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.
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.
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: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:V. Yanishpolskii, A. Pavlenko, V. Tertykh, V. Il'in, R. Leboda, and J. Skubiszewska-Zieba
Mesoporous titanium-containing silicas with TiO2 contents from 1 up to 70 mol% were prepared. The obtained samples have been characterized by the powder X-ray diffraction
data, the diffuse reflectance infrared Fourier transform method, and nitrogen adsorption at 77 K. Specific surface area, total
pore volume, distribution pore volume on pore sizes were determined from nitrogen adsorption isotherm for synthesized titanosilicas.
Authors:V. Sydorchuk, S. Khalameida, V. Zazhigalov, J. Skubiszewska-Zięba, and R. Leboda
Physicochemical processes during thermal treatment of vanadium and phosphorus oxides mixture (1) as well as with diammonium
hydrophosphate (2) in the closed system (autoclave) have been studied. In the first case, at 300 °C, the defective structure
γ-VOPO4 is formed and in the second case, there was established possibility of synthesis of vanadyl hydrophosphate—the precursor
of vanadyl pyrophosphate (the catalyst of n-butane oxidation to maleic anhydride). At the same time, various phases of mixed ammonium and vanadium phosphates were obtained
at lower and higher temperatures.
Authors:Yu. Trach, V. Sydorchuk, O. Makota, S. Khalameida, R. Leboda, J. Skubiszewska-Zięba, and V. Zazhigalov
Deposited catalysts composition H3PMo12O40/SiO2 and Ag/H3PMo12O40/SiO2 have been synthesized on the basis of fumed silica, including milling technique. Physical–chemical characteristics of prepared catalysts have been studied by means of XRD, DTA-TG, FTIR, UV–Vis spectroscopy, and adsorption of nitrogen. Catalysts possess meso- or meso-macroporous structure and contain deposited Keggin heteropolycompounds. Deposition of heteropolycompounds on support with high specific surface area results in increase of selectivity to epoxide in epoxidation reactions. The use of milling during catalyst synthesis leads to further growth of selectivity of epoxides formation.