1,721,137 research outputs found
Insights into the cyclic CO2 capture and catalytic methanation over highly performing Li-Ru/Al2O3 dual function materials
No full textThe combined CO2 capture and in-situ methanation using renewable hydrogen over dual function sorbent-catalyst materials is a chemical looping process with strong potential to increase the efficiency and reduce the cost of current CCU technologies. In this work, we set out to develop highly performing Lithium-Ruthenium/Al2O3 investigating synergic and mechanistic aspects involved in the alternate CO2 adsorption and hydrogenation phases. Catalysts with low Ru loading (max 1% wt.) and fixed dispersion on Al2O3 spheres were promoted with variable amounts of Li (1–5% wt.) and characterized by BET, PSD, XRD, H2 chemisorption, CO2-TPD, TG-MS, H2-TPSRx and CO2 catalytic methanation under continuous flow conditions. Transient CO2 storage/methanation cycles were studied in a fixed bed reactor that was operated at several temperature levels (250–350 °C) with alternate feed conditions of variable duration. The cycled CO2 adsorption and methanation were also investigated by in-situ DRIFT comparing results for xLi-Ru/Al2O3 materials against the reference Ru/Al2O3 catalyst. The favourable synergism existing at the nanoscale between the Li-aluminate sorbent phase and the catalytic Ru sites enhances the intrinsic activity of the DFMs that can guarantee high methane productivity and selectivity with low noble metal loadings
Enhancement of hydrothermal stability of Cu-ZSM5 catalyst for NO decomposition
No full textRECu-ZSM5 samples (RE = La, Sm or Ce) have been prepared by ion-exchange of H-ZSM5 with rare earth and copper ions in an aqueous solution both simultaneously and consecutively (RE before copper),
and their physico-chemical and catalytic properties in NO decomposition have been compared with those of a Cu-ZSM5 with a similar copper content. The catalysts have been characterized by N
2 adsorption at 77 K (BET) and XRD before and after aging cycles under wet (2–2.5 vol % H2O) conditions at 450–500°C. NO decomposition tests have been carried out in a fixed bed reactor at 450°C under dry or wet conditions on both fresh and
aged catalysts. NO adsorption tests have been performed at 120
° C on the same samples. The addition of RE does not affect the crystalline structure, surface area, and porosity but strongly enhances the catalytic activity and the hydrothermal stability of Cu-ZSM5, which, on the contrary, is completely deactivated under wet conditions.
The two-step exchanged catalysts provide better performances likely due to the larger RE exchange level obtained with this method. A unique linear correlation between the amount of N2O produced in the NO adsorption tests, related to the reoxidation of prereduced Cu
+ sites, and the TOF, estimated from the catalytic
activity tests, has been found for both fresh and aged catalysts
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
ON THE ROLE OF REDOX PROPERTIES OF CuO/CeO2 CATALYSTS IN THE PREFERENTIAL OXIDATION OF CO in H2-RICH GASES
No full textCuO/CeO2 catalysts with CuO content ranging from 0.5 wt.% to 8 wt.%, prepared by wet impregnation of commercial ceria, have been tested for the preferential oxidation of CO (CO-PROX) under H2-rich conditions at 70-210°C. Catalytic activity increases up to 4 wt.% CuO content, with less concentrated catalysts showing higher intrinsic activity. Catalysts have been characterized by means of XRD, BET analysis and UV spectroscopy. Formation of segregated CuO clusters has been detected for Cu richest CuO/CeO2 sample. Redox properties have been deeply investigated using TP analysis (H2 TPR, CO TPR, TPO) of fresh or pre-treated samples. Participation of surface ceria, induced by the strong interaction with copper, to reduction/oxidation reactions in the temperature range explored (up to 430*C) has been demonstrated. Different copper species and their reactivity towardsH2 and CO have been individuated by comparing TPR of fully oxidized catalysts with those of partially oxidized catalysts. Active species have been identified as copper-ceria sites able to oxidize CO even at room temperature and to be re-oxidized by O2 at the same temperature. Transient experiments have been carried out at different temperature using a diluted mixture starting from oxidized or reduced catalysts and followed by a H2 TPR of the used samples. The results of these tests have showed that active centres for CO oxidation contain copper in the +2 oxidation state. At T > 100°C some reduced copper sites are stabilized which promote H2 oxidation thus lowering the selectivity of the CO-PROX proces
KINETICS OF THE PREFERENTIAL OXIDATION OF CO OVER CuO/CeO2 CATALYSTS IN H2-RICH GASES
No full textThe influence of reaction parameters such as temperature, contact time, and O2, CO, H2, CO2, and H2O partial pressures on the catalytic performances of 4 wt % CuO/CeO2 in the CO-PROX process (the preferential oxidation of CO) has been investigated in a fixed-bed reactor. Catalyst appears very active (light-off at 70 C) and selective; reaction kinetics is weakly depressed by CO2 and H2O and not significantly increased with increasing O2 concentration, while the reaction order in CO is variable with temperature ranging from values <1 up to 110 C and >1 at higher temperatures. A power-law rate equation fitted the experimental data under typical CO-PROX conditions in order to evidence the lower activation energy of the catalytic oxidation of CO with respect to H2. A Langmuir-Hinshelwood type reaction rate is able to describe the catalytic behavior in the whole field of experimental conditions explore
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
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