Pt/SiO2 Sonogels: Synthesis and Characterization

Bosch, P.; López, T.; Asomoza, M.; Gómez, R.; Cauqui, M.A.; Rodrı́guez-Izquierdo, J.M.

doi:10.1021/la00011a026

Cited by 10 publications

(4 citation statements)

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“…Finally, we should mention characterization 146,147 for Pt catalysts prepared with silica sonogels as supports; the authors concluded that the method followed for the preparation determines the surface acidic properties of the catalysts, thus modulating their catalytic behavior.…”

mentioning

confidence: 99%

Sonogels and derived materials

Blanco¹,

Esquivias²,

Litrán³

et al. 1999

Appl. Organometal. Chem.

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Nowadays the sol–gel process is used by an increasing number of researchers for the preparation of various products, including bulk materials, films, membranes or fibers. The application of ultrasound (sonocatalysis) to the precursors gives rise to materials with new properties, known as sonogels. The absence of additional solvent and, mainly, the effects of ultrasonic cavitation create a unique environment for sol–gel reactions leading to particular features in the resulting gels: high density, fine texture, homogeneous structure etc. These properties determine the evolution of sonogels on further processing and the final material structure. In this sense, the full exploitation of sonocatalysis requires a thorough understanding of the processes involved and their sensitivity to reaction parameters. For this purpose, we have used diverse techniques to investigate the microstructural evolution during different steps in the sonogel process. The results of these studies are reported here. Finally, we present an overview of some applications for which the mechanical, textural and optical characteristics of sonogels are quite useful. Copyright © 1999 John Wiley & Sons, Ltd.

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confidence: 99%

Sonogels and derived materials

Blanco¹,

Esquivias²,

Litrán³

et al. 1999

Appl. Organometal. Chem.

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“…Furthermore, the catalyst surface becomes homogeneous and active centre coverage is decreased correspondingly [49,50]. Firstly, the agglomeration can be inhibited and/or boehmite particles broken up by sonication, resulting in smaller Pd particle sizes and more active centres [44].…”

Section: Comparison Of Ultrasonic Hydrogenation Of Pa Over Various Camentioning

confidence: 99%

Ultrasonically improved semi-hydrogenation of alkynes to (Z-)alkenes over novel lead-free Pd/Boehmite catalysts

Cravotto

Gaudino

et al. 2017

Ultrasonics Sonochemistry

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This paper reports the application of ultrasound in the semi-hydrogenation of alkynes over two novel Pd/Boehmite catalysts. The semi-hydrogenations of phenylacetylene, diphenylacetylene and 2-butyne-1,4-diol have either been investigated in an ultrasonic bath under atmospheric hydrogen pressure, or in an ultrasonic horn reactor under 0.1-0.5MPa hydrogen pressure. Alkyne hydrogenation was suppressed by sonication under atmospheric hydrogen pressure, but promoted by sonication under 0.1MPa of hydrogen pressure. Sonication increased selectivity towards the semi-hydrogenated products in both cases. Catalyst loading, hydrogen pressure, temperature and the presence of quinoline, all impacted on hydrogenation rate, activity and selectivity to semi-hydrogenated products. Palladium leaching from the catalyst was evaluated in ethanol and hexane both under plain stirring and sonication.

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“…The intensity values were acquired in the 2θ range from 4 to 130°, with a step of 0.125° at a scan rate of 1° per min. In this way, it was possible to reach the high values of the angular parameter (s = 4π sin θ/λ, where θ is the Bragg angle and λ is the Mo Kα wavelength), which are recommended to estimate the average interatomic distances in nanocrystalline materials [35,36]. The radial distribution function was obtained by inputting the experimental data in software based on the Fortran IV program developed by Magini and Cabrini [37], and it was interpreted in terms of the reported ionic radii (r i ).…”

Section: X-ray Powder Diffractionmentioning

confidence: 99%

Effect of Chromium Doping on Visible Light Absorption of Nanosized Titania Sol-Gel

Pedraza-Avella

López

Ortega

et al. 2009

JNanoR

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Visible light absorption of TiO2 can be induced by the addition of transition metal impurities. However, many dissimilar results have been reported about this subject and there are various interpretations about the origin of these absorption features. In this work, samples of chromium-doped titania (TiO2-Cr) with different dopant contents (0.1, 0.5, 1.0 and 5.0 wt. %) were prepared by a sol-gel method. Their particle size was determined by dynamic light scattering and it was on the nanometer scale (18 nm). X-ray powder diffraction and Raman spectroscopy showed only the presence of anatase phase in all samples. X-ray photoelectron spectroscopy reveals that the oxidation state of chromium in the prepared materials is different than in the dopant precursor. This change can be associated to the oxidative gelling conditions used in the materials preparation. UV VIS diffuse reflectance spectroscopy showed that the chromium doping, until 1.0 wt. %, did not effectively narrow the TiO2 band-gap but it induces the visible light absorption probably through the formation of color centers.

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Pt/SiO2 Sonogels: Synthesis and Characterization

Cited by 10 publications

References 0 publications

Sonogels and derived materials

Sonogels and derived materials

Ultrasonically improved semi-hydrogenation of alkynes to (Z-)alkenes over novel lead-free Pd/Boehmite catalysts

Effect of Chromium Doping on Visible Light Absorption of Nanosized Titania Sol-Gel

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