Beata Michalkiewicz

Low temperature growth of carbon nanotubes from methane catalytic decomposition over nickel supported on a zeolite

Multi-walled carbon nanotubes from 8 to 63 nm in diameter and from 60 to 413 nm in length, were synthesized over nickel supported on a zeolite by the chemical vapor deposition of methane in the relatively low temperature range 400-550 degrees C. The carbon deposited was analyzed by x-ray powder diffraction, Raman spectroscopy, and scanning and transmission electron microscopy. The effects of the reaction temperature on the carbon nanotube formation and relative purity were evaluated.

A new polymeric complex of silver(I) with a hybrid pyrazine–bipyridine ligand – synthesis, crystal structure and its photocatalytic activity

The 2,3-bis(6′-methyl-2,2′-bipyridin-6-yl)pyrazine ligand L reacts with trifluoromethanesulfonate silver(I) to give a coordination polymer {[AgL](CF3SO3)}n in which metal ions are in a distorted tetragonal pyramidal coordination geometry. The complex has been characterized by spectroscopic techniques, elemental analysis, X-ray diffraction, and UV-Vis spectroscopy. The methylene blue (MB) degradation was studied using UV-Vis spectrophotometry. After 400 min of exposure to UV light MB was completely decomposed. Degradation of MB after exposure to sunlight was considerably slower: 34% after 400 min and 90% after 133 h. Photodegradation of the dye follows second-order kinetics. {[AgL](CF3SO3)}n is an active photocatalyst for MB degradation under UV-Vis and sunlight irradiation.

Zeolite membranes for hydrogen production from natural gas: state of the art

Currently, hydrogen is produced industrially by processes requiring high energy consumption, especially by cracking fossil fuels and by splitting water. In recent years, research has been devoted to the use of membrane catalytic reactors in order to achieve higher hydrogen yield. Zeolite membranes have been shown to be very promising as they are stable to contaminants (such as H2S) and do not have the disadvantages that palladium and silica membranes exhibit. The aim of this work is to summarize the state of the art of hydrogen selective zeolite membranes that can be applied for hydrogen separation after syngas production from reforming streams. In addition, zeolite membrane applications in membrane reactors for hydrogen production are discussed.

Synthesizing Multi-walled Carbon Nanotubes over a Supported-nickel Catalyst

Supported-NiO catalysts obtained with grinded and impregnated method were tested in the synthesis of carbon nanotubes by catalytic decomposition of methane at 650°C. Catalytic activity was characterized by the conversion levels of methane during the first 15 minutes of the reaction. Ni catalysts supported on Al2O3, MgO, SiO2 and Al2O3-SiO2 showed activities for the methane decomposition, whereas the catalysts supported MgO were less active. The yield and quality of carbon nanotubes were determined using transmission electron microscopy and Raman spectroscopy. The catalytic performance of the supported-NiO catalysts and the outer diameter of carbon nanotubes produced were discussed based on the X-ray diffraction results of the catalysts.

Titanium dioxide modified with various amines used as sorbents of carbon dioxide

In this study, titanium dioxide was modified with various amines through hydrothermal treatment for adsorption of CO2. The carbon dioxide adsorption performance of the prepared samples was measured using an STA 449 C thermobalance (Netzsch Company, Germany). The morphological structures, functional groups and elemental compositions of the unmodified and amine-modified titanium dioxide sorbents were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR/DR) and scanning electron microscopy (SEM), respectively. The results showed that modification of TiO2 with amines through hydrothermal treatment is a simple method to prepare CO2 sorbents with high adsorption capacities. Moreover, the results revealed that TEPA-modified titanium dioxide shoved the highest adsorption capacity, enabling an increase in CO2 uptake from 0.45 mmol CO2 g−1 in the case of raw TiO2 to 1.63 mmol CO2 g−1. This result could be indirectly related to the fact that TEPA has the highest amino group content among the three amines used in our research. Additionally, durability tests performed by cyclic adsorption–desorption revealed that TEPA modified titanium dioxide also possesses excellent stability, despite a slight decrease in adsorption capacity over time.

Bromine catalyst for the methane to methyl bisulfate reaction

Abstract A catalytic system KBr - oleum is effective at catalyzing the selective oxidation of methane to methanol via. methyl bisulfate. The influences of methane pressure, sulfur trioxide and temperature on turnover frequency were investigated.

An analysis of the effect of the additional activation process on the formation of the porous structure and pore size distribution of the commercial activated carbon WG-12

The paper presents the results of research into the effects of the additional activation process of the commercial activated carbon WG-12 with KOH, ZnCl2, KOH/ZnCl2 and K2CO3 as activating agents on the formation of the porous structure and the adsorptive properties of that material. The numerical analyses were carried out on the basis of the isotherms of nitrogen adsorption with the use of the method based on the Brunauer-Emmett-Teller, the Dubinin-Radushkevich equations, the non-local and the quenched solid density functional theories as well as the LBET method with the unique fast multivariate procedure of porous structure identification and the new LBET class adsorption models. Also, the research in question yielded information regarding the usefulness of the said methods of carbonaceous adsorbent porous structure description for practical technological applications and scientific research, as well as the possibilities to make practical use of the research results.

Adsorption of carbon dioxide on TEPA-modified TiO2/titanate composite nanorods

A titanate–TiO2 composite was obtained through hydrothermal treatment of TiO2 in KOH solution. The presence of a titanate phase was confirmed by X-ray diffraction (XRD), whereas scanning electron microscopy (SEM) measurements showed the porous nanorod structure of the material. The obtained nanorods were treated with tetraethylenepentamine (TEPA). Such synthesized sorbents were applied for CO2 removal. The CO2 capacity under a pressure of 1 bar and at 80 °C was 0.47, 0.34, and 3.11 mmol g−1 for the starting TiO2, the titanate–TiO2 composite and the TEPA–titanate–TiO2 composite (27.4 wt% of TEPA), respectively. The experimental isotherms of CO2 were analysed using the Langmuir, Freundlich, Sips, Toth, Unilan, Redlich–Peterson, Radke–Prausnitz, Dubinin–Radushkevich, Temkin and Pyzhev, and Jovanovich models. The error sums of squares (SSR) function was used to test the fit of the models. The analysis revealed that the Sips isotherm is the best-fitting model for the CO2 adsorption on the starting TiO2, whereas the Freundlich equation should be used to describe the CO2 adsorption isotherm on the titanate–TiO2 composite. The CO2 adsorption on the TEPA-modified sorbents was proposed to be described using the Sips isotherm for physical sorption and the modified Sips model for chemical sorption. The calculated isosteric heat of adsorption was found to be ≈46 kJ mol−1, which is about two times higher than the heat of CO2 absorption in liquid TEPA reported in the literature (i.e. ≈85 kJ mol−1). Therefore, it was concluded that the TEPA–titanate–TiO2 composite is an attractive alternative for liquid amines due to the lower energy of regeneration in the sorption–desorption process. The material was proved to be stable during multiple sorption–desorption cycles. Moreover, its thermal stability up to 150 °C was confirmed by thermogravimetric analysis (TGA). All these features make it a promising alternative for sorbents based on liquid amines.

Increase the Microporosity and CO2 Adsorption of a Commercial Activated Carbon

Microporous carbons prepared from commercial activated carbon WG12 by KOH and/or ZnCl2 treatment were examined as adsorbents for CO2 capture. The micropore volume and specific surface area of the resulting carbons varied from 0.52 cm3/g (1374 m2/g) to 0.70 cm3/g (1800 m2/g), respectively. The obtained microporous carbon materials showed high CO2 adsorption capacities at 40 bar pressure reaching 16.4 mmol/g.

A Comparison of Hydrogen Storage in Pt, Pd and Pt/Pd Alloys Loaded Disordered Mesoporous Hollow Carbon Spheres

Comprehensive study to evaluate the ability of hydrogen uptake by disordered mesoporous hollow carbon spheres doped witch metal such as Pt, Pd or Pt/Pd was conducted. They were synthesized facilely using sonication and then calcination process under vacuum at the temperature of 550 °C. The effect on hydrogen sorption at neat-ambient conditions (40 °C, up to 45 bar) was thoroughly analyzed. The results clearly revealed that metal functionalization has a significant impact on the hydrogen storage capacity as the mechanism of gas uptake depends on two factors: metal type and certain size of particles. Thus, functionalized spheres adsorb hydrogen by physisorption forming metal hydrides or metal hydrides combined with hydrogen spillover effect. As a result, a sample with narrower distribution of nanoparticles and smaller specific size exhibited enhanced hydrogen uptake.