Characterization of microstructures in nickel alumina catalysts by analytical electron microscopy

Lamber, Ryszard; Schulz‐Ekloff, G.

doi:10.1016/0039-6028(91)90906-9

Cited by 49 publications

(5 citation statements)

References 45 publications

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“…The effect of alumina on hydrogen adsorption on supported nickel may be connected with the size and structure of Ni crystallites (electronic properties of small particles, different proportion of Ni planes, steps, edges, kinks, corners, and various defects) and decoration of Ni crystallites with alumina species. The decoration is an experimentally established fact, , but distribution of the decorants on Ni crystallites and their role in the modification of a Ni surface are still unknown. It is supposed that the decorants locate primarily on the corners and edges of Ni crystallites …”

Section: Resultsmentioning

confidence: 99%

Interaction of Hydrogen with Unsupported and Supported Nickel

Znak

Zieliński

2006

Langmuir

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The adsorption of molecular hydrogen on Ni powder and on Ni/Al(2)O(3) and Ni/SiO(2) catalysts was studied by the temperature-programmed desorption (TPD) method. The examinations were performed in the flow system, starting the TP measurements at low temperatures of 100 or 78 K, which resulted in the formation of complete characteristics of the interaction of hydrogen with nickel. Generally, three forms of chemisorbed hydrogen were distinguished: alpha, adsorbed on Ni surface, beta, adsorbed in the "second layer", and gamma, located in the subsurface region of nickel. The comparison of the results of this work with those obtained in vacuum systems for various Ni surfaces has led to the conclusion that the same form of hydrogen desorbs from nickel above 200 K in vacuum systems but above 300 K in flow systems. The examinations performed for Ni/Al(2)O(3) and Ni/SiO(2) samples show that alumina suppresses but silica enhances the formation of the beta-form of hydrogen.

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Section: Resultsmentioning

confidence: 99%

Interaction of Hydrogen with Unsupported and Supported Nickel

Znak

Zieliński

2006

Langmuir

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“…TEM measurements could additionally prove this assumption. However, it is known that the contrast between the -Al 2 O 3 support and the Ni particles is very weak and that Ni particles cannot be clearly distinguished from the support [41,[44][45][46]. Thus, particle size measurements of Ni particles on -Al 2 O 3 can reliably only be conducted with special techniques like microdiffraction [46] or HAADF [41].…”

Section: Characterization Of the Aged Catalyst Samplesmentioning

confidence: 99%

“…However, it is known that the contrast between the -Al 2 O 3 support and the Ni particles is very weak and that Ni particles cannot be clearly distinguished from the support [41,[44][45][46]. Thus, particle size measurements of Ni particles on -Al 2 O 3 can reliably only be conducted with special techniques like microdiffraction [46] or HAADF [41]. With common TEM measurements, the question whether the Ni particles are located inside the pores of -Al 2 O 3 can usually not be answered.…”

Section: Characterization Of the Aged Catalyst Samplesmentioning

confidence: 99%

Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

et al. 2021

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We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the catalyst at 600 or 700 °C, which leads to a catalyst with nearly constant conversion after a much shorter time period compared to normal aging. The hydrothermally aged catalysts are characterized by N2 adsorption, X-ray powder diffraction, temperature-programmed reduction and H2 chemisorption. The catalytic performance of the aged catalysts is comparable to the one of a catalyst deactivated in a long-term measurement with up to 720 h on stream. The time needed for reaching a stable conversion can be diminished by rapid aging by a factor of 10. The investigations also showed that the long-term deactivation is caused by Ni particle sintering and that the support pores limit the Ni particle size. Graphical Abstract

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“…Lamber and Schulz-Ekloff examined model catalysts with transmission electron microscopy (TEM) and electron diffraction [46]. Nickel was vacuum deposited on thin films of Al 2 O 3 and oxidized in air at 500 • C. These authors found evidence for NiO and NiAl 2 O 4 , with epitaxial growth of NiO crystallites indicated for ␥-Al 2 O 3 but not ␣-Al 2 O 3 .…”

Section: Introductionmentioning

confidence: 97%