Structure of Supported Metal Catalysts Derived from Molecular Bimetallic Clusters

AbstractRe-containing molecular bimetallic clusters were used as precursors for gamma alumina supported catalysts. Characterization by XPS and XAS after hydrogen reduction showed Re valence states in the order Re monometallic > Re-Os bimetallic > Re-Pt bimetallic > zero. These results suggest that industrial bimetallic catalysts are not best understood in terms of alloys, but rather as multifunctional, with each element contributing its own activity.

Download Full-text

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.

Download Full-text

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

Download Full-text

ChemInform Abstract: Supported Metal Catalysts Prepared from Bimetallic Clusters: ReOs3 Clusters on γ-Al2O3.

ChemInform ◽

10.1002/chin.198911022 ◽

1989 ◽

Vol 20 (11) ◽

Author(s):

A. S. FUNG ◽

P. A. TOOLEY ◽

M. R. MCDEVITT ◽

B. C. GATES ◽

M. J. KELLEY

Keyword(s):

Metal Catalysts ◽

Bimetallic Clusters ◽

Supported Metal Catalysts ◽

Supported Metal

Download Full-text

Phase and facet-engineering of transition alumina leads to (hydro)thermally stable alumina-supported metal catalysts

10.33774/chemrxiv-2021-tq1kw ◽

2021 ◽

Author(s):

Konstantin Khivantsev ◽

Ja-Hun Kwak ◽

Nicholas Jaegers ◽

Yong Wang ◽

Janos Szanyi ◽

...

Keyword(s):

Rare Earth ◽

High Surface ◽

Metal Catalysts ◽

Supported Metal Catalysts ◽

Thermally Stable ◽

Gamma Alumina ◽

Hydrothermal Aging ◽

Pd Catalysts ◽

Transition Alumina ◽

Supported Metal

Inherent thermal instability of gamma-alumina above 800-900 ⁰C leads to deactivation of noble metal-supported alumina catalysts used in automotive applications. This is typically solved by adding toxic (barium) and/or rare-earth (lanthanum, cerium) elements. We show that facet-dependent engineering of transition-alumina leads to (hydro)thermally stable supported metal catalysts in the absence of toxic and rare-earth additives. Since pure high-surface area theta-alumina can be prepared at 1,050-1,100 ⁰C directly from gamma-alumina (or boehmite), and because of its stable major (100) facet with very low surface energy of 597 mJ/m2, we succeeded in preparing ~0.07 wt% Rh and ~3 wt% Pd catalysts active in NO reduction and hydrocarbon oxidation that survive hydrothermal aging up to 1,100 ⁰C with little-to-no deactivation.

Download Full-text