Bismuth Oxychloride Nanoplatelets by Breakdown Anodization

Herein, the synthesis of BiOCl nanoplatelets of various dimensions is demonstrated. These materials were prepared by anodic oxidation of Bi ingots in diluted HCl under dielectric breakdown conditions, triggered by a sufficiently high anodic field. Additionally, it is shown that the use of several other common diluted acids (HNO3, H2SO4, lactic acid) resulted in the formation of various different nanostructures. The addition of NH4F to the acidic electrolytes accelerated the growth rate resulting in bismuth based nanostructures with comparably smaller dimensions and an enormous volume expansion observed during the growth. On the other hand, the addition of lactic acid to the acidic electrolytes decelerated the oxide growth rate. The resulting nanostructures were characterized using SEM, XRD and TEM. BiOCl nanoplatelets received by anodization in 1 M HCl were successfully employed for the photocatalytic decomposition of methylene blue dye and showed a superior performance compared to commercially available BiOCl powder with a similar crystalline structure, confirming its potential as a visible light photocatalyst

Struktura a reaktivita zeolitů modifikovaných přechodnými kovy

Hlavní přínos prací předložených v habilitační práci je v potvrzení rozdílné energie vazby Cu+ iontů v jednotlivých kationtových polohách určené z rozdílného desorpčního tepla CO-TPD technikou a rozdílné redukovatelnosti Cu iontů na základě studia modelových Cu-zeolitů.Dokončená práce s úspěšnou obhajobo

Catalysis in Zeolites and Zeotypes—Cornerstone of Chemical Industry and Permanent Subject of Research

Mankind has been aware of zeolites since 1756, when the Swede, Axel Fredrik Cronstedt (1722–1765), observed the strange behavior of a certain natural mineral (probably stellerite with some amounts of stilbite) [...

Povrchové jevy na pevných látkách

Cílem těchto skript, je poskytnout magisterským studentům přehled základních znalostí o adsorpčních jevech a jejich zkoumání. teoretické části jsou shrnuty základní přístupy k popisu adsorpčních rovnováh a odvození základních, a v praxi nejčastěji užívaných, vztahů. Učební text je doplněn rozborem reálných experimentálních výsledků a jejich interpretace, modelovými výpočty a příklady pro procvičení získaných znalostí

Catalytic oxidation of hydrocarbons on zeolites

Katedra fyzikální chemieDokončená práce s úspěšnou obhajobo

Effect of zeolite matrices on the redox and catalytic properties of the Cu ions

Cílem disertace bylo proniknout do vztahů mezi strukturou a redox vlastnostmi Cu iontů ve vysokosilikátových zeolitech a jejich aktivitou v oxidaci propanu.Dokončená práce s úspěšnou obhajobo

Oxidative dehydrogenation of propane by N2O over Fe-MFI zeolities with various concentration of iron and prepared by different methods

The catalitic performance of FeMFI zeolites in oxidative dehydrogenation of propane (ODHP) with N2O and O2 is discussed in this paper. A set of Fe-MFI samples was investigated which differed in the concentration of iron, ways of preparation and activation. Iron species in zeolites do not significantly activate molecular oxygen, as all the investigated zeolites exhibited low activity in the propane oxidation with molecular oxygen. The yield of propene reached a maximum of 2 %. On the other hand, particularly over steamed Fe-zeolites, propane oxidation with nitrous oxide resulted in high propene yields, and formation of propanal and acetone. The reaction pathway. Sites exhibiting acidic properties (Broensted and Lewis sites), if present, yield significant amount of C4 hydrocarbons and aromates, and are responsible for the catalysts deactivation by coke. Steam-activated Fe-zeolites exhibited much higher activity than calcined zeolites and a lower rate of deactivation caused by lower concentration of Broensted acid sites. The propene yields range from 10 to 20 % depending on the population of the individual Fe species. We suggest that a part of well-isolated Fe species is extremely active in the propane conversion to propene, whereas there is no evidence for the activity of the oxide-like species

Příprava a charakterizace nanodestiček grafen-oxidu funkcionalizovaného thiosemicarbazidem pro odstranění olovnatých kationtů

A facial and novel method for removal of Pb+2 based on the appealing interaction between thiosemicarbazide-modified graphene oxide nanosheets and Pb+2 is reported in this work. Textural and chemical characterization of graphite, graphene oxide, esterified graphene oxide and thiosemicarbazide-modified graphene oxide nanosheets was investigated using thermogravimetric analysis (TGA), nitrogen adsorption at - 196 degrees C, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Adsorption of Pb+2 was confirmed by Langmuir model with maximum adsorption capacity of 192.7 mg/g for thiosemicarbazide-modified graphene oxide nanosheets at 27 degrees C and initial pH value of 5.0. Kinetic studies showed that the adsorption of lead ions on the solid adsorbents follows pseudo-first order and Elovich kinetic models. Regeneration of graphene oxide, esterified graphene oxide and thiosemicarbazide-modified graphene oxide nanosheets was studied using different eluents (H2O, 0.1 M HCl, 0.1 M EDTA) at different pH values. Both of disodium salt of ethylenediaminetetraacetic acid (EDTA) and HCl solutions (0.1 M) are efficient eluents to desorb lead cations from the solid adsorbent surface. Desorption efficiency of HCl solution decreases with increasing its pH value.V této práci je oznámena nová metoda odstranění Pb+2 založená na interakci mezi nanodestičkami grafen oxidu modifikovaného thiosemikarbazidem a Pb+2

On the effect of cobalt loading on catalytic activity of Co-BEA zeolites in ethane oxidative dehydrogenation and ammoxidation

Metal ion species introduced into zeolite seem to be attractive redox catalysts. There is a great effort to convert light paraffins into more valuable chemicals. Zeolites of BEA type modified by cobalt exhibited the highest activity and selectivity in ammoxidation and oxidative dehydrogenation of ethane in comparison with other high-silica zeolite matrices modified by cobalt. In this paper a set of sample with different cobalt loading has been prepared and their catalytic activity was compared. It was found that the catalytic activity was increased with the increasing cobalt concentration up to molar ratio Co/Al 0.5 in oxidative dehydrogenation. At higher level of ion exchange there was observed a dramatic decrease in activity, , which can be ascribed to formation of oxide clusters of cobalt. Cobalt oxides cause the non-seslctive oxidation of ethane to carbon oxides. On the contrary, in ammoxidation of ethane the catalysts exhibited the activity independent of cobalt content up to Co/Al molar ratio 0.4, which is much higher than activity in oxidative dehydrogenation. This enhanced activity is explained by formation of ammonia adsorption complexes or presence of reactive surface oxygen rising from decomposition of nitrous oxide produced by oxidation of ammonia. At high cobalt loading the activity has the similar history as in oxidative dehydrogenation of ethane. Besides bare cobalt ions and cobalt oxide clusters, the oxygen bridged cobalt dimers are formed in the Co-BEA zeolites with cobalt loading close to theoretical exchange level. These complexes exhibit specific reactivity, which differs from both highly dispersed cobalt oxide and atomically dispersed CO2+ ions in the cationic site of BEA framework