Ex SituTransmission Electron Microscopy: A Fixed-Bed Reactor Approach

A fixed-bed reactor has been designed and constructed for ex situ transmission electron microscopy (TEM) studies of heterogeneous catalysts. Theex situfacility exposes a fully prepared TEM sample on a grid to actual process conditions (e.g., temperature, pressure, gas composition, etc.) by placing the grid at the exit section of a conventional fixed-bed reactor. A unique reactor design allows grid transfer into the electron microscope and back into the reactor again under a controlled (inert) environment, thus allowing time-resolved monitoring of catalyst morphology changes under realistic, well-controlled conditions. This facility stands completely independent of the TEM. Thus, no special TEM modifications are required and long-termex situstudies do not impact microscope utilization. The utility of the facility is demonstratedviathe oxidation of intermediate size (∼20–∼80 nm) supported copper particles.

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Catalytic Dry Reforming and Cracking of Ethylene for Carbon Nanofilaments and Hydrogen Production Using a Catalyst Derived from a Mining Residue

Catalysts ◽

10.3390/catal9121069 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1069 ◽

Cited By ~ 1

Author(s):

Abir Azara ◽

El-Hadi Benyoussef ◽

Faroudja Mohellebi ◽

Mostafa Chamoumi ◽

François Gitzhofer ◽

...

Keyword(s):

Electron Microscopy ◽

Fixed Bed ◽

Dry Reforming ◽

Fixed Bed Reactor ◽

Molar Ratio ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Spent Catalysts ◽

Temperature Programmed

In this study, iron-rich mining residue (UGSO) was used as a support to prepare a new Ni-based catalyst via a solid-state reaction protocol. Ni-UGSO with different Ni weight percentages wt.% (5, 10, and 13) were tested for C2H4 dry reforming (DR) and catalytic cracking (CC) after activation with H2. The reactions were conducted in a differential fixed-bed reactor at 550–750 °C and standard atmospheric pressure, using 0.5 g of catalyst. Pure gases were fed at a molar ratio of C2H4/CO2 = 3 for the DR reaction and C2H4/Ar = 3 for the CC reaction. The flow rate is defined by a GHSV = 4800 mLSTP/h.gcat. The catalyst performance is evaluated by calculating the C2H4 conversion as well as carbon and H2 yields. All fresh, activated, and spent catalysts, as well as deposited carbon, were characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), temperature programmed reduction (TPR), and thermogravimetric analysis (TGA). The results so far show that the highest carbon and H2 yields are obtained with Ni-UGSO 13% at 750 °C for the CC reaction and at 650 °C for the DR reaction. The deposited carbon was found to be filamentous and of various sizes (i.e., diameters and lengths). The analyses of the results show that iron is responsible for the growth of carbon nanofilaments (CNF) and nickel is responsible for the split of C–C bonds. In terms of conversion and yield efficiencies, the performance of the catalytic formulations tested is proven at least equivalent to other Ni-based catalyst performances described by the literature.

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Synthesis of Catalysts and Its Application for Low-Temperature CO Oxidation

Journal of Catalysts ◽

10.1155/2013/586364 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 5

Author(s):

Der-Shing Lee ◽

Yu-Wen Chen

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Co Oxidation ◽

Fixed Bed ◽

Fixed Bed Reactor ◽

Narrow Particle Size Distribution ◽

High Catalytic Activity ◽

Incipient Wetness Impregnation ◽

X Ray ◽

Transmission Electron

A series of Au/-TiO2 with various Co/Ti ratios prepared. /TiO2 was prepared by incipient wetness impregnation with aqueous solution of cobalt nitrate. Au catalysts were prepared by deposition-precipitation (DP) method at pH 7 and 338 K. The catalysts were characterized by inductively coupled plasma-mass spectrometry, temperature programming reduction, X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The reaction was carried out in a fixed bed reactor with a feed containing 1% CO in air at weight hourly space velocities of 120,000 mL/h g and 180,000 mL/h g. High gold dispersion and narrow particle size distribution were obtained by DP method. The addition of into Au/TiO2 enhanced the activity of CO oxidation significantly. Au/5% -TiO2 had the highest catalyst among all the catalysts. was mainly in the form of nanosize Co3O4 which could stabilize the Au nanoparticles. donated partial electrons to Au. The interactions among Au, , and TiO2 account for the high catalytic activity for CO oxidation.

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Catalyzed Decomposition of Methane into COx-free Hydrogen and Filamentous Carbons over NiO-CuO/SiO2: Effect of NiO-CuO Loadings

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.1997 ◽

2010 ◽

Vol 8 (1) ◽

Author(s):

Siang-Piao Chai ◽

Abdul Rahman Mohamed

Keyword(s):

Electron Microscopy ◽

Fixed Bed ◽

Fixed Bed Reactor ◽

Impregnation Method ◽

Spent Catalyst ◽

Carbonaceous Deposits ◽

Transmission Electron ◽

Free Hydrogen ◽

Decomposition Of Methane ◽

Loading Amount

Methane decomposition in the presence of NiO-CuO/SiO2 catalyst into COx-free hydrogen and filamentous carbons was investigated. The reaction was performed in a vertical fixed-bed reactor at 700°C. The catalyst was prepared via conventional impregnation method. The amounts of NiO-CuO loaded on SiO2 were varied from 10 to 90 wt%. Examination of the effect of NiO-CuO loading disclosed that 80 wt% loading gave the highest yields of hydrogen and carbon, being 2344 mol H2/mol NiO+CuO and 18600% respectively. Transmission electron microscopy and scanning electron microscopy were used to study the texture of the spent catalyst. It was demonstrated that the carbonaceous deposits on the catalyst were made up of filamentous carbons. Depending on the loading amount, the structural properties of the filamentous carbons changed.

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Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154287 ◽

1989 ◽

Vol 47 ◽

pp. 462-463

Author(s):

D. Loretto ◽

J. M. Gibson ◽

S. M. Yalisove

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Diffraction ◽

High Vacuum ◽

High Energy ◽

Energy Electron ◽

Ultra High Vacuum ◽

Ex Situ ◽

Transmission Electron

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.

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