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Studies on Catalytic and catalytic photo-assisted propene hydration in the presence of H3PW12O40 supported on different oxides
No full textKeggin heteropolyacid H3PW12O40 supported on different oxides for catalytic and catalytic photo-assisted propene hydration
Full text linkCatalytic and catalytic photo-assisted hydration of propene to form 2-propanol in gas–solid regime at
atmospheric pressure and 85 1C were carried out by using a heteropolyacid (POM) supported on different
oxides. Binary materials were prepared by impregnation of H3PW12O40 on different commercial and
home prepared supports (TiO2, SiO2, WO3, ZrO2, ZnO, Al2O3). Some of the composites were active both
for catalytic and catalytic photo-assisted reactions. The Keggin type POM was completely and partially
degraded, when supported on ZnO and Al2O3, respectively, and these binary solids always resulted as
inactive for both catalytic and catalytic photo-assisted reactions. The supported Keggin POM species
played a key role both for the catalytic and the photo-assisted catalytic reactions, due to their strong
acidity and ability to form strong oxidant species under UV irradiation, respectively. The contemporary
presence of heat and UV light improved the activity of almost all POM supported materials. All materials
were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM), diffuse
reflectance spectroscopy (DRS), determination of the conduction and valence band energy by photovoltage
measurements, Fourier transform infrared spectroscopy (FTIR), NH3-TPD experiments and time
resolved microwave conductivity (TRMC).
Introduction
Propene hydration to obtain 2-propanol is a reaction carried
out at moderate temperatures (ca. 150–200 1C) and pressure
(2MPa) in the presence of an acid catalyst;1 however the realization
of this reaction at ambient conditions is of great interest.
The us
The role of different oxides as supports of an heteropolyacid in the catalytic and catalytic photo-assisted propene hydration
No full textThe role of different oxides as supports of an heteropolyacid in the catalytic and catalytic photo-assisted propene hydration
No full textRole of Cr(III) deposition during the photocatalytic transformation of hexavalent chromium and citric acid over commercial TiO2 samples
Full text linkRemoval of Cr(VI) and citric acid (Cit) by heterogeneous photocatalytic Cr(VI) transformation under UV light over two commercial TiO2 samples (1 g L−1), Evonik P25 and Hombikat UV100, was studied at pH 2 and Cr(VI) concentrations between 0.2 and 3 mM, with a fixed [Cit]0/[Cr(VI)]0 molar ratio (MR) of 2.5. In both cases, up to complete Cr(VI) removal, the temporal profiles of Cr(VI) and Cit were well adjusted to a pseudo- first order rate law with the same rate constant, evidencing that Cr(VI) removal controls the kinetics of the system. Once Cr(VI) is fully removed, Cit degradation continues with a Langmuir?Hinshelwood behaviour. In all cases, the rate constants decreased with increasing [Cr(VI)]0, and time resolved microwave conductivity (TRMC) measurements revealed that this was due to an increasing retention of Cr(III) on the surface of the photocatalysts, which reduces the lifetime of the electrons. Both kinetic experiments and TRMC measure- ments confirm that UV100 is not only more efficient than P25 for Cr(VI) and Cit removal, but it is also less influenced by the poisoning of the surface, consistent with its larger specific area. The use of Cit as the sacrificial agent improves the rate and efficiency of the photocatalytic Cr(VI) removal, and also the stability of the photocatalyst by preventing Cr(III) deposition, due to the formation of soluble Cr(III)-complexes, envi- saged as a general result of the presence of oligocarboxylic acids in the photocatalytic Cr(VI) system.Fil: Montesinos, Victor Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Salou, C.. Universite de Paris XI. Laboratoire de Chimie Physique; Francia. Centre National de la Recherche Scientifique; FranciaFil: Meichtry, Jorge Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); ArgentinaFil: Colbeau Justin, C.. Universite de Paris XI. Laboratoire de Chimie Physique; Francia. Centre National de la Recherche Scientifique; FranciaFil: Litter, Marta Irene. Universidad Nacional de San Martín. Instituto de Investigación en Ingeniería Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Seguridad Nuclear y Ambiente. Gerencia de Química (CAC); Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
The property-governed activity of silver-modified titania photocatalysts: The influence of titania matrix
Full text linkThis is the accepted manuscript version of the work published in its final form as Yoshiiri, K., Karabiyik, B., Wang, K., Wei, Z., Colbeau-Justin, C., & Kowalska, E. (2022). The property-governed activity of silver-modified titania photocatalysts: The influence of titania matrix. The Journal of Chemical Physics, 156(24), 244706. https://doi.org/10.1063/5.0097762
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Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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