Search results

1

Preparation, Characterization and Catalytic Properties of SBA-15-SO₃H Supported Tungstophosphoric Acid for Esterification Reaction

100%

Erdem B., Erdem S., Çıtak A., Yavru C., Öksüzoğlu R.

Acta Physica Polonica A

|

2017

|

vol. 132

|

issue 3

1041-1044

EN

SBA-15-SO₃H supported tungstophosphoric acid (TPA, H₃PW₁₂O₄₀) mesoporous materials were synthesized by impregnation of TPA into the hydrothermally synthesized SBA-15-SO₃H and the catalytic performances were compared for the esterification reaction. The physical and chemical properties of the catalysts were characterized by XRD, SEM/EDX, FT-IR and N₂ adsorption/desorption techniques. The characterization results show that TPA/SBA-15-SO₃H retained the typical mesoporous structure of SBA-15-SO₃H. The experimental results indicated that TPA/SBA-15-SO₃H is a more efficient catalyst than SBA-15-SO₃H for the esterification reaction. The higher activity of TPA/SBA-15-SO₃H compared with that of SBA-15-SO₃H was consistent with the material having the low pKa value, confirming that the esterification rate was mostly dependent on the acid strength of the additional functional groups of solid acid catalyst. Accordingly, the reason for the catalytic activity difference was simply explicated by the effect of TPA, having low pKa value, affecting the pore structure and the total acidity.

2

Effect of an Adsorbed Atom on Resonant Charge Exchange in Atom Scattering on Metal Surfaces

80%

Taranko R., Taranko E., Wiertel M.

Acta Physica Polonica A

|

2003

|

vol. 103

|

issue 5

483-497

EN

A simple model describing resonant charge transfer between the free-electron metal surface and an atom colliding with it at some distance from another adsorbed atom is presented. The negative ionization probability of a scattered atom is studied within the time-dependent Anderson-Newns model and the time-evolution operator approach. With appropriate models for the considered system, the ionization probability is shown to oscillate with the distance between the adsorbed atom and the collision point of the scattered atom with the metal surface. These oscillations are results of the indirect interaction between the adsorbed and the scattered atoms due to the coupling of both atoms with the metal energy band.

3

Synthesis, Structure, and Catalytic Activity of Au/Poly(ethylene terephthalate) Composites

80%

Mashentseva A., Borgekov D., Zdorovets M., Russakova A.

|

vol. 125

|

issue 6

1263-1267

EN

A standard technique of electroless gold deposition was modified by changing the composition of Ag-based activation solution. This allows preparation of two types of poly(ethyleneterephthalate) (PET) track etched membranes coated entirely with gold after 1, 5, and 24 h of reaction at 4°C. After dissolving the polymer template, gold nanotubes with outer diameter of 70-80 nm were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Reduction of p-nitrophenol to p-aminophenol by sodium borohydride was used to investigate the catalytic activity of as-prepared Au/PET membrane. All experiments were carried out for five consecutive cycles and rate constant of the pseudo-first-order reaction was calculated. It was found that Au/Ag/PET composites prepared after activation for 3 min in Ag-based solution (with potassium sodium tartrate as reducing agent) more effective catalyst (k=0.087 min^{-1}) was obtained when the Au/PET samples activated with ammonia silver nitrate solution (k=0.041 min^{-1}).

4

Resonant Charge Exchange in Atom Scattering on Atoms Adsorbed on Metal Surfaces

80%

Wiertel M., Taranko E., Taranko R.

Acta Physica Polonica A

|

2002

|

vol. 101

|

issue 6

837-855

EN

The ionization probability of an atom scattered from an atom adsorbed on a metal surface has been studied theoretically within the time-dependent Anderson-Newns model. The effect of the metal electron density of states, the band filling as well as the relative position of the scattered atom and adsorbed atom energy levels have been considered and the comparison with the results obtained for clean surfaces has been made.

5

Chemically Modified Activated Carbons as Catalysts of Oxidative Dehydrogenation of n-Butane

80%

Malaika A., Wower K., Kozłowski M.

|

issue 3

459-464

EN

Commercial availability and low price of light alkanes make them very attractive in many branches of industry. Potentially interesting is their use in the process of oxidative dehydrogenation leading to production of olefins. This study was undertaken to characterise the oxidative dehydrogenation of n-butane to 1,3-butadiene (important substrate in production of synthetic rubber and polyamides) taking place over the modified carbon catalysts obtained from peach stones precursor. The catalytic tests were performed in the temperature range 250-450°C at oxygen/n-butane ratio of 1:1. For the majority of the activated carbon samples studied at the lowest temperature the only product was CO_2. At 300°C the products of dehydrogenation of n-butane and side products appeared. With increasing temperature the amount of compounds generated increased and in the group of C4 hydrocarbons the dominant were 1-butene and 1,3-butadiene. The most effective catalyst was the sample oxidised with air, the least effective was the sample modified with ammonium peroxydisulphate.

6

Temperature Dependent Catalytic Activity of Ag/PET Ion-Track Membranes Composites

80%

Borgekov D., Mashentseva A., Kislitsin S., Kozlovskiy A., Russakova A., Zdorovets M.

Acta Physica Polonica A

|

2015

|

vol. 128

|

issue 5

871-874

EN

Electroless deposition has been used to coat finely porous polyethylene terephthalate (PET) track-etched membranes with silver, forming silver nanotubes within the pores with inner and outer diameters of 60 and 100 nm. The sample's X-ray diffraction pattern shows a face-centered cubic crystalline phase of silver with the lattice constant 4.0838 nm. The average size of silver nanoclusters, as obtained from the scanning electron microscopy analysis is about 30 nm which is consistent with the X-ray diffraction results. The temperature dependent catalytic activity of prepared composites is demonstrated for two model reactions such as reduction of 4-nitrophenol (4-NP) and decomposition of hydrogen peroxide. Apparent constant rates and activation energy as well as reusability of catalysts were determined. The developed composite catalyst could be used consecutively for several runs without any damages for 4-NP reduction. For hydrogen peroxide reaction decomposition the reaction rate of the second cycle is reduced 2.4 times. Moreover, the second reuse reduced conversion of H₂O₂ to 54.7% suggests removal of active Ag centers during the first cycle of testing.

7

Structure Characterization and Catalytic Properties of Cr_2O_3 Doped with MgO Supported on MgF_2

80%

Goslar J., Wojciechowska M., Zieliński M., Tomska-Foralewska I., Przystajko W.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 2

323-330

EN

A characterization of double oxide systems containing Cr_2O_3 doped with MgO and supported on MgF_2 was carried out. The catalysts were prepared by impregnation and co-impregnation methods and characterized by the Brunauer-Emmett-Teller method, EPR, and temperature programmed reduction. The results proved the interactions between supported oxides and the presence of spinel-like phase after treatment at 400ºC. Magnesium oxide clearly influences the catalytic activity as well as selectivity of chromium catalysts supported on MgF_2. The MgO-Cr_2O_3/MgF_2 systems were active and selective in the reaction of CO oxidation at the room temperature and in the dehydrogenation of cyclohexene.

8

Structural Characterization of Al_2O_3 and CeO_2 Supported Ni, Co Loaded Ceramic Monolithic Catalysts

80%

Guldal N., Baykara S.

|

vol. 125

|

issue 2

281-284

EN

This paper discusses structural characterizations of monolithic catalysts prepared by incorporating Ni and Co supported over a porous alumina and ceria layer by using respective nitrates and H_2PtCl_6 as precursors. Monolithic catalysts were synthesized by dip-coating of 400 cpsi cordierite ceramic monolithic pieces cut in 20 × 13 mm^2 (L× D) into appropriate solutions of metals, followed by calcination in air at 800C for 4 h. Phases of catalysts were characterized with X-ray diffraction. Morphological analysis and elemental composition were determined by scanning electron microscope and energy dispersive spectroscopy. The specific surface area analysis have been studied using the Brunauer-Emmett-Teller method. Metal contents were determined by inductively coupled plasma optical emission spectrometry.

9

Silicon Etching in XeF_2 Environment

80%

Knizikevičius R.

Acta Physica Polonica A

|

2013

|

vol. 124

|

issue 1

137-140

EN

Enhancement of silicon etching rate in XeF_2 environment is considered by a proposed model, which includes processes of adsorption, activation, chemical reactions, relaxation, desorption, and sputtering. The enhancement of silicon etching rate is explained by considering hydrocarbon molecules from background gas contamination in the vacuum chamber, and assuming that hydrocarbon radicals enhance the etching rate. The composition of the adsorbed layer during silicon etching in XeF_2 environment is calculated. It is found that hydrocarbon radicals intensify reaction of XeF_2 molecules with Si atoms on the surface and that this changes the kinetics of the etching rate. Using the obtained theoretical results the difference in kinetics of the etching rates of first and subsequent run is explained.

10

Carbonaceous Materials Obtained from Sewage Sludge for NO_2 Removal under Wet Conditions at Room Temperature

70%

Pietrzak R.

|

issue 3

487-492

EN

The effect of the processes of carbonisation and activation on adsorbents obtained from sewage sludge and their sorption properties towards NO_2 were studied. Carbonaceous adsorbents were obtained by carbonisation of sewage sludge at 600°C for four different times 30, 60, 90 and 120 min followed by activation of the carbonisates by CO_2 at 800°C for 60 min. Adsorption of NO_2 was carried out in wet air. It has been shown that by appropriate thermal and chemical treatment of sludge, mesoporous adsorbents capable of NO_2 removal can be obtained. The sorption abilities of the carbonised and activated samples to adsorb NO_2 have been shown to increase with increased time of carbonisation and reach maximum for the carbonisation maintained for 90 min. Further increase in this time causes a decrease in the adsorption abilities of the samples. The sorption properties of the carbonisates have been proved to be determined by the chemical character of the surface, while those of the activated samples - by the porous structure.

11

Synthesis, Characterization and Application οf Al,Fe-Pillared Clays

70%

Banković P., Milutinović-Nikolić A., Jović-Jovičić N., Dostanić J., Čupić Ž., Lončarević D., Jovanović D.

Acta Physica Polonica A

|

2009

|

vol. 115

|

issue 4

811-815

EN

Al,Fe-pillared clay was synthesized from domestic clay from Bogovina according to a common procedure: grinding, sieving, Na exchange, pillaring, drying and calcination. Two synthesized samples differing only in calcining conditions were prepared. Phase composition and textural properties of the starting clay and synthesized pillared clays were characterized using X-ray diffraction and physisorption of nitrogen. Catalytic tests were performed using sample with better textural properties being the one submitted to milder calcining conditions. Catalytic wet peroxide oxidative degradation of aromatic compounds phenol and tartrazine on the synthesized catalyst was confirmed showing better efficiency in the case of tartrazine.

12

The Influence of the Au Nanoparticles Dimension on the Photocatalytic Performances of TiO_2-Au Porous Composites

61%

Melinte G., Baia M., Georgescu D., Baia L., Iancu V., Diamandescu L., Popescu T., Cotet L., Barbu-Tudoran L., Danciu V., Simon S.

Acta Physica Polonica A

|

2012

|

vol. 121

|

issue 1

208-210

EN

The influence of Au nanoparticles dimension on the photocatalytic performances of the TiO_2 aerogels-Au composites was evaluated. Structural and morphological peculiarities of the TiO_2 aerogel, unloaded and loaded with 5 and 22 nm Au nanoparticles, were studied by transmission electron microscopy technique, X-ray diffraction and N_2-sorption measurements. UV-Vis diffuse reflectance measurements were performed to determine the band gap energies. The photocatalytic activity was evaluated by monitoring the salicylic acid photodegradation. It was found that the Au nanoparticles promote the anatase phase crystallization and produce the decrease of the specific surface area and band gap energy values. The porous composite with the smallest Au nanoparticles dimension exhibits the best photocatalytic performances.

13

EPR Characteristics of Activated Carbon for Hydrogen Production by the Thermo-Catalytic Decomposition of Methane

61%

Więckowski A., Najder-Kozdrowska L., Rechnia P., Malaika A., Krzyżyńska B., Kozłowski M.

Acta Physica Polonica A

|

2016

|

vol. 130

|

issue 3

701-704

EN

The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750°C), 1123 K (850°C) and 1223 K (950°C). The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ΔBₚₚ, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.

Refine search results

Preparation, Characterization and Catalytic Properties of SBA-15-SO₃H Supported Tungstophosphoric Acid for Esterification Reaction

Effect of an Adsorbed Atom on Resonant Charge Exchange in Atom Scattering on Metal Surfaces

Synthesis, Structure, and Catalytic Activity of Au/Poly(ethylene terephthalate) Composites

Resonant Charge Exchange in Atom Scattering on Atoms Adsorbed on Metal Surfaces

Chemically Modified Activated Carbons as Catalysts of Oxidative Dehydrogenation of n-Butane

Temperature Dependent Catalytic Activity of Ag/PET Ion-Track Membranes Composites

Structure Characterization and Catalytic Properties of Cr_2O_3 Doped with MgO Supported on MgF_2

Structural Characterization of Al_2O_3 and CeO_2 Supported Ni, Co Loaded Ceramic Monolithic Catalysts

Silicon Etching in XeF_2 Environment

Carbonaceous Materials Obtained from Sewage Sludge for NO_2 Removal under Wet Conditions at Room Temperature

Synthesis, Characterization and Application οf Al,Fe-Pillared Clays

The Influence of the Au Nanoparticles Dimension on the Photocatalytic Performances of TiO_2-Au Porous Composites

EPR Characteristics of Activated Carbon for Hydrogen Production by the Thermo-Catalytic Decomposition of Methane