0000000000008200
AUTHOR
Giulio Deganello
showing 92 related works from this author
Effect of Gold on the HDS Activity of Supported Palladium Catalysts
2002
Abstract The effect of gold on palladium catalysts supported on amorphous aluminosilicate was investigated in the hydrodesulfurization of thiophene. A series of bimetallic AuxPdy catalysts was prepared by the slow deposition–precipitation method with decomposition of urea. The structural and surface properties of the samples were analyzed by X-ray diffraction and X-ray photoelectron spectroscopy techniques at different stages of the catalyst life. After calcination at 673 K, gold-enriched solid solutions of approximately Au90Pd10 and Au80Pd20 composition were formed for all samples of different Au/Pd ratios, along with free palladium phases. Au80Pd20 was the prevailing phase. Hydrogen treat…
Surface Study of Pumice Supported Nickel Catalysts Used in the Hydrogenation of CO
1998
A series of pumice supported nickel catalysts used in the CO hydrogenation reaction were characterised by X-ray photoelectron spectroscopy. Qualitative and quantitative analysis of the XPS peaks have shown the effect of the calcination conditions on the chemical state of the nickel before hydrogenation and the particle size of the metal after reduction. Calcination at high temperature determined enrichment of sodium ions on the surface of the support and also on the metal particles. After exposure to the gas mixture CO/H2, formation of nickel carbides and other carbon species was checked. The correlation found between the surface atomic ratio Na/Si and the activity and selectivity of the ca…
Structural evolution of Pt/ceria-zirconia TWC catalysts during the oxidation of carbon monoxide
2004
The structural evolution of two Pt/ceria–zirconia catalysts, characterized by different amounts of supported Pt, was monitored by in situ X-ray diffraction during the anaerobic oxidation of CO at different temperatures. In a first phase, oxygen coming from the surface layers of the ceria–zirconia mixed oxide is consumed and no structural variation of the support is observed. After this induction time, bulk reduction of Pt/ceria–zirconia takes place as a step-like process, while the CO2 production continues at a nearly constant rate. This behavior is totally different from that of the metal-free support in similar reaction conditions, that show a gradual bulk reduction. In repeated oxidation…
Gold catalysis in southern Italy
2009
Thermal stability, structural properties and catalytic activity of Pd catalysts supported on Al2O3–CeO2–BaO mixed oxides prepared by sol–gel method
2003
Abstract Al2O3–CeO2–BaO oxides with constant Al/Ba mass ratio and increasing cerium content were prepared, using the sol–gel procedure, and calcined at 1000 °C for 5 h. The influence of barium oxide on the thermal stability and on the morphological and structural properties of the corresponding supports, in terms of increasing surface area of alumina and ceria dispersion, was studied. The corresponding Pd (1 wt.%) catalysts were prepared by a stepwise impregnation method with a solution of palladium acetylacetonate in benzene. Palladium was introduced in two sequential steps by impregnation 0.5 wt.% of Pd each time. The structural and textural properties of the materials were studied by X-r…
X-ray Photoelectron-spectroscopy Investigation of Pumice-supported Nickel-catalysts
1995
Pumice-supported nickel catalysts, prepared by the method of slow homogeneous precipitation with urea, were analysed by x-ray photoelectron spectroscopy (XPS). By comparison with similarly prepared silica- and alumina-supported nickel catalysts, a preferential interaction of Ni2+ with Al3+ of the support has been determined. A quantitative XPS analysis indicated large segregation of nickel to the surface. The treatment with H2 at 673 K and 1073 K produced a partial reduction of Ni+2 to Ni0. The extent of the reduction was largest at 1073 K and in this case the reduced Ni in the metallic phase was detectable by x-ray diffraction. A decrease of the Ni 2p/Si 2p intensity ratio occurring in the…
Mesoporous SBA-15 silica modified with cerium oxide: Effect of ceria loading on support modification
2010
Abstract The present work investigates the effect of ceria loading on silica SBA-15. Five CeO2/SBA-15 samples with CeO2 content equal to 5, 10, 15, 20 and 30 wt% were prepared by wetness-impregnation of the support with cerium nitrate hexahydrate, as precursor, dissolved in ethanol. After drying at room temperature, the resulting samples were calcined at 400 °C for 2h. Characterizations by BET surface area and pore-size distribution, XRD, NH3-TPD and H2-TPR were performed.
Pd and PdAu on mesoporous silica for methane oxidation: Effect of SO2
2007
Abstract Palladium and gold–palladium catalysts supported on mesoporous silica were prepared by incipient wetness impregnation. They were characterized by XPS, XRD, BET, and FTIR acidity measurements. The activity was tested in the oxidation of methane under lean conditions. The effect of adding SO 2 to the reactant mixture was investigated. Test reactions were consecutively performed to evaluate the thermal stability and poisoning reversibility. The palladium catalyst performed quite well in terms of the light-off temperature ( T 50 300 °C) and SO 2 tolerance. Moreover, the activity, which decreased after a night treatment in SO 2 at 350 °C, was completely recovered in subsequent cycles. …
A study of the behaviour of Pt supported on CeO2–ZrO2/Al2O3–BaO as NO storage–reduction catalyst for the treatment of lean burn engine emissions
2002
Abstract The behaviour of a Pt(1 wt.%) supported on CeO2–ZrO2(20 wt.%)/Al2O3(64 wt.%)–BaO(16 wt.%) as a novel NOx storage–reduction catalyst is studied by reactivity tests and DRIFT experiments and compared with that of Pt(1%)–BaO(15 wt.%) on alumina. The former catalyst, designed as a hydrothermally stable sample, is composed of an alumina modified with Ba ions and an overlayer of ceria-zirconia. The results pointed out that during the calcination barium ions migrates over the surface of the catalyst which thus show a good NOx storage–reduction behaviour comparable with that of Pt–BaO on alumina, although Ba ions result much better dispersed.
Combined effect of noble metals (Pd, Au) and support properties on HDS activity of Co/SiO2 catalysts
2009
Abstract Cobalt-based catalysts supported on different types of SiO 2 are studied in the hydrodesulfurization of thiophene. Amorphous silica and siliceous MCM-41 and HMS, characterized by different texture and surface acidity are used as carriers. The effects due to the modification of the support by impregnation with palladium precursor and to the co-impregnation of cobalt and gold are considered. The catalysts are characterized by N 2 physisorption (BET), XRD, TPR and XPS techniques. The use as supports of the ordered mesoporous silica with higher surface area with respect to amorphous silica, produces a better dispersion of the cobalt oxides particles. Moreover, the addition of palladium…
Nature of cobalt active species in hydrodesulfurization catalysis: combined support and preparation method effects
2007
Abstract Co/γ-Al2O3, Co/SiO2, Co/MCM-41, Co/ASA and Co/S2 (amorphous aluminosilicate with Al/Si = 0.13 and with Al/Si ≈ 2, respectively) were prepared by the method of wet impregnation and by the method of precipitation in the presence of sodium carbonate. The samples were characterised by XPS, XRD and TPR. The catalytic activity was tested in the hydrodesulfurization of thiophene using a continuous flow reactor. Among the wet impregnated catalysts those supported on the amorphous and ordered mesoporous silica exhibited higher HDS activity as compared to the alumina containing supports. Particularly, the use of the mesoporous, high surface area MCM-41 support, determined the best performing…
Liquid phase selective oxidation of benzyl alcohol over Pd–Ag catalysts supported on pumice
2001
Abstract Selective oxidation of benzyl alcohol to benzaldehyde was carried out over pumice supported bimetallic and monometallic Pd and Ag catalysts. Preliminary kinetic studies were performed at 333 K in autoclave, at pressure of 2 atm in pure oxygen. Under these conditions, small amounts of benzoic acid were detected with the monometallic Pd pumice being the most active catalyst. The reaction was also carried out under flowing oxygen at atmospheric pressure and at 348 K. Under these conditions, the selectivity to benzaldehyde was 100%. The catalytic activity of the catalysts was measured after different oxidation and reduction treatments at high temperature. In addition, two mechanical mi…
Chemical effect on the XPS spectra of the valence band and on O KLL and Pd MNN Auger spectra in pumice-supported catalysts
1992
X-ray photoelectron spectra of the valence band and X-ray-excited O KLL Auger transition of pumice-supported Pd and Pt catalysts have been obtained and compared to the corresponding spectra of pumice (a naturally occurring amorphous aluminosilicate). The changes observed indicate interaction between metal and support. The valence region of the catalysts consists of three large peaks: one due to the d band of the metals and the other to the O 2p non-bonding orbitals and bonding-type orbitals formed by a mixing of the atomic orbitals (O 2p, Si 3s and Si 3p) of oxygen and silicon from the support. The intensity decrease of the component due to the bonding orbitals, observed in the catalyst spe…
Supported Au catalysts for low-temperature abatement of propene and toluene, as model VOCs: Support effect
2011
3-4 Ousmane, M. Liotta, L. F. Di Carlo, G. Pantaleo, G. Venezia, A. M. Deganello, G. Retailleau, L. Boreave, A. Giroir-Fendler, A.; In this work gold nanoparticles supported over ceria (Au/CeO2), titania (Au/TiO2), alumina (Au/Al2O3) and Ce doped alumina (Au/7.5Ce/Al2O3) were prepared by deposition-precipitation (DP) method with NaOH solution and characterized by BET, XRD, H-2-TPR, TEM and XPS techniques. The catalytic activity was evaluated in the total oxidation of propene and toluene, chosen as model VOC molecules. The attention was focused on the catalyst stability. To this aim, three consecutive catalytic cycles in propene and toluene oxidation were performed for each catalyst. The act…
Influence of barium and cerium oxides on alumina supported Pd catalysts for hydrocarbon combustion
2002
Abstract The effects of baria and ceria additions to alumina-supported palladium catalysts have been investigated. Two series of binary Al 2 O 3 –BaO and ternary oxides Al 2 O 3 –CeO 2 –BaO were prepared using a sol–gel method and then characterized, after high-temperature treatments, by XRD, BET, TG, TEM and EDXS analyses. The influence of baria and ceria on the thermal stability and morphology of the supports was examined. A baria content of 12 wt.% appears the most effective for alumina stabilization. Palladium catalysts were prepared by impregnation method using Pd(NH 3 ) 4 (NO 3 ) 2 and were characterized by XRD and TEM. The catalysts showed high activity in the total oxidation of meth…
Influence of Sodium on the Structure and HDS Activity of Co–Mo Catalysts Supported ON Silica and Aluminosilicate
2000
Abstract Structural changes and catalytic performances of hydrodesulfurization (HDS) Co–Mo catalysts, supported on amorphous aluminosilicate (ASA) and amorphous SiO 2 were investigated as a function of the amount of sodium ions added to the supports. The catalysts were prepared according to the incipient wet impregnation method using (NH 4 ) 6 Mo 7 O 24 as molybdenum precursor and CoCl 2 or Co(NO 3 ) 2 as cobalt precursor. Structural and morphological characterisations of the materials were performed with X-ray diffraction (XRD) and surface area measurements (BET). In the case of the ASA-supported catalysts, increasing the amount of sodium resulted in a gradual decrease of the catalyst surf…
Combined CO/CH4 oxidation tests over Pd/Co3O4 monolitic catalyst: effects of high reaction temperature and SO2 exposure on the deactivation process
2007
Abstract CO and CH 4 combined oxidation tests were performed over a Pd (70 g/ft 3 )/Co 3 O 4 monolithic catalyst in conditions of GHSV = 100,000 h −1 and feed composition close to that of emission from bi-fuel vehicles. The effect of SO 2 (5 ppm) on CO and CH 4 oxidation activity under lean condition ( λ = 2) was investigated. The presence of sulphur strongly deactivated the catalyst towards methane oxidation, while the poisoning effect was less drastic in the oxidation of CO. Saturation of the Pd/Co 3 O 4 catalytic sites via chemisorbed SO 3 and/or sulphates occurred upon exposure to SO 2 . A treatment of regeneration to remove sulphate species was attempted by performing a heating/coolin…
Surface and bulk changes of a Pt 1%/Ce0.6Zr0.4O2 catalyst during CO oxidation in the absence of O2
2004
The reduction of a Pt 1%/Ce0.6Zr0.4O2 catalyst by CO in the absence of gaseous oxygen was studied by transient reactivity tests, temperature programmed surface reaction with CO, flow thermogravimetric tests and DRIFTS experiments, in order to obtain information generally on the OSC properties and, specifically, on the mechanism of CO oxidation over both, Pt catalyst and support-only sample (Ce0.6Zr0.4O2). The results of thermogravimetric experiments showed the presence of an induction time in the weight change % of the catalyst, depending on the CO concentration in the gas flow. This induction time could be related to the presence of two oxygen reactive sites. The first one leads to strongl…
Catalytic performances of Co3O4/CeO2 and Co3O4/CeO2-ZrO2Composite oxides for methane combustion: influence of catalyst pretreatment temperature and o…
2007
Abstract The influence of catalyst pre-treatment temperature (650 and 750 °C) and oxygen concentration ( λ = 8 and 1) on the light-off temperature of methane combustion has been investigated over two composite oxides, Co 3 O 4 /CeO 2 and Co 3 O 4 /CeO 2 –ZrO 2 containing 30 wt.% of Co 3 O 4 . The catalytic materials prepared by the co-precipitation method were calcined at 650 °C for 5 h (fresh samples); a portion of them was further treated at 750 °C for 7 h, in a furnace in static air (aged samples). Tests of methane combustion were carried out on fresh and aged catalysts at two different WHSV values (12 000 and 60 000 mL g −1 h −1 ). The catalytic performance of Co 3 O 4 /CeO 2 and Co 3…
Model Pumices Supported Metal Catalysts
1997
The catalyzed, selective hydrogenation, in liquid phase, of 1,3-cyclooctadiene was studied on a series of Pd catalysts supported on natural pumice, model pumices (with variable content of alkali metal ions), silica, and sodium-doped silica. At constant pressure of H2(1 atm.) the reaction follows a zero-order kinetic for all the Pd catalysts. At low metal dispersion (Dx < 20%), Pd/pumice catalysts exhibit higher activity as compared to Pd/silica catalysts; the turnover frequency is maintained even at high metal dispersion in Pd/pumice but Pd/silica and Pd/model pumices without alkali ions show a decrease in activity. At increasingDx, the binding energy shift of Pd 3dlevel is negative in Pd/p…
Pumice-Supported Nickel Catalysts
1997
A series of nickel catalysts supported on pumice was prepared by precipitation and impregnation techniques. The influence of the calcination and reduction temperatures on the structural properties such as lattice parameters and particle dimensions of the oxide precursors and of the reduced catalysts was investigated by X-ray diffraction measurements. The effect of structural changes on the catalytic activity in the hydrogenation of carbon monoxide has been evaluated. The turnover frequencies, as well as product distributions, are discussed in terms of the influence of the support properties and of its interaction with the metal. Changes of the C2+yield over CH4yield ratio versus nickel disp…
Structural characterisation of silica supported CoMo catalysts by UV Raman spectroscopy, XPS and X-ray diffraction techniques
2002
The structure of Co-Mo catalysts supported on commercial silica, doped with various amounts of sodium ions, was investigated by means of X-ray diffraction (XRD), UV-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Two series of samples were considered. One series was prepared by classic incipient wet impregnation (WI) and the other series by co-impregnation in the presence of nitrilotriacetic acid (NTA). The effect of sodium on the catalyst structure depended on the preparation procedure: in the case of the WI catalysts, sodium promoted the transformation of the polymolybdate species into monomolybdate Na2MoO4; in the case of the NTA prepared samples, sodium induced transforma…
The structure of pumice: An XPS and27Al MAS NMR study
1992
In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS …
Activity of SiO2 supported gold-palladium catalysts in CO oxidation
2003
Abstract Bimetallic Au-Pd catalysts supported on silica with different Au/Pd atomic ratios were prepared by simultaneous reduction of palladium and gold precursors by ethanol in the presence of the polymer, polyvinylpyrrolidone (PVP). Formation of alloyed particles was detected by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO chemisorption measurements. The catalysts were tested in the catalytic oxidation of CO using a plug–flow reactor. The CO conversion was determined as a function of temperature. The monometallic palladium and the palladium-rich catalysts behaved quite similarly and were the most active catalysts. …
EXAFS and XRD study of Pd–Ag bimetallic catalysts supported on pumice from organometallic precursors
2001
Abstract Silver–palladium bimetallic catalysts were supported on pumice following different procedures, based on mild treatments of organometallic precursors. The experiments for the structural characterization of the synthesized samples, wide angle X-ray diffraction (XRD) and X-ray absorption spectroscopy, were carried out at the beamline GILDA of the European Synchrotron Radiation Facility. The analysis of the data demonstrated that alloying took place with a degree of homogeneity depending on the different preparation routes.
Catalytic CO oxidation over pumice supported Pd–Ag catalysts
2001
Abstract Results on the catalytic oxidation of CO at 523 K over bimetallic Pd–Ag catalysts supported on pumice are reported and compared with those obtained from the monometallic Pd and Ag catalysts. The catalysts were prepared by organometallic precursors and were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) after different treatments with air and with hydrogen. The activity of the catalysts decreases with increasing Ag/Pd atomic ratio, the monometallic palladium exhibiting the highest activity. Furthermore, the treatment with air and with hydrogen always results in a better catalytic performance. On the basis of the structural characterization by XRD…
Time-resolved X-ray powder diffraction on a three-way catalyst at the GILDA beamline
2003
Time-resolved X-ray diffraction experiments carried out at the beamline BM08-GILDA of ESRF allowed a study of the structural modifications taking place in a Pt/ceria-zirconia catalyst while the CO oxidation reaction was in progress. The capillary tube in which the sample is stored acts effectively as a chemical microreactor that ensures homogeneity of the sample treatments and minimization of diffusion effects. During the flowing of the reactant CO/He mixture, the investigated catalyst undergoes a fast Ce(IV)-Ce(III) partial reduction that involves the release of one O atom for every two reduced Ce cations. Because Ce(III) has a larger ionic radius than Ce(IV), the structural modification p…
Structure of natural water-containing glasses from Lipari (Italy) and Eastern Rhodopes (Bulgaria): SAXS, WAXS and IR studies
1998
Abstract Two natural water-containing glasses with rhyolite composition originating from two different areas (perlite from Lipari, Italy, and expanded perlite from the Eastern Rhodopes, Bulgaria) have been characterised for chemical composition, atomic structure and specific surface area, with the ultimate goal of exploitation of volcanic glasses as carriers for heterogeneous metal catalysts. The two samples have similar chemical composition and total water content. The local structure, as determined by radial distribution function analysis of the wide angle X-ray scattering patterns, is similar, the medium-range structure being slightly more ordered for the Lipari glass. These results are …
Direct synthesis of methyl isobutyl ketone in gas-phase reaction over palladium-loaded hydroxyapatite
2005
Several compositions of palladium-loaded calcium hydroxyapatite Pd(x)/CaHAp were prepared and characterized by XRD, IR, and UV–visible spectroscopy and temperature-programmed reduction (TPR). The acid–base properties of the samples were studied with the use of butan-2-ol conversion and IR spectroscopy coupled with lutidine adsorption/desorption. Calcium hydroxyapatite bears Lewis acid sites of moderate strength and a limited number of Bronsted acid sites, which produce butenes by dehydration. The selectivity of the dehydrogenation reaction (formation of methyl ethyl ketone) is very limited in the absence of oxygen but indicates the existence on the surface of phosphate of basic sites that a…
Citrate–nitrate auto-combustion synthesis of perovskite-type nanopowders: A systematic approach
2009
Abstract Citrate–nitrate auto-combustion synthesis is used to prepare an iron, a cobalt and a cerium-perovskite. The influence of different synthesis conditions on the combustion process, phase composition, textural and morphological properties is studied in detail by X-ray diffraction, nitrogen adsorption and scanning electron microscopy. Results show that the combustion intensity increases from iron, to cerium, to cobalt-perovskite. Conversely, the combustion intensity decreases and thus the safety and the gain of the combustion process increase by using high fuel/oxidant ratios, low pH values or combustion reactors with high heat dispersion capacity. High fuel/oxidant ratios increase par…
CoMo catalysts supported on aluminosilicates: synergy between support and sodium effects
2004
Abstract The structural properties and the hydrodesulfurization (HDS) activity of sodium doped and sodium free CoMo catalysts supported on amorphous aluminosilicates (ASA) were investigated as a function of different SiO2:Al2O3 ratios. The support yielding the most active catalyst, (66% alumina) doped with different amounts of sodium, was used for a series of similar catalysts in order to study the effect of the alkali ion on the catalytic performance. The supports were prepared by sol–gel method and the catalysts were prepared by incipient wet impregnation method. The structure and the surface of the various samples were investigated by X-ray diffraction (XRD), temperature-programmed reduc…
“Supported Co3O4-CeO2 monoliths: effect of preparation method and Pd-Pt promotion on the CO/CH4 oxidation activity”
2006
Abstract Two structured composite oxides, Co3O4(30wt%)-CeO2(70wt%), have been prepared by washcoating commercial cordierite monoliths with a CeO2-γAl2O3 layer, on which the active phase Co3O4-CeO2 was added through two different methods: dip-coating from a suspension containing the preformed active oxide or impregnation with a solution of the cobalt and cerium precursors. Morphological characterizations of the monoliths have been performed by BET, and SEM-EDAX analyses. Electronic and reduction properties have been evaluated by XPS and H2-TPR, respectively. The effect of the preparation method has been investigated in the catalytic oxidation of CO, whereas the promotion by a low content of …
Relationship between structure and CO oxidation activity of ceria supported gold catalysts
2005
Gold catalysts supported on cerium oxide were prepared by solvated metal atom dispersion (SMAD), by deposition-precipitation (DP), and by coprecipitation (CP) methods and were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The catalytic activity was tested in the CO oxidation reaction. The structural and surface analyses evidenced the presence of a modified ceria phase in the case of the DP sample and the presence of pure ceria and gold metal crystallites in the case of the SMAD and CP samples. The DP sample, after a mild treatment in air at 393 K, exhibited only ionic gold, and it was very active below 273 K. By…
Influence of the preparation method on the thiophene HDS activity of silica supported CoMo catalysts
2002
Abstract The effect of the preparation method of CoMo/SiO2 catalysts with and without sodium ions, on the hydrodesulfurization (HDS) of thiophene was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 physisorption (BET). The samples were prepared by total sol–gel route, by classic wetness impregnation and by co-impregnation, in the presence of nitrilotriacetic acid (NTA), of commercial and sol–gel prepared silica. The influence of sodium ions added to the sol mixture and to the silica before the impregnation with Co and Mo salt solution, was also considered. The presence of sodium favoured the phase transition of amorphous silica to cristobalite with con…
Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy
1996
Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminat…
ChemInform Abstract: Sol-Gel Entrapped Chromium(VI): A New Selective, Efficient and Recyclable Oxidizing System.
2010
Abstract The sol-gel entrapment of chromium(VI) within a silica matrix, obtained by oxidation with ozone of the corresponding entrapped chromium(III), was found to be an efficient and recyclable oxidizing system (at least up to 16 times) for benzylic alcohols. No leaching of chromium in solution was observed, which prevented any environmental pollution.
Alumina supported Pt(1%)/Ce0.6Zr0.4O2 monolith: Remarkable stabilization of ceria–zirconia solution towards CeAlO3 formation operated by Pt under red…
2009
Abstract A structured Pt(1 wt%)/ceria–zirconia/alumina catalyst and the metal-free ceria–zirconia/alumina were prepared, by dip-coating, over a cordierite monolithic support. XRD analyses and Rietveld refinements of the structural data demonstrate that in the Pt supported catalysts ceria–zirconia is present as a Ce 0.6 Zr 0.4 O 2 homogeneous solid solution and that the deposition over the cordierite doesn’t produce any structural modification. Moreover no Pt sintering occurs. By comparing the XRD patterns recorded on Pt/ceria–zirconia/alumina and ceria–zirconia/alumina after three redox cycles, it results that Pt, favouring the structural reorganization of the ceria–zirconia into one cubic …
STACKING-FAULTS IN VERY FINE PALLADIUM PARTICLES SUPPORTED ON PUMICE
1990
By means of an X-ray diffraction study, carried out with best-fitting procedures, of the asymmetry and peak maximum shifts of some reflections, stacking-faults in the FCC lattice of very fine palladium particles supported on pumice were detected using the Warren-Wagner-Cohen theoretical approach.
Pd/Co3O4 catalyst for CH4 emissions abatement: study of SO2 poisoning effect
2007
A catalyst with 0.7 wt% Pd load supported over Co3O4 oxide was investigated in the methane oxidation by operating under CH4/O2 stoichiometric conditions. The effect of the noble metal addition on the activity of bare Co3O4 was evaluated. Samples were characterized by BET, XRD, TPR and XPS analyses. The SO2 poisoning of Pd catalyst and Co3O4 was studied by performing CH4 oxidation tests under stoichiometric conditions in SO2 (1 ppm or 10 ppm). Experiments evidenced that in our conditions the low amount of SO2 doesn’t influence the Pd behaviour, whereas in presence of 10 ppm of SO2 some deactivation occurs that becomes more evident above 450 °C at which the catalyst doesn’t reach 100% of meth…
Total oxidation of propene at low temperature over Co3O4–CeO2 mixed oxides: Role of surface oxygen vacancies and bulk oxygen mobility in the catalyti…
2008
Liotta, L. F. Ousmane, M. Di Carlo, G. Pantaleo, G. Deganello, G. Marci, G. Retailleau, L. Giroir-Fendler, A.; Co3O4, CeO2 and Co3O4-CeO2 mixed oxides with Co/Ce nominal atomic ratio 0.1:5, prepared by co-precipitation method with sodium carbonate, were tested in the oxidation of propene under lean condition and the catalyst stability was checked by performing three consecutive heating-cooling cycles. Characterization of the textural properties were performed by surface area measurement BET, X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. Among the Co3O4-CeO2 mixed oxides, Co3O4 (30 Wt%)-CeO2 (70 wt%) gives the best activity attaining full propene conversion at …
XPS study of pumice-supported palladium and platinum catalysts
1992
An XPS study has been performed on samples of monometallic of palladium and platinum and on bimetallic Pd-Pt catalysts supported on pumice. A negative shift of about 0.5 eV in the Pd 3d and Pt 4f binding energies of the catalysis relative to the energies of the same levels in the pure metals suggested an increase in the electron density in both metals. A quantitative XPS analysis indicated that the supported metals did not modify the surface atomic composition of pumice
Oxidative degradation properties of Co-based catalysts in the presence of ozone
2007
Four series of cobalt-based catalysts, such as bare Co3O4 and CoO, CoOx-CeO2 mixed oxides, CoOx supported over alumina and alumina-baria and CoMgAl and CoNiAl hydrotalcites have been synthesized and investigated for the oxidative degradation of phenol in the presence of ozone. Characterizations were obtained by several techniques in order to investigate the nature of cobalt species and their morphological properties, depending on the system. Analyses by XRD, BET, TPR, UV-visible diffuse reflectance spectroscopy and TG/DT were performed. The CoNiAl hydrotalcite exhibits, after 4 h of reaction, the highest phenol ozonation activity followed by Co(3 wt%)/Al2O3-BaO and CoMgAl. The samples Co(1 …
Characterization of Pumice-Supported Ag–Pd and Cu–Pd Bimetallic Catalysts by X-Ray Photoelectron Spectroscopy and X-Ray Diffraction
1999
Bimetallic Ag–Pd and Cu–Pd catalysts supported on pumice have been prepared in order to be used in the selective hydrogenation of dienes. The catalysts were obtained by the classical impregnation method and in the case of the Cu–Pd system also by organometallic precursors. They were analysed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). XPS allowed us to determine the surface distribution and chemical state of the two elements; XRD yielded the lattice parameters and allowed us to establish the possible formation of alloys. The two bimetallic systems behave differently. In the case of the Ag-Pd catalysts, Pd particles covered by silver atoms along with highly dispers…
Structural and morphological properties of Co-La catalysts supported on alumina/lanthana for hydrocarbons oxidation
2004
Abstract Two Al 2 O 3 (24 wt%)–La 2 O 3 (76 wt%) supported Co–La oxides with Co loading 4 wt% and different La content (1 and 9 wt%) were prepared by co-impregnation of the support, the aluminum–lanthanum oxide, with cobalt and lanthanum nitrates in aqueous solution and successive calcination at 800 °C for 4 h. The alumina–lanthana was synthesized by the sol–gel method. The samples were characterized by X-ray diffraction (XRD) and Rietveld refinement in order to identify the crystalline phases and their relative weight. H 2 -TPR (Temperature Programmed Reduction) experiments were recorded with the aim to identify the different Co phases present. Co 3 O 4 and LaCoO 3 were formed for La loadi…
Sol-gel entrapped chromium(VI): a new selective, efficient and recyclable oxidizing system
2001
Abstract The sol-gel entrapment of chromium(VI) within a silica matrix, obtained by oxidation with ozone of the corresponding entrapped chromium(III), was found to be an efficient and recyclable oxidizing system (at least up to 16 times) for benzylic alcohols. No leaching of chromium in solution was observed, which prevented any environmental pollution.
The Influence of Alkali Metal Ions in the Chemisorption of CO and CO2on Supported Palladium Catalysts: A Fourier Transform Infrared Spectroscopic Stu…
1996
Two series of palladium-based catalysts were compared on the basis of the adsorption of CO and CO2, monitored by Fourier transform infrared spectroscopy. The first series is represented by a silica-supported palladium catalyst and by some catalysts derived from it by addition of different amounts of sodium ion, 0 ≤ R ≤ 25.6, whereRis the atomic ratio Na/Pd. The second series consists of palladium catalysts supported on “model” and natural pumices. The model pumices, obtained by sol-gel techniques, are silico-aluminates containing variable amounts of sodium so that the corresponding Pd catalysts have anRvalue in the range 0 ≤ R ≤ 6.1. In the Pd/natural pumice catalysts, changes of the atomic…
Co3O4/CeO2 and Co3O4/CeO2–ZrO2 composite catalysts for methane combustion: Correlation between morphology reduction properties and catalytic activity
2005
Abstract Co3O4/CeO2 and Co3O4/CeO2–ZrO2 composite catalysts have been prepared by two different techniques, co-precipitation by citrate method and impregnation with cobalt nitrate of pre-formed ceria and ceria–zirconia oxides. The materials, as prepared and after ageing at 750 °C 7 h, were tested for methane combustion and the catalytic performances were compared with those of a commercial Co3O4, used as reference. A significant improvement of the activity was observed in the composite oxide Co3O4(30 wt%)/CeO2(70 wt%), prepared by citrate method, which exhibits the lowest light-off temperature of methane (T50 = 400 °C) and does not suffer deactivation after calcination at 750 °C 7 h.
Support effect on the structure and CO oxidation activity of Cu-Cr mixed oxides over Al2O3 and SiO2
2009
Abstract Cu-Cr based catalysts supported on silica and alumina with 5 wt% total loading of (CuO + Cr2O3), in different molar ratios, were prepared by wet impregnation. The samples were studied by nitrogen adsorption isotherms (BET), temperature-programmed reduction (TPR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their catalytic activity was tested in the CO oxidation reaction. Different structures were obtained in dependence of the support, the atomic ratio and the calcination temperature. In particular, whereas on Al2O3 there was no experimental evidence for interaction between Cu and Cr, over the silica supported systems formation of new phases CuCr2O4 and CuCrO…
CoOx catalysts supported on alumina and alumina-baria: influence of the support on the cobalt species and their activity in NO reduction by C3H6 in l…
2003
Abstract CoO x catalysts (Co 1 and 3 wt.%) were prepared by incipient-wetness impregnation of the supports, Al 2 O 3 and Al 2 O 3 (80 wt.%)-BaO (20 wt.%), and calcined at 500 and 800 °C. The samples were characterized by X-ray diffraction (XRD) and BET techniques. H 2 -temperature programmed reduction (TPR) and UV-Vis diffuse reflectance spectroscopy (DRS) spectra were recorded with the aim to identify the different Co species formed. The presence of Co 2+ species tetrahedrally and octahedrally coordinated appears strongly influenced by the nature of the support and the cobalt content. Co 3 O 4 particles were detected after calcination at 500 °C, a successive treatment at 800 °C promotes th…
Honeycomb supported Co3O4/CeO2 catalysts for CO/CH4 emissions abatement: effect of low Pd-Pt content on the catalytic activity
2007
Abstract A structured Co3O4–CeO2 composite oxide, containing 30% by weight of Co3O4, has been prepared over a cordieritic honeycomb support. The bimetallic, Pd–Pt catalyst has been obtained by impregnation of the supported Co3O4–CeO2 with Pd and Pt precursors in order to obtain a total metal loading of 50 g/ft3. CO, CH4 combined oxidation tests were performed over the catalyzed monoliths in realistic conditions, namely GHSV = 100,000 h−1 and reaction feed close to emission from bi-fuel vehicles. The Pd–Pt un-promoted Co3O4–CeO2 is promising for cold-start application, showing massive CO conversion below 100 °C, in lean condition. A strong enhancement of the CH4 oxidation activity, between 4…
Influence of SMSI effect on the catalytic activity of a Pt(1%)/ Ce0.6Zr0.4O2 catalyst: SAXS, XRD, XPS and TPR investigations
2004
Abstract The steady-state activity of NO reduction by C3H6, in lean conditions, was studied on a Pt(1%)/Ce0.6Zr0.4O2 catalyst, in a plug-flow reactor, in the temperature range 100–500 °C. The influence of reductive pre-treatments on the catalytic performance at low temperature (250 °C) was investigated. Enhancement of the activity was found for the catalyst pre-treated in hydrogen at 350 °C as compared to the sample pre-treated in H2 at 800 and 1050 °C. Moreover, transient reactivity tests of NO reduction by hydrogen were also carried out. As previously observed, the sample reduced at 350 °C was the most active catalyst. In both types of reactions the temperature and the nature of pre-treat…
Effect of the Al/Si atomic ratio on surface and structural properties of sol-gel prepared aluminosilicates
2003
Abstract A series of aluminosilicates with an Al/Si ratio ranging from 0 to ∞ (0 for pure silica and ∞ for pure alumina) was prepared by sol–gel process and characterized by surface and structure techniques. Aluminum tri sec butoxide and tetramethylorthosilicate were used as precursors for the sol–gel synthesis. The acidic properties of the oxides were studied by determination of the zero point charges, through mass titration method, and, for selected samples, by FT-IR spectroscopy of adsorbed pyridine used as a probe for both Bronsted and Lewis acidity. A dependence of the acidity on the Al/Si atomic ratio was found. According to the X-ray diffraction patterns, all the oxides have an amorp…
Pumice-supported Cu-Pd catalysts: Influence of copper on the activity and selectivity of palladium in the hydrogenation of phenylacetylene and but-1-…
1999
Abstract Pumice-supported copper–palladium catalysts prepared from organometallic precursor have been tested in the hydrogenation of phenylacetylene and in the hydrogenation/isomerization of the but-1-ene. The structure and catalytic behaviour of the bimetallic catalysts depended on the different temperatures of reduction. The presence of CuO or Cu metal in an alloyed state with Pd influenced the two reactions. The system containing CuO is the most active and selective towards the formation of the monoalkene in the hydrogenation of the highly unsaturated hydrocarbon. The system containing Cu partially alloyed with Pd is more active and selective towards the isomerization of the but-1-ene. T…
Hydrogenation of acetylene in ethylene rich feedstocks: Comparison between palladium catalysts supported on pumice and alumina
1998
Abstract The activity–selectivity patterns of Pd/pumice catalysts are compared with industrial and home prepared Pd/Al2O3 catalysts in the hydrogenation of acetylene in ethylene rich feedstocks (front-end and tail-end cuts). The iso-kinetic relationship (IKR) approach and a new mathematical model, surface site evolution model (SSEM), are employed in this comparison. Pumice and alumina supported Pd catalysts show different metal redox properties. A similar reaction mechanism is adequate to describe the reaction pathway independently by the catalysts and the gas mixtures considered. This mechanism involves the formation of surface polymers during the catalytic reactions and different catalyti…
Palladium on pumice: new catalysts for the stereoselective semihydrogenation of alkynes to (Z)-alkenes
2001
Abstract High selectivities (93–99%) and excellent stereoselectivities (>99%) in the semihydrogenation of CC triple bonds were achieved using palladium on pumice with a metal loading of 0.5, 1.5 or 3.0% wt as catalyst. The reactions were carried out in ethanol or tetrahydrofuran with only 2.5% of ethylenediamine allowing a self-terminating semihydrogenation independently on the CC triple bond.
ChemInform Abstract: Palladium on Pumice: New Catalysts for the Stereoselective Semihydrogenation of Alkynes to (Z)-Alkenes.
2010
Abstract High selectivities (93–99%) and excellent stereoselectivities (>99%) in the semihydrogenation of CC triple bonds were achieved using palladium on pumice with a metal loading of 0.5, 1.5 or 3.0% wt as catalyst. The reactions were carried out in ethanol or tetrahydrofuran with only 2.5% of ethylenediamine allowing a self-terminating semihydrogenation independently on the CC triple bond.
Metal-support interaction and redox behavior of Pt(1 wt %)/Ce0.6Zr0.4O2
2006
The catalyst Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L(III) edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce(0.6)Zr(0.4)O(2) is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formati…
Chromia on silica and zirconia oxides as recyclable oxidizing system: structural and surface characterization of the active chromium species for oxid…
2004
Chromium oxide samples supported over silica and zirconia were prepared by wet impregnation of the supports with aqueous solution of CrO3. In order to investigate the influence of the preparation method on the chromium dispersion and oxidation state, one sample was prepared by sol-gel technique. The materials were structurally characterized by XRD analysis. The oxidation states of chromium species were investigated by XPS, DRS and TPR/TPO techniques. EPR analyses were also carried out for the sample Cr/SiO2, that due to the low crystalline state exhibits broad XPS signals. In this case, particular attention was paid to the presence of Cr(V) and Cr (III) species and their concentration. The …
Hydrodesulfurization cobalt-based catalysts modified by gold
2007
Cobalt catalysts supported on amorphous SiO2 and ordered mesoporous silica (MCM-41) were prepared by incipient wetness impregnation. Gold was added by consecutive impregnation or by co-impregnation. The materials were characterised by XPS, XRD and TPR techniques and evaluated in the hydrodesulfurization (HDS) of thiophene in order to investigate the effect of the noble metal on the structure and on the catalytic behaviour of the supported cobalt. Co/MCM-41 exhibited higher HDS activity and higher stability than the Co/SiO2. Moreover, in contrast to silica case, the gold impregnated MCM-41, produced an enhancement of the cobalt catalytic activity, and this is likely to be related to an incre…
Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity
2006
Abstract Co 3 O 4 /CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3 O 4 ) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3 O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co 3 O 4 in correspondence of Co 3 O 4 –CeO 2 containing 30% by weight of Co 3 O 4 . The combined effect of cobalt oxide…
Catalytic reduction of nitrates and nitrites in water solution on pumice-supported Pd–Cu catalysts
2000
Abstract Two series of pumice-supported palladium and palladium–copper catalysts, prepared by impregnation with different palladium and copper precursors, were tested for the hydrogenation of aqueous nitrate and nitrite solutions. Measurements were performed in a stirred tank reactor, operating in batch conditions, in buffered water solution at atmospheric pressure and at 293 K. The activities of the catalysts were calculated in terms of nitrate and/or nitrite removal. With the monometallic Pd/pumice, the reduction of nitrite is highly selective; only 0.2% of the initial nitrite content is converted to ammonium ions. The activity in terms of turn over frequency (TOF) is higher as compared t…
Selective homogeneous hydrogenation of cycloocta-1,5, and cycloocta-1,3-diene to cyclooctene in the presence of (η4-cycloocta-1,5-diene)(η6-cycloocta…
1983
Cyclooctadiene isomers (1,3- and 1,5-COD) are selectively, homogenously hydrogenated to cyclooctene (C8H14) in tetrahydrofuran (THF) solution, under mild conditions of temperature (20 °C) and hydrogen pressure (1 atm), in the presence of catalytic amounts of (cycloocta-1,5-diene)(cycloocta-1,3,5,-triene)ruthenium(0), [Ru(η4-COD)(η6-C8H10)] (1). The rate of hydrogenation is higher when 1,3-COD is the substrate. Evidence for the isomerization 1,5-COD → 1,3-COD is reported. Similar studies carried out in several alcoholic solutions, although showing a decreased selectivity in the hydrogenation, confirm the isomerization 1,5-COD → 1,3-COD, and allow a discrimination between the isomerization an…
Characterization of the porous structure of Chilean volcanic soils by nitrogen adsorption and mercury porosimetry
2004
Pore volume, specific surface area (SSA), and total intragranular porosity (TIP) of Chilean soils derived from volcanic materials were studied. Soil samples involving the 0-15 and 15-30 cm depth of virgin and cultivated Collipulli (Ultisol) and Diguillin (Andisol) soils at two particle size fractions (<1 mm and <2 µm) were considered. From mercury porosimetry and N2 adsorption, mainly mesopores (pore diameter, dpore, about 10 nm) were determined for <1 mm Collipulli samples. Diguillin <1 mm soil shows macroporosity with dpore from 70 nm to 7000 nm. The clay fraction of Collipulli has macropores (dpore from 2000 nm to 40000 nm) and mesopores (dpore from 3 nm to 23 nm), while for Diguillin cl…
Selective hydrogenation of acetylene in ethylene feedstocks on Pd catalysts
1996
Abstract Pumice supported palladium catalysts were compared with Pd SiO 2 and Pd Al 2 O 3 in the hydrogenation of acetylene using typical industrial ethylene feedstocks: front-end and tail-end cuts. Pd/pumice catalysts exhibit good activity and excellent selectivity and stability in the title reaction. Their activity/selectivity pattern is controlled by the composition of the reaction mixture. The turnover frequency (TOF) increases, and the apparent activation energy (Ea) decreases, with the H 2 C 2 H 2 ratio, but they are not affected by the C 2 H 2 C 2 H 4 ratio. The selectivity to ethane (SE) does not change with acetylene conversion at low H 2 C 2 H 2 ratio (tail-end cut) and increases …
Effects of redox treatments on the structural composition of a ceria–zirconia oxide for application in the three-way catalysis
2003
Abstract The influence of calcination and redox cycles on the structural modification and redox properties of a ceria–zirconia mixed oxide of nominal composition Ce 0.6 Zr 0.4 O 2 were investigated by XRD and Rietveld refinement, by BET measurement, TPR and OSC analyses. The material is characterized by high total OSC and retains this property after several redox and calcination cycles up to 1273 K, despite the loss of porosity and the decrease of surface area. The Rietveld analysis of the diffractograms allowed to establish that at least two solid solutions are present in the as-prepared sample: a cubic phase, space group Fm-3m, richer in cerium compared to the nominal composition, a tetra…
Structural and morphological investigation of a cobalt catalyst supported on alumina-baria: effects of redox treatments on the activity in the NO red…
2004
Abstract Temperature-programmed reduction (TPR) and temperature-programmed oxidation (TPO) have been used to study the various cobalt species formed in a cobalt catalyst (Co 1 wt.%) supported on alumina-baria, with composition Al2O3(80 wt.%)–BaO (20 wt.%). The catalyst was synthesized by incipient-wetness impregnation of the support with a water solution of cobalt acetylacetonate and calcined at 550 °C for 5 h. In order to investigate the structure and morphology of the sample, XRD, BET and SEM analyses were performed. Depending on the temperature and nature of pre-treatment (reductive or oxidative) different Co species (Co3O4, Co3+, surface Co2+, CoAl2O4) were formed. Activity tests in the…
Synthesis of high-surface area CeO2 through silica xerogel template: influence of cerium salt precursor”;
2010
Abstract Ceria nanosized oxides with high surface area were synthesized by means of a templating approach, using a porous silica xerogel with surface area as high as 718 m2/g. After impregnation of the silica template with the cerium salt solution and further calcination at 600 °C, the final ceria oxide was recovered by dissolving the silica framework in NaOH solution. The effect of cerium counteranion, nitrate or chloride, on the textural and reduction properties of the ceria oxide was examined. Characterizations by BET and pore size distribution, XRD, TPR and SEM/EDX techniques were performed. The silica xerogel templated approach resulted in the preparation of ceria with surface area of …