| 1. |
- Ajaikumar, Samikannu, et al.
(författare)
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Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by DPU method
- 2011
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Ingår i: Applied Catalysis A. - Amsterdam : Elsevier. - 0926-860X .- 1873-3875. ; 392:1-2, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.
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| 2. |
- Boily, Jean-Francois, et al.
(författare)
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X-ray photoelectron spectroscopy of fast-frozen hematite colloids in aqueous solutions. 2. tracing the relationship between surface charge and electrolyte adsorption
- 2010
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:6, s. 2613-2616
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Tidskriftsartikel (refereegranskat)abstract
- Colloidal-sized hematite spheroids exposed to aqueous NaCl solutions were investigated by X-ray photoelectron spectroscopy using the fast-frozen technique. The O 1s region provided evidence for (de)protonation reactions of surface (hydr)oxo groups of OH-enriched/O-depleted hematite Surfaces. These results were also correlated to changes in sodium (Na 1s) and chloride (Cl 2p) contents with pH. Electrolyte ion surface loadings were successfully predicted using a classic thermodynamic adsorption model normalized for surface site density. These efforts pointed to ion-specific inner-Helmholtz plane capacitances.
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| 3. |
- Bukhanko, Natalia, et al.
(författare)
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Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route
- 2013
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 1:8, s. 883-893
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of 1-ethyl chloride in the gas-phase mixture of ethanol and hydrochloric acid over ZnCl2/Al2O3 catalysts was studied in a continuous reactor using both commercial and tailor-made supports. The catalytic materials were characterized by the means of structural (XPS, TEM, XRD, and BET) and catalytic activity (selectivity and conversion) measurements. The reaction parameters such as temperature, pressure, and feedstock flow rates were optimized for the conversion of ethanol to ethyl chloride. The new tailor-made highly porous Al2O3-based catalyst outperformed its commercial counterpart by exhibiting high conversion and selectivity (98%) at the temperature of 325 °C. Long-term stability tests (240 h) confirmed the excellent durability of the tailor-made alumina catalysts. The process demonstrated here poses an efficient and economic “green” large-scale on-site synthesis of this industrially important reactant in industry, where bioethanol is produced and 1-ethyl chloride is necessary, e.g., for ethylation of cellulose and synthetic polymer products. On-site in situ production of ethyl chloride avoids the problems associated with the transportation and storage of toxic and flammable 1-ethyl chloride.
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| 4. |
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Dehydroisomerization of α-pinene over metal supported Si-SBA-15 mesoporous molecular sieves
- 2013
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Proceedings (redaktörskap) (refereegranskat)abstract
- The effective dispersion of active metal species on mesoporous Si-SBA-15 is acquired by means of deposition-precipitation method. In order to achieve this, the surface of Si-SBA-15 was first modified with TiO2 via grafting method, followed by deposition-precipitation method (DP) to obtain a fine dispersion of metallic nanoparticles over TiO2 modified Si-SBA-15. The structural features of the synthesized materials were characterized by means of X-ray diffraction (XRD), nitrogen sorption (BET), XPS and HR-TEM. A valuable platform chemical, p-cymene, was produced over the prepared catalyst by dehydroisomerization of α-pinene under vapour-phase conditions. A stable catalyst for one-spot synthesis of renewable p-cymene from α-pinene was developed.
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| 5. |
- Domashevskaya, E. P., et al.
(författare)
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Electronic structure of undoped and doped SnOx nanolayers
- 2013
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 537, s. 137-144
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Tidskriftsartikel (refereegranskat)abstract
- Results of electronic structure investigations for tin oxide nanolayers obtained by tin magnetron sputtering and their following oxidation in air at different temperatures are presented. Using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy techniques it was shown that at the 240 degrees C anneal a predominant phase in the sample surface layers is tin monoxide. With the annealing temperature increase up to 450 degrees C the phase composition corresponds to tin dioxide. Rather high sorption sensitivity for the samples oxidized at 450 degrees C was found. The compositional model of the gap structure based on XANES and XPS data matching for SnOx nanolayers revealed occurrence of the crossed transitions with the energy of similar to 3.7 eV in the presence of two phases: the SnO and the SnO2 or SnOx with vacancies. Under surface doping of SnO2 nanolayers with palladium PdO and PdO2 is observed where PdO is the most intensive component. O-2 and H-2 multiple alternate exposures resulted in the disappearance of palladium dioxide and PdO recovery to the metallic Pd. Under Pd bulk doping of nanolayers PdO and PdO2 were observed in the surface layers. In this case PdO2 was presented by two types of particles different in size, one of them having the greatest binding energy of Pd 3d(5/2) (339.0 eV). (C) 2013 Elsevier B.V. All rights reserved.
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| 6. |
- Fischer, A I, et al.
(författare)
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Crystal and molecular structures of mixedvalence octanuclear cobalt(II,III) propionate and butyrate with an etagerelike core
- 2012
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Ingår i: Russian chemical bulletin. - : Springer Science+Business Media B.V.. - 1066-5285 .- 1573-9171. ; 61:4, s. 821-827
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Tidskriftsartikel (refereegranskat)abstract
- The new mixed-valence octanuclear cobalt carboxylate complexes [CoII4CoIII4(μ4-O)4-(μ3-OMe)4(μ-O2CR)6(O2CR)2(H2O)6]·4H2O, where R = Et (3) or n-Pr (4), were investigated by X-ray diffraction analysis. Complexes 3 and 4 have a molecular octanuclear structure, and they are valence trapped, and contain four cobalt atoms Co3+ in the central cubane fragment with four cobalt atoms Co2+ at the periphery of the molecules. The molecules of the complexes are stabilized by four intramolecular hydrogen bonds and are linked, together with water solvent molecules, by intermolecular hydrogen bonds to form a three-dimensional supramolecular system.
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| 7. |
- Golyakov, A. M., et al.
(författare)
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Electrochemical and spectral properties of the polymer form of Cu(II) complex with N,N '-bis(salicylidene)-1,3-propylenediamine
- 2013
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Ingår i: Russian journal of general chemistry. - 1070-3632 .- 1608-3350. ; 83:3, s. 423-429
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Tidskriftsartikel (refereegranskat)abstract
- A conductive polymer based on the Cu(II) complex with N,N'-bis(salicylidene)-1,3-propylenediamine was obtained electrochemically. The optimal mode of the synthesis of the polymer under potentiostatic conditions was found. We determined the charge diffusion coefficient and activation barrier and elucidated the nature of the limiting step of the charge transfer in the polymer bulk in the electrolyte medium. The azomethine base, Cu(II) complex, and its polymer form in the oxidized and reduced states were characterized by X-ray photoelectron spectroscopy and electron absorption spectroscopy.
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| 8. |
- Golyakov, A M, et al.
(författare)
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Electrochemical Synthesis and Spectroscopy of the Polymeric Form of N,N '-Bis(3-methoxysalicylidene)-1,3-propylenediamine
- 2011
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Ingår i: Russian journal of applied chemistry. - : Springer. - 1070-4272 .- 1608-3296. ; 84:2, s. 317-324
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical oxidation of N,N '-bis(3-methoxysalicylidene)-1,3-propylenediamine leads to the formation of a conducting polymer on the electrode surface. The diffusion coeffi cient and activation barrier of the charge transfer in the bulk of the polymer in an electrolyte medium were determined. The Schiff base and its polymeric form in the oxidized and reduced states were characterized by IR, X-ray photoelectron, and electronic absorption spectroscopy. Reversible changes in the polymer structure, accompanying its electrochemical oxidation–reduction, are substantiated.
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| 9. |
- Gracia-Espino, Eduardo, et al.
(författare)
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Understanding the Interface of Six-Shell Cuboctahedral and Icosahedral Palladium Clusters on Reduced Graphene Oxide : Experimental and Theoretical Study
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:18, s. 6626-6633
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Tidskriftsartikel (refereegranskat)abstract
- Studies on noble-metal-decorated carbon nanostructures are reported almost on a daily basis, but detailed studies on the nanoscale interactions for well-defined systems are very rare. Here we report a study of reduced graphene oxide (rGOx) homogeneously decorated with palladium (Pd) nanoclusters with well-defined shape and size (2.3 +/- 0.3 nm). The rGOx was modified with benzyl mercaptan (BnSH) to improve the interaction with Pd clusters, and N,N-dimethylformamide was used as solvent and capping agent during the decoration process. The resulting Pd nanoparticles anchored to the rGOx-surface exhibit high crystallinity and are fully consistent with six-shell cuboctahedral and icosahedral clusters containing similar to 600 Pd atoms, where 45% of these are located at the surface. According to X-ray photoelectron spectroscopy analysis, the Pd clusters exhibit an oxidized surface forming a PdOx shell. Given the well-defined experimental system, as verified by electron microscopy data and theoretical simulations, we performed ab initio simulations using 10 functionalized graphenes (with vacancies or pyridine, amine, hydroxyl, carboxyl, or epoxy groups) to understand the adsorption process of BnSH, their further role in the Pd cluster formation, and the electronic properties of the graphene-nanoparticle hybrid system. Both the experimental and theoretical results suggest that Pd clusters interact with fiinctionalized graphene by a sulfur bridge while the remaining Pd surface is oxidized. Our study is of significant importance for all work related to anchoring of nanoparticles on nanocarbon-based supports, which are used in a variety of applications.
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| 10. |
- Halonen, Niina, et al.
(författare)
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Low-temperature growth of multi-walled carbon nanotubes by thermal CVD
- 2011
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Ingår i: Physica status solidi. B, Basic research. - Malden : Wiley-Blackwell. - 0370-1972 .- 1521-3951. ; 248:11, s. 2500-2503
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Tidskriftsartikel (refereegranskat)abstract
- Low-temperature thermal chemical vapor deposition (thermal CVD) synthesis of multi-walled carbon nanotubes (MWCNTs) was studied using a large variety of different precursor compounds. Cyclopentene oxide, tetrahydrofuran, methanol, and xylene: methanol mixture as oxygen containing heteroatomic precursors, while xylene and acetylene as conventional hydrocarbon feedstocks were applied in the experiments. The catalytic activity of Co, Fe, Ni, and their bi-as well as tri-metallic combinations were tested for the reactions. Low-temperature CNT growth occurred at 400 degrees C when using bi-metallic Co-Fe and tri-metallic Ni-Co-Fe catalyst (on alumina) and methanol or acetylene as precursors. In the case of monometallic catalyst nanoparticles, only Co (both on alumina and on silica) was found to be active in the low temperature growth (below 500 degrees C) from oxygenates such as cyclopentene oxide and methanol. The structure and composition of the achieved MWCNTs products were studied by scanning and transmission electron microscopy (SEM and TEM) as well as by Raman and X-ray photoelectron spectroscopy (XPS) and by X-ray diffraction (XRD). The successful MWCNT growth below 500 degrees C is promising from the point of view of integrating MWCNT materials into existing IC fabrication technologies. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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