The transport of Ni(II) ions by the tube menbrane in continual dialysing equipment

Katedra fyzikální chemieDokončená práce s úspěšnou obhajobo

Catalytic oxidative dehydrogenation of isobutyric acid to methacrylic acid in gas phase

Práce se zabývá přípravou a katalytickým testováním katalyzátorů pro oxidativní dehydrogenaci kyseliny isomáselné na kyselinu methakrylovou. Dále pojednává o povrchových vlastnostech pro tuto reakci významných katalyzátorech založených na bázi kyseliny fosfomolybdenové.Dokončená práce s úspěšnou obhajobo

Studium povrchových jevů metodami reakční kinetiky

Práce se zabývá studiem povrchových jevů metodami reakční kinetiky. Přispívá k pochopení mechanismu několika kalytických parciálně oxidačních reakcí za použití aparátu formální reakční kinetiky.Katedra fyzikální chemieDokončená práce s úspěšnou obhajobo

Influence of Substrate Concentration on Kinetic Parameters of Ethanol Dehydration in MFI and CHA Zeolites and Relation of These Kinetic Parameters to Acid–Base Properties

The catalytic activity of zeolites is often related to their acid–base properties. In this work, the relationship between the value of apparent activation energy of ethanol dehydration, measured in a fixed bed reactor and by means of a temperature-programmed surface reaction (TPSR) depending on the amount of ethanol in the zeolite lattice and the value of activation energy of H/D exchange as a measure of acid–base properties of MFI and CHA zeolites, was studied. Tests in a fixed bed reactor were unable to provide reliable reaction kinetics data due to internal diffusion limitations and rapid catalyst deactivation. Only the TPSR method was able to provide activation energy values comparable to the activation energy values obtained from the H/D exchange rate measurements. In addition, for CHA zeolite, it has been shown that the values of ethanol dehydration activation energies depend on the amount of ethanol in the CHA framework, and this effect can be attributed to the substrate clustering effects supporting the deprotonation of zeolite Brønsted centers

Dialysis of nickel sulfate with simultaneous monitoring of changes of solutions dialyzed

The paper deals with dialysis of aqueous solutions of nickel sulfate against aqueous sulfuric acid through a cation-selective membrane NEOSEPTA CM-2 in batch arrangement. The concentration changes of both dialyzed and stripping solutions were monitored spectrophotometrically during the dialysis. At the same time, also the volume changes of both solutions were measured; these changes are due to the osmotic flow of water through the membrane caused by different concentrations of ions in the two solutions dialyzed. The experimental data were evaluated on the basic of a mathematical model based on phenomenological description of the process. Extrapolation from the dependence of total dialysis coefficients on stirring rate of both solutions gave the permeability coefficient of the membrane for the given of NiSO4/H2SO4

Characterization of V-based supported catalysts for oxidative dehydrogenation of propane and partial oxidation of crotonaldehyde

The vanadium oxide supported catalysts (1 wt. % of vanadium on SiO2- (silica, aerosil), TiO1- anatase, ZrO2, Al2O3 - y-alumina, MgO) were prepared by impregnation method and characterized by means of XRF, N2-BETH, H2-TPR methods. By means of H2-TPR, four different VOx units were determined on the catalyst surface - monomer VOx, oligomer VOx units, bulk V2O5 and inter-oxide species for the basic supports. The catalytic activity of these catalysts was tested in two different oxidation reactions: oxidative dehydrogenation of propane and partial oxidation of crotonaldehyde (but-2-enal) in gas phase. The catalyst prepared were active in both studied reactions, but the activity of the catalyst in each reaction was attributed to different catalytic active sites. The reaction rate of both reactions is in correlation with the given types of active sites: monomer VOx exhibited activity in C3H8 oxudative dehydrogenation, on the other hand oligomer units of VOx were active in partial oxidation of crotonaldehyde. Using of the most acid catalysts resulted in high celectivity in oxidative dehydrogenation reaction. Moreover, reaction scheme for crotonaldehyde oxidation was suggested where the formation of furan proceeds via the oxidative dehydrogenation of ciscrotonaldehyde isomerized on an acid site of the catalysts, followed by the possiblesubsequent oxidation of furan to maleic anhydride (furan-(2,5)-dione). The partical oxidation of crotonaldehyde via crotonic acid (but-2-enoic acid) is the second parallel pathway of the formation of maleic anhydride

Kombinovaná oxidativní a ne-oxidativní dehydrogenace n-butanu pomocí VOX částic nanesených na HMS

The combination of oxidative and non-oxidative dehydrogenation of n-butane as an attractive possibility for production of C-4 olefins was studied over VOX based catalyst. Long-term activity and selectivity to desired products could be achieved over the catalysts with well dispersed monomeric vanadium oxide species supported on mesoporous silica support.Kombinace oxidativní a ne-oxidativní dehydrogenace n-butanu jako atraktivní možnost produkce C-4 olefínů byla studována pomocí VOX katalyzátorů. Dlouhodobá aktivita a selektivita na požadovaný produkt mohla být dosažena pomocí katalyzátoru s dobře dispergovanými monomerickými částicemi oxidů vanadu nanesenými na mezoporézní siliku

Vliv substrátové koncentrace na kinetické parametry dehydratace etanolu na MFI a CHA zeolitech a vztah těchto parametrů k acido-bazickým vlastnostem

The catalytic activity of zeolites is often related to their acid-base properties. In this work, the relationship between the value of apparent activation energy of ethanol dehydration, measured in a fixed bed reactor and by means of a temperature-programmed surface reaction (TPSR) depending on the amount of ethanol in the zeolite lattice and the value of activation energy of H/D exchange as a measure of acid-base properties of MFI and CHA zeolites, was studied. Tests in a fixed bed reactor were unable to provide reliable reaction kinetics data due to internal diffusion limitations and rapid catalyst deactivation. Only the TPSR method was able to provide activation energy values comparable to the activation energy values obtained from the H/D exchange rate measurements. In addition, for CHA zeolite, it has been shown that the values of ethanol dehydration activation energies depend on the amount of ethanol in the CHA framework, and this effect can be attributed to the substrate clustering effects supporting the deprotonation of zeolite Bronsted centers.Připravené MFI a CHA zeolity byly testovány jako katalyzátory v dehydrataci etanolu. Vztah mezi aktivační energií dehydratace a H/D výměny byl studován. Jen TPSR metoda byla schopna stanovit hodnoty aktivační energie srovnatelné s aktivační energií získanou z měření rychlosti H/D výměny. Navíc, pro CHA zeolity, se ukázalo, že hodnoty aktivační energie dehydratace závisí na množství etanolu v CHA mřížce a tento efekt byl přiřazen vlivu substrátu na deprotonaci Bronstedových center zeolitu

Study of structural relaxation of Ge-Se and Ge-S chalcogenide glasses

The structural relaxation of chalcogenide glasses related to the viscosity behaviour of their undercooled liquids was studied. Both volume and enthalpy relaxation were studied under isothermal and nonisothermal conditions. It was found that the equilibrium time scale of relaxation experiments are practically the same for both volume and enthalpy relaxation. Relaxation behaviour of studied chalcogenide glasses was described by Tool-Narayanaswamy-Moynihan model and the parameters of this model were determined. The volume and enthalpy relaxation can be sufficiently well predicted by using the same set of TNM parameters. The effective activation energy of TNM model is close to the activation energy of viscous flow of undercooled liguid