scholarly journals A Brief Overview of Recent Progress in Porous Silica as Catalyst Supports

2021 ◽  
Vol 5 (3) ◽  
pp. 75
Author(s):  
Preeti S. Shinde ◽  
Pradnya S. Suryawanshi ◽  
Kanchan K. Patil ◽  
Vedika M. Belekar ◽  
Sandeep A. Sankpal ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Textural Properties ◽  
Silica Particles ◽  
Catalyst Supports ◽  
Silica Supports ◽  
Low Degree ◽  
Transfer Properties

Porous silica particles have shown applications in various technological fields including their use as catalyst supports in heterogeneous catalysis. The mesoporous silica particles have ordered porosity, high surface area, and good chemical stability. These interesting structural or textural properties make porous silica an attractive material for use as catalyst supports in various heterogeneous catalysis reactions. The colloidal nature of the porous silica particles is highly useful in catalytic applications as it guarantees better mass transfer properties and uniform distribution of the various metal or metal oxide nanocatalysts in solution. The catalysts show high activity, low degree of metal leaching, and ease in recycling when supported or immobilized on porous silica-based materials. In this overview, we have pointed out the importance of porous silica as catalyst supports. A variety of chemical reactions catalyzed by different catalysts loaded or embedded in porous silica supports are studied. The latest reports from the literature about the use of porous silica-based materials as catalyst supports are listed and analyzed. The new and continued trends are discussed with examples.

Porous Al2O3/Al catalyst supports fabricated by an Al(OH)3/Al mixture and the effect of agglomerates

2005 ◽  
Vol 20 (3) ◽  
pp. 672-679 ◽  
Author(s):  
Zhen-Yan Deng ◽  
Yoshihisa Tanaka ◽  
Yoshio Sakka ◽  
Yutaka Kagawa
Keyword(s):  
Surface Area ◽  
Compaction Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Supports ◽  
Al Content ◽  
Starting Mixture ◽  
Mechanical And Electrical Properties ◽  
Uniform Microstructure ◽  
Compact Density

Porous Al2O3/Al catalyst supports were fabricated using a mixture of Al(OH)3 and Al powders, followed by pressureless sintering at a temperature of 600 °C in vacuum. Different pressures were used to prepare green compacts. High compaction pressure led to a high surface area and good mechanical and electrical properties for the sintered specimens. However, when the Al content in the sintered specimen exceeded a definite value, high compaction pressure decreased the surface area abruptly. Scanning electron microscopy observations revealed that agglomeration in the starting mixture has a significant effect on the microstructure of the sintered specimens. High compaction pressure greatly eliminated the agglomerates and led to a uniform microstructure for the sintered specimens. However, when the Al content in the starting mixture was too high, Al particles in the compacts prepared by the high pressure were largely sintered due to the high compact density so that most of the pores were closed. The present study indicates that a suitable compaction pressure is critical to obtaining superior Al2O3/Al supports.

Metal nanoparticles: ligand free approach towards coupling reactions

2021 ◽  
Vol 01 ◽  
Author(s):  
Sharwari K. Mengane ◽  
Ronghui Wu ◽  
Liyun Ma ◽  
Chhaya S. Panse ◽  
Shailesh N. Vajekar ◽  
...  
Keyword(s):  
Heterogeneous Catalysis ◽  
Metal Nanoparticles ◽  
Surface Area ◽  
Heterogeneous Catalysts ◽  
High Surface ◽  
High Surface Area ◽  
Reaction Medium ◽  
Coupling Reactions ◽  
Research Activities ◽  
Ligand Free

: Catalysis is the multidisciplinary field involving many areas of chemistry, notably in organometallic chemistry and materials science. It has great applications in synthesis of many industrially applicable compounds such as fuels and fine chemicals. The activity and selectivity are a key issue in catalysis that generally allied to high surface area. The current research activities mainly deal with the homogeneous and heterogeneous catalysis. Homogeneous and heterogeneous catalysis have certain drawbacks which restricts their application to great extent but have their own advantages. Hence, it has a predominant concern of current research to find out an alternate to overcome their drawbacks. Therefore, it is highly desirable to find a catalytic protocol that offers high selectivity and excellent product yield with quick and easy recovery. Along with their various applications as alternatives to conventional bulk materials nanomaterial have established its great role in different industrial and scientific applications. Nanocatalysis has emerged as new alternative to the conventional homogeneous and heterogeneous catalysis. The nanomaterials are responsible to enhance surface area of the catalyst, which ultimately increases the catalyst reactants contacts. In addition, it acts as robust material and has high surface area like heterogeneous catalysts. Insolubility of such nanomaterial in reaction medium makes them easily separable, hence, catalyst can be easily separate from the product. Hence, it has been proven that nanocatalysts behave like homogeneous as well as heterogeneous catalysts which work as a bridge between the conventional catalytic systems. Considering these merits; researchers has paid their attention towards applications of nanocatalyst in several organic reactions. This review article focused on the catalytic applications of metal nanoparticles (MNPs) such as Pd, Ag, Au, Cu, Pt in ligand free coupling reactions. In addition, it covers applications of bimetallic and multimetallic nanoparticles in ligand free coupling reactions.

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.

Selective molecular sorption by high surface area catalyst supports

1993 ◽  
Vol 226 ◽  
pp. 333-342 ◽  
Author(s):  
Gregory S. Hickey ◽  
Pramod K. Sharma
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Supports ◽  
Molecular Sorption

scholarly journals Synthesis and characterization of porous silica and polyaniline-porous silica composite materials with high surface area

2014 ◽  
Vol 49 (1) ◽  
pp. 1-8
Author(s):  
US Akhtar ◽  
MK Hossain ◽  
MS Miran ◽  
MYA Mollah
Keyword(s):  
Electron Microscopy ◽  
Pore Size ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Nitrogen Adsorption ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Cylindrical Pore

Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014

Porous Silicas for Enhanced Drug Release

2014 ◽  
Vol 91 ◽  
pp. 79-81
Author(s):  
Abina M. Crean ◽  
Robert J. Ahern ◽  
Rakesh Dontireddy ◽  
Walid Faisil ◽  
John P. Hanrahan ◽  
...  
Keyword(s):  
Surface Area ◽  
Water Solubility ◽  
Solid Dispersions ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
High Energy ◽  
Drug Dissolution ◽  
Drug Candidates ◽  
Drug Molecules

Low drug water-solubility is a major challenge to overcome in the development of tablet or capsule dosage forms for a large number of promising drug candidates. Strategies to improve drug solubility and dissolution involve chemical, physical and formulation approaches. An emerging formulation approach to increase drug dissolution and solubility involves the creation of solid dispersions of drug molecules on to a high surface area inorganic carrier, such as porous silica. The combined benefits of a hydrophilic inorganic substrate, increased drug surface area and a high-energy drug form facilitate rapid drug dissolution into aqueous based media and can create supersaturated drug solutions. The work presented provides a brief overview of the silica grades investigated, processes employed to load drugs onto the silica substrates, provide some examples of the ability of silica to enhance drug dissolution and highlight some of the challenges in the development of these novel drug delivery systems.

scholarly journals The Geode Process I: Hollow Silica Microcapsules as a High Surface Area Substrate for Semiconductor Nanowire Growth

2019 ◽  
Author(s):  
Maritza Mujica ◽  
Gozde Tutuncuoglu ◽  
Amar Mohabir ◽  
Victor Breedveld ◽  
Sven Behrens ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Silica Particles ◽  
Nanowire Growth ◽  
Si Nanowires ◽  
Hollow Silica ◽  
Semiconductor Nanowire ◽  
Interior Surface ◽  
Emulsion Templating

<div><div><div><p>We introduce and demonstrate critical steps toward the Geode process for the bottom-up synthesis of semiconductor nanowires. Central to the process is the design and fabrication of an unconventional, high surface area substrate: the interior surface of hollow silica microcapsules, assembled from silica particles via emulsion templating, and featuring porous walls to enable efficient gas transport. The interior surface of these hollow silica microcapsules is decorated with gold nanoparticles that seed nanowire growth via the vapor-liquid-solid (VLS) mechanism. We demonstrate the production of the necessary microcapsules and show how microcapsule structure and stability upon drying is influenced by the type of silica particles and use of a particle cross-linking agent. Finally, we demonstrate the synthesis of Si nanowires in the microcapsule interior.</p></div></div></div>

scholarly journals Synthesis and characterization of mesoporous materials with SBA and MCM structure types

Cerâmica ◽  
2019 ◽  
Vol 65 (376) ◽  
pp. 585-591
Author(s):  
R. A. Sacramento ◽  
O. M. S. Cysneiros ◽  
B. J. B. Silva ◽  
A. O. S. Silva
Keyword(s):  
Surface Area ◽  
Mesoporous Materials ◽  
High Surface ◽  
High Surface Area ◽  
Textural Properties ◽  
N2 Adsorption ◽  
Structure Directing Agent ◽  
Type Iv ◽  
Xrd Patterns ◽  
Adsorption Desorption

Abstract Mesoporous materials are promising structures for application in catalysis and adsorption due to high surface area and large pore size. Mesoporous materials were synthesized by the hydrothermal method with novel surfactants, distinct from those observed in the literature, in order to carry out a study of its structure and to obtain materials with better textural properties. The structures synthesized with the surfactants Igepal CO630 and Brij O20 presented the best results of specific surface area, 1074 and 1075 m2.g-1, respectively. The obtained materials were characterized by XRD, TG/DTG, N2 adsorption-desorption, and FTIR techniques. XRD patterns indicated that the highly ordered mesoporous silica structures, such as MCM-41 and MCM-48, using CTMABr as the structure-directing agent and the SBA-15, SBA-16 and other SBA structures using different block copolymers were obtained. Through N2 adsorption-desorption isotherms, it was observed type IV isotherms, attributed to mesoporous materials. The FTIR spectra presented similar behaviors with characteristic vibrational bands of MCM and SBA type materials.

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