Paula Putanov

Structural and textural properties of the NiOAl2O3 catalyst

Influence of nickel oxide loading (5; 10; 20 wt% Ni) and temperature of heat treatment (400, 700, 1100°C) on the structure, texture and reducibility of coprecipitated NiOAl2O3 catalyst was investigated. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), low temperature nitrogen adsorption (LTNA) and hydrogen reduction confirmed significant changes in physico-chemical properties as the function of mentioned variables. The results showed that the interactions in coprecipitated NiOAl2O3 system are intensive even at 400°C. At 700°C the observed interactions in coprecipitated NiOAl2O3 system are surface area, reducibility and the coordination of Ni(II), while at 1100°C treatment intensive structural and textural changes were registered.

Effects of the method of preparation of MgC2O4 as a support precursor on the properties of iron/magnesium oxide catalysts

Abstract Samples of iron/magnesium oxide catalyst in which magnesium oxalate was used as a common support precursor were prepared alternatively from magnesium nitrate (N) and from magnesium acetate (A) and were tested in hydrocarbon synthesis. Sample N showed the higher activity by one order of magnitude while sample A showed better initial selectivity towards alkenes and a slower initial deactivation. BET, X-ray diffraction (XRD), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and Mossbauer spectroscopy analysis revealed different methods for the formation of the catalyst in all the stages of preparation. Lower activity of sample A was explained by hindered reducibility of the iron component, due to the fact that support effects were affected by individual properties of the support precursor parent materials, as well as by the preparation conditions which they imposed.

Catalytic concept of mineralizing effects

The subject of this work is the mechanism of phase transformations and chemical reactions of pure aluminas and kaolinite doped by Cu2+, Mn3+/Mn2+ and Fe3+/Fe2+ ions. Accelerated phase transformations of metastable aluminas and mullite formation of metal doped samples are explained by catalytic mechanism in terms of Jahn-Teller effect.

Acid Sites in HZSM‐5 Upon Copper Exchange by FTIR and DSC Using Ammonia

The acidity of the parent HZSM-5 zeolite and Cu-HZSM-5 catalyst has been examined by FTIR and DSC using ammonia desorption. Sites of different strength were found in HZSM-5, desorbing ammonia at a relative temperature difference of about 100 °C. Upon copper exchange a fraction of Bronsted sites were transformed to Lewis sites, but the acid strength of the remaining Bronsted sites was increased. Aside from Lewis sites originating from copper exchange, there might be some additional sites formed from precipitated copper. This could explain the quantity of adsorbed NH3 on Cu-ZSM-5 which is higher than theoretically expected. While changing their nature, acid sites of higher strength keep their location, which is manifested by some diffusion effect towards ammonia.

The effects of the architecture of the Ziegler-Natta catalyst on the morphology of polypropylene

Abstract The study of replication effects in propylene polymerization by TiCl3 Ziegler-Natta catalysts is made by comparison of optical microscope (OM) and scanning electron microscope (SEM) pictures of the catalyst and the polymer, obtained either in standard conditions or in absence of hydrogen, with corresponding values of “calculated” replication factor (Rc) and “found” replication factor (Rf). It has been shown that under given conditions replication is evident both in structure and substructure details; it is not influenced noticeably by polymerization pressure, but may depend on the time of polymerization in a way dependent on the architecture of the catalyst.

Ht-XRD, DSC and X-ray microprobe analysis of Cu and Al promoted Fe/MgO

Promoter effects of Cu were related to the shifts of the temperature of iron reduction, to the changes of iron particles in reaction conditions and to Cu−Fe distribution over the support. “Skin effect” of Al promoter was checked by the analysis of Al distribution.AbstractВлияние промотера Cu сказывалось на сдвиге температуры восстановления железа, изменении частиц железа в условиях восстановления и в распределении Cu−Fe на носителе. “Кожный эффект” промотера Al проверяли анализом распределения Al.