Novel Xerogel Catalyst Materials for Hydrogenation Reactions and the Role of Atomic Scale Interfaces

1999 ◽  
Vol 5 (S2) ◽  
pp. 704-705
Author(s):  
P.L. Gai ◽  
K. Kourtakis ◽  
H. Dindi ◽  
S. Ziemecki
Keyword(s):  
High Resolution ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Low Voltage ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Hydrogenation Reactions

We are developing a new family of heterogeneous catalysts for hydrogenation catalysis. Catalyst synthesis is accomplished using colloidal polymerization chemistry which produce high surface area xerogel catalysts. These xerogels have been synthesized by one-step sol gel chemistry. These catalysts contain ruthenium and modifiers such as gold occluded or incorporated in a titanium oxide matrix. The materials, especially the modified systems exhibit favorable performance in microreactor evaluations for hydrogenation reactions and exhibit high activities. Nanostructural studies have revealed that the materials contain dispersed catalyst clusters which are desirable microstructures for the catalysis since the majority of the atoms are exposed to catalysis and are potentially active sites.The composition and atomic structure of the xerogel catalysts containing ruthenium and other metals have been examined using our in-house developments of environmental high resolution electron microscopy (EHREM) the atomic scale [1-3] and low voltage high resolution SEM (LVSEM)[4] methods.

Electron holography of catalysts

1995 ◽  
Vol 53 ◽  
pp. 416-417
Author(s):  
A. K. Datye ◽  
D. S. Kalakkad ◽  
L. F. Allard ◽  
E. Völkl
Keyword(s):  
Heterogeneous Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Scale ◽  
Nano Particles ◽  
Phase Image ◽  
Electron Holography ◽  
Specimen Thickness ◽  
Phase Information ◽  
Particle Structure

The active phase in heterogeneous catalysts consists of nanometer-sized metal or oxide particles dispersed within the tortuous pore structure of a high surface area matrix. Such catalysts are extensively used for controlling emissions from automobile exhausts or in industrial processes such as the refining of crude oil to produce gasoline. The morphology of these nano-particles is of great interest to catalytic chemists since it affects the activity and selectivity for a class of reactions known as structure-sensitive reactions. In this paper, we describe some of the challenges in the study of heterogeneous catalysts, and provide examples of how electron holography can help in extracting details of particle structure and morphology on an atomic scale.Conventional high-resolution TEM imaging methods permit the image intensity to be recorded, but the phase information in the complex image wave is lost. However, it is the phase information which is sensitive at the atomic scale to changes in specimen thickness and composition, and thus analysis of the phase image can yield important information on morphological details at the nanometer level.

Visibility of Small Metalllic Catalyst Particles in High-Resolution Secondary and Backscattered Electron Images

1999 ◽  
Vol 5 (S2) ◽  
pp. 720-721
Author(s):  
Jingyue Liu
Keyword(s):  
High Resolution ◽  
Metallic Nanoparticles ◽  
Low Voltage ◽  
High Surface ◽  
High Surface Area ◽  
Metal Catalyst ◽  
Catalyst Supports ◽  
Metallic Particles ◽  
Backscattered Electrons ◽  
Backscattered Electron

Metallic nanoparticles finely dispersed onto high surface-area supports play an important role in heterogeneous catalysis. The performance of a supported metal catalyst can be directly related to the size and spatial distribution of the metallic nanoparticles. With the recent development of highresolution SEM instruments, it is now possible to observe nanoparticles in a field emission SEM. At low voltages, surface details of catalyst supports as well as metallic nanoparticles can be observed. The particle contrast in low voltage SEM images, however, is still not well understood. We have previously shown that the contrast of metallic particles can be enhanced if a small positive potential is applied to the sample. It is suggested that backscattered electrons (BE) significantly contribute to the visibility of metallic nanoparticles in high-resolution SE images. In this paper, we report further study on the origin of particle contrast in high-resolution SE images.Figure 1 shows a set of SE images of the same area of a carbon supported Pt catalyst.

scholarly journals Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
Samira Bagheri ◽  
Nurhidayatullaili Muhd Julkapli ◽  
Sharifah Bee Abd Hamid
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
Catalyst Support ◽  
High Surface Area ◽  
Supported Metal Catalysts ◽  
Support Material ◽  
Oxidation Reactions ◽  
Base Property ◽  
Metal Support Interaction

The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2supported metal catalysts have attracted interest due to TiO2nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2as a support material for heterogeneous catalysts and its potential applications.

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

2008 ◽  
Vol 105 (40) ◽  
pp. 15241-15246 ◽  
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.

scholarly journals Homochiral metal–organic frameworks as heterogeneous catalysts

2018 ◽  
Vol 5 (7) ◽  
pp. 1512-1523 ◽  
Author(s):  
Andreea Gheorghe ◽  
Martijn A. Tepaske ◽  
Stefania Tanase
Keyword(s):  
Surface Area ◽  
Asymmetric Catalysis ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
Metal Organic Frameworks ◽  
High Surface Area ◽  
Metal Organic

Homochiral metal–organic frameworks (HMOFs) are attractive materials for asymmetric catalysis because they possess high surface area and uniform active sites.

In Situ Nanoscale Studies of Liquid Polymerization Reactions in the Manufacture of Polyamides and.Combinatorial Catalysis

2001 ◽  
Vol 7 (S2) ◽  
pp. 1060-1061
Author(s):  
Pratibha L. Gai ◽  
K. Kourtakis ◽  
S. Ziemecki
Keyword(s):  
Low Temperature ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Single Step ◽  
Heterogeneous Catalytic ◽  
Rutile Titania ◽  
Real Time Information

Low temperature heterogeneous catalytic routes for polymers are of considerable interest in the chemical sciences and technology because they are economical and environmentally beneficial. However such routes have been difficult because of an incomplete understanding of process control and low yields. Currently, hydrogenation of aliphatic dintriles in solvents is used in the chemical industry to manufacture the corresponding diamenes which are subsequently reacted with adipic acid solutions and polymerized to produce the polyamide, nylon (6,6).Here we report an alternative, low temperature heterogeneous catalytic process for the polymerization reactions using novel environmental-HRTEM (EHREM) in liquid environments. EHREM under simulated reaction conditions provides direct, in situ real-time information on the dynamic structural and chemical changes and reaction modes of operation. We prepared high surface area heterogeneous catalysts including cobalt-ruthenium nanoclusters supported on rutile titania using a single step sol-gel technique, (shown in Fig. 1).

What catalysis needs from the electron microscopist

1988 ◽  
Vol 46 ◽  
pp. 694-695
Author(s):  
Alexis T. Bell
Keyword(s):  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Catalyst Deactivation ◽  
Surface Composition ◽  
Internal Surface ◽  
Active Phase ◽  
Atomic Scale ◽  
Metal Catalyst ◽  
Internal Surface Area ◽  
Porous Support

Heterogeneous catalysts, used in industry for the production of fuels and chemicals, are microporous solids characterized by a high internal surface area. The catalyticly active sites may occur at the surface of the bulk solid or of small crystallites deposited on a porous support. An example of the former case would be a zeolite, and of the latter, a supported metal catalyst. Since the activity and selectivity of a catalyst are known to be a function of surface composition and structure, it is highly desirable to characterize catalyst surfaces with atomic scale resolution. Where the active phase is dispersed on a support, it is also important to know the dispersion of the deposited phase, as well as its structural and compositional uniformity, the latter characteristics being particularly important in the case of multicomponent catalysts. Knowledge of the pore size and shape is also important, since these can influence the transport of reactants and products through a catalyst and the dynamics of catalyst deactivation.

Metal-organic-framework derived hollow manganese nickel selenide spheres confined with nanosheets on nickel foam for hybrid supercapacitors

2021 ◽  
Author(s):  
Bahareh ameri ◽  
Akbar Mohammadi Zardkhoshoui ◽  
Saied Saeed Hosseiny Davarani
Keyword(s):  
Active Sites ◽  
Nickel Foam ◽  
Metal Organic Framework ◽  
High Surface ◽  
Metal Organic Frameworks ◽  
High Surface Area ◽  
Supercapacitive Performance ◽  
Hybrid Supercapacitors ◽  
Porous Networks ◽  
Metal Organic

Metal-organic frameworks (MOFs) derived nanoarchitectures have special features, such as high surface area (SA), abundant active sites, exclusive porous networks, and remarkable supercapacitive performance when compared to traditional nanoarchitectures. Herein,...

Studies of Supported Metal Catalysts Using Low Voltage Biased Secondary Electron Imaging in a JSM-6320f Fe-SEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1223-1224
Author(s):  
J. Liu ◽  
R. L. Ornberg ◽  
J. R. Ebner
Keyword(s):  
Secondary Electron ◽  
Low Voltage ◽  
Supported Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Incident Beam ◽  
Active Species ◽  
Supported Metal Catalysts ◽  
Active Components ◽  
Electron Imaging

Many industrial catalysts have a complex geometric structure to enable reacting gases or fluids to reach as much of the active surface of the catalyst as possible. The catalyzing surface frequently consists of a complex chemical mixture of different phases produced by an evolved chemical process. The active components are often very small particles dispersed on high-surface-area supports. The catalytic properties of this type of catalyst depend on the structure, composition, and morphology of the active species as well as the supports. TEM/STEM and associated techniques have been used extensively to characterize the structure and composition of supported catalysts. Surface morphology of supported catalysts is generally examined by secondary electron imaging, especially at low incident beam energies. It is, however, frequently found that small metal particles are not usually seen in SE images because of the complication of support topography

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