Spectroscopic Characterization of Mixed Titania-Silica Xerogel Catalysts

1999 ◽  
Vol 590 ◽  
Author(s):  
MA Holland ◽  
DM Pickup ◽  
G Mountjoy ◽  
SC Tsang ◽  
GW Wallidge ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Pore Structure ◽  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Xerogel ◽  
Test Reaction ◽  
Saxs Data ◽  
Surface Areas

ABSTRACTThe synthesis of high surface area (TiO2)0.18(SiO2)0.82xerogels has been achieved using the sol-gel route. Heptane washing was used before the drying stage to minimise capillary pressure and hence preserve pore structure and maximise the surface area. The as-prepared xerogels were tested for their catalytic activity using the epoxidation of cyclohexene with tert-butyl hydrogen peroxide (TBHP) as a test reaction. Surface areas up to 450 m2g-1 were achieved with excellent selectivities and reasonable percent conversions. SAXS data has identified that heptane washing during drying, in general, results in a preservation of the pore structure, and produces more effective catalysts with higher surface areas and larger pore diameters. Fr-IR spectroscopy has revealed that the catalytic activity is dependant upon the number of Si-O-Ti linkages, inferring intimate mixing of the precursors at the atomic level. XANES data reveals the presence of reversible 4/6-fold Ti sites that are thought to be ‘active’ catalytic sites. The most effective catalyst was produced with a calcination temperature of 500°C, and a heating rate of 5 °Cmin-l

Pyrolysis of Organosilicon Gels to Silicon Carbide

1986 ◽  
Vol 73 ◽  
Author(s):  
Joseph R. Fox ◽  
Douglas A. White ◽  
Susan M. Oleff ◽  
Robert D. Boyer ◽  
Phyllis A. Budinger
Keyword(s):  
Silicon Carbide ◽  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Carbon Chain ◽  
Carbon Chain Length ◽  
Pyrolysis Products ◽  
Surface Areas ◽  
Physical Measurements

AbstractSol-gel precursors to silicon carbide have been prepared using trifunctional chloro and alkoxysilanes which contain both the silicon and carbon necessary for SiC formation. Crosslinked gels having the ideal formula [RSiO1 5].]n have been synthesized by a hydrolysis/condensation scheme for a series of saturated and unsaturated R groups. The starting gels have been characterized by a variety of elemental analysis, spectroscopic and physical measurements including IR. XRD. TGA.. surface area and pore volume. A particularly powerful method for characterizing these gels is the combination of 13C and 29 Si solid state NMR which can provide information about the degree of crosslinking as well as residual hydroxy/alkoxy content.The controlled pyrolysis of these gels has been used to prepare silicon carbide-containing ceramic products with surface areas in excess of 600m2/gm. The pyrolysis products are best described as a partially crystalline, partially amorphous mixture of β-SiC, silica and carbon. The effect of carbon chain length and the degree of unsaturation in the R group on the composition and surface area of the product has been determined. The origin of the high surface area of the pyrolysis products has been identified and its implications on potential uses of these materials is discussed.

Nitrogen and Water Sorption Properties of Ethyl-Substituted Silica Aerogels and Xerogels

1994 ◽  
Vol 371 ◽  
Author(s):  
Chunling Liu ◽  
Sridhar Komarneni
Keyword(s):  
Pore Structure ◽  
Surface Area ◽  
Water Sorption ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Modified Silica ◽  
Surface Areas ◽  
Water Sorption Properties

AbstractHigh surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.

Synthesis of High Surface Area Porous Silicon Carbide by Employing Soft Template in the Sol-Gel Process

2010 ◽  
Vol 148-149 ◽  
pp. 1629-1633
Author(s):  
Dong Hua Wang ◽  
Xin Fu
Keyword(s):  
Silicon Carbide ◽  
Porous Silicon ◽  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Xerogel ◽  
Porous Silicon Carbide ◽  
Gel Method ◽  
Sol Gel Process

High surface area porous silicon carbide was synthesized by a modified sol-gel method. In the sol-gel method, furfuryl alcohol and tetraethoxysilane were used respectively as carbon and silicon precursors for preparing a carbonaceous silica xerogel. Polymethylhydrosiloxane (PMHS) was employed as pore-adjusting agent in the sol-gel process. SiC was obtained by the carbothermal reduction of the carbonaceous silica xerogel at 1300 oC in argon flow and then purified by removing excess silica, carbon and other impurities. XRD、FTIR、SEM、HRTEM and BET were used to characterize the SiC samples. The results show that the SiC products are found to have high specific surface area of 135 m2 /g. PMHS has important effect on the surface area, pore volume of the SiC products. It is therefore suggested that PMHS plays the role of structure-directing agent that enhances the production of mesoporous pores in the SiC products.

Evaluation of The Catalytic Activity of A High Surface Area, Regular, Porous Solid Formed From The Clusters of Clusters, MII4O[(CO)9Co3CCO2]6, M = Co, Zn

1992 ◽  
Vol 286 ◽  
Author(s):  
Wei Cen ◽  
Thomas P. Fehlner ◽  
Zbigniew Kalenik ◽  
Eduardo E. Wolf
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Catalytic Properties ◽  
High Surface ◽  
High Surface Area ◽  
Molecular Clusters ◽  
Porous Solid ◽  
Test Reaction ◽  
Solid Materials ◽  
Highly Porous

ABSTRACTThe discrete molecular clusters of clusters, M1140[(CO)9Co3CCO2]6, M = Co, Zn undergo thermolysis with the production of highly porous solid materials. Evaluation of the catalytic properties of these materials has been investigated using the hydrogenation of 1,3- butadiene as a test reaction. These experiments suggest it is the unique structure of the porous materials that is responsible for the high activities and the selectivities observed.

High-Surface-Area Alumina-Silica Nanocatalysts Prepared by a Hybrid Sol-Gel Route Using a Boehmite Precursor

2010 ◽  
Vol 93 (12) ◽  
pp. 4047-4052 ◽  
Author(s):  
Padmaja Parameswaran Nampi ◽  
Padmanabhan Moothetty ◽  
Wilfried Wunderlich ◽  
Frank John Berry ◽  
Michael Mortimer ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area

Synthesis and structural characteristics of high surface area TiO2 aerogels by ultrasonic-assisted sol–gel method

2018 ◽  
Vol 29 (7) ◽  
pp. 075702 ◽  
Author(s):  
Feng Qingge ◽  
Cai Huidong ◽  
Lin Haiying ◽  
Qin Siying ◽  
Liu Zheng ◽  
...  
Keyword(s):  
Surface Area ◽  
Structural Characteristics ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Gel Method ◽  
Sol Gel Method ◽  
Ultrasonic Assisted

Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

2013 ◽  
Vol 284-287 ◽  
pp. 230-234
Author(s):  
Yu Jen Chou ◽  
Chi Jen Shih ◽  
Shao Ju Shih
Keyword(s):  
Surface Area ◽  
Calcination Temperature ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Bioactive Glasses ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

Sign in / Sign up

Export Citation Format

Share Document