1,720,973 research outputs found
Co-exchanged mordenites: preparation, characterization and catalytic activity for the abatement of NO with CH4 in the presence of excess O2
No full textVIETRI, 20-23 SEPTEMBER 2003
Simultaneous abatement of NO and N2O with CH4 over modified Al2O3 supported Pt,Pd,Rh
No full textPt, Pd and Rh supported on Al2O3-SiO2 and Al2O3-ZrO2, prepared by adsorbing noble metal ions from salt aqueous solutions on well-mixed supports, were characterized by XRD, N2 physisorption and FESEM, and studied for the simultaneous abatement of NO and N2O by selective catalytic reduction in the presence of O2 using CH4 as reductant (SCRsim). To give a better insight into the simultaneous process, the reactions related to SCRsim (SCRNO, SCRN2O, CH4 combustion), as well as the abatements in the absence of O2 (CRsim, CRNO, CRN2O), and the N2O decomposition by itself and in the presence of O2 and NO, were investigated. The catalytic measurements were performed in a flow apparatus with GC analysis of reactants and products. Catalytic results showed that Pt,Pd,Rh/Al2O3-SiO2 and Pt,Pd,Rh/Al2O3-ZrO2 are effective catalysts for SCRsim above 400 °C from feeds containing O2/CH4 less than 1, yielding complete NO and N2O conversions and complete selectivity to CO2 and N2. At lower temperatures, N2O and NO are unconverted and only the competitive CH4 combustion occurs. Compared to the separate NO and N2O abatement reactions, a slight shift in activity towards higher temperatures occurs in SCRsim. Such a shift can be related to the possible formation of strongly adsorbed NOy-like species formed in the presence of NO and competing with the N2O adsorption sites. The poisoning effect of these species disappears above a threshold-like temperature (about 300 °C), suggesting that above this temperature the high surface-O mobility, guaranteeing a partial reduction of the noble metal ions by CH4, sustains the reductive reactions of both NO and N2O
Cobalt supported on ZrO2: catalysts characterisation and their activity for the reduction of NO with C3H6 in the presence of excess O2
No full textCoOx/ZrO2 catalysts, prepared by impregnation were characterized by beams of DRS, XPS, FTIR and volumetric CO adsorption. Catalysts awere studied for the catalytic activity for NO reduction with propene in the presence of O2
CoOx/sulphated-ZrO2 and CoSO4/ZrO2 as catalysts for the abatement of NO with C3H6 in the presence of excess O2
No full textCobalt-sulphated zirconia catalysts were prepared by two different methods and characterized by UV-Vis, DRS, XRD, XPS and FTIR spectroscopies. Samples were tested for the NO reduction with C3H6 in the presence of excess O2
CuOx/sulphated-ZrO2, in situ sulphated CuOx/ZrO2, and CuSO4/ZrO2 as catalysts for the abatement of NO with C3H6 in the presence of excess O2
No full text
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
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
In situ sulphated CuOx/ZrO2 and CuOx/sulphated-ZrO2 as catalysts for the reduction of NOx with NH3 in the presence of excess O2
Full text linkSulphated catalysts containing the same amount of sulphates (2.6 SO4 nm2) and a different amount of copper (0.3–3.9 Cu atoms nm2),
Cu/SZ, were prepared by impregnation of sulphated-ZrO2 with toluene solutions of Cu(acetylacetonate)2. Sulphated catalysts containing the
same amount of copper (0.3 or 2.5 atoms nm2) and a different amount of sulphates (up to 4.9 SO2 nm2), Cu/ZSg, were prepared by
sulphation of CuOx/ZrO2 (Cu/Z) via the gas-phase. Samples were characterised by Fourier transformed IR spectroscopy. The selective
catalytic reduction of NO with NH3 in the presence of excess O2 (SCR reaction), the NH3 + O2 and the NO + O2 reactions were studied in a
flow apparatus.
Activity and selectivity did not depend on the sulphation method used for catalyst preparation but depended on the amount of copper and
sulphate, particularly on the sulphate/copper ratio.
As on Cu/Z, on Cu/SZ CuII was active for both SCR and NH3 + O2 reactions. The presence of covalent sulphates caused lower reducibility
of CuII to CuI and higher Lewis acid strength of CuI in Cu/SZ than in Cu/Z.
For (i) SCR, (ii) NH3 + O2 and (iii) NO + O2, Cu/ZSg were less active than the parent Cu/Z. As the sulphate content in Cu/ZSg increased,
the NO yield in the NH3 + O2 reaction markedly decreased, thus accounting for the increased selectivity in the SCR reaction. In CuOx/
sulphated-ZrO2 copper ions were less prone reversibly to undergo the redox process CuII/CuI.
These findings provide new information on the role of copper and sulphate in determining the activity and selectivity for the SCR with
NH
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