Characterization of Supported Metal Particles in Heterogeneous Catalysts: Part II. Studies of Low Surface Area, Model Materials

A detailed understanding of catalytic processes requires structural knowledge of the catalyst system. The surface properties of small metal particles which are highly dispersed on insulating supports must play a dominant role in determining this system's catalytic behavior. Therefore characterization of surface topography and composition of heterogeneous catalysts is important. Surface topography of the carrier materials can be obtained by high resolution secondary electron imaging (SEI) in a STEM. The small metal particles can also be located and their topographic relationship with the support morphology determined. However, an elementally specific signal such as the Auger electrons must be used to extract chemical information about the surface species. High resolution Auger electron spectroscopy (AES) and scanning Auger microscopy (SAM) have recently been incorporated into a UHV STEM. In this paper we report some results from the application of this instrumentation to the study of supported metal clusters.

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Metal carbonyl clusters as precursors of heterogeneous catalysts: Hydrogenation and disproportionation of monoenes, dienes, and arenes in the presence of H2Ru4(CO)13, H2FeRu3(CO)13, and HRuCo3(CO)12 supported and activated on chromosorb. Characterization of the metal particles derived from H2Ru4(CO)13 by means of IR spectroscopy and TEM microscopy

Journal of Cluster Science ◽

10.1007/bf02764115 ◽

1997 ◽

Vol 8 (3) ◽

pp. 381-405 ◽

Cited By ~ 9

Author(s):

Mario Castiglioni ◽

Stefano Deabate ◽

Edoardo Garrone ◽

Roberto Giordano ◽

Barbara Onida ◽

...

Keyword(s):

Ir Spectroscopy ◽

Heterogeneous Catalysts ◽

Metal Carbonyl ◽

Metal Particles ◽

Carbonyl Clusters ◽

Metal Carbonyl Clusters ◽

Tem Microscopy

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Synthesis of heterogeneous catalysts with well shaped platinum particles to control reaction selectivity

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.0805691105 ◽

2008 ◽

Vol 105 (40) ◽

pp. 15241-15246 ◽

Cited By ~ 198

Author(s):

Ilkeun Lee ◽

Ricardo Morales ◽

Manuel A. Albiter ◽

Francisco Zaera

Keyword(s):

Surface Area ◽

Heterogeneous Catalysts ◽

Colloidal Particles ◽

Supported Catalysts ◽

High Surface ◽

Sol Gel ◽

High Surface Area ◽

Metal Particles ◽

Platinum Particles

Colloidal and sol-gel procedures have been used to prepare heterogeneous catalysts consisting of platinum metal particles with narrow size distributions and well defined shapes dispersed on high-surface-area silica supports. The overall procedure was developed in three stages. First, tetrahedral and cubic colloidal metal particles were prepared in solution by using a procedure derived from that reported by El-Sayed and coworkers [Ahmadi TS, Wang ZL, Green TC, Henglein A, El-Sayed MA (1996) Science 272:1924–1926]. This method allowed size and shape to be controlled independently. Next, the colloidal particles were dispersed onto high-surface-area solids. Three approaches were attempted: (i) in situ reduction of the colloidal mixture in the presence of the support, (ii) in situ sol-gel synthesis of the support in the presence of the colloidal particles, and (iii) direct impregnation of the particles onto the support. Finally, the resulting catalysts were activated and tested for the promotion of carbon–carbon double-bond cis-trans isomerization reactions in olefins. Our results indicate that the selectivity of the reaction may be controlled by using supported catalysts with appropriate metal particle shapes.

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Quantitative nano-characterization of heterogeneous catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138361 ◽

1995 ◽

Vol 53 ◽

pp. 398-399

Author(s):

P.A. Crozier ◽

M. Pan

Keyword(s):

Heterogeneous Catalysts ◽

Low Dose ◽

Imaging Techniques ◽

Structural Features ◽

Catalyst Characterization ◽

New Developments ◽

Double Phase ◽

Phase Systems ◽

Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

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Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015112x ◽

1993 ◽

Vol 51 ◽

pp. 1058-1059

Author(s):

J. Liu ◽

M. Pan ◽

G. E. Spinnler

Keyword(s):

Supported Catalysts ◽

Imaging Techniques ◽

Nano Particles ◽

Metal Particles ◽

Shape Structure ◽

Dynamical Simulations ◽

Small Metal Particles ◽

Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

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HREM image simulations for supported metal particle catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149519 ◽

1993 ◽

Vol 51 ◽

pp. 736-737 ◽

Cited By ~ 1

Author(s):

Ming-Hui Yao ◽

David J. Smith

Keyword(s):

Fine Particles ◽

Amorphous Material ◽

Chemical Properties ◽

Morphological Features ◽

Metal Particles ◽

Plan View ◽

Profile View ◽

Imaging Conditions ◽

Image Simulations ◽

Supported Metal

The chemical properties of catalysts often depend on the size, shape and structure of the supported metal particles. To characterize these morphological features and relate them to catalysis is one of the main objectives for HREM study of catalysts. However, in plan view imaging, details of the shape and structure of ultra-fine supported particles (<2nm) are often obscured by the overlapping contrast from the support, and supported sub-nanometer particles are sometimes even invisible. Image simulations may help in the interpretation at HREM images of supported particles in particular to extract useful information about the size, shape and structure of the particles. It should also be a useful tool for evaluating the imaging conditions in terms of visibility of supported particles. P. L. Gai et al have studied contrast from metal particles supported on amorphous material using multislice simulations. In order to better understand the influence of a crystalline support on the visibility and apparent morphological features of supported fine particles, we have calculated images of Pt and Re particles supported on TiO2(rutile) in both plan view and profile view.

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Development and Characterization of Amine-Clay Hybrid Adsorbents for CO2 Capture

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1133.547 ◽

2016 ◽

Vol 1133 ◽

pp. 547-551 ◽

Cited By ~ 2

Author(s):

Ali E.I. Elkhalifah ◽

Mohammad Azmi Bustam ◽

Azmi Mohd Shariff ◽

Sami Ullah ◽

Nadia Riaz ◽

...

Keyword(s):

Adsorption Capacity ◽

Surface Area ◽

Surface Properties ◽

Molar Mass ◽

Adsorption Ability ◽

Stepwise Increase ◽

Inverse Effect ◽

Bet Method ◽

Sodium Form

The present work aims at a better understanding of the influences of the intercalated mono-, di- and triethanolamines on the characteristics and CO2 adsorption ability of sodium form of bentonite (Na-bentonite). The results revealed that the molar mass of intercalated amines significantly influenced the structural and surface properties as well as the CO2 adsorption capacity of Na-bentonite. In this respect, a stepwise increase in the d-spacing of Na-bentonite with the molar mass of amine was recorded by XRD technique. However, an inverse effect of the molar mass of amine on the surface area was confirmed by BET method. CO2 adsorption experiments on amine-bentonite hybrid adsorbents showed that the CO2 adsorption capacity inversly related to the molar mass of amine at 25 ͦC and 101 kPa. Accordingly, Na-bentonite modified by monoethanolammonium cations adsorbed as high as 0.475 mmol CO2/g compared to 0.148 and 0.087 mmol CO2/g for that one treated with di- and triethanolammonium cations, respectively.

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