The thermal properties of complex carbon-silica adsorbents (carbosils) were investigated using differential thermal analysis. The adsorbents were prepared by pyrolysis of methylene chloride. Pyrolysis reaction on silica surface was carried out at different temperatures (400–700 °C) and at different pressures of CH2Cl2 vapours. Thermal analysis was carried out in air atmosphere. The following parameters characterizing the properties of the adsorbents were determined: carbon content, specific surface area, carbon layer thickness, pore volume, mean pore radius, differential of heats of adsorption ofn-hexane and benzene, and micrographs. The correlation between topography and morphology of carbon deposits (dependent on the parameters of the pyrolysis process) and the courses of DTA and TG curves corresponding to individual carbosils have been determined.
A derivatograph was used for the thermal modification of the surface properties of different silica gels. Analogous investigations were carried out with an isothermal method. The possibility of using the thermal method of temperature programming to modify adsorbents is discussed.
Authors:V. Sydorchuk, S. Khalameida, J. Skubiszewska-Zięba, and R. Leboda
Compositions based on oxides and containing 5–20% w/w of ammonium molybdophosphate have been synthesized by means of different routes. Prepared samples have been studied using nitrogen adsorption–desorption, XRD, DTA–TG, and FTIR spectroscopy. Keggin structure is retained at incorporation of ammonium molybdophosphate into siliceous framework or its deposition on oxide surface and duration following calcinations up to 500 °C. Compositions possess porous structure from micromesoporous to mesomacroporous depending on the preparation method.
Authors:J. Skubiszewska-Zięba, R. Leboda, B. Charmas, W Grzegorczyk, and R. Szmigielski
Thermal analysis was used to study thermal behavior of the sulfonated
ion exchange resin Duolite C20 in the hydrogen, sodium and calcium forms.
The aim of this paper was to prepare spherical carbon adsorbents. SEM and
AFM microscopic methods have been applied to describe their surface characteristics.
It was stated that structural parameters of prepared active carbons depend
on the kind of cation present in the resin. The use of calcium form of Duolite
C20 as the initial polymer precursor allowed to obtain the active carbon with
better yield and better developed pore structure compared with other forms
of this ion exchanger.
Authors:S. Khalameida, V. Sydorchuk, J. Skubiszewska-Zięba, R. Leboda, and V. Zazhigalov
In this article, mechanochemical synthesis of barium titanate from different raw materials was studied. The prepared nanodispersed
powders were investigated by means of XRD, DTA-TG, DSC, FTIR, Raman, UV–VIS, ESR spectroscopy, and low-temperature adsorption
of nitrogen. Barium titanate possessing high specific surface area was produced directly during dry milling from the mixtures
of barium oxides and titanium dioxide low-temperature forms (amorphous and anatase).
Authors:S. Khalameida, J. Skubiszewska-Zięba, V. Zazhigalov, R. Leboda, and K. Wieczorek-Ciurowa
Mechanochemical treatment (MChT) in various media (water, air, ethanol) of the V2O5/ammonium dimolybdate composition at the ratio V:Mo = 0.7:0.3 has been carried out. Physicochemical transformations in this
system have been studied by means of X-ray powder diffraction (XRD) and thermal analysis as well as FTIR spectroscopy. Ammonium
dimolybdate undergoes hydration with formation of 4-aqueous ammonium paramolybdate during the MChT in water. Changes of phase
and chemical composition at activation are determined first of all by nature of medium in which milling was carried out. Maximal
interaction of components occurs during modification of the studied system in water.
Authors:V. Sydorchuk, O. Makota, S. Khalameida, L. Bulgakova, J. Skubiszewska-Zięba, R. Leboda, and V. Zazhigalov
The deposition of molybdenum and vanadium oxides onto fumed silica, titania, and alumina as supports through dry milling has been carried out. The structure of prepared compositions has been investigated by means of XRD, DTA–TG, FTIR, and UV–Vis spectroscopy, nitrogen adsorption. The deposited crystal phases are sufficiently uniformly distributed on support surface. The supported oxides are subjected to dispersion in process of milling to the state of oligomeric or isolated species. Milled bulk and deposited MoO3 (first of all, on alumina) possesses improved catalytic performance in process of epoxidation of 1-octene. Vanadium pentoxide also has higher activity in this process.
Authors:J. Skubiszewska-Zięba, B. Charmas, R. Leboda, V. A. Tertykh, and V. V. Yanishpolskii
Mesoporous titanium-containing silicas with different Titania contents were investigated. The structural parameters of the materials were characterized by low-temperature adsorption/desorption of nitrogen and X-ray diffraction analysis. The thermodesorption of water using the quasi-isothermal thermogravimetry as well as the differential scanning calorimetry were used to characterize thermal and surface properties of these materials. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent/water interfaces were calculated. It was stated that the increase of Titania content causes a gradual decrease of specific surface area and formation of biporous structure inside the tested materials. The water thermodesorption from the surface proceeds in two or three stages, which is connected mainly with pore distribution and TiO2 content. One can observe the increase of the total surface free energy (ΔGΣ) with the increasing TiO2 content, but the largest ΔGΣ value at the adsorbent/strongly bound water interface is exhibited by the adsorbent of intermediate content (30%) of TiO2. Freezing temperature of water contained in the pores of the studied materials is connected largely with their porous structure. Due to the well developed porous structure, the water freezing process is a multi-stage one.