56 research outputs found
Recuperación de V y Mo de catalizadores gastados de la industria petroquímica. Parte II
En el presente trabajo se desarrollaron dos procesos
para la recuperación de los metales vanadio,
molibdeno y níquel contenidos en catalizadores de
desecho de la industria petroquímica.
El vanadio y el molibdeno son recuperados a
partir de catalizadores gastados de la industria petroquímica
en las formas de vanadato y molibdato
de sodio por lixiviación con soluciones acuosas de
NH3 o NaOH después de un tratamiento preliminar
del catalizador con CS2 o solventes orgánicos.
El uso de solventes reciclados permite recuperar el
azufre y minimizar la contaminación atmosférica
debida a las cantidades considerables de gas SO2
que se emiten. La caracterización de los productos
obtenidos en cada una de las etapas de extracción
y recuperación de los productos finales se llevó a
cabo por las técnicas de difracción de rayos X por el
método de polvos, absorción atómica y análisis termogravimétrico,
simplificando así la ruta crítica de su extracción.
Diferentes concentraciones de las soluciones de
NH3 y NaOH y dierentes condiciones de operación
fueron investigadas. Estos metales se extrajeron selectivamente
por diferentes técnicas empleadas. Los
resultados muestran que con un simple tratamiento
del catalizador con el hidróxido de sodio y el hidróxido
de amonio, que son agentes alcalinos relativamente
comunes y de bajo costo, se pueden recuperar
dos de los metales contenidos en mayor
proporción en el catalizador, que son el vanadio en
un 98% y el molibdeno en un 92% respectivamente
en forma de sales, permitiendo así su posterior
reutilización. El método de recuperación presentado
en este trabajo resulta ser una buena alternativa
para la Industria Petroquímica por ser efectivo y a
la vez factible, gracias precisamente a la reutilización
de estos metales, la cual representa una gran ventaja
económica competitiva a nivel comercial
Recent Trends of Reinforcement of Cement with Carbon Nanotubes and Fibers
Recent achievements in the area of formation of carbon nanotubes (CNTs), nanocomposites, with cement are reviewed. The peculiarities of dispersion of CNTs in cementitious matrices are discussed, paying major attention to the CNT diameter, length and length-to-diameter ratio, concentration, functionalization, annealing, combination with other nanomaterials, and water-cement ratio. Several effects upon dispersion of carbon allotropes in concrete-water media are emphasized. It is also pointed out that the health impact should also be considered in further experiments on construction materials reinforced with CNTs
Mini-review: Ferrite nanoparticles in the catalysis
Recent applications of ferrite nanoparticles as catalysts in organic processes are reviewed. Catalytic applications include the use of mainly cobalt, nickel, copper, and zinc ferrites, as well as their mixed-metal combinations with Cr, Cd, Mn and sometimes some lanthanides. Core–shell nanostructures with silica and titania are also used without loss of magnetic properties. The ferrite
nanomaterials are obtained mainly by wet-chemical sol-gel or co-precipitation methods, more rarely by the sonochemical technique, mechanical high-energy ball milling, spark plasma sintering, microwave heating or hydrothermal route. Catalytic processes with application of ferrite nanoparticles include decomposition (in particular photocatalytic), reactions of dehydrogenation, oxidation, alkylation, C–C coupling, among other processes. Ferrite nano catalysts can be easily recovered from reaction systems and reused up to several runs almost without loss of catalytic activity
Técnicas para la preparación de ftalocianinas
Se reportan diversas técnicas de preparación de los ftalocianinatos de metales de los bloques d y f a partir de distintos precursores (ftalonitrilo, urea y anhídrido ftálico, ftalimida y ácido ftálico, entre otros). Se presentan los métodos tradicionales de síntesis, así como algunos no convencionales de uso actual como son las síntesis con ultrasonido, láser, microondas o por transformación nuclear. Se presta especial atención a la electrosíntesis directa de las ftalocianinas y a su obtención a temperaturas relativamente bajas. Se examinan grupos selectos de ftalocianinas tales como los ftalocianinatos
de actínidos y los radicales ftalocianinas. Se comparan las diferentes técnicas
sintéticas, así como sus posibles combinaciones
Metal Complexes Containing Natural and Artificial Radioactive Elements and Their Applications
Recent advances (during the 2007–2014 period) in the coordination and organometallic chemistry of compounds containing natural and artificially prepared radionuclides (actinides and technetium), are reviewed. Radioactive isotopes of naturally stable elements are not included for discussion in this work. Actinide and technetium complexes with O-, N-, N,O, N,S-, P-containing ligands, as well π-organometallics are discussed from the view point of their synthesis, properties, and main applications. On the basis of their properties, several mono-, bi-, tri-, tetra- or polydentate ligands have been
designed for specific recognition of some particular radionuclides, and can be used in the processes of nuclear waste remediation, i.e., recycling of nuclear fuel and the separation of actinides and fission products from waste solutions or for analytical determination of
actinides in solutions; actinide metal complexes are also usefulas catalysts forcoupling gaseous carbon monoxide,as well as antimicrobial and anti-fungi agents due to their
biological activity. Radioactive labeling based on the short-lived metastable nuclide technetium-99m (99mTc) for biomedical use as heart, lung, kidney, bone, brain, liver or cancer imaging agents is also discussed. Finally, the promising applications of technetium labeling of nanomaterials, with potential applications as drug transport and delivery vehicles, radiotherapeutic agents or radiotracers for monitoring metabolic pathways, are
also described
Iron-based Nanomaterials in the Catalysis
Available data on catalytic applications of the iron-containing nanomaterials are reviewed. Main synthesis methods of nZVI, nano-sized iron oxides and hydroxides, core-shell and alloy structures, ferrites, iron-containing supported forms, and composites are described. Supported structures include those coated and on the basis of polymers or inert inorganic materials (i.e., carbon, titania or silica). Description of catalytic processes includes the decomposition reactions (in particular photocatalytic processes), reactions of dehydrogenation, oxidation, alkylation, C–C coupling, among a series of other processes. Certain attention is paid to magnetic recovery of catalysts from reaction systems and their reuse up to several runs almost without loss of catalytic activity
Preparation and characterization of Cu and Ni on alumina supports and their use in the synthesis of low-temperature metal-phthalocyanine using a parallel-plate reactor
Ni- and Cu/alumina powders were prepared and characterized by X-ray diffraction (XRD), scanning electronic microscope (SEM), and N2 physisorption isotherms were also determined. The Ni/Al2O3 sample reveled agglomerated (1 μm) of nanoparticles
of Ni (30–80 nm) however, NiO particles were also identified, probably for the low temperature during the H2 reduction treatment (350 °C), the Cu/Al2O3 sample presented agglomerates (1–1.5 μm) of nanoparticles (70–150 nm), but only of pure copper. Both surface morphologies were different, but resulted in mesoporous material, with a higher specificity for the Ni sample. The surfaces were used in a new proposal for producing
copper and nickel phthalocyanines using a parallel-plate reactor. Phthalonitrile was used and metallic particles were deposited on alumina in ethanol solution with CH3ONa at low temperatures; ≤60 °C. The mass-transfer was evaluated in reaction testing with a recent
three-resistance model. The kinetics were studied with a Langmuir-Hinshelwood model. The activation energy and Thiele modulus revealed a slow surface reaction. The nickel sample was the most active, influenced by the NiO morphology and phthalonitrile adsorption
N-[3-(2,6-Dimethylanilino)-1-methylbut-2-enylidene]-2,6-dimethylanilinium chloride1
The title salt, C21H27N2
+·Cl− resulted from the condensation between 2,6-dimethylaniline and acetylacetone in acidified ethanol. The bulky cation is stabilized in a β-iminoenamine tautomeric form, and presents a W-shaped conformation. The benzene rings are arranged almost parallel, with a dihedral angle of 6.58 (4)° between the mean planes. Both N—H groups in the cation form strong hydrogen bonds with two symmetry-related chloride anions. The resulting supramolecular structure is a one dimensional polymer running along [001], alternating cations and anions. The π–π interaction observed in the molecule, characterized by a centroid–centroid separation of 4.298 (4) Å, is thus extended to the chains, with separations of 5.222 (4) Å between benzene rings of neighbouring cations in the crystal
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