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Artigo Revisado por pares

Jorge Enrique Rodríguez Páez, A. Mafla, Gustavo F. S. Andrade, Alicia Durán,

La tecnica Sol-Gel se ha utilizado para sintetizar una serie de sistemas multicomponentes, entre ellos SiO2 ? TiO2. El mayor problema en la obtencion de geles multicomponentes estables es la desigual velocidad de hidrolisis y condensacion que presentan los alcoxidos precursores de los cationes de interes. En este trabajo se muestra como adicionando acetilacetona, acacH, al sistema TEOS ? Ti(OBu)4 ? H2O se puede obtener un sol estable. Se tomaron diferentes concentraciones de los precursores de silicio ...

Tópico(s): Mesoporous Materials and Catalysis

2004 - Elsevier BV | Boletín de la Sociedad Española de Cerámica y Vidrio

Artigo Acesso aberto Brasil Produção Nacional

Lı́dia Moreira Lima,

... diferentes espécies vegetais tem ampla aplicação na indústria química como precursor sintético do butóxido de piperonila, piperonal e de ...

Tópico(s): Ethnobotanical and Medicinal Plants Studies

2015 - Brazilian Society of Chemistry | Revista Virtual de Química

Artigo Acesso aberto

Miguel Ángel Espinosa Rodríguez, Luis Armando Bernal-Jácome, Marisol Gallegos García, Raúl Delgado-Delgado, Lizeth Olvera-Izaguirre,

... 2.2 y 10 veces, respectivamente. La modificación química aplicada al precursor, así como su formación a CA, amplió su ...

Tópico(s): Botanical Research and Applications

2020 - Mexican Chemical Society | Journal of the Mexican Chemical Society

Artigo

Fabián Parada‐Alfonso, Carmenza Duque,

... Composition and Characterization of Some Glucoconjugates as Aroma Precursors Fabian Parada, Fabian Parada Departamento de Química, Universidad Nacional de Colombia, AA 14490, Bogotá, ColombiaSearch ...

Tópico(s): Pineapple and bromelain studies

1998 - Wiley | Journal of High Resolution Chromatography

Artigo Revisado por pares

Tópico(s): Advanced Materials Characterization Techniques

1995 - Elsevier BV | Fuel and Energy Abstracts

Artigo Acesso aberto Revisado por pares

Jorge Enrique Rodríguez Páez, A. Mafla, G. Andrade, Alicia Durán,

La técnica Sol-Gel se ha utilizado para sintetizar una serie de sistemas multicomponentes, entre ellos SiO 2 -TiO 2 .El mayor problema en la obtención de geles multicomponentes estables es la desigual velocidad de hidrólisis y condensación que presentan los alcóxidos precursores de los cationes de interés.En este trabajo se muestra cómo adicionando acetilacetona, acacH, al sistema TEOS -Ti(OBu) 4 -H 2 O se puede obtener un sol estable.Se tomaron diferentes concentraciones de los precursores de silicio ...

Tópico(s): Zeolite Catalysis and Synthesis

2004 - Elsevier BV | Boletín de la Sociedad Española de Cerámica y Vidrio

Artigo Revisado por pares

Andreas Taubert,

Ein „grüner“ Weg zu anorganischen Nanostrukturen: CuCl-Nanoplättchen (siehe Bild) wurden aus Mischungen eines Cu-haltigen ionischen Flüssigkristalls und 6-O-Palmitoylascorbinsäure erhalten. Größe, Dicke und Verknüpfungsgrad können über die Reaktionstemperatur eingestellt werden. Die Cu-haltige Vorstufe dient als Templat und Cu-Quelle; der Ligand wird bei der Fällung nicht verbraucht und kann wiederverwendet werden.

Tópico(s): Catalysis for Biomass Conversion

2004 - Wiley | Angewandte Chemie

Artigo Revisado por pares

Andreas Taubert,

Green approach to inorganic nanostructures: CuCl nanoplatelets (see picture) were synthesized from mixtures of a Cu-containing ionic liquid crystal and 6-O-palmitoyl ascorbic acid. The particle size, thickness, and connectivity can be adjusted through varying the reaction temperature. The copper-containing precursor acts as both the template and the copper source. The ligand is not consumed in the precipitation and can be reused.

Tópico(s): Surfactants and Colloidal Systems

2004 - Wiley | Angewandte Chemie International Edition

Artigo Acesso aberto Revisado por pares

Tópico(s): Photochemistry and Electron Transfer Studies

2003 - Wiley | Bulletin of the Korean Chemical Society

Artigo Revisado por pares

Tópico(s): Microwave-Assisted Synthesis and Applications

2002 - Wiley | Organic Syntheses

Artigo

L. Maya,

The preparation of a target compound, AI(NH2)3, was attempted by various means including the preparation of an intermediate, KAI(NH2)4, by anodic oxidation of aluminum in liquid ammonia. A metathetical reaction of AIBr3 with KNH2 in liquid ammonia led to a solid having the empirical formula corresponding to (AI(NH2)NH)n. A similar stoichiometry is observed in the product of the reaction between AIH3 · Et2O and ammonia in ether. Conversion of the amide-imide into the nitride was studied by TG/DTA and ...

Tópico(s): Advanced ceramic materials synthesis

1986 - Wiley | Advanced Ceramic Materials

Artigo Revisado por pares

Josefa Anaya, Derek H. R. Barton, Stephan D. Géro, Manual Grande, N. MARTIN, Catherine Tachdijian,

... in the Preparation of Substituted Methyl Carbapenem Antibiotic Precursors† Dr. Josefa Anaya, Corresponding Author Dr. Josefa Anaya Universidad de Salamanca, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Plaza de los ...

Tópico(s): Synthetic Organic Chemistry Methods

1993 - Wiley | Angewandte Chemie International Edition

Artigo Revisado por pares

Haisheng Zeng,

Barium-promoted Ru/HTAC (hydrogen-treated active carbon) is reported to be a promising ammonia catalyst. However, deactivation and regeneration have been observed under some conditions. In this study, the activity change of this catalyst was studied in detail. The effects of the reaction temperature, Ba(NO3)2 decomposition temperature, and the water vapor pressure on the ammonia-synthesis activity were investigated to elucidate the cause. It was found that the promoter components under reaction conditions ...

Tópico(s): Nanomaterials for catalytic reactions

2002 - Elsevier BV | Journal of Catalysis

Artigo Acesso aberto Revisado por pares

Youichi Shimizu,

Tópico(s): Advanced Battery Materials and Technologies

2000 - Elsevier BV | Solid State Ionics

Artigo Revisado por pares

Wanqin Jin,

Tópico(s): Magnetic and transport properties of perovskites and related materials

2000 - Elsevier BV | Journal of Membrane Science

Artigo Revisado por pares

Kazuyuki Tatsumi,

An amorphous salt was precipitated by reacting barium bromide with a solution of peroxo-polytungstic acid. Heating it in a hydrogen stream at temperature near 550 °C yielded a hexagonal form of barium tungsten bronze, BaxWO3, in a pure phase with x being in the range 0.19–0.24. At temperature higher than 620 °C, this metastable compound was transformed into the tetragonal bronze phase. An unreported lead tungsten bronze in the hexagonal form (a = 7.407, c = 7.565 Å, for Pb0.29WO3) was synthesized similarly ...

Tópico(s): Catalysis and Oxidation Reactions

1997 - Elsevier BV | Solid State Ionics

Artigo Revisado por pares

Guangyu Shen,

Transformation of biomass and CO2 into renewable value-added chemicals and fuels has been identified as a promising strategy to fulfill high energy demands, lower greenhouse gas emissions, and exploit under-utilized resources. Cost-effective and performance-efficient catalysts are of great importance to lowering the conversion cost of biomass and CO2. Significant progress has been made to advance the catalyst design for these processes, with metal catalysts playing a critical role in many involved ...

Tópico(s): Catalysis and Oxidation Reactions

1992 - Elsevier BV | Journal of Catalysis

Artigo Revisado por pares

C WOKAUN,

Conversion of ethanol was investigated on supported (ceria, zirconia and ceria–zirconia) cobalt oxide catalysts. The catalysts were prepared by support impregnation with cobalt nitrate–citric acid solution and they were explored by comparing results from different characterization techniques: X-ray fluorescence, X-ray diffraction, Raman spectroscopy and nitrogen adsorption techniques. Their catalytic properties at 693 K were characterized in a fixed-bed reactor. The CoOx/CeO2 catalyst displayed the ...

Tópico(s): Catalysis and Oxidation Reactions

1991 - Elsevier BV | Journal of Catalysis

Artigo Revisado por pares

B. Grzybowska,

The effect of the conditions of preparation and thermal treatment on the phase composition of Bi-Mo oxide catalysts at the atomic ratio BiMo = 11 has been studied. It has been shown that bismuth molybdate of the composition Bi2O3·2MoO3 (β-phase) is formed on crystallization of the precipitate prepared from appropriate salts at pH = 2 without additional reactions in the solid state. In the case of precipitation at pH = 7 and subsequent filtering, the calcined catalysts contained Bi2O3·MoO3 (γ-phase). The ...

Tópico(s): Catalysis and Hydrodesulfurization Studies

1972 - Elsevier BV | Journal of Catalysis

Artigo Revisado por pares

Daniel Gasser,

Amorphous vanadium pentoxide was prepared using the sol-gel process and vanadyl triisobutoxide as precursor. The catalytic properties of this material for methanol oxidation to formaldehyde were investigated in the temperature range 300 to 520 K. At 520 K the initial activity of the amorphous V2O5 was very low. However, during in situ activation at this temperature the activity increased steadily and reached a steady-state value which was about 30 times higher than the initial activity of the amorphous ...

Tópico(s): Oxidative Organic Chemistry Reactions

1988 - Elsevier BV | Journal of Catalysis

Artigo Revisado por pares

Christophe Copéret,

Heterogeneous catalysts are complex by nature, making particularly difficult to assess the structure of their active sites. Such complexity is inherited in part from their mode of preparation, which typically involves coprecipitation or impregnation of metal salts in aqueous solution, and the associated complex surface chemistries. In this context, surface organometallic chemistry (SOMC) has emerged as a powerful approach to generate well-defined surface species, where the metal sites are introduced ...

Tópico(s): Mesoporous Materials and Catalysis

2019 - American Chemical Society | Accounts of Chemical Research

Artigo Acesso aberto Revisado por pares

Robert J. P. Corriu,

The elaboration of solids from the molecular scale by a kinetically controlled methodology is one of the main challenges of molecular chemistry. In the long term, this should permit the design of solids with desired properties. Here, some examples are given which show a few methods that have been used for the preparation of solids from molecular precursors. The one-pot synthesis of rheologically controlled SiC is described. Access to a new kind of ceramic is obtained by the same methodology using ...

Tópico(s): Synthetic Organic Chemistry Methods

2000 - Wiley | Angewandte Chemie International Edition

Artigo Revisado por pares

Nicolaos Economidis,

The performance of several TiO2-based polyoxide supports loaded with vanadia was tested for the selective catalytic reduction of NO with ammonia as reductant. It is remarkable to note that the valence of vanadium in the precursor solution during the impregnation step is crucial for the synthesis of efficient DeNOx catalysts. More specifically, V5+ in the precursor solution yields lower-performance catalysts compared to the case of V4+ under identical conditions. Aging the vanadium precursor solution, ...

Tópico(s): Transition Metal Oxide Nanomaterials

1999 - Elsevier BV | Applied Catalysis B Environment and Energy

Artigo Revisado por pares

Douglas K. Russell,

A. Introduction and background B. The chemistry of the semi-conductor industry. C. Experimental methodologies D. Investigations, results, and comments (i) Trimethyl aluminium, TMAl. (ii) Dimethyl aluminium hydride, DMAlH (iii) Exchange reactions in aluminium and gallium precursors (a) TMAl and TMGa (b) TMAl+DMAlH or DMAID (c) TMGa+DMAlH or DMAlD (iv) Exchange studies of trimethylamine alane and trialkylgallium compounds. (v) IR LPHP of TMGa (vi) IR LPHP of triethylgallium, TEGa. (vii) IR LPHP of tributyl ...

Tópico(s): Electron and X-Ray Spectroscopy Techniques

1992 - Elsevier BV | Coordination Chemistry Reviews

Artigo Revisado por pares

Keith R. Barnard,

Simultaneous oxidation/co-precipitation of an equimolar mixture of La(III) and Co(II) nitrates afforded a hydroxide-containing gel, which was converted to LaCoO3 on calcination at 600°C. A material with surface area in excess of 40 m2/g has been produced, provided the hydroxide gel was washed with a nonaqueous solvent before dehydration. The resultant LaCoO3 perovskite sintered readily on heating above 700°C. Rates for oxidation for CO and propane showed a linear dependence upon the surface area ...

Tópico(s): Mesoporous Materials and Catalysis

1990 - Elsevier BV | Journal of Catalysis

Artigo Acesso aberto Revisado por pares

Carlos Dı́az, Marı́a Luisa Valenzuela, DENISSE GARRIDO, Pedro Aguirre,

Inclusion of the organometallic MLn = [HOC 5 H 4 N•Cp 2 TiCl][PF 6 ] (1), HOC 5 H 4 N•W(CO) 5 (2), HOC 5 H 4 N•Mo(CO) 5 (3), [HOC 6 H 4 CH 2 CN•Cp 2 TiCl][PF 6 ] (4), HOC 6 H 4 CH 2 CN•W(CO) 5 (5) and HOC 6 H 4 CH 2 CN•Mo(CO) 5 ( 6) into amorphous silica using the gelator precursor TEOS and N 3 P 3 {NH[CH 2 ] 3 Si[OEt] 3 } 6 afford the gels (MLn)(SiO 2 ) n .The inorganic-organic hybrid nanocomposites were pyrolyzed under air at 800°C to give nanostructured metal oxides and/or metal pyrophosphates (phosphates) included in ...

Tópico(s): Silicone and Siloxane Chemistry

2012 - Sociedad Chilena de Química | Journal of the Chilean Chemical Society

Artigo Acesso aberto Revisado por pares

P. Harris,

Non-graphitizing carbon, or char, has been intensively studied for decades, but there is still no agreement about its detailed atomic structure. The first models for graphitizing and non-graphitizing carbons were proposed by Rosalind Franklin in the early 1950s, and while these are correct in a broad sense, they are incomplete. Subsequent models also fail to explain fully the structure of non-graphitizing carbons. The discovery of the fullerenes and related structures stimulated the present author ...

Tópico(s): Fullerene Chemistry and Applications

2019 - | Eurasian Chemico-Technological Journal

Revisão Revisado por pares

Tetsuhiro Nemoto,

Abstract In this personal account, our recent studies of novel synthetic methods of 3,4‐fused tricyclic indole derivatives using 3‐alkylidene indoline derivatives as versatile precursors are discussed. Two types of cascade reactions producing 3,4‐fused tricyclic 3‐alkylidene indolines were developed based on a palladium‐catalyzed intramolecular Heck insertion to an allene‐allylic amination cascade and a platinum‐catalyzed intramolecular Friedel‐Crafts type C−H coupling‐allylic amination cascade. ...

Tópico(s): Oxidative Organic Chemistry Reactions

2018 - Wiley | The Chemical Record

Artigo Revisado por pares

Kamal M.S. Khalil,

Mesoporous ceria/alumina, CeO2/Al2O3, composites containing 10, 20 and 30% (w/w) ceria were prepared by a novel gel mixing method. In the method, ceria gel (formed via hydrolysis of ammonium cerium(IV) nitrate by aqueous ammonium carbonate solution) and alumina gel (formed via controlled hydrolysis of aluminum tri-isopropoxide) were mixed together. The mixed gel was subjected to subsequent drying and calcination for 3 h at 400, 600, 800 and 1000 °C. The uncalcined (dried at 110 °C) and the calcined composites ...

Tópico(s): Catalysis and Oxidation Reactions

2006 - Elsevier BV | Journal of Colloid and Interface Science

Artigo Revisado por pares

Aparna Mondal, S. Ram,

Monolithic t ‐ZrO 2 (tetragonal structure) nanopowder is synthesized with an amorphous ZrO(OH) 2 · x H 2 O polymer precursor. The H 2 O molecules impart the structure and promote reconstructive thermal decomposition of the structure to t ‐ZrO 2 nanoparticles on heating at temperatures as low as 200°C. A prevalent endothermic heat output in the dissociation process controls the local temperature in exothermic nucleation and growth of various groups of the reaction species so that it is self‐controlled ...

Tópico(s): Catalysis and Oxidation Reactions

2004 - Wiley | Journal of the American Ceramic Society