1,721,032 research outputs found
On the catalytic activity of cobalt oxide for the steam reforming of ethanol
No full textThe paper presents an investigation on the
catalytic activity for the ethanol steam reforming of Co3O4
oxidized, reduced and supported on MgO, and of CoO in
MgO solid solution. Only samples containing metallic
cobalt are found to be active for reforming reaction. H2-
TPR characterization of aged samples shows that reaction
mixture oxidizes a small fraction of metallic cobalt to Co+2.
A distinct role of Co+2 and Co0 in the reaction is
enlightened
Reducibility of nano-sized cobalt oxides for catalytic applications
Full text linkCo3O4, pure or supported, is an active catalyst for important industrial processes involving hydrogen such as Fischer-Tropsch Reaction, Water Gas Shift, Steam Reforming, Oxidative Dehydrogenation. The activation of cobalt catalyst in these reactions requires the formation of metallic cobalt and it has been shown that the catalyst performances can be influenced by the reduction procedures. The Co3O4 reduction proceeds in two steps Co3O4CoOCo and the particles size is a determining factor in both reduction processes and activity.
The ethanol Steam Reforming Reaction (SRR), CH3CH2OH+3H2O6H2+2CO2 has been investigated by us, on pure and supported Co3O4. Pure Co3O4 exhibits good performances with 100% ethanol conversion, 70% H2 selectivity and 7% CO selectivity at 450°C[1]. Cobalt reduction can be obtained in reaction conditions or in a pre-reduction in pure H2. The reduction in reaction conditions gave higher catalytic activity, because of a lesser sintering of Co with respect to H2 pre-reduction[1].
An investigation on the preparation and characterization of Co3O4 nano-sized[2], allowed us to infer that the different reducibility of nano Co3O4 with respect of micro Co3O4, may influence the Steam Reforming activity. Therefore results on reducibility and catalytic activity of nano Co3O4 are reported and discussed in terms of reduction parameters and of stream stability.
Crystalline Co3O4, a cubic spinel structure, with different particle dimensions, was prepared by different methods[2]. The surface area, the average particle dimensions and the morphology were evaluated by BET, XRD and TEM[2], and the cobalt reducibility by H2-Temperature-Programmed-Reduction. The catalytic activity was tested with [EtOH] 5.8x10-5 M, H2O/EtOH=4, GHSV=59000 h-1
Decomposition of nitrous oxide on CoOx/ZrO2, CuOx/ZrO2 and FeOx/ZrO2 catalysts
No full textCuOx/ZrO2, CoOx/ZrO2 and FeOx/ZrO2 catalysts were characterized and studied for the decomposition of nitrous oxid
V. Indovina, M. Occhiuzzi, D. Pietrogiacomi and S. Tuti “The surface composition of CuOX/ZrO2 catalysts as determined by FTIR, XPS, ESR spectroscopies and volumetric CO adsorption” J. Phys. Chem. B (1999) 103, 9967-9977
No full textCuOx/ZrO2 samples were prepared and characterized by means of FTIR,XPS,ESR,DRS, volumetric CO adsoption, redox cycles with H2 and O2
Correlation between Iron Reducibility in Natural and Iron-Modified Clays and Its Adsorptive Capability for Arsenic Removal
Full text linkThe study reports aspects that allowed to correlate structural and redox properties of iron species
deposited on clay minerals with the capacity of geomaterials for arsenic removal. Natural ferruginous
clays as well as an iron-poor clay chemically modified with Fe(III) salt (ferrihydrite species)
were investigated as adsorbents of the arsenate(V) in water. The study, carried out from minerals
from abundant Argentinean deposits, was conducted with the aid of different techniques such as
X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDS), Raman Spectroscopy, ICP-AES
(Inductively Coupled Plasma) chemical analysis and Temperature Programmed Reduction (TPR)
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
Dry reforming of methane on bimetallic Co-Ni/CeO2 catalyst
No full textIn the present work, monometallic Co/CeO2 (Co 7.5 wt.%) and Ni/CeO2 (Ni 7.5 wt.%) catalysts, were compared with the bimetallic Co-Ni/CeO2 (Co 3.75 wt.%, Ni 3.75 wt.%) catalyst. CeO2 has been selected for its redox properties that may mitigate the carbon deposition. The synthesis by surfactant assisted co-precipitation method allowed us to obtain powders with high surface area and homogeneous dispersion of cobalt and nickel nanometric particles. Samples were characterized by XRD, BET, TPR, TG-DTA and tested for DRM with CH4:CO2:Ar 20:20:60 vol.% (GHSW = 30000 mL g-1 h-1). After activation in H2 at 800°C, Co-Ni/CeO2 clearly showed the presence of a cobalt and nickel alloy phase. The bimetallic Co-Ni/CeO2 catalyst was more active and more selective for the DRM reaction than monometallic Co/CeO2 and Ni/CeO2 samples. In particular the CH4 conversion on Co-Ni/CeO2 was 50% at 600°C, and 97% at 800°C, with a H2/CO ratio in the range 0.9-1.0. After 16 hours streaming, Ni/CeO2 showed 25 wt.% of carbonaceous deposit and a catalytic activity decrease of 8%, while both cobalt containing catalysts showed 6 wt.% of carbon on the surface and a decrease of activity less than 2%. Theses features suggest that cobalt-nickel alloy combines the high activity of nickel with the carbon suppression property of cobalt
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
CO2-recycling for CH4 production on rare-earth modified Ni-Alumina catalysts
No full textThe chemical recycling of greenhouse gas CO2 produced in hydrocarbon combustion is an attractive alternative to CO2 storage in the underground [1]. Recently have attracted particular interest the conversion of CO2 into syn-gas by the dry reforming of methane [2] and the direct conversion of CO2 into synthetic natural gas (CH4) by the methanation reaction CO2 + 4H2 CH4 + 2H2O [3]. In addition to abating the CO2 emission, the methanation has the advantage to convert hydrogen into a more easily exploitable source of energy, as is CH4. This reaction also have the advantage being thermodinamically favoured at low temperatures (H° = −165 kJ mol−1). However the methanation is helpful for greenhouse gas mitigation only if it utilizes H2 produced by non-fossil sources. Nickel containing catalysts have been reported to be very active for this reaction []. Nickel loading, support nature and the effect of promoters have been widely investigated for the removal of CO2 and CO from H2-rich streams, but only scarcely studied for CH4 production using concentrated CO2 flow. In the present work, catalysts based on nickel supported on -Al2O3, modified by rare earth oxides CeO2 and La2O3, and by MgO were prepared by wet impregnation and tested for the production of synthetic natural gas. The catalyst metal compositions were tailored in order to improve the catalytic performances at low temperature (300-400°C) and high space velocity (75000 mL h-1 g-1). Catalysts were characterized by XRD, SEM, H2-TPR, CO2-TPD, BET in order to investigate the role of promoters on nickel dispersion and surface basicity, and tested with pure reagent CO2:H2 stechiometric flow. Some tests were performed on structured catalyst, prepared washcoating active powder on cordierite monolith, with the aim of increase the gas-solid interface and the temperature stability and reduce the pressure drop along the catalyst bed
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