Thermally stable, silica-based amorphous porous mixed oxides prepared by sol–gel procedures

Klein, Jens; Lettmann, Christian; Maier, Wilhelm F.

doi:10.1016/s0022-3093(01)00317-9

Cited by 15 publications

(12 citation statements)

References 35 publications

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“…Additionally, when synthesizing mixed metal oxides, precipitation and phase separation of one metal oxide during the sol− gel synthesis can be avoided when using an acid as a catalyst. 115,116 Initially, all 72 catalysts were screened for the hydrogenation of toluene, naphthalene, pyridine, indole, quinoline, thiophene and benzothiophene at a pressure of 75 psi H 2 (∼5 atm) for a period of 4 h using a Symyx heated orbital shaker system.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Screening of Heterogeneous Multimetallic Nanoparticle Catalysts Supported on Metal Oxides for Mono-, Poly-, and Heteroaromatic Hydrogenation Activity

et al. 2012

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A series of oxide supported mono-, bi-, and trimetallic nanoparticle catalysts were synthesized and screened for catalytic activity for the hydrogenation of mono-, poly-, and heteroaromatic substrates. Seventy-two different catalysts were screened for catalytic activity for the hydrogenation of toluene, naphthalene, pyridine, indole, quinoline, thiophene, and benzothiophene under mild conditions; five of these seven substrates were successfully hydrogenated under the reaction conditions. Bulk kinetic studies, including temperature and pressure studies, were performed using select catalysts for the hydrogenation of one hydrocarbon (naphthalene) and oneheteroatom substituted-substrate (quinoline). A quinoline loading study was also conducted in which the ratio of substrate/ catalyst was varied. Standard materials characterization techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were also used to acquire information about the size, oxidation state, and crystallinity of the nanoparticle catalysts.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Screening of Heterogeneous Multimetallic Nanoparticle Catalysts Supported on Metal Oxides for Mono-, Poly-, and Heteroaromatic Hydrogenation Activity

et al. 2012

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“…In this reactive surface hydroxyl group are silylated and hinder the rearrangement of surface structure and thus result in the stability of amorphous mixed oxides. [142,143].…”

Section: Catalystsmentioning

confidence: 99%

Amorphous Porous Mixed Oxides: A New and Highly Versatile Class of Materials

Pandey

Mishra

2012

Intelligent Nanomaterials

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Porous solids are a rapidly developing class of materials with an ever-increasing range of applications. Among these materials, amorphous porous mixed oxides possess the extraordinary properties of fine tuning the chemical composition, microstructure, porosity and surface properties. The tailor made composition of the mixed oxides can be fabricated from the availability of variety of precursor, additives and modifiers. Besides, their performance can be found close to that of crystalline phase. These amorphous mixed oxides can easily be synthesized using acid / base catalyzed one-pot sol-gel procedure. Sol-gel processes allow for a relatively facile tailoring of the morphology of mixed oxides to the desired application in the field of nanotechnology. Pore volume, porosity, specific surface area, and surface acidity are typical parameters that can be tailored. This chapter deals with the preparation methodology, characterization techniques, and application of amorphous porous mixed oxides.

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“…Os óxidos mistos SiO 2 /M x O y obtidos pelo processo sol-gel, designados de compósitos, normalmente aliam as propriedades mecânicas e químicas da sílica gel com as propriedades químicas do óxido metálico (M x O y ) livre [1][2][3][4]. Esses materiais apresentam propriedades importantes, das quais podem-se destacar: elevado grau de dispersão e homogeneidade das partículas de M x O y na matriz de SiO 2; elevada resistência mecânica e química; e caráter ácido de Brønsted e de Lewis [1][2][3].…”

Section: Introductionunclassified

“…Esses materiais apresentam propriedades importantes, das quais podem-se destacar: elevado grau de dispersão e homogeneidade das partículas de M x O y na matriz de SiO 2; elevada resistência mecânica e química; e caráter ácido de Brønsted e de Lewis [1][2][3]. A preparação desses materiais pelo processo sol-gel não é trivial, pois a cinética de hidrólise, catalisada por ácido, é diferenciada para cada precursor, existindo deste modo uma correlação entre as características do compósito obtido e os parâmetros de síntese.…”

Section: Introductionunclassified

“…A preparação desses materiais pelo processo sol-gel não é trivial, pois a cinética de hidrólise, catalisada por ácido, é diferenciada para cada precursor, existindo deste modo uma correlação entre as características do compósito obtido e os parâmetros de síntese. Além disso, o processo sol-gel permite a obtenção de sólidos com alta área superficial e com tamanho e distribuição de poros controlados nos quais o óxido metálico (M x O y ) está altamente disperso na matriz de sílica [1][2][3][4], característica extremamente importante para aplicações em eletrocatálise.…”

Section: Introductionunclassified

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Síntese de óxidos mistos SiO2 /Mn xOy para aplicação na reação de redução de O2

et al. 2013

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RESUMOOs óxidos mistos SiO 2 /M x O y obtidos pelo processo sol-gel, designados de compósitos, normalmente aliam as propriedades mecânicas e químicas da sílica gel com as propriedades químicas do óxido metálico (M x O y ), apresentando propriedades tais como: elevado grau de dispersão e homogeneidade das partículas do óxido metálico na matriz de sílica, assim como elevada resistência mecânica e química. O objetivo deste trabalho foi o de preparar e caracterizar materiais do sistema SiO 2 /Mn x O y , obtidos pelo processo sol-gel, utilizando diferentes concentrações dos precursores de Mn (II), acetato ou nitrato. A técnica de fluorescência de raios X (FRX) mostrou que a concentração do óxido metálico nos materiais é dependente do precursor utilizado e da sua concentração no meio reacional, variando de 9,4% até 20,9% em massa. A maior concentração de óxido de manganês foi obtida quando se utilizou como precursor o (CH 3 CO 2 ) 2 Mn.4H 2 O. Os espectros de infravermelho indicam que a rede de SiO 2 é pouco perturbada pelo aumento da quantidade de óxido de manganês, sugerindo que o Mn x O y está disperso na superfície da matriz de sílica. Os difratogramas de raiosX (DRX) mostram que os materiais apresentam baixa cristalinidade. No entanto, observa-se uma mudança no DRX em 2θ = 35,7 o quando o material é aquecido a 400 0 C, provavelmente devido à formação de cristalitos de Mn 3 O 4 . O método de síntese proposto para os materiais SiO 2 /Mn x O y é reprodutível. A aplicação destes materiais como eletrodos para a redução de O 2 foi avaliada e observou-se que a atividade eletrocatalítica desses materiais pode ser aumentada através do seu aquecimento a 400 0 C. Palavras-chave:Sol-Gel, óxidos mistos, sílica gel, óxido de manganês, compósito. ABSTRACTThe mixed oxides SiO 2 /M x O y obtained by the sol-gel process, designated as composites, usually combine both mechanical and chemical properties of silica gel with the chemical properties of metal oxide (M x O y ), showing properties such as: high degree of dispersion and homogeneity of metal oxide particles in the silica matrix, as well as high mechanical and chemical resistance. The goal of this work was to prepare and characterize materials in the system SiO 2 /Mn x Oy obtained by the sol-gel process, using different concentrations of Mn (II) precursors (acetate or nitrate). The technique of X-ray fluorescence showed that the concentration of metal oxide in the materials is dependent on the precursor used and its concentration, ranging from 9.4% up to 20.9% by mass. The highest concentration of manganese oxide was obtained when (CH 3 CO 2 ) 2 Mn.4H 2 O was used as precursor. The infrared spectra indicate that the network of SiO 2 is not disturbed by the increase in the quantity of manganese oxide, suggesting that the Mn x O y is dispersed on the surface of the silica matrix. The X-ray diffraction showed the low crystallinity of these materials. However, there is a change in the XRD on 2θ = 35.7 0 when the material is heated to 400 0 C, probably due to the formation of Mn 3...

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Thermally stable, silica-based amorphous porous mixed oxides prepared by sol–gel procedures

Cited by 15 publications

References 35 publications

Screening of Heterogeneous Multimetallic Nanoparticle Catalysts Supported on Metal Oxides for Mono-, Poly-, and Heteroaromatic Hydrogenation Activity

Screening of Heterogeneous Multimetallic Nanoparticle Catalysts Supported on Metal Oxides for Mono-, Poly-, and Heteroaromatic Hydrogenation Activity

Amorphous Porous Mixed Oxides: A New and Highly Versatile Class of Materials

Síntese de óxidos mistos SiO2 /Mn xOy para aplicação na reação de redução de O2

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