| 1. |
- Bourajoini, Hasna, et al.
(författare)
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Calcium manganese oxide catalysts for water oxidation : Unravelling the influence of various synthesis strategies
- 2016
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Ingår i: Materials research bulletin. - : Elsevier. - 0025-5408 .- 1873-4227. ; 79, s. 133-137
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Three different mixed oxide catalysts primarily consisting of calcium and manganese oxides targeting artificial photosynthesis were synthesized and studied. According to the results, their catalytic activity for water oxidation was enhanced by the presence of mixed valence states of Mnn+ ions (3.0 ≤ n ≪ 4.0), while the specific surface area had negligible effect.
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| 2. |
- Bukhanko, Natalia, et al.
(författare)
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Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina and flexible 3-D carbon foam supported catalysts
- 2017
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Ingår i: Applied Catalysis A. - : Elsevier. - 0926-860X .- 1873-3875. ; 542:25, s. 212-225
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Tidskriftsartikel (refereegranskat)abstract
- Isopropyl chloride synthesis from isopropanol and HCl in gas phase over ZnCl2 catalysts supported on Al2O3 as well as flexible carbon foam was studied in a continuous reactor. A series of catalytic materials were synthesised and characterised by BET, XPS, SEM, TEM, XRD and NH3-TPD methods. Catalytic activity tests (product selectivity and conversion of reactants) were performed for all materials and optimal reaction conditions (temperature and feedstock flow rates) were found. The results indicate that the highest yield of isopropyl chloride was obtained over 5 wt.% ZnCl2 on commercial Al2O3 (No. II) (95.3%). Determination of product mixture compositions and by-product identification were done using a GC-MS method. Carbon foam variant catalyst, 5 wt.% ZnCl2/C, was found to perform best out of the carbon-supported materials, achieving ∼75% yield of isopropyl chloride. The kinetic model describing the process in a continuous packed bed reactor was proposed and kinetic parameters were calculated. The activation energy for the formation of isopropyl chloride reaction directly from isopropanol and HCl was found to be ∼58 kJ/mol.
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| 3. |
- Gemo, Nicola, et al.
(författare)
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TiO2 nanoparticles vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis : the influence of N and Au doping
- 2016
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 6:105, s. 103311-103319
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Tidskriftsartikel (refereegranskat)abstract
- The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product.
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| 4. |
- Kirilin, Alexey V., et al.
(författare)
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Aqueous-phase reforming of xylitol over Pt/C and Pt/TiC-CDC catalysts : catalyst characterization and catalytic performance
- 2014
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Ingår i: Catalysis Science & Technology. - : RSC Publishing. - 2044-4753. ; 4:2, s. 387-401
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Tidskriftsartikel (refereegranskat)abstract
- The aqueous phase reforming (APR) of xylitol was studied over five Pt/C catalysts. The correlation between physico-chemical properties of the catalysts and catalytic performance was established. The Pt/C catalysts have different textural properties as well as different mean Pt cluster sizes and surface acidity. The average Pt cluster size was investigated by means of CO chemisorption as well as by TEM. The reaction was found to be structure sensitive and TOF linearly increases with increasing average Pt cluster size in the studied domain. The catalysts which possess higher surface acidity favoured higher rates of hydrocarbon production. On the contrary the Pt/C materials with lower acidities generated hydrogen with high selectivity and TOF.
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| 5. |
- Kordas, Krisztian, et al.
(författare)
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On the Interaction of Metal Nanoparticles with Supports
- 2015
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Ingår i: Topics in catalysis. - : Springer Science+Business Media B.V.. - 1022-5528 .- 1572-9028. ; 58:14-17, s. 1127-1135
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Tidskriftsartikel (refereegranskat)abstract
- Metal nanoparticles supported on surfaces often undergo sintering even at moderate temperatures. The degree of sintering is typically influenced by the surface chemistry indicating that besides the commonly believed Ostwald ripening also other processes associated with metal surface diffusion are responsible for the nanoparticle size growth. In addition to the deterioration in metal dispersion, carbon supports can show chemical instability leading to their partial degradation in the proximity of the nanoparticles both in reducing and oxidizing environments at elevated temperatures. This work reports a study of Pd, Pt and Ni nanoparticles anchored on carbon (activated carbon, graphite and carbon nanotubes) as well as titania (nanoparticles and microparticles) surfaces frequently applied as catalyst materials in heterogeneous catalysis and photocatalysis, and evaluate the potential events causing metal sintering and degradation of the supports using transmission electron microscopy analysis.
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| 6. |
- 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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| 7. |
- Leino, Ewelina, et al.
(författare)
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Synthesis and characterization of ceria-supported catalysts for carbon dioxide transformation to diethyl carbonate
- 2018
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Ingår i: Catalysis Today. - : Elsevier. - 0920-5861 .- 1873-4308. ; 306, s. 128-137
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Tidskriftsartikel (refereegranskat)abstract
- The support materials Al2O3, SiO2 and TiO2 were modified with 16 wt% CeO2, using two different preparation methods evaporation-impregnation and precipitation-deposition. The synthesized 16 wt% CeO2-Al2O3, 16 wt% CeO2-SiO2 and 16 wt% CeO2-TiO2 materials were characterized by means of X-ray powder diffraction for the phase purity, scanning electron microscopy for the morphology, nitrogen physisorption to determine the specific surface area and X-ray photo electron spectroscopy for the oxidation state of the Ce in the TiO2, Al2O3 and SiO2 matrices. Transmission electron microscopy was used to study the particle size of CeO2 whereas CO2-temperature programmed desorption (TPD) was used to determine the basicity of ceria-modified TiO2, Al2O3 and SiO2 catalysts. Furthermore, the catalytic performance of the as prepared CeO2-modified catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CO2 using butylene oxide as the dehydrating agent. The physico-chemical characterization results were correlated with the catalytic activity results and discussed in detail.
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| 8. |
- Mohl, Melinda, et al.
(författare)
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Titania nanofibers in gypsum composites : an antibacterial and cytotoxicology study
- 2014
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Ingår i: Journal of Material Chemistry B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 2:10, s. 1307-1316
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Tidskriftsartikel (refereegranskat)abstract
- Further developments of antibacterial coatings based on photocatalytic nanomaterials could be a promising route towards potential environmentally friendly applications in households, public buildings and health care facilities. Hereby we describe a simple chemical approach to synthesize photocatalytic nanomaterial-embedded coatings using gypsum as a binder. Various types of TiO2 nanofiber-based photocatalytic materials (nitrogen-doped and/or palladium nanoparticle decorated) and their composites with gypsum were characterized by means of scanning (SEM) and transmission (TEM) electron microscopy as well as electron and X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) techniques. These gypsum-based composites can be directly applied as commercially available paints on indoor walls. Herein we report that surfaces coated with photocatalytic composites exhibit excellent antimicrobial properties by killing both methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) under blue light. In the case of MSSA cells, the palladium nanoparticle-decorated and nitrogen-doped TiO2 composites demonstrated the highest antimicrobial activity. For the MRSA strain even pure gypsum samples were proven to be efficient in eradicating Gram-positive human pathogens. The cytotoxicity of freestanding TiO2 nanofibers was revealed by analyzing the viability of HeLa cells using MTT and fluorescent cell assays.
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| 9. |
- Ngoc Pham, Tung, et al.
(författare)
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Catalytic Hydrogenation of d-Xylose Over Ru Decorated Carbon Foam Catalyst in a SpinChem® Rotating Bed Reactor
- 2016
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Ingår i: Topics in catalysis. - New York : Springer. - 1022-5528 .- 1572-9028. ; 59:13-14, s. 1165-1177
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Tidskriftsartikel (refereegranskat)abstract
- In this work the activity of ruthenium decorated carbon foam (Ru/CF) catalyst was studied in three phase hydrogenation reaction of d-xylose to d-xylitol. The developed catalyst was characterized by using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectrometry and nitrogen adsorption–desorption measurement. Kinetic measurements were carried out in a laboratory scale pressurized reactor (Parr®) assisted by SpinChem® rotating bed reactor (SRBR), at pre-defined conditions (40–60 bar H2 and 100–120 °C). The study on the influence of reaction conditions showed that the conversion rate and selectivity of hydrogenation reaction of d-xylose was significantly affected by temperature. These results have been proved by a competitive kinetics model which was found to describe the behavior of the novel system (Ru/CF catalyst used together with the SRBR) very well. Besides, it was revealed that the catalytic activity as well as the stability of our Ru/CF-SRBR is comparable with the commercial ruthenium decorated carbon catalyst (Ru/AC) under identical reaction conditions. Moreover, all steps from catalyst preparation and catalyst recycling as well as catalytic testing can be performed in an easy, fast and elegant manner without any loss of materials. Briefly, the developed Ru/CF catalyst used together with the SRBR could be used an excellent alternative for the conventional Raney nickel catalyst in a slurry batch reactor and offers an attractive concept with obvious industrial applicability.
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| 10. |
- Ngoc Pham, Tung, et al.
(författare)
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Industrially benign super-compressible piezoresistive carbon foams with predefined wetting properties : from environmental to electrical applications
- 2014
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- In the present work electrically conductive, flexible, lightweight carbon sponge materials derived from open-pore structure melamine foams are studied and explored. Hydrophobic and hydrophilic surface properties - depending on the chosen treatment conditions - allow the separation and storage of liquid chemical compounds. Activation of the carbonaceous structures substantially increases the specific surface area from ,4 m2 g21 to ,345 m2 g21 , while retaining the original three-dimensional, open-pore structure suitable for hosting, for example, Ni catalyst nanoparticles. In turn the structure is rendered suitable for hydrogenating acetone to 2-propanol and methyl isobutyl ketone as well for growing hierarchical carbon nanotube structures used as electric double-layer capacitor electrodes with specific capacitance of ,40 F/g. Mechanical stress-strain analysis indicates the materials are super-compressible (.70% volume reduction) and viscoelastic with excellent damping behavior (loss of 0.69 6 0.07), while piezoresistive measurements show very high gauge factors (from ,20 to 50) over a large range of deformations. The cost-effective, robust and scalable synthesis - in conjunction with their fascinating multifunctional utility - makes the demonstrated carbon foams remarkable competitors with other three-dimensional carbon materials typically based on pyrolyzed biopolymers or on covalently bonded graphene and carbon nanotube frameworks.
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