scholarly journals XANES studies of zirconia-ceria/Ni during partial/total methane oxidation

2014 ◽  
Vol 70 (a1) ◽  
pp. C130-C130
Author(s):  
Rebeca Bacani ◽  
Márcia Fantini ◽  
Tereza Martins ◽  
Susana Larrondo ◽  
Diego Lamas
Keyword(s):  
Methane Oxidation ◽  
Ccd Camera ◽  
Structural Features ◽  
Oxygen Storage ◽  
Total Oxidation ◽  
Oxidation Of Methane ◽  
Pluronic P123 ◽  
Release Capacity ◽  
Mesoporous Support ◽  
Temperature Programmed

Zirconia-ceria solid-solutions are extensively used as promoters for three-way catalysts, in addition, these materials can be used as anodes in solid oxide fuel cells (SOFCs) operated with hydrocarbons. The structural features of ZrO2-CeO2 materials in combination with oxygen storage/release capacity (OSC) are crucial for various catalytic reactions. The direct use of hydrocarbons as fuel for the SOFC (instead of pure H2), without the necessity of reforming and purification reactors can improve global efficiency of the system. The samples preparation method was developed using Zr and Ce chloride precursors, HCl aqueous solution, Pluronic P123, NH4OH and a Teflon autoclave. The samples were dried and calcined, until 540°C. The NiO impregnation was made with an ethanol dispersion of Ni(NO3)×6H2O, calcinated in air until 350°C for 2 hours. In-situ XANES experiments are capable to evaluate the reduction/oxidation potencial of Ni and Ce species in ZrO2-CeO2/Ni samples during partial/total methane oxidation and reduction reactions with H2. The experiments at the Ni K-edge/Ce L3-edge were collected at the LNLS D06A-DXAS beam line in transmission mode, using a Si(111) monochromator and a CCD camera as detector. The data were acquired during a series of temperature programmed reduction steps (TPR), under a 5% H2/He until 600°C, and mixtures of 20%CH4:5%O2/He with 2:1, 1:1 and 1:2 ratios. After each process with CH4 and O2, a TPR procedure was performed in order to evaluate the reduction capacity of the sample after reactions with CH4. The results demonstrated that NiO embedded in the porous ZrO2-CeO2 matrix, reduces at lower temperatures than standard NiO, measured in the same conditions, revealing that the mesoporous support improves the reduction of impregnated NiO. For both edges, there was formation of H2 during partial methane oxidation at 600°C. The total oxidation of methane was observed in lower temperatures (500°C). These results reveal that a high ceria content (90%) could be a great candidate for the SOFC anode.

scholarly journals Total oxidation of methane over Pd/Al2O3 at pressures from 1 to 10 atm

2020 ◽  
Vol 10 (16) ◽  
pp. 5480-5486
Author(s):  
Carl-Robert Florén ◽  
Cansunur Demirci ◽  
Per-Anders Carlsson ◽  
Derek Creaser ◽  
Magnus Skoglundh
Keyword(s):  
Methane Oxidation ◽  
Multiscale Simulations ◽  
Total Oxidation ◽  
Oxidation Of Methane ◽  
Temperature Programmed ◽  
Monolith Catalyst ◽  
Kinetics Of

The kinetics of total methane oxidation over a 0.15 wt% Pd/Al2O3 monolith catalyst has been measured during temperature programmed methane oxidation experiments at total pressures from 1 to 10 atm and compared with multiscale simulations.

scholarly journals Effect of Preparation Method of Co-Ce Catalysts on CH4 Combustion

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 219 ◽  
Author(s):  
Sofia Darda ◽  
Eleni Pachatouridou ◽  
Angelos Lappas ◽  
Eleni Iliopoulou
Keyword(s):  
Methane Oxidation ◽  
Transition Metal Oxides ◽  
Synergistic Effects ◽  
Synthesis Method ◽  
Catalytic Efficiency ◽  
Blue Shift ◽  
Oxygen Storage ◽  
Oxidation Activity ◽  
Mixed Oxide Catalysts ◽  
Oxidation Of Methane

Transition metal oxides have recently attracted considerable attention as candidate catalysts for the complete oxidation of methane, the main component of the natural gas, used in various industrial processes or as a fuel in turbines and vehicles. A series of novel Co-Ce mixed oxide catalysts were synthesized as an effort to enhance synergistic effects that could improve their redox behavior, oxygen storage ability and, thus, their activity in methane oxidation. The effect of synthesis method (hydrothermal or precipitation) and Co loading (0, 2, 5, and 15 wt.%) on the catalytic efficiency and stability of the derived materials was investigated. Use of hydrothermal synthesis results in the most efficient Co/CeO2 catalysts, a fact related with their improved physicochemical properties, as compared with the materials prepared via precipitation. In particular, a CeO2 support of smaller crystallite size and larger surface area seems to enhance the reducibility of the Co3O4/CeO2 materials, as evidenced by the blue shift of the corresponding reduction peaks (H2-TPR, H2-Temperature Programmed Reduction). The limited methane oxidation activity over pure CeO2 samples is significantly enhanced by Co incorporation and further improved by higher Co loadings. The optimum performance was observed over a 15 wt% Co/CeO2 catalyst, which also presented sufficient tolerance to water presence.

scholarly journals Total Oxidation of Methane on Oxide and Mixed Oxide Ceria-Containing Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 427
Author(s):  
Marius Stoian ◽  
Vincent Rogé ◽  
Liliana Lazar ◽  
Thomas Maurer ◽  
Jacques C. Védrine ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Methane Oxidation ◽  
Catalytic Combustion ◽  
Oxygen Vacancies ◽  
High Heat ◽  
Atmospheric Environment ◽  
Total Oxidation ◽  
Oxidation Of Methane ◽  
Ceo2 Sample ◽  
Crystallographic Facets

Methane, discovered in 1766 by Alessandro Volta, is an attractive energy source because of its high heat of combustion per mole of carbon dioxide. However, methane is the most abundant hydrocarbon in the atmosphere and is an important greenhouse gas, with a 21-fold greater relative radiative effectiveness than CO2 on a per-molecule basis. To avoid or limit the formation of pollutants that are dangerous for both human health and the atmospheric environment, the catalytic combustion of methane appears to be one of the most promising alternatives to thermal combustion. Total oxidation of methane, which is environmentally friendly at much lower temperatures, is believed to be an efficient and economically feasible way to eliminate pollutants. This work presents a literature review, a statu quo, on catalytic methane oxidation on transition metal oxide-modified ceria catalysts (MOx/CeO2). Methane was used for this study since it is of great interest as a model compound for understanding the mechanisms of oxidation and catalytic combustion on metal oxides. The objective was to evaluate the conceptual ideas of oxygen vacancy formation through doping to increase the catalytic activity for methane oxidation over CeO2. Oxygen vacancies were created through the formation of solid solutions, and their catalytic activities were compared to the catalytic activity of an undoped CeO2 sample. The reaction conditions, the type of catalysts, the morphology and crystallographic facets exposing the role of oxygen vacancies, the deactivation mechanism, the stability of the catalysts, the reaction mechanism and kinetic characteristics are summarized.

Comparative surface and ultrastructural views of methylotrophic bacteria by TEM, STEM, SE, and freeze-etch electron microscopy.

1987 ◽  
Vol 45 ◽  
pp. 792-793
Author(s):  
T.A. Fassel ◽  
M.J. Schaller ◽  
M.E. Lidstrom ◽  
C.C. Remsen
Keyword(s):  
Cytoplasmic Membrane ◽  
Structural Features ◽  
Methylotrophic Bacteria ◽  
Type I ◽  
Type Ii ◽  
Membrane Complex ◽  
Oxidation Of Methane ◽  
Methane Oxidizing Bacteria ◽  
Wall Structures ◽  
Methylomonas Albus

Methylotrophic bacteria play an Important role in the environment in the oxidation of methane and methanol. Extensive intracytoplasmic membranes (ICM) have been associated with the oxidation processes in methylotrophs and chemolithotrophic bacteria. Classification on the basis of ICM arrangement distinguishes 2 types of methylotrophs. Bundles or vesicular stacks of ICM located away from the cytoplasmic membrane and extending into the cytoplasm are present in Type I methylotrophs. In Type II methylotrophs, the ICM form pairs of peripheral membranes located parallel to the cytoplasmic membrane. Complex cell wall structures of tightly packed cup-shaped subunits have been described in strains of marine and freshwater phototrophic sulfur bacteria and several strains of methane oxidizing bacteria. We examined the ultrastructure of the methylotrophs with particular view of the ICM and surface structural features, between representatives of the Type I Methylomonas albus (BG8), and Type II Methylosinus trichosporium (OB-36).

Effect of calcination temperature on cation arrangement and oxygen storage/release capacity in cation-ordered Ce oxides

2021 ◽  
pp. 122192
Author(s):  
Yoshihiro Goto ◽  
Akira Morikawa ◽  
Ai Yatsuhashi ◽  
Hiromochi Tanaka ◽  
Masahide Miura ◽  
...  
Keyword(s):  
Calcination Temperature ◽  
Oxygen Storage ◽  
Release Capacity ◽  
Cation Arrangement

scholarly journals Simultaneous Catalytic Oxidation of a Lean Mixture of CO-CH4 over Spinel Type Cobalt Based Oxides

2020 ◽  
Vol 15 (2) ◽  
pp. 490-500
Author(s):  
Neha Neha ◽  
Ram Prasad ◽  
Satya Vir Singh
Keyword(s):  
Mixed Oxides ◽  
Structural Disorder ◽  
Catalytic Performance ◽  
Molar Ratio ◽  
Total Oxidation ◽  
Spinel Type ◽  
Molar Ratios ◽  
Long Term Stability ◽  
Nickel Cobalt ◽  
Temperature Programmed

A series of nickel-cobalt bimetal oxides in varying molar ratios and its single metal oxides were synthesized by reactive calcination of coprecipitated basic-carbonates. Several characterization techniques, such as: Bruneuer Emmett Teller (BET), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infra Red (FTIR), and Hydrogen Temperature Programmed Reduction (H2-TPR), were performed over the oxides. Activities of oxides were evaluated in methane total oxidation in the presence or the absence of CO. The best catalytic performance was observed over NiCo catalyst with a Ni/Co molar ratio of 1:1, and the complete conversion of CO-CH4 mixture was achieved at 390 °C. Moreover, the presence of carbon monoxide improves CH4 total oxidation over nickel-cobalt mixed oxides. Structural analysis reveals that the insertion of nickel into the spinel lattice of cobalt oxide causes the structural disorder, which probably caused the increase of the amount of octahedrally coordinated divalent nickel cations that are responsible for catalytic activity. Stability of the best-performed catalyst has been tested in the two conditions, showing remarkable long-term stability and thermal stability, however, showed deactivation after thermally ageing at 700 °C. Copyright © 2020 BCREC Group. All rights reserved 

scholarly journals Lanthanum modified Fe-ZSM-5 zeolites for selective methane oxidation with hydrogen peroxide

2021 ◽  
Author(s):  
Songmei Sun ◽  
Alexandra Barnes ◽  
Xiaoxiao Gong ◽  
Richard Lewis ◽  
Nicholas F. Dummer ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Methane Oxidation ◽  
Partial Oxidation ◽  
Partial Oxidation Of Methane ◽  
Ambient Conditions ◽  
Oxidation Of Methane

Selective partial oxidation of methane to methanol under ambient conditions is a great challenge in chemistry. Iron modified ZSM-5 catalysts are shown to be effective for this reaction using H2O2...

scholarly journals Subgroup Characteristics of Marine Methane-Oxidizing ANME-2 Archaea and Their Syntrophic Partners as Revealed by Integrated Multimodal Analytical Microscopy

2018 ◽  
Vol 84 (11) ◽  
Author(s):  
Shawn E. McGlynn ◽  
Grayson L. Chadwick ◽  
Ariel O'Neill ◽  
Mason Mackey ◽  
Andrea Thor ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Methane Oxidation ◽  
Three Dimensional ◽  
Fluorescence Labeling ◽  
Anaerobic Oxidation Of Methane ◽  
Methane Seep ◽  
Bacterial Populations ◽  
Symbiotic Associations ◽  
Iron Mineral ◽  
Oxidation Of Methane

ABSTRACTPhylogenetically diverse environmental ANME archaea and sulfate-reducing bacteria cooperatively catalyze the anaerobic oxidation of methane oxidation (AOM) in multicelled consortia within methane seep environments. To better understand these cells and their symbiotic associations, we applied a suite of electron microscopy approaches, including correlative fluorescencein situhybridization-electron microscopy (FISH-EM), transmission electron microscopy (TEM), and serial block face scanning electron microscopy (SBEM) three-dimensional (3D) reconstructions. FISH-EM of methane seep-derived consortia revealed phylogenetic variability in terms of cell morphology, ultrastructure, and storage granules. Representatives of the ANME-2b clade, but not other ANME-2 groups, contained polyphosphate-like granules, while some bacteria associated with ANME-2a/2c contained two distinct phases of iron mineral chains resembling magnetosomes. 3D segmentation of two ANME-2 consortium types revealed cellular volumes of ANME and their symbiotic partners that were larger than previous estimates based on light microscopy. Polyphosphate-like granule-containing ANME (tentatively termed ANME-2b) were larger than both ANME with no granules and partner bacteria. This cell type was observed with up to 4 granules per cell, and the volume of the cell was larger in proportion to the number of granules inside it, but the percentage of the cell occupied by these granules did not vary with granule number. These results illuminate distinctions between ANME-2 archaeal lineages and partnering bacterial populations that are apparently unified in their ability to perform anaerobic methane oxidation.IMPORTANCEMethane oxidation in anaerobic environments can be accomplished by a number of archaeal groups, some of which live in syntrophic relationships with bacteria in structured consortia. Little is known of the distinguishing characteristics of these groups. Here, we applied imaging approaches to better understand the properties of these cells. We found unexpected morphological, structural, and volume variability of these uncultured groups by correlating fluorescence labeling of cells with electron microscopy observables.

scholarly journals Anaerobic oxidation of methane in grassland soils used for cattle husbandry

2012 ◽  
Vol 9 (10) ◽  
pp. 3891-3899 ◽  
Author(s):  
A. Bannert ◽  
C. Bogen ◽  
J. Esperschütz ◽  
A. Koubová ◽  
F. Buegger ◽  
...  
Keyword(s):  
Methane Oxidation ◽  
Enrichment Culture ◽  
Anaerobic Oxidation Of Methane ◽  
Anaerobic Oxidation ◽  
Incubation Experiment ◽  
Nutrient Source ◽  
Oxidation Activity ◽  
Oxidation Of Methane ◽  
Cattle Husbandry

Abstract. While the importance of anaerobic methane oxidation has been reported for marine ecosystems, the role of this process in soils is still questionable. Grasslands used as pastures for cattle overwintering show an increase in anaerobic soil micro-sites caused by animal treading and excrement deposition. Therefore, anaerobic potential methane oxidation activity of severely impacted soil from a cattle winter pasture was investigated in an incubation experiment under anaerobic conditions using 13C-labelled methane. We were able to detect a high microbial activity utilizing CH4 as nutrient source shown by the respiration of 13CO2. Measurements of possible terminal electron acceptors for anaerobic oxidation of methane were carried out. Soil sulfate concentrations were too low to explain the oxidation of the amount of methane added, but enough nitrate and iron(III) were detected. However, only nitrate was consumed during the experiment. 13C-PLFA analyses clearly showed the utilization of CH4 as nutrient source mainly by organisms harbouring 16:1ω7 PLFAs. These lipids were also found as most 13C-enriched fatty acids by Raghoebarsing et al. (2006) after addition of 13CH4 to an enrichment culture coupling denitrification of nitrate to anaerobic oxidation of methane. This might be an indication for anaerobic oxidation of methane by relatives of "Candidatus Methylomirabilis oxyfera" in the investigated grassland soil under the conditions of the incubation experiment.

scholarly journals Synthesis of Fe2SiO4-Fe7Co3 Nanocomposite Dispersed in the Mesoporous SBA-15: Application as Magnetically Separable Adsorbent

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 1016 ◽  
Author(s):  
Monickarla da Silva ◽  
Felipe Barbosa ◽  
Marco Morales Torre ◽  
Jhonny Villarroel-Rocha ◽  
Karim Sapag ◽  
...  
Keyword(s):  
Adsorption Capacity ◽  
High Surface ◽  
High Surface Area ◽  
Dye Adsorption ◽  
Santa Barbara ◽  
Mesoporous Support ◽  
Magnetically Separable ◽  
Temperature Programmed ◽  
Positive Effect ◽  
Isolated Species

The mixture containing alloy and oxide with iron-based phases has shown interesting properties compared to the isolated species and the synergy between the phases has shown positive effect on dye adsorption. This paper describes the synthesis of Fe2SiO4-Fe7Co3-based nanocomposite dispersed in Santa Barbara Amorphous (SBA)-15 and its application in dye adsorption followed by magnetic separation. Thus, it was studied the variation of reduction temperature and amount of hydrogen used in synthesis and the effect of these parameters on the physicochemical properties of the iron and cobalt based oxide/alloy mixture, as well as the methylene blue adsorption capacity. The XRD and Mössbauer results, along with the temperature-programmed reduction (TPR) profiles, confirmed the formation of Fe2SiO4-Fe7Co3-based nanocomposites. Low-angle XRD, N2 isotherms, and TEM images show the formation of the SBA-15 based mesoporous support with a high surface area (640 m2/g). Adsorption tests confirmed that the material reduced at 700 °C using 2% of H2 presented the highest adsorption capacity (49 mg/g). The nanocomposites can be easily separated from the dispersion by applying an external magnetic field. The interaction between the dye and the nanocomposite occurs mainly by π-π interactions and the mixture of the Fe2SiO4 and Fe7Co3 leads to a synergistic effect, which favor the adsorption.

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