Pages: 60-68
Time of Publication: 2018
Abstract Electrochemical promotion of the CO2 hydrogenation to CH4 and CO on a nanodispersed Ru-Co catalyst has been achieved via slurry deposition of the nanodispersed catalyst on an interlayer Ru film deposited on a BZY (BaZr0.85Y0.15O3) proton conducting solid electrolyte disc. The effect of current is nonFaradaic, with Faradaic efficiency values as high as 60 and leads to a reversible variation of the selectivity to CH4 between 16% and 41%. Due to thermal spillover of protons on the Ru-Co catalyst surface, the open circuit selectivity to CO is quite high, i.e. up to 84% and similar values are obtained via negative potential application, i.e. proton supply to the Ru catalyst film deposited on BZY before the deposition of the nanodispersed catalyst. These results underline the similarity between electrochemical promotion and metal support interactions when using proton conducting supports. They also show the usefulness of electrochemical promotion for mechanistic investigations. The electrochemical promotion of nanodispersed catalysts is a promising step for the practical utilization of electrochemical promotion.
Keywords Electrochemical promotion, EPOC, NEMCA effect, CO2 hydrogenation, Dispersed catalyst, BZY
Remark https://doi.org/10.1016/j.apcatb.2018.03.031
Link
ID=462

Amorphous-cathode-route towards low temperature SOFC

Authors Andrea Cavallaro, Stevin S. Pramana, Enrique Ruiz-Trejo, Peter C. Sherrell, Ecaterina Ware, John A. Kilner and Stephen J. Skinner
Source
Volume: 2, Pages: 862-875
Time of Publication: 2018
Abstract Lowering the operating temperature of solid oxide fuel cell (SOFC) devices is one of the major challenges limiting the industrial breakthrough of this technology. In this study we explore a novel approach to electrode preparation employing amorphous cathode materials. La0.8Sr0.2CoO3−δ dense films have been deposited at different temperatures using pulsed laser deposition on silicon substrates. Depending on the deposition temperature, textured polycrystalline or amorphous films have been obtained. Isotope exchange depth profiling experiments reveal that the oxygen diffusion coefficient of the amorphous film increased more than four times with respect to the crystalline materials and was accompanied by an increase of the surface exchange coefficient. No differences in the surface chemical composition between amorphous and crystalline samples were observed. Remarkably, even if the electronic conductivities measured by the Van Der Pauw method indicate that the conductivity of the amorphous material was reduced, the overall catalytic properties of the cathode itself were not affected. This finding suggests that the rate limiting step is the oxygen mobility and that the local electronic conductivity in the amorphous cathode surface is enough to preserve its catalytic properties. Different cathode materials have also been tested to prove the more general applicability of the amorphous-cathode route.
Remark DOI: 10.1039/C7SE00606C
Link
ID=438

Comparative study of the electrochemical promotion of CO2 hydrogenation on Ru using Na+, K+, H+ and O2 − conducting solid electrolytes

Authors I.Kalaitzidou, M. Makri, D. Theleritis, A. Katsaounis, C.G. Vayenas
Source
Surface Science
Volume: 646, Pages: 194-203
Time of Publication: 2016
Abstract The kinetics and the electrochemical promotion of the hydrogenation of CO2 to CH4 and CO are compared for Ru porous catalyst films deposited on Na+, K+, H+ and O2 − conducting solid electrolyte supports. It is found that in all four cases increasing catalyst potential and work function enhances the methanation rate and selectivity. Also in all four cases the rate is positive order in H2 and exhibits a maximum with respect to CO2. At the same time the reverse water gas shift reaction (RWGS) which occurs in parallel exhibits a maximum with increasing and is positive order in CO2. Also in all cases the selectivity to CH4 increases with increasing and decreases with increasing . These results provide a lucid demonstration of the rules of chemical and electrochemical promotion which imply that (∂r/∂Φ)(∂r/∂pD) > 0 and (∂r/∂Φ)(∂r/∂pA) < 0, where r denotes a catalytic rate, Φ is the catalyst work function and pD and pA denote the electron donor and electron acceptor reactant partial pressures respectively.
Keywords Electrochemical promotion of catalysis, Ion conducting support, Hydrogenation of CO2, Ruthenium catalyst, Rules of promotion, Metal&#8211;support interactions
Remark https://doi.org/10.1016/j.susc.2015.09.011
Link
ID=432

Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells

Authors
Source
International Journal of Hydrogen Energy
Volume: 43, Issue: 2, Pages: 885–893
Time of Publication: 2018
Abstract Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-doped-ceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 °C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au-doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H2O mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Nisingle bondAu surface alloy that inhibited carbonisation and poisoning of the active nickel surface.
Keywords SOFC; Ultrathin film anodes; Magnetron sputtering; Gadolinia doped ceria; Carbon-tolerant; Gold doping
Remark https://doi.org/10.1016/j.ijhydene.2017.11.020
Link
ID=403

Composite mixed ionic-electronic conducting ceramic for intermediate temperature oxygen transport membrane

Authors Ming Wei Liao, Tai Nan Lin, Wei Xin Kao, Chun Yen Yeh, Yu Ming Chen, Hong Yi Kuo
Source
Ceramics International
Volume: 43, Issue: 1, Pages: S628-S632
Time of Publication: 2017
Abstract The dense ceramic substrate formed by a mixed ionic-electronic conducting (MIEC) material can be used as an oxygen transport membrane (OTM), enabling the transport of high flux oxygen with certain selectivity and gas separation at high temperatures (800 ~ 900 °C). In recent years, Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) has been reported to be a promising MIEC material for oxygen permeation due to its relatively high oxygen ion conductivity at high temperatures. However, the catalytic efficiency of BSCF is relatively low among the MIEC materials, resulting in the dramatic decrease of oxygen permeation at temperatures below 800 °C. In the present study, a composite MIEC ceramic consisting of a BSCF substrate and the catalytic La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) layer has been proposed. A simple method of laser surface melting is executed to fabricate the composite oxygen transport membrane. The scanning electron microscope (SEM) investigations show that LSCF powders can be well-adherent to the BSCF surface after laser scanning melting process. The oxygen permeation flux reaches 0.5 ml min−1 cm−2 for pure BSCF membrane with thickness of 420 µm, while the BSCF membrane substrate with laser scanning LSCF exhibits substantial improvement on oxygen permeation up to 60% at 700 °C. The result suggests that the composite MIEC ceramic has significant potential for intermediate temperature oxygen transport membrane.
Keywords Membranes, Composites, Laser surface melting
Remark https://doi.org/10.1016/j.ceramint.2017.05.222
Link
ID=352

Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor

Authors
Source
Science
Volume: 353, Issue: 6299, Pages: 563-566
Publisher: American Association for the Advancement of Science (AAAS), ISBN: Print ISSN:0036-8075 Online ISSN:1095-9203, Time of Publication: 2016-08
Abstract Nonoxidative methane dehydroaromatization (MDA: 6CH4 ↔ C6H6 + 9H2) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability. Methane gas is expensive to ship. It is usually converted into carbon monoxide and hydrogen and then liquefied. This is economically feasible only on very large scales. Hence, methane produced in small amounts at remote locations is either burned or not extracted. A promising alternative is conversion to benzene and hydrogen with molybdenumzeolite catalysts. Unfortunately, these catalysts deactivate because of carbon buildup; plus, hydrogen has to be removed to drive the reaction forward. Morejudo et al. address both of these problems with a solid-state BaZrO3 membrane reactor that electrochemically removes hydrogen and supplies oxygen to suppress carbon buildup.
Keywords CMR, MDA, catalytic membrane reactor, ZSM-5, MCM-22, FBR, FBR-PolyM, Pd-CMR, Co-ionic CMR, FT, ProboStat CMR base unit (NORECS)
Remark http://science.sciencemag.org/highwire/filestream/682540/field_highwire_adjunct_files/0/Morejudo.SM.pdf
BaZrO3
BaZrO3
Link
ID=349

Synthesis and characterization of robust, mesoporous electrodes for solid oxide fuel cells

Authors
Source
Journal of Materials Chemistry A
Time of Publication: 2016
Abstract The use of mesoporous electrodes in solid oxide cells would lead to a significant enhancement of the performance due to their high surface area and large number of active sites for electrochemical reactions. However, their application in real devices is still hindered by the potential instability of the mesostructure and morphology at high temperatures required for device fabrication and under severe conditions for high-current, long-term operation. Here we report our findings on the preparation and characterization of mesoporous electrodes based on ceria infiltrated with catalysts: an anode consisting of a Ce0.8Sm0.2O1.9 (SDC) scaffold infiltrated with Ni and a cathode consisting of an SDC scaffold infiltrated with Sm0.5Sr0.5CoO3−δ (SSC). In particular, a doped-zirconia electrolyte supported cell with a mesoporous Ni–SDC anode and a mesoporous SSC–SDC cathode demonstrates an excellent peak power density of 565 mW cm−2 at 750 °C (using humidified hydrogen as the fuel). More importantly, both mesoporous electrodes display remarkable stability, yielding a combined electrode virtual non-degradation for the last 500 hours of the test at a constant current density of 635 mA cm−2 at 750 °C, demonstrating the potential of these mesoporous materials as robust electrodes for solid oxide fuel cells or other high-temperature electrochemical energy storage and conversion devices.
Remark DOI: 10.1039/C6TA00321D
Link
ID=332

Exceptional hydrogen permeation of all-ceramic composite robust membranes based on BaCe0.65Zr0.20Y0.15O3−δ and Y- or Gd-doped ceria

Authors
Source
Energy Environ. Sci.
Volume: 8, Pages: 3675-3686
Time of Publication: 2015
Abstract Mixed proton and electron conductor ceramic composites were examined as hydrogen separation membranes at moderate temperatures (higher than 500 °C). In particular, dense ceramic composites of BaCe0.65Zr0.20Y0.15O3−δ (BCZ20Y15) and Ce0.85M0.15O2−δ (M = Y and Gd, hereafter referred to as YDC15 and GDC15), as protonic and electronic conducting phases respectively, were successfully prepared and tested as hydrogen separation membranes. The mixture of these oxides improved both chemical and mechanical stability and increased the electronic conductivity in dual-phase ceramic membranes. The synthetic method and sintering conditions were optimized to obtain dense and crack free symmetric membranes. The addition of ZnO as a sintering aid allowed achieving robust and dense composites with homogeneous grain distribution. The chemical compatibility between the precursors and the influence of membrane composition on electrical properties and H2 permeability performances were thoroughly investigated. The highest permeation flux was attained for the 50 : 50 volume ratio BCZ20Y15–GDC15 membrane when the feed and the sweep sides of the membrane were hydrated, reaching values of 0.27 mL min−1 cm−2 at 755 °C on a 0.65 mm thick membrane sample, currently one of the highest H2 fluxes obtained for bulk mixed protonic–electronic membranes. Increasing the temperature to 1040 °C, increased the hydrogen flux up to 2.40 mL min−1 cm−2 when only the sweep side was hydrated. The H2 separation process is attributed to two cooperative mechanisms, i.e. proton transport through the membrane and H2 production via the water splitting reaction coupled with oxygen ion transport. Moreover, these composite systems demonstrated a very good chemical stability under a CO2-rich atmosphere such as catalytic reactors for hydrogen generation.
Remark DOI: 10.1039/C5EE01793A
Link
ID=327

Electrochemical promotion of the hydrogenation of CO2 on Ru deposited on a BZY proton conductor

Authors I. Kalaitzidou, A. Katsaounis, T. Norby, C.G. Vayenas
Source
Journal of Catalysis
Volume: 331, Pages: 98–109
Time of Publication: 2015
Abstract he kinetics and the electrochemical promotion of the hydrogenation of CO2 on polycrystalline Ru deposited on BZY (BaZr0.85Y0.15O3−α + 1 wt% NiO), a proton conductor in wet atmospheres, with α ≈ 0.075, was investigated at temperatures 300–450 °C and atmospheric pressure. Methane and CO were the only detectable products and the selectivity to CH4 could be reversibly controlled between 15% and 65% by varying the catalyst potential by less than 1.2 V. The rate and the selectivity to CH4 are very significantly enhanced by proton removal from the catalyst via electrochemically controlled spillover of atomic H from the catalyst surface to the proton-conducting support. The effect is strongly non-Faradaic and the apparent Faradaic efficiency of methanation takes values up to 500 and depends strongly on the porous Ru catalyst film thickness. The observed strong promotional effect, in conjunction with the observed reaction kinetics, is in good agreement with the rules of electrochemical and chemical promotion.
Keywords Hydrogenation of CO2; CO2 methanation; Ru catalyst; RWGS reaction; BZY proton conducting support; Selectivity modification; Electrochemical promotion of catalysis (EPOC); Non-faradaic electrochemical modification of catalytic activity (NEMCA effect)
Remark doi:10.1016/j.jcat.2015.08.023
Link
ID=313

Praseodymium-deficiency Pr0.94BaCo2O6-δ double perovskite: A promising high performance cathode material for intermediate-temperature solid oxide fuel cells

Authors Fuchang Meng, Tian Xia, Jingping Wang, Zhan Shi, Hui Zhao
Source
Journal of Power Sources
Volume: 239, Pages: 741–750
Time of Publication: 2015
Abstract Praseodymium-deficiency Pr0.94BaCo2O6-δ (P0.94BCO) double perovskite has been evaluated as a cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction pattern shows the orthorhombic structure with double lattice parameters from the primitive perovskite cell in Pmmm space group. P0.94BCO has a good chemical compatibility with Ce0.9Gd0.1O1.95 (CGO) electrolyte even at 1000 °C for 24 h. It is observed that the Pr-deficiency can introduce the extra oxygen vacancies in P0.94BCO, further enhancing its electrocatalytic activity for oxygen reduction reaction. P0.94BCO demonstrates the promising cathode performance as evidenced by low polarization are-specific resistance (ASR), e. g. 0.11 Ω cm2 and low cathodic overpotential e. g. −56 mV at a current density of −78 mA cm−2 at 600 °C in air. These features are comparable to those of the benchmark cathode Ba0.5Sr0.5Co0.8Fe0.2O3-δ. The fuel cell CGO-Ni|CGO|P0.94BCO presents the attractive peak power density of 1.05 W cm−2 at 600 °C. Furthermore, the oxygen reduction kinetics of P0.94BCO material is also investigated, and the rate-limiting steps for oxygen reduction reaction are determined.
Keywords Intermediate-temperature solid oxide fuel cell; Cathode material; Double perovskite; Electrochemical performance; Oxygen reduction reaction
Remark doi:10.1016/j.jpowsour.2015.06.007
Link
ID=294

Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system

Authors Jonathan M. Polfus, Wen Xing, Marie-Laure Fontaine, Christelle Denonville, Partow P. Henriksen, Rune Bredesen
Source
Journal of Membrane Science
Volume: 479, Pages: 39–45
Time of Publication: 2015
Abstract Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes.
Keywords Hydrogen separation; Dense ceramic membrane; Ceramic&#8211;ceramic composite; Lanthanum tungstate; Lanthanum chromite
Remark doi:10.1016/j.memsci.2015.01.027
Link
ID=188

Transient Oxygen Permeation and Surface Catalytic Properties of Lanthanum Cobaltite Membrane under Oxygen–Methane Gradient

Author Tyler T. Norton and Y. S. Lin
Source
Ind. Eng. Chem. Res.
Volume: 51, Issue: 39, Pages: 12917–12925
Time of Publication: 2012-09
Abstract Oxygen permeation through mixed-conducting ceramic membranes in an air/methane gradient is important for their applications in membrane reactors for air separation and partial oxidation of hydrocarbons. This study examines transient characteristics of oxygen permeation and surface catalytic properties of La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) membranes in an oxygen/methane gradient for an extended period of time. Upon exposure to an oxygen/methane gradient, the oxygen permeation flux of the membrane increases to a maximum at around 55 h, then decreases and reaches a steady-state value at around 200 h. The maximum and steady-state flux is approximately 60% and 30% higher than the initial flux of the fresh membrane, respectively. The surface catalytic properties of the membrane exposed to methane also change with the exposure time in a similar fashion. However, the apparent activation energy for oxygen permeation for the membranes at various stages of the transient study is nearly constant while the effects of temperature, feed pressure, and sweep flow rate on catalytic properties are also similar for the fresh and aged membranes. The surface of a LSCF membrane reacts with methane resulting in a formation of a thin porous layer which changes the surface catalytic properties. The membrane surface becomes more active for reaction with increased selectivity for carbon monoxide formation upon exposure to methane. This lowers oxygen partial pressure in the permeate side and increases the driving force for oxygen permeation and, therefore, increases oxygen permeation flux. Under the studied experimental conditions the membrane can reach steady-state for continuous operation.
Remark Link
ID=139

Effects of (LaSr)(CoFeCu)O3-δ Cathodes on the Characteristics of Intermediate Temperature Solid Oxide Fuel Cells

Authors Sea-Fue Wang, Chun-Ting Yeh, Yuh-Ruey Wang, Yung-Fu Hsu
Source
Journal of Power Sources
Volume: 201, Pages: 18–25
Time of Publication: 2012-03
Abstract In this study, Cu2+ ions doped La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes are prepared for use in solid oxide fuel cells (SOFCs). The maximum electrical conductivities of the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ (438 S cm−1) and the La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ (340 S cm−1) discs are higher than that of the La0.6Sr0.4Co0.2Fe0.8O3−δ disc (LSCF; 81 S cm−1) sintered at 1100 °C. The substitution of Cu2+ over Fe3+ leads to a higher coefficients of thermal expansion (CTE), while the replacement of Co3+ by Cu2+ results in a lower CTE. Single cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 650 °C and 550 °C show similar ohmic resistance (R0) values while the polarization resistance (RP) values of the cells with the La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ and a0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes are slightly lower than that of the single cell with the La0.6Sr0.4Co0.2Fe0.8O3−δ cathode, indicating that the Cu2+-doped LSCF cathode exhibits a greater electrochemical catalytic activity for oxygen reduction. Maximum power densities of the cells with the La0.6Sr0.4Co0.2Fe0.8O3−δ, La0.6Sr0.4Co0.2Fe0.7Cu0.1O3−δ, and La0.6Sr0.4Co0.1Fe0.8Cu0.1O3−δ cathodes operating at 700 °C read respectively 1.07, 1.15, and 1.24 W cm−2. It is evident that the doping of Cu2+ ions in LSCF is beneficial to the electrochemical performance of the cells.
Keywords Solid oxide fuel cell; cathode; cathode; impedance; Cell performance
Remark Link
ID=135

Autothermal Reforming of Methane in Proton-Conducting Ceramic Membrane Reactor

Authors Jay Kniep , Matthew Anderson , and Jerry Y.S. Lin
Source
Ind. Eng. Chem. Res.
Volume: 50, Issue: 22, Pages: 12426–12432
Time of Publication: 2011-10
Abstract Endothermic steam reforming of methane for hydrogen production requires heat input with selective oxidation of methane. Dense SrCe0.75Zr0.20Tm0.05O3-δ perovskite membranes were combined with a reforming catalyst to demonstrate the feasibility of a heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation of permeated hydrogen. The reforming catalyst used was a prereduced nickel based catalyst supported on γ-Al2O3. Hydrogen produced via the steam reforming of methane or water gas shift reaction was able to diffuse through the catalyst bed and transport through the membrane. The permeated hydrogen reacted with oxygen (from air) to produce heat for the steam reforming of methane on the other side of the membrane. The membrane reactor avoids the use of an expensive air separation unit to produce pure oxygen. The influence of experimental conditions, such as temperature, gas hourly space velocity, and the steam to carbon (S/C) ratio, on the membrane reactor was investigated. SrCe0.75Zr0.20Tm0.05O3-δ showed good chemical stability in steam reforming conditions as X-ray diffraction analysis of the membrane surface exposed to steam-reforming conditions for 425 h showed only minor CeO2 formation. The experimental data demonstrate the feasibility of using a proton conducting ceramic membrane in the heat-exchange membrane reactor for steam reforming of methane coupled with selective oxidation.
Remark Link
ID=126

Partial Oxidation of Methane and Oxygen Permeation in SrCoFeOx Membrane Reactor with Different Catalysts

Author Jay Kniep and Y.S. Lin
Source
Ind. Eng. Chem. Res.
Volume: 50, Issue: 13, Pages: 7941–7948
Time of Publication: 2011-05
Abstract Partial oxidation of methane (CH4) and oxygen permeation in a dense SrCoFeOx disk membrane reactor were studied with the reducing side of the membrane packed with different catalysts (catalyst support γ-Al2O3, La0.6Sr0.4Co0.8Fe0.2O3−δ, and 10 wt % Ni/γ-Al2O3) of increasing reaction activities for CH4 oxidation. The influence of temperature, flow rates, and inlet CH4 concentration (diluted with helium) on the performance of the different membrane reactors was investigated. The oxygen permeation flux and CH4 conversion increased in the following order: γ-Al2O3 < La0.6Sr0.4Co0.8Fe0.2O3−δ < 10% Ni/γ-Al2O3. The membrane reactor with the reforming catalyst of 10 wt % Ni/γ-Al2O3 had the highest CH4 conversion (90%), CO selectivity (97%), and oxygen permeation flux (2.40 mL/(cm2 min)) at 900 °C. The improvement of the oxygen permeation through the membranes with different catalysts emphasizes the effect of the CH4 oxidation reaction rate on the reducing side of the membrane on the oxygen permeation flux through the mixed-conducting ceramic membranes. Under identical conditions, the oxygen permeation flux through mixed-conducting ceramic membrane with a reducing gas is a strong function of the catalytic activity for the oxidation of the reducing gas.
Remark Link
norecs.com

This article is the property of its author, please do not redistribute or use elsewhere without checking with the author.