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Kordas, Krisztian
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Publications (10 of 12) Show all publications
Bukhanko, N., Samikannu, A., Larsson, W., Shchukarev, A., Leino, A.-R., Kordas, K., . . . Mikkola, J.-P. (2013). Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route. ACS Sustainable Chemistry & Engineering, 1(8), 883-893
Open this publication in new window or tab >>Continuous gas phase synthesis of 1-ethyl chloride from ethyl alcohol and hydrochloric acid over Al2O3-based catalysts: the ‘green’ route
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2013 (English)In: ACS Sustainable Chemistry & Engineering, Vol. 1, no 8, p. 883-893Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
ethyl chloride, ethanol, heterogeneous catalysis, zinc chloride, high-porosity aluminum oxide
National Category
Chemical Sciences Chemical Engineering
Identifiers
urn:nbn:se:umu:diva-71424 (URN)10.1021/sc300171m (DOI)000322863100004 ()
Available from: 2013-05-29 Created: 2013-05-29 Last updated: 2018-06-08Bibliographically approved
Samikannu, A., Golets, M., Larsson, W., Shchukarev, A., Kordas, K., Leino, A.-R. & Mikkola, J.-P. (2013). Effective dispersion of Au and Au-M (M = Co, Ni, Cu and Zn) bimetallic nanoparticles over TiO2 grafted SBA-15: their catalytic activity on dehydroisomerization of α-pinene. Microporous and Mesoporous Materials, 173, 99-111
Open this publication in new window or tab >>Effective dispersion of Au and Au-M (M = Co, Ni, Cu and Zn) bimetallic nanoparticles over TiO2 grafted SBA-15: their catalytic activity on dehydroisomerization of α-pinene
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2013 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 173, p. 99-111Article in journal (Refereed) Published
Abstract [en]

Mesostructured siliceous SBA-15 was synthesized via direct hydrothermal crystallization from acidic solution of poly-(ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol)-copolymer and tetraethyl orthosilicate. The amorphous surface of the calcined Si-SBA-15 was modified with 20wt.% of TiO2 by chemical grafting method using titanium isopropoxide as the titanium source in ethanol solution. Various metal nanoparticles Au, Au-M (M = Co, Ni, Cu and Zn) were supported on TiO2/SBA-15 by deposition-precipitation method (DP) using urea as the precipitating agent. The structural features of the synthesized materials were characterized by various physico-chemical techniques such as X-ray diffraction, nitrogen sorption, XPS and HR-TEM. BET results of Si-SBA-15 revealed the formation of mesoporous structure with an average pore size of 5.9nm, pore volume of 1.12 cm3/g and the specific surface area of 846 m2/g. HR-TEM results demonstrated that metal nanoparticles were highly dispersed over TiO2/SBA-15 and long range ordering of hexagonal mesopores of Si-SBA-15 was well retained after loading of 20 wt.% TiO2 and 3 wt.% of bimetallic nanoparticles. The catalytic performances of the prepared catalysts were studied on dehydroisomerization of α-pinene under gas phase conditions using hydrogen atmosphere. The stability and catalytic activity of Au-M-TiO2/SBA-15 (DP) catalysts upon conversion of α-pinene in to p-cymene was explored in comparison with the catalysts prepared by conventional method. AuNi-TiO2/SBA-15 catalysts prepared via DP method were found to be stable upon longer reaction time as well as superior in terms of conversion and selective towards the formation of p-cymene.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2013
Keywords
Supported bimetal catalysts, TiO2/SBA-15, Dehydroisomerization, α-Pinene, p-Cymene
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-65772 (URN)10.1016/j.micromeso.2013.02.015 (DOI)000318210100015 ()
Available from: 2013-02-11 Created: 2013-02-11 Last updated: 2018-06-08Bibliographically approved
Wu, M.-C., Liao, H.-C., Cho, Y.-C., Toth, G., Chen, Y.-F., Su, W.-F. & Kordás, K. (2013). Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts. Journal of Materials Chemistry A, 1(18), 5715-5720
Open this publication in new window or tab >>Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts
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2013 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 18, p. 5715-5720Article in journal (Refereed) Published
Abstract [en]

This is an in-depth study on the photocatalytic performance characterization for single filament of TiO2 nanofiber photocatalysts by the novel photo-Kelvin probe force microscopy technique (photo-KPFM) and first principles calculations. Three kinds of TiO2 nanofibers: anatase TiO2 nanofibers (anatase TiO2 NFs), nitrogen doped TiO2 nanofibers (N-TiO2 NFs), and nitrogen doped TiO2 nanofibers decorated with platinum nanoparticles (N-TiO2-Pt NFs) were investigated. The N-TiO2-Pt NFs exhibit the largest negative photo surface potential shift (-182 mV) as compared to anatase TiO2 NFs (-29 mV). The first-principles calculations based on density functional theory (CASTEP simulation software) indicate that the significant photo surface potential shift obtained by adding nitrogen and platinum into TiO2 NFs is induced by two mechanisms: (1) enhancement in absorbance to increase exciton generation and (2) decreased charge recombination to increase surface charge. These changes in the photo surface potential of various TiO2 nanofibers are closely correlated with their photocatalytic activity. Thus, this novel photo-KPFM provides a useful technique to easily monitor the photocatalytic capability of materials in the development of high performance photocatalysts.

National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-71331 (URN)10.1039/c3ta01011b (DOI)000317584700033 ()
Available from: 2013-05-28 Created: 2013-05-26 Last updated: 2018-06-08Bibliographically approved
Gemo, N., Biasi, P., Canu, P., Menegazzo, F., Pinna, F., Ajaikumar, S., . . . Mikkola, J.-P. (2013). Reactivity aspects of SBA15-based doped supported catalysts: H2O2 direct synthesis and disproportionation reactions. Paper presented at 15th Nordic Symposium on Catalysis, Mariehamn, Åland, June 16–18, 2012. Topics in catalysis, 56(9-10), 540-549
Open this publication in new window or tab >>Reactivity aspects of SBA15-based doped supported catalysts: H2O2 direct synthesis and disproportionation reactions
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2013 (English)In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, p. 540-549Article in journal (Refereed) Published
Abstract [en]

Pd and PdAu catalysts supported on SBA15 and SiO2 were prepared and investigated for H2O2 direct synthesis in a batch autoclave (10 °C and 17.5 bar) and in the absence of halides and acids. The SiO2 supported catalysts exhibited inferior performances compared to the mesoporous ordered SBA15. A good control of both the catalysts dispersion and nanoparticle stability was achieved using SBA15. Catalysts were doped with bromine, a promoter in the H2O2 direct synthesis. Productivity and selectivity decreased when bromine was incorporated in the catalysts, thus indicating a possible poisoning due to the grafting process. A synergetic effect between Pd and Au was observed both in presence and absence of bromopropylsilane grafting on the catalyst surface. Three modifiers of the SBA15 support (Al, CeO2 and Ti) were chosen to elucidate the influence of the surface properties on metal dispersion and catalytic performance. Higher productivity and selectivity were achieved incorporating Al into the SBA15 framework, whereas neither Ti nor CeO2 improved H2O2 yields. The enhanced performance observed for the Prau/Al–SBA15 catalysts was attributed to the increased number of Brønsted acid sites. A modification of this catalyst with bromine was confirmed to impair both productivity and selectivity, possibly due to the broader particle size distribution and the poor stability of the metal nanoparticles, as demonstrate by transmission electron microscopy (TEM) images. H2O2 disproportionation was also investigated. A much slower reaction rate was observed compared to the H2O2 production, suggesting that the major contributor in the process of H2O2 destruction must be connected to the hydrogenation reaction.

Place, publisher, year, edition, pages
New York: Springer, 2013
Keywords
Hydrogen peroxide, Direct synthesis, SBA15, Silica, Palladium
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-64222 (URN)10.1007/s11244-013-0009-2 (DOI)000320500200005 ()
Conference
15th Nordic Symposium on Catalysis, Mariehamn, Åland, June 16–18, 2012
Available from: 2013-01-21 Created: 2013-01-21 Last updated: 2018-06-08Bibliographically approved
Toth, G., Halonen, N., Maklin, J., Kukkola, J. & Kordas, K. (2013). Thermal management of micro hotspots in electric components with carbon nanotubes. International Journal of Nanotechnology, 10(1-2), 57-62
Open this publication in new window or tab >>Thermal management of micro hotspots in electric components with carbon nanotubes
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2013 (English)In: International Journal of Nanotechnology, ISSN 1475-7435, E-ISSN 1741-8151, Vol. 10, no 1-2, p. 57-62Article in journal (Refereed) Published
Abstract [en]

The excellent thermal and electrical conductivity as well as the remarkable mechanical properties of Carbon Nanotubes (CNTs) all point towards an unbeatable and facile route towards replacing traditional thermal management materials, like copper, in the electronics industry. In spite of that, the technology is still suffering from considerable challenges. In order to realise an actual electronics, which uses CNTs for thermal management, inevitable trade-offs have to be made. Our work is focusing on proposing novel ideas and manufacturing techniques which show a reasonable potential and could justify the practicality of this technology. The paper is reporting on the recent results in hotspot removal by using tailored multi-layer chips and CNTs grown directly on the heat affected zone.

Place, publisher, year, edition, pages
InderScience Publishers, 2013
Keywords
Carbon nanotubes, Electronics cooling, Thermal management
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-63572 (URN)10.1504/IJNT.2013.050881 (DOI)000312373200007 ()
Available from: 2013-01-03 Created: 2013-01-03 Last updated: 2018-06-08Bibliographically approved
Kukkola, J., Mohl, M., Leino, A.-R., Toth, G., Wu, M.-C., Shchukarev, A., . . . Kordas, K. (2012). Inkjet-printed gas sensors: metal decorated WO3 nanoparticles and their gas sensing properties. Journal of Materials Chemistry, 22(34), 17878-17886
Open this publication in new window or tab >>Inkjet-printed gas sensors: metal decorated WO3 nanoparticles and their gas sensing properties
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2012 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 34, p. 17878-17886Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:umu:diva-59361 (URN)10.1039/c2jm32499g (DOI)000307305700069 ()
Available from: 2012-09-12 Created: 2012-09-12 Last updated: 2018-06-08Bibliographically approved
Sarkar, A., Shchukarev, A., Leino, A.-R., Kordas, K., Mikkola, J.-P., Petrov, P. O., . . . Tuchin, V. V. (2012). Photocatalytic activity of TiO2 nanoparticles: effect of thermal annealing under various gaseous atmospheres. Nanotechnology, 23(47), 475711-475719
Open this publication in new window or tab >>Photocatalytic activity of TiO2 nanoparticles: effect of thermal annealing under various gaseous atmospheres
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2012 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 47, p. 475711-475719Article in journal (Refereed) Published
Abstract [en]

The structure, composition and photocatalytic activity of TiO2 nanoparticles annealed in various gas atmospheres (N2, NH3 and H2) were studied in this work. The effect of treatment on crystal structure, particle size, chemical composition and optical absorbance were assessed by means of x-ray diffraction, transmission electron microscopy, x-ray photoelectron spectroscopy and diffuse optical reflectance/transmittance measurements, respectively. Photocatalytic properties of the materials were evaluated by three different methods: degradation of methyl orange in water, killing of Staphylococcus aureus bacteria and photogeneration of radicals in the presence of 3-carboxy-2,2,5,5-tetramethyl pyrrolidine-1-oxyl (PCA) marker molecules. The results indicate that the correlation between pretreatment and the photocatalytic performance depends on the photocatalytic processes and cannot be generalized.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2012
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-60447 (URN)10.1088/0957-4484/23/47/475711 (DOI)
Available from: 2012-10-12 Created: 2012-10-12 Last updated: 2018-06-08Bibliographically approved
Wu, M.-C., Toth, G., Sapi, A., Leino, A.-R., Konya, Z., Kukovecz, A., . . . Kordas, K. (2012). Synthesis and Photocatalytic Performance of Titanium Dioxide Nanofibers and the Fabrication of Flexible Composite Films from Nanofibers. Paper presented at International Conference on Electronic Materials (IUMRS-ICEM), AUG 22-27, 2010, Seoul, SOUTH KOREA. Journal of Nanoscience and Nanotechnology, 12(2), 1421-1424
Open this publication in new window or tab >>Synthesis and Photocatalytic Performance of Titanium Dioxide Nanofibers and the Fabrication of Flexible Composite Films from Nanofibers
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2012 (English)In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 12, no 2, p. 1421-1424Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

Titanium dioxide nanofibers were synthesized and applied in flexible composite films that are easy to handle and recycle after use. The nanofibers were obtained in a multi-step procedure. First, sodium titanate nanofibers were prepared from TiO2 nanoparticles through the alkali hydrothermal method. In the next step, sodium hydrogen titanate nanofibers were made by washing the sodium titanate nanofibers in HCI solution. Finally, the sodium hydrogen titanate nanofibers were transformed to TiO2 anatase nanofibers by calcination in air. The photocatalytic activity of TiO2 anatase nanofibers were evaluated and compared to a TiO2 nanoparticle catalyst by decomposing methyl orange dye in aqueous solutions. The achieved reaction rate constant of TiO2 anatase nanofibers was comparable to that of Degussa P25. Paper-like flexible composite films were prepared by co-filtrating aqueous dispersions of TiO2 catalyst materials and cellulose. The composite films made from the nanofibers exhibit better mechanical integrity than those of the nanoparticle-cellulose composites.

Keywords
TiO2, Nanofiber, Nanowire, Nanoparticle, Flexible Film, Photocatalyst
National Category
Nano Technology
Identifiers
urn:nbn:se:umu:diva-55681 (URN)10.1166/jnn.2012.4655 (DOI)000303280000107 ()
Conference
International Conference on Electronic Materials (IUMRS-ICEM), AUG 22-27, 2010, Seoul, SOUTH KOREA
Available from: 2012-05-28 Created: 2012-05-28 Last updated: 2018-06-08Bibliographically approved
Toth, G., Kordas, K., Myllymaki, S. & Jantunen, H. (2012). Towards fully printed, antenna-based proximity sensors. Zhongguó wùli xuékan, 50(6), 910-918
Open this publication in new window or tab >>Towards fully printed, antenna-based proximity sensors
2012 (English)In: Zhongguó wùli xuékan, ISSN 0577-9073, Vol. 50, no 6, p. 910-918Article in journal (Refereed) Published
Abstract [en]

In this work, we describe proximity sensors using functional coatings as sensing elements. The planar inductor-capacitor resonant circuit is fabricated by conventional PCB fabrication techniques and also by using low cost drop-on-demand inkjet printing technology. The permittivity and conductivity is changing in the system as a function of humidity, which simulates the presence of a body. This change in turn modifies the resonant frequency of the sensor. The performance of the fabricated proximity sensors are good, especially using the PCB resonant circuit and the gypsum / sodium-hydrogen titanate nanowire composites as sensitizing elements.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-66422 (URN)10.6122/CJP.50.910 (DOI)000313547300003 ()
Available from: 2013-02-22 Created: 2013-02-19 Last updated: 2018-06-08Bibliographically approved
Reinik, J., Heinmaa, I., Kirso, U., Kallaste, T., Ritamäki, J., Boström, D., . . . Mikkola, J.-P. (2011). Alkaline modified oil shale fly ash: Optimal synthesis conditions and preliminary tests on CO(2) adsorption. Journal of Hazardous Materials, 196, 180-186
Open this publication in new window or tab >>Alkaline modified oil shale fly ash: Optimal synthesis conditions and preliminary tests on CO(2) adsorption
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2011 (English)In: Journal of Hazardous Materials, ISSN 0304-3894, E-ISSN 1873-3336, Vol. 196, p. 180-186Article in journal (Refereed) Published
Abstract [en]

Environmentally friendly product, calcium-silica-aluminum hydrate, was synthesized from oil shale fly ash, which is rendered so far partly as an industrial waste. Reaction conditions were: temperature 130 and 160°C, NaOH concentrations 1, 3, 5 and 8M and synthesis time 24h. Optimal conditions were found to be 5M at 130°C at given parameter range. Original and activated ash samples were characterized by XRD, XRF, SEM, EFTEM, (29)Si MAS-NMR, BET and TGA. Semi-quantitative XRD and MAS-NMR showed that mainly tobermorites and katoite are formed during alkaline hydrothermal treatment. Physical adsorption of CO(2) on the surface of the original and activated ash samples was measured with thermo-gravimetric analysis. TGA showed that the physical adsorption of CO(2) on the oil shale fly ash sample increases from 0.06 to 3-4mass% after alkaline hydrothermal activation with NaOH. The activated product has a potential to be used in industrial processes for physical adsorption of CO(2) emissions.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2011
Keywords
Oil shale fly ash, Tobermorite synthesis, CO2 thermo-gravimetric analysis
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-48273 (URN)10.1016/j.jhazmat.2011.09.006 (DOI)21943923 (PubMedID)
Available from: 2011-10-13 Created: 2011-10-13 Last updated: 2018-06-08Bibliographically approved
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