CuO/ceria and CuO/Y-doped ceria catalysts were synthesized. The Y-modified supports (1.0, 2.5 and 5.0 wt% Y2O3) were prepared by coprecipitation. CuO (3 wt% Cu) was loaded by deposition-precipitation. Having in mind the known effect of Y3+ modification for the generation of oxygen vacancies in ceria, its positive role on the water-gas shift (WGS) performance was expected. However, the catalytic test showed a trend of decreased WGS activity by increasing the Y-dopant amount, nevertheless that the differences were not very substantial. On the basis of XRD, XPS, EPR, Raman spectroscopy and H-2-TPR results the explanation related to the key role of the oxygen mobility influenced by Y-doping could be proposed. The reason of the inferior WGS performance with increasing Y-content would be the higher amount of surface oxygen vacancies around Y3+ ions which disturbed the Cu-O-vac-Ce active sites for WGS reaction. Though, during the long run catalytic tests in WGS reaction a positive effect of Y-doping for improved stability of CuO/ceria catalysts was evidenced. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The formation of the inclusion complexes of five thioureea derivatives both with α- and β-cyclodextrins is studied. The most stable conformers of these thioureea derivatives are selected. The deformation, binding and stabilization energies are evaluated by DFT calculations considering the dispersion corrections at the level D3. Basis set superposition errors were computed by counterpoise procedure. It is proved that a thioureea derivative can be inserted both in the cavity of a single cyclodextrin and of a cyclodextrin dimer, forming in both cases a soluble supramolecular structure. In the latter case the stability of the inclusion complex is mainly due to interaction between the two cyclodextrins. The formation of a supramolecular structure composed by one thioureea derivative and two cyclodextrins is possible by the insertion of a thioureea derivative in a cyclodextrin dimer as well as by the addition of a second cyclodextrin to an inclusion complex formed by one thioureea derivative and one cyclodextrin.

Gold catalysts on Y-doped ceria dispersed on high surface area gamma-Al2O3 were synthesized and tested in preferential CO oxidation in hydrogen rich stream (PROX). The effect of ceria loading (10, 20 or 30 wt%) was studied. The gold catalyst with the lowest ceria amount exhibited the highest PROX activity. The addition of Y2O3 (1 wt%) led to improved performance. The most favorable effect was observed in the sample with 20 wt% ceria amount. This gold catalyst showed good PROX activity and stability in the presence of CO2 and water. Catalysts characterization by XRD, HRTEWHAADF, XPS and H-2-TPR was used to elucidate the relationship between the chemical composition, state of gold, support features and catalytic properties. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

The reducibility of Au catalysts on CeO2 supports doped with 1 and 2.5 mass% Y2O3 by two types of preparation methods (impregnation and co-precipitation) has been studied by temperature-programmed reduction and compared with that of pure Au/CeO2. The kinetic parameters of reduction were determined simulating each reduction process. The capacities of these catalysts to retain oxygen have been evaluated by temperature-programmed desorption. The catalytic activities in water gas shift reaction were determined measuring CO conversion between 413 and 623 K. The catalytic performances of all these catalysts were explained in terms of mobility of the oxygen ions of the CeO2 lattice.

New mixed-ligand Co(II) and Ni(II) complexes with enrofloxacin and 1,10-phenanthroline/8-hydroxyquinoline have been synthesized. The metal complexes have been characterized by elemental analyses, molar conductance, FT-IR, solid reflectance, magnetic moment, thermal analyses, X-ray powder diffraction (XRD) and SEM analysis. Conductance measurements indicate that all the complexes are non-electrolytes. Spectral IR data showed that the deprotonated enrofloxacin is bidentately bound to the metal ion through the pyridone oxygen and the carboxylated oxygen; 1,10-phenanthroline acts as neutral bidentate ligand coordinated through two nitrogen donor atoms, and the deprotonated 8-hydroxyquinoline is coordinated through nitrogen and oxygen donor atoms. The geometry of the complexes was elucidated with solid reflectance UV and magnetic moments. Thermal analysis recorded that TG/DTG/DSC experiments revealed the thermal stability of metal complexes and confirmed their compositions suggested by the analytical data. In addition to experimental data, a molecular modelling study has been performed to establish the optimized geometries of metal complexes. The XRD analysis of powders evidences the nanocrystalline nature of all complexes. The results are in agreement with molecular modelling data. SEM images revealed highly agglomerated particles with irregular shape with sizes in the micrometre range. The ligand and their metal complexes were screened for their antimicrobial activity against Escherichia coli 25922, Staphylococcus aureus 25923, Pseudomonas aeruginosa 27853 and Candida albicans 10231. The metal complexes were also investigated for their cytotoxicity using an in vitro assay.

The reducibility of Au catalysts on CeO2 supports doped with 1 and 2.5 mass% Y2O3 by two types of preparation methods (impregnation and co-precipitation) has been studied by temperature-programmed reduction and compared with that of pure Au/CeO2. The kinetic parameters of reduction were determined simulating each reduction process. The capacities of these catalysts to retain oxygen have been evaluated by temperature-programmed desorption. The catalytic activities in water gas shift reaction were determined measuring CO conversion between 413 and 623 K. The catalytic performances of all these catalysts were explained in terms of mobility of the oxygen ions of the CeO2 lattice.

When there is a saturated homogeneous ternary mixture, composed by two immiscible liquids and an amphiphilic one, it is possible to prepare a second one starting from the first. The compositions of the two mixtures are uniquely determined if their solubility curve is known. In this work, one describes a new procedure to determine these compositions. The procedure is applied to a ternary system known in literature: water + n-propanol + n-butanol at 294.15 K and atmospheric pressure. Comparing the results obtained by the new procedure to those determined by measuring the refractive index one concludes that the two analysis methods have similar accuracies.

The WGS activity of gold catalysts on ceria doped with Pr (5 and 10 aff Pr) was studied. The supports were synthesized by impregnation (IM) and microemulsion (ME) method. Gold (3 wt%) was introduced by deposition-precipitation method. The samples were characterized by means of XRD, TEM, XPS and TPR measurements. The catalytic activity in WGSR of fresh catalysts did not differ significantly. After reoxidation following the first catalytic run, the activity of gold catalyst on IM support with 5 at% Pr increased, while a significant drop in activity of the gold catalyst on ME support containing 10 at% Pr was registered. In the latter case the presence of very small gold particles were responsible for the initial WGS activity, while their agglomeration after the catalytic reaction caused the observed activity decrease. In the former case the higher activity during the second catalytic run could be explained by: (i) the redox behavior, showing that only in this case the most mobile oxygen could be fully recovered; (ii) the morphology of the support, revealing better crystallization of the support after WGS catalytic test as compared to the presence of partially amorphous ceria in the fresh gold catalyst. (C) 2015 Elsevier B.V. All rights reserved.

Very high catalytic activity in complete benzene oxidation (CBO) was observed over gold catalyst on prepared by mechanochemical mixing CeO2–Co3O4 (10wt.% of dopant). It was significantly higher compared with gold catalysts supported on ceria doped with 5wt.% or 15wt.% Co3O4. The presence of Co3O4 phase and Co-modified ceria was observed by XRD data. The HRTEM/HAADF results revealed that the doping with 10wt.% Co3O4 was favorable for the higher gold dispersion. The highest reducibility, i. e. ability of oxygen supplying of gold catalyst on ceria doped with 10wt.% Co3O4 correlates with the highest oxidation activity in CBO.

Gold catalysts supported on ceria doped with FeO x were studied. The mixed supports were synthesized by two methods: co-precipitation (CP) or mechanochemical activation (MA). Depending on the preparation method, the structure of the mixed supports was different: using CP, only a Fe-modified ceria phase exists, while supplementary to ceria, a second hematite phase presents in the case of MA preparation. The reduction behavior of the gold catalysts and the initial supports was commented on the basis of hydrogen consumption and kinetic parameters of the individual reduction process. Their assignment was proposed using also the data of Mössbauer measurements. It was established that the existing separate Fe-containing phase could participate in a redox process at relatively low temperatures (LTs) and it could be promising for improvement of the catalytic performance of the mechanochemically prepared gold catalyst.

From the peculiarities of Temperature-programmed reduction (TPR) method and using the Sestak–Berggren conversion function, we describe first the TPR curve simulation procedure. The influence of the Sestak–Berggren exponents on the TPR peak maximum and shape is demonstrated, by analyzing several synthetic TPR profiles. Finally, the kinetic parameters of Au/CeO2 promoted with yttrium as well as those of Au/CeO2–Al2O3 promoted with V2O5 are discussed.

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman’s iso-conversional method and another one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti and Baiker, the Friedman’s method, although gives values of the activation energy smaller than the real values, indicates a very similar dependence of these on the reduction degree. On the basis of some synthetic data one shows that the errors are very large when these recommendations are neglected, being possible to determine a false dependence on the degree of reduction.

Dehydrogenation of 1,4-butanediol to 2,3-dihydrofuran over kaolin-supported Co and Co–Au catalysts has been investigated. Catalytic test and XRD analysis show that the presence of metallic cobalt with hexagonal structure is favourable for selectivity to 2,3-dihydrofuran of the reaction studied. It was established by XPS method that an optimal for the reaction selectivity Co0/Co2+ ratio in Co/kaolin and Co–Au/kaolin catalysts exists. Quantum chemical calculations suggest that the initial step of 1,4-butanediol dehydrogenation on cobalt catalyst surface may be the cleavage of OH bond to form alkoxide species on Co2+ ion. Based on the effect of metallic and ionic cobalt on the catalyst selectivity, it could be presumed that both cobalt species are involved in the rate-determining step in dehydrogenation of 1,4-butanediol into 4-hydroxybutanal intermediate.

The reduction behaviour of nine gold-vanadia/ceria and vanadia/ceria catalyst samples prepared by different methods has been studied using the temperature programmed reduction method. Fitting each computed TPR pattern to the experimental one, the kinetic parameters and the hydrogen consumption corresponding to all individual reduction processes were determined. It was shown that the gold content of every sample is reflected both by the values of parameters of the Sestak-Berggren function and by the dependence of the activation energy of reduction on the degree of reduction.The reduction behaviour of every sample has been studied taking into account the composition of each sample as well as the values of the kinetic parameters together with those of the Sestak-Berggren exponents and the dependence of the activation energy on the degree of reduction. It is shown that upon comparing the TPR results it is possible to select the most active catalytic systems in the complete oxidation of hydrocarbons. (C) 2004 Elsevier B.V. All rights reserved.

The temperature-programmed reduction of Cu/Fe 3 O 4 in hydrogen was analyzed. The values of the apparent activation energy characteristic of this process were determined using the most widely known iso-conversional methods. In all cases a variation of the apparent activation energy with the degree of reduction was shown. The values of the pre-exponential factor were evaluated assuming various kinetic models. In all cases both the apparent activation energy and pre-exponential factor depend on the degree of reduction. Their values vary according to the relationship of the compensation effect : ln A = a · E + b. The analysis of the data suggested that the reduction of Cu/Fe 3 O 4 takes place passing through three consecutive stages, in which the reduction mechanisms are different. The existence of these reduction stages was tentatively explained taking into account the possible structural changes, which accompany the increase of the reduction degree.

The temperature programmed reduction (TPR) method has been used to study the effect of residual sulfur on the reducibility of α-Fe2O3 prepared both using iron(II) and iron(III) sulfate. The values of the kinetic parameters characteristic of the reduction of the hematite to magnetite, of the magnetite to metallic iron, as well as of the processes involved in the elimination of the sulfate anions, were evaluated by simulation of the TPR curves. The effect on the reducibility of α-Fe2O3 is reflected in the values of the kinetic parameters when the sulfur is dispersed into the sample's bulk. If the sulfur exists only on the surface, its influence on the reducibility of the sample is mainly due to the fact that the reduction of the hematite starts only after the elimination of the sulfate anions begins.

Kinetic parameters were evaluated by simulation of experimental temperature-programmed reduction spectra of α-Fe2O3 and Auα-Fe2O3 systems. It was established that gold influences only the first reduction step Fe2O3 → Fe3O4, the pre-exponential value for Auα-Fe2O3 being substantially higher than that for α-Fe2O3. The presence of hydroxyl coverage entails decreasing of the activation energy of this step.

The results of some temperature programmed reduction experiments are analyzed. One evidences the effects of the gold nanoparticles on the reduction behaviour of several gold promoted metal oxide catalysts: α-Fe2O3, V2O5/TiO2, V2O5/ZrO2 and V2O5/CeO2. The effects of gold particles on the values of the kinetic parameters are also analyzed.