Size distributions for supported metal catalysts *1Coalescence growth versus ostwald ripening

Supported metal particles play an important role in heterogeneous catalysis. It has been shown lately that the size of the metal crystallites in the supported metal catalysts has a profound effect on the catalytic activity, thus necessitating the need for synthesis methods aimed at a strict control of the metal crystallite size in these catalysts. The classical methods used to synthesize supported metal catalysts typically yield a wide metal crystallite size distribution, and average crystallite sizes which are difficult to control. Suitable techniques have been developed to obtain supported metal catalysts with defined crystallite size distributions, inter alia impregnation of reverse micelle microemulsions, colloid impregnation following reverse micelle precipitation or crystallization, and deposition-precipitation. Using these techniques, a series of supported Ru/γ-Al2O3, Co/SiO2, Fe/γ-Al2O3, Fe/C, and Au/ZnO catalysts have been prepared and characterized.

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High-Resolution Scanning Electron Microscopy and Microanalysis of Supported Metal Catalysts

MRS Proceedings ◽

10.1557/proc-589-259 ◽

1999 ◽

Vol 589 ◽

Cited By ~ 1

Author(s):

Jingyue Liu

Keyword(s):

High Resolution ◽

Low Voltage ◽

Supported Catalysts ◽

Metal Catalysts ◽

Supported Metal Catalysts ◽

Surface Sensitivity ◽

Brightness Field ◽

Backscattered Electron ◽

Enhanced Surface ◽

Supported Metal

AbstractThe use of a high-brightness field emission gun and novel secondary electron detection systems makes it possible to acquire nanometer-resolution surface images of bulk materials, even at low electron beam voltages. The advantages of low-voltage SEM include enhanced surface sensitivity, reduced sample charging on non-conducting materials, and significantly reduced electron range and interaction volume. High-resolution images formed by collecting the backscattered electron signal can give information about the size and spatial distribution of metal nanoparticles in supported catalysts. Low-voltage XEDS can provide compositional information of bulk samples with enhanced surface sensitivity and significantly improved spatial resolution. High-resolution SEM techniques enhance our ability to detect and, subsequently, analyze the composition of nanoparticles in supported metal catalysts. Applications of high-resolution SEM imaging and microanalysis techniques to the study of industrial supported catalysts are discussed.

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C-H bond functionalization using Pd and Au supported catalysts with mechanistic insights of the active species

Synthesis ◽

10.1055/a-1468-1455 ◽

2021 ◽

Author(s):

Tamao Ishida ◽

Zhenzhong Zhang ◽

Haruno Murayama ◽

Eiji Yamamoto ◽

Makoto Tokunaga

Keyword(s):

Aromatic Compounds ◽

Reaction Mechanisms ◽

Bond Activation ◽

Supported Catalysts ◽

Metal Catalysts ◽

Active Species ◽

Supported Metal Catalysts ◽

Bond Functionalization ◽

Bond Forming ◽

Supported Metal

The C–H functionalization has been extensively studied as a direct C–C bond forming reaction with high atomic efficiency. The efforts have also been made on the reaction using supported catalysts, which are superior in terms of catalyst separation from the reaction mixture and reusability. In this review, an overview of the C–H functionalization reactions, especially for Pd and Au supported catalysts will be described. In particular, we discuss reaction mechanisms, active species, leaching, reusability, etc. 1 Introduction 2 Types of supported metal catalysts and their active species 3 Modes of C–H bond activation 4 Oxidative C–H C–H coupling of aryl compounds 5 C–H C–H coupling where one side is aromatic 6 C–H acylation of aromatic compounds and related reactions 7 Conclusion

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