| 1. |
- Leino, Ewelina, et al.
(författare)
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Influence of the synthesis parameters on the physico-chemical and catalytic properties of cerium oxide for application in the synthesis of diethyl carbonate
- 2013
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Ingår i: Materials Chemistry and Physics. - : Elsevier. - 0254-0584 .- 1879-3312. ; 143:1, s. 65-75
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of cerium (IV) oxide by means of room temperature precipitation method was carried out. The effect of preparation variables such as synthesis time, calcination temperature and pH of the solution on resulting CeO2 properties was discussed. Moreover, the comparison of CeO2 samples prepared in a static and rotation mode of synthesis is presented. The solid catalysts were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, nitrogen physisorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy using pyridine as a probe molecule and temperature programmed desorption of CO2. Significant variations in physicochemical properties of CeO2 by varying the preparation conditions were observed. Furthermore, the catalytic performances of CeO2 catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CeO2 using butylene oxide as a dehydrating agent. The dependence of CeO2 properties on its catalytic activity is evaluated in detail. (C) 2013 Elsevier B.V. All rights reserved.
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| 2. |
- Leino, Ewelina, et al.
(författare)
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The influence of various synthesis methods on the catalytic activity of cerium oxide in one-pot synthesis of diethyl carbonate starting from CO2, ethanol and butylene oxide
- 2013
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 210, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Different synthesis methods such as homogeneous precipitation at room temperature and supercritical water (T > 647 K and P > 22.1 MPa) were employed for cerium oxide preparation. Additionally, deposition of ceria on silica mesoporous material, SBA-15, was carried out. The obtained materials were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, X-ray photoelectron spectroscopy and CO2 temperature programmed desorption. Considerable variations in physico-chemical properties of the resulting materials were observed. The catalytic activities of pristine cerium oxide and ceria loaded on SBA-15 support were compared. The test reaction was synthesis of diethyl carbonate starting from carbon dioxide and ethanol using butylene oxide as the dehydrating agent.
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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. |
- Eta, Valerie, et al.
(författare)
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Synthesis of dimethyl carbonate from methanol and carbon dioxide : Circumventing thermodynamic limitations
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society. - 0888-5885 .- 1520-5045. ; 49:20, s. 9609-17
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of dimethyl carbonate from methanol and CO2 catalyzed by ZrO2 doped with KCl was investigated using chemical traps for water to circumvent thermodynamic limitations. The reaction, promoted by magnesium, occurred via the formation of carbonated magnesium methoxide (CMM) which adsorbed on the surface of ZrO2. The surface migration of the oxygen atom of ZrO2 to the surface methoxy groups of CMM resulted in the formation of dimethyl carbonate. The resulting MgO then reacted with methanol forming water and regenerating magnesium methoxide. The water formed reacted with the dehydrating agent, thus shifting the equilibrium toward a higher yield of DMC. The yield of 7.2 mol % DMC and 13.6 mol % conversion of methanol was obtained when methanol reacted with CO2 at 150 °C and 9.5 MPa for 8 h. The plausible reaction pathway is described.
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| 6. |
- 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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| 7. |
- Kukkola, Jarmo, et al.
(författare)
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Electrical transport through single-wall carbon nanotube-anodic aluminum oxide-aluminum heterostructures
- 2010
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 21:3, s. 35707-
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Tidskriftsartikel (refereegranskat)abstract
- Aluminum foils were anodized in sulfuric acid solution to form thick porous anodic aluminum oxide (AAO) films of thickness approximately 6 microm. Electrodes of carboxyl-functionalized single-wall carbon nanotube (SWCNT) thin films were inkjet printed on the anodic oxide layer and the electrical characteristics of the as-obtained SWCNT-AAO-Al structures were studied. Nonlinear current-voltage transport and strong temperature dependence of conduction through the structure was measured. The microstructure and chemical composition of the anodic oxide layer was analyzed using transmission and scanning electron microscopy as well as x-ray photoelectron spectroscopy. Schottky emission at the SWCNT-AAO and AAO-Al interfaces allowed by impurity states in the anodic aluminum oxide film together with ionic surface conduction on the pore walls of AAO gives a reasonable explanation for the measured electrical conduction. Calcined AAO is proposed as a dielectric material for SWCNT-field effect transistors.
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| 8. |
- Kukkola, Jarmo, et al.
(författare)
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Inkjet-printed gas sensors : metal decorated WO3 nanoparticles and their gas sensing properties
- 2012
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 22:34, s. 17878-17886
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Tidskriftsartikel (refereegranskat)abstract
- Inkjet deposition is an attractive technology to localize nanomaterials in an area-selective manner on virtually any kind of surfaces. Great advantages of the method are effective usage of materials, low processing temperatures and few required manufacturing steps, thus enabling rapid prototyping and bulk production with reasonably low cost. A number of different electrical devices such as light emitting diodes, transistors and solar cells have already been demonstrated, reflecting the versatility of inkjet printing. In this paper, we collect the contemporary results on inkjet deposited gas sensors and show examples of such gas sensing devices based on surface modified WO3 nanoparticles for efficient discrimination of various gaseous analytes from sub-ppm up to nearly 0.1% concentration levels in air.
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| 9. |
- Kukkola, Jarmo, et al.
(författare)
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Room temperature hydrogen sensors based on metal decorated WO3 nanowires
- 2013
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 186, s. 90-95
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Tidskriftsartikel (refereegranskat)abstract
- The emerging hydrogen economy has created a demand for the development of improved hydrogen sensors operating at room temperature. In this work, we present hydrogen detectors based on metal decorated WO3 nanowires that were able to detect 1000 ppm of H-2, even at room temperature (30 degrees C), with relatively short recovery time and high sensitivity. The nanowires were synthesized by a hydrothermal process and decorated with PdO and PtOx nanoparticles by decomposition of Pd(acac)(2) and Pt(acac)(2) precursors. The gas responses were tested for H-2, NO, H2S and CO analyte gases in an air buffer at 150,200 and 250 degrees C (H-2 also at 30,70 and 130 degrees C).
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| 10. |
- Leino, Anne-Riikka, et al.
(författare)
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Low-temperature catalytic oxidation of multi-walled carbon nanotubes
- 2013
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 57, s. 99-107
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Tidskriftsartikel (refereegranskat)abstract
- When in a pure form, carbon nanotubes are known to be stable in air up to ∼800 K making them attractive for a large variety of applications. In this work, we report a significant decrease of ignition temperature (in some cases occurring at ∼500 K) and a reduction in the apparent activation energy for oxidation in air as a result of impregnation with nanoparticles (<2 nm) of metal (Pt, Pd, Ni and Co) acetylacetonates or by decoration with corresponding oxides. Surprisingly, defects introduced by partial oxidation of the carbon nanotubes do not in practice have any influence on the enhancement of further oxidation. Reduction temperatures of metal oxides with H2 were close to those of other carbon supported catalyst materials. However, the carbon nanotubes showed a tendency for low temperature gasification in the presence of hydrogenation catalyst metals (Pt, Pd).
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