Recursos de colección

RUA (124.683 recursos)

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INV - MCMA - Artículos de Revistas

Mostrando recursos 1 - 14 de 14

  1. Structured carbons as supports for hydrogenation hybrid catalysts prepared by the immobilization of a Rh diamine complex

    Gheorghiu, Constanta Cristina; García-Bordejé, Enrique; Job, Nathalie; Román-Martínez, M. Carmen
    A CNF-monolith sample (carbon nanofibres grown on a ceramic monolith), and a granular carbon xerogel have been used as supports for hybrid catalysts where the active species is an Rh diamine complex. The advantages of these supports are their open porous structure and their morphology, which make catalyst handling easier and avoid difficult separation processes. The obtained catalysts are noticeably more active than the homogeneous Rh complex and are stable against leaching. At first use, partial reduction of the Rh complex takes place and nanometer-sized Rh particles develop, which increases the catalyst activity. Despite the open porous structure, mass transport...

  2. Enhancement of the hydrogenation activity of a Pd-tridecilamine (TDA) complex by confinement in carbon nanotubes

    Such-Basañez, Ion; Román-Martínez, M. Carmen; Serp, Philippe
    An active hydrogenation Pd complex has been immobilised by impregnation on CNTs submitted to several treatments that lead to important differences in their surface chemistry and in the proportion of tubes with both ends open. Most of the hybrid catalysts are more active than the complex in homogeneous phase, but the support properties have an important impact in the catalytic activity. In general, the more developed the surface chemistry, the lower the activity. However, when CNTs are open at both ends, the Pd complex can enter the tubular cavity and an important enhancement of the catalytic activity due to a...

  3. Factors governing the adsorption of ethanol on spherical activated carbons

    Romero Anaya, Aroldo José; Lillo-Rodenas, Maria Angeles; Linares-Solano, Angel
    Ethanol adsorption on different activated carbons (mostly spherical ones) was investigated covering the relative pressure range from 0.001 to 1. Oxygen surface contents of the ACs were modified by oxidation (in HNO3 solution or air) and/or by thermal treatment in N2. To differentiate the concomitant effects of porosity and oxygen surface chemistry on ethanol adsorption, different sets of samples were used to analyze different relative pressure ranges (below 1000 ppmv concentration and close to unity). To see the effect of oxygen surface chemistry, selected samples having similar porosity but different oxygen contents were studied in the low relative pressure range....

  4. Spherical carbons: Synthesis, characterization and activation processes

    Romero Anaya, Aroldo José; Ouzzine, Mohammed; Lillo-Rodenas, Maria Angeles; Linares-Solano, Angel
    Spherical carbons have been prepared through hydrothermal treatment of three carbohydrates (glucose, saccharose and cellulose). Preparation variables such as treatment time, treatment temperature and concentration of carbohydrate have been analyzed to obtain spherical carbons. These spherical carbons can be prepared with particle sizes larger than 10 μm, especially from saccharose, and have subsequently been activated using different activation processes (H3PO4, NaOH, KOH or physical activation with CO2) to develop their textural properties. All these spherical carbons maintained their spherical morphology after the activation process, except when KOH/carbon ratios higher than 4/1 were used, which caused partial destruction of the spheres....

  5. Spherical activated carbon as an enhanced support for TiO2/AC photocatalysts

    Ouzzine, Mohammed; Romero Anaya, Aroldo José; Lillo-Rodenas, Maria Angeles; Linares-Solano, Angel
    Titanium dioxide nanoparticles prepared in situ by sol–gel method were supported on a spherical activated carbon to prepare TiO2/AC hybrid photocatalysts for the oxidation of gaseous organic compounds. Additionally, a granular activated carbon was studied for comparison purposes. In both types of TiO2/AC composites the effect of different variables (i.e., the thermal treatment conditions used during the preparation of these materials) and the UV-light wavelength used during photocatalytic oxidation were analyzed. The prepared materials were deeply characterized (by gas adsorption, TGA, XRD, SEM and photocatalytic propene oxidation). The obtained results show that the carbon support has an important effect on...

  6. Photocatalytic oxidation of propene in gas phase at low concentration by optimized TiO2 nanoparticles

    Ouzzine, Mohammed; Lillo-Rodenas, Maria Angeles; Linares-Solano, Angel
    In the present study, nanocrystalline titanium dioxide (TiO2) was prepared by sol–gel method at low temperature from titanium tetraisopropoxide (TTIP) and characterized by different techniques (gas adsorption, XRD, TEM and FTIR). Variables of the synthesis, such as the hydrolyzing agent (acetic acid or isopropanol) and calcination temperatures (300–800 °C), were analyzed to get uniform size TiO2 nanoparticles. The effect that these two variables have on the structure of the resultant TiO2 nanoparticles and on their photocatalytic activity is investigated. The photocatalytic activities of TiO2 nanoparticles were evaluated for propene oxidation at low concentration (100 ppmv) under two different kinds of...

  7. Activation of a spherical carbon for toluene adsorption at low concentration

    Romero Anaya, Aroldo José; Lillo-Rodenas, Maria Angeles; Linares-Solano, Angel
    This paper complements a previous one [1] about toluene adsorption on a commercial spherical activated carbon and on samples obtained from it by CO2 or steam activation. The present paper deals with the activation of a commercial spherical carbon (SC) having low porosity and high bed density (0.85 g/cm3) using the same procedure. Our results show that SC can be well activated with CO2 or steam. The increase in the burn-off percentage leads to an increase in the gravimetric adsorption capacity (more intensively for CO2) and a decrease in bed density (more intensively for CO2). However, for similar porosity developments...

  8. Synthesis of high surface area TiO2 nanoparticles by mild acid treatment with HCl or HI for photocatalytic propene oxidation

    Ouzzine, Mohammed; Maciá Agulló, Juan Antonio; Lillo-Rodenas, Maria Angeles; Quijada Tomás, César; Linares-Solano, Angel
    Nanostructured TiO2 photocatalysts with small crystalline sizes have been synthesized by sol-gel using the amphiphilic triblock copolymer Pluronic P123 as template. A new synthesis route, based on the treatment of TiO2 xerogels with acid-ethanol mixtures in two different steps, synthesis and extraction-crystallization, has been investigated, analyzing two acids, hydrochloric and hydriodic acid. As reference, samples have also been prepared by extraction-crystallization in ethanol, being these TiO2 materials amorphous and presenting higher porosities. The prepared materials present different degrees of crystallinity depending on the experimental conditions used. In general, these materials exhibit high surface areas, with an important contribution of microporosity...

  9. NaOH and KOH for preparing activated carbons used in energy and environmental applications

    Linares-Solano, Angel; Lillo-Rodenas, Maria Angeles; Marco Lozar, Juan Pablo; Kunowsky, Mirko; Romero Anaya, Aroldo José
    Alkaline hydroxides, especially sodium and potassium hydroxides, are multi-million-ton per annum commodities and strong chemical bases that have large scale applications. Some of them are related with their consequent ability to degrade most materials, depending on the temperature used. As an example, these chemicals are involved in the manufacture of pulp and paper, textiles, biodiesels, soaps and detergents, acid gases removal (e.g., SO2) and others, as well as in many organic synthesis processes. Sodium and potassium hydroxides are strong and corrosive bases, but they are also very stable chemicals that can melt without decomposition, NaOH at 318ºC, and KOH at...

  10. New insights on the direct activation of isotropic petroleum pitch by alkaline hydroxides

    Vilaplana-Ortego, Eduardo; Lillo-Rodenas, Maria Angeles; Alcañiz-Monge, Juan; Cazorla-Amorós, Diego; Linares-Solano, Angel
    The paper provides interesting evidences that a low softening point isotropic petroleum pitch can be used as a good carbon precursor for the preparation of activated carbons. The activation is carried out by KOH and/or NaOH and the resulting activated carbons present well developed porosity. Such hydroxide activations can be done directly on the pristine petroleum pitch (P) or on the pitch that has been submitted to an air stabilisation followed by a N2 heat treatment (TAN). In general, KOH activation produces better results than NaOH, both in terms of porosity and yield, the results obtained for the activation of...

  11. Isotropic petroleum pitch as a carbon precursor for the preparation of activated carbons by KOH activation

    Vilaplana-Ortego, Eduardo; Lillo-Rodenas, Maria Angeles; Alcañiz-Monge, Juan; Cazorla-Amorós, Diego; Linares-Solano, Angel
    Results show that it is possible to activate a low softening point isotropic petroleum pitch, without intermediate pre-treatments, by chemical activation with KOH. The chemical activation is carried out by direct heat treatment of a mixture of the isotropic pitch and KOH. It produces activated carbons (ACs) with micropore volumes as high as 1.12 cm3/g, and BET surface areas around 3000 m2/g. The activating agent/precursor ratios studied (from 1/1 to 4/1; wt./wt.) show, as expected, that increasing the ratio enhances the adsorption characteristics of the resulting AC.

  12. NO adsorption on activated carbon fibers from iron-containing pitch

    Alcañiz-Monge, Juan; Bueno López, Agustín; Lillo-Rodenas, Maria Angeles; Illán-Gómez, María José
    Iron-containing activated carbon fibers (Fe-ACF) have been prepared by a novel method consisting of mixing an iron precursor with raw pitch before carbon fiber formation, and further CO2 activation of the Fe-CF. The NO adsorption experiment revealed that iron species are accessible to gases and that they activate NO improving adsorption into the fiber microporosity. The chemisorption of NO and the subsequent dimer (N2O2) formation is, in general, the rate-limiting step. Metallic iron and/or partially reduced iron compounds are the most active iron species. However, in the fibers with narrow micropores dimer diffusion in the microporosity is the slowest step and, consequently, an appropriate pore...

  13. SO2 retention on CaO/activated carbon sorbents. Part I: importance of calcium loading and dispersion

    Macías Pérez, María Carmen; Bueno López, Agustín; Lillo-Rodenas, Maria Angeles; Salinas Martínez de Lecea, Concepción; Linares-Solano, Angel
    Sorbents for SO2 retention at low temperature consisting of CaO supported on activated carbons have been prepared by different methods (physical mixing, incipient wetness impregnation, rotary evaporator impregnation, complex formation and ionic exchange). Ca(OH)2, CaCO3, CaO, Ca(CH3COO)2 and Ca(C2H5COO)2 have been used as calcium precursors. The preparation method affects calcium loading as well as calcium dispersion. SO2 retention depends both on the calcium loading and on the calcium dispersion. The best preparation method, among those tested, was impregnation of the activated carbon with calcium acetate. Similar calcium loading can be obtained by the physical mixing method but the resulting calcium dispersion is low. On the...

  14. The influence of iron chloride addition to the precursor pitch on the formation of activated carbon fibers

    Alcañiz-Monge, Juan; Lillo-Rodenas, Maria Angeles; Bueno López, Agustín; Illán-Gómez, María José
    The addition of a suitable metal compound to the precursor pitch before the preparation of carbon fibers is a promising way for obtaining activated carbon fibers with defined porosity and preparing carbon-supported metal catalysts. The introduction of only 0.1 wt.% of FeCl3 modifies not only the textural properties of the carbon fibers, but also their activation behaviour. The metal addition leads to activated carbon fibers with porosities that differ from those obtained using the pristine precursor. The method is interesting for the preparation of activated carbon fiber-supported iron compounds because it is easy and produces dispersed particles.

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