Precipitated K-promoted Co-Mn-Al mixed oxides for direct NO decomposition: Preparation and properties

Direct decomposition of nitric oxide (NO) proceeds over Co-Mn-Al mixed oxides promoted by potassium. In this study, answers to the following questions have been searched: Do the properties of the K-promoted Co-Mn-Al catalysts prepared by different methods differ from each other? The K-precipitated Co-Mn-Al oxide catalysts were prepared by the precipitation of metal nitrates with a solution of K2CO3/KOH, followed by the washing of the precipitate to different degrees of residual K amounts, and by cthe alcination of the precursors at 500 degrees C. The properties of the prepared catalysts were compared with those of the best catalyst prepared by the K-impregnation of a wet cake of Co-Mn-Al oxide precursors. The solids were characterized by chemical analysis, DTG, XRD, N-2 physisorption, FTIR, temperature programmed reduction (H-2-TPR), temperature programmed CO2 desorption (CO2-TPD), X-ray photoelectron spectrometry (XPS), and the species-resolved thermal alkali desorption method (SR-TAD). The washing of the K-precipitated cake resulted in decreasing the K amount in the solid, which affected the basicity, reducibility, and non-linearly catalytic activity in NO decomposition. The highest activity was found at ca 8 wt.% of K, while that of the best K-impregnated wet cake catalyst was at about 2 wt.% of K. The optimization of the cake washing conditions led to a higher catalytic activity.Web of Science97art. no. 59

Co-Mn-Al mixed oxides promoted by K for direct NO decomposition: Effect of preparation parameters

Fundamental research on direct NO decomposition is still needed for the design of a sufficiently active, stable and selective catalyst. Co-based mixed oxides promoted by alkali metals are promising catalysts for direct NO decomposition, but which parameters play the key role in NO decomposition over mixed oxide catalysts? How do applied preparation conditions affect the obtained catalyst's properties? Co4MnAlOx mixed oxides promoted by potassium calcined at various conditions were tested for direct NO decomposition with the aim to determine their activity, stability and selectivity. The catalysts were prepared by co-precipitation of the corresponding nitrates and subsequently promoted by KNO3. The catalysts were characterized by atomic absorption spectrometry (AAS)/inductive coupled plasma (ICP), X-ray photoelectron spectrometry (XPS), XRD, N-2 physisorption, temperature programmed desorption of CO2 (TPD-CO2), temperature programmed reduction by hydrogen (TPR-H-2), species-resolved thermal alkali desorption (SR-TAD), work function measurement and STEM. The preparation procedure affects physico-chemical properties of the catalysts, especially those that are associated with the potassium promoter presence. The addition of K is essential for catalytic activity, as it substantially affects the catalyst reducibility and basicity-key properties of a deNO catalyst. However, SR-TAD revealed that potassium migration, redistribution and volatilization are strongly dependent on the catalyst calcination temperature-higher calcination temperature leads to potassium stabilization. It also caused the formation of new phases and thus affected the main properties-S-BET, crystallinity and residual potassium amount.Web of Science97art. no. 59

Students´ Taxation in the Czech Republic

Bakalářská práce se zaměřuje na zdanění příjmů studentů. První část obsahuje daňovou teorii, kde jsou vysvětleny základní informace ke zdaňování příjmů. V druhé části najdeme obecné informace k dani z příjmů fyzických osob, předmět daně z příjmů a výpočet daňové povinnosti. Třetí část obsahuje jednotlivé druhy pracovních poměrů. Čtvrtá a pátá část se pak zabývá systémem sociálního a zdravotního pojištění. V poslední šesté části jsou uvedeny praktické příklady výpočtu daňové povinnosti. Cílem práce je nalezení optimálního zdanění příjmů studentů a zhodnocení výhodnosti jednotlivých smluv.The bachelor’s thesis focuses on the taxation of revenues students. The first part contains the taxation theory, where explains the basic information to the taxation of incomes. In the second part we find general information on income tax of persons, subject to tax on income and tax calculation. The third part contains different kinds of tax. The fourth and fifth part deals with the system of social and health insurance. In the last sixth part provides practical examples of calculation of tax liability. The goal is to find the optimal taxation of revenues students and evaluation of the advantages of individual contracts.

Co–Mn–Al mixed oxides as catalysts for ammonia oxidation to N2ON_2O

Mixed oxide catalysts containing Co, Mn, and Al in a molar ratio of 4:1:1 were prepared by heating precursors obtained by a mechanochemical method (when appropriate nitrates were milled with ammonium hydrogen carbonate) or by coprecipitation. The precursors and related mixed oxides obtained at 500 °C were characterized by XRD, TG/DTA, UV–Vis, IR spectroscopy, TPR and NH3-TPD, and were tested for activity and selectivity in ammonia oxidation to N2O. The precursors prepared by mechanochemical reaction showed very similar phase composition to that of the coprecipitated product. All examined mixed oxide catalysts were active in the low temperature range (100 % conversion of NH3 was achieved at 250 °C), but the selectivity was sensitive to catalyst composition and the method used for preparation of the precursors. Non-modified Co–Mn–Al mixed oxide catalyst obtained from the coprecipitated precursor exhibited higher selectivity towards N2O formation than the calcined product prepared by the mechanochemical method. Modification of the latter mixed oxide catalysts with cesium promoter (1 wt%) significantly increased their selectivity to nitrous oxide. The yield of N2O at 250 °C was close to 100 %.Web of Science4232690266

Structure–activity relationship in the N2O decomposition over Ni-(Mg)-Al and Ni-(Mg)-Mn mixed oxides prepared from hydrotalcite-like precursors

The decomposition of the nitrous oxide over catalysts prepared by thermal decomposition of Ni-(Mg)-MIII (MIII =Al or Mn) hydrotalcite-like precursors was studied. The mixed oxides obtained at 500 ◦C were characterized using various techniques—X-ray diffraction (XRD), BET surface area measurements, temperature-programmed desorption (TPD) and temperature-programmed reduction (TPR). The N2O decomposition was performed in the temperature range 300–450 ◦C, at 0.05–0.15 mol% inlet N2O concentrations; oxygen and nitrogen dioxide were added in some runs. The Ni-Al and Mg-Mn catalysts exhibited high catalytic activity but those containing both transition metal cations (i.e. Ni and Mn) were less active. Their lower activity was interpreted in terms of different oxidation states of manganese and nickel in the mixed oxide systems. Up to a certain value of oxygen pressure the presence of oxygen in the reaction mixture caused an inhibition of the reaction rate, while at higher oxygen pressures the N2O conversion remained nearly constant. The correlation between the observed oxygen inhibition and the proposed N2O decomposition mechanism as well as the relationship between the observed activity and the amount of reducible components determined from TPR experiments are discussed

Cobalt oxides supported over ceria-zirconia coated cordierite monoliths as catalysts for deep oxidation of ethanol and N2O decomposition

Cordierite monoliths coated with ceria-zirconia supporting cobalt oxide were prepared, examined in the deep oxidation of ethanol and N2O decomposition, and compared with pelletized commercial cobalt oxide catalyst. Interaction of Co3O4 with ceria-zirconia washcoat led to formation of Co3O4 particles with slightly worse structure ordering resulting in better reducibility than that observed for the commercial Co3O4 catalyst. In oxidation of ethanol, activity of the Co3O4-containing monoliths was comparable with that of pelletized cobalt oxide catalyst with nearly seven times higher content of active components. However, conversions of N2O over the monolith catalysts were lower. Nevertheless, incorporation of Co3O4 onto ZrO2-CeO2 washcoat increased rate of both catalytic reactions, i.e., N2O decomposition and deep ethanol oxidation.Web of Science14761391137

Direct decomposition of NO over Co-Mn-Al mixed oxides: Effect of Ce and/or K promoters

Co-Mn-Al mixed oxides promoted by potassium are known as active catalysts for the direct decomposition of nitric oxide (NO). In this study, the answer to the following question has been considered: does the presence of cerium in K-promoted Co-Mn-Al catalysts substantially affect the physical-chemical properties, activity, and stability in direct NO decomposition? The Co-Mn-Al, Co-Mn-Al-Ce, and Co-Mn-Al-Ce-K mixed oxide catalysts were prepared by the precipitation of corresponding metal nitrates with a solution of Na2CO3/NaOH, followed by the washing of the precipitate and calcination. Two other catalysts were prepared by impregnation of the Ce-containing catalysts with Co and Co+K nitrates. After calcination, the solids were characterized by chemical analysis, XRD, N(2)physisorption, FTIR, temperature-programmed reduction, CO(2)and O(2)desorption (H-2-TPR, CO2-TPD, O-2-TPD), and X-ray photoelectron spectrometry (XPS). Cerium and especially potassium occurring in the catalysts affected the basicity, reducibility, and surface concentration of active components. Adding cerium itself did not contribute to the increase in catalytic activity, whereas the addition of cerium and potassium did. Catalytic activity in direct NO decomposition depended on combinations of both reducibility and the amount of stronger basic sites determined in the catalysts. Therefore, the increase in cobalt concentration itself in the Co-Mn-Al mixed oxide catalyst does not determine the achievement of high catalytic activity in direct NO decomposition.Web of Science107art. no. 80

Cobalt oxide catalysts supported on CeO2-TiO2 for ethanol oxidation and N2O decomposition

Cobalt oxide catalysts deposited on titania-ceria supports were examined in deep ethanol oxidation and N2O decomposition. Supports with various molar ratio of CeO2/TiO2 were prepared by the sol-gel method and cobalt components were introduced by impregnation and subsequent calcination. The supports and catalysts were examined by chemical analysis, X-ray diffraction, nitrogen physisorption, H-2-TPR, and NH3-TPD. It was found out that the ethanol conversion at 200 degrees C is proportional to the CeO2/(CeO2 + TiO2) molar ratio in the supports, and temperature T-50 of ethanol oxidation is proportional to the amount of components reducible in the temperature range of 20-500 degrees C. A comparison of specific catalytic activities in both ethanol oxidation and N2O decomposition proved a lower rate of N2O decomposition than that of oxidation of ethanol (approximately 25 times). The findings confirmed the great importance of the supports surface areas on specific activity of cobalt catalysts in both reactions. The obtained results showed that ceria is the best support of cobalt oxides for both deep ethanol oxidation and N2O decomposition when reaction rates are related to unit amount of active component in the catalysts.Web of Science121113912

Effect of Mn/Al ratio in Co–Mn–Al mixed oxide catalysts prepared from hydrotalcite-like precursors on catalytic decomposition of N2O

The Co–Mn–Al mixed oxide catalysts were prepared by thermal decomposition of hydrotalcite-like precursors with Co/(Mn + Al) molar ratio of 2 and Mn/Al molar ratio varying from 0 to 2. The obtained catalysts were characterized by powder XRD, XPS, BET surface area and TPR measurements and tested in N2O decomposition. The most active Co4MnAl catalyst exhibited both the optimum Mn/Al molar ratio and the optimum amount of components reducible in the temperature region in which the catalytic reaction proceeds (350–450 °C)

Cobalt-Copper Oxide Catalysts for VOC Abatement: Effect of Co:Cu Ratio on Performance in Ethanol Oxidation

The effect of the Co-Cu oxide catalysts composition on their physicochemical properties and performance in the deep oxidation of ethanol was studied. The catalysts with Co:Cu molar ratios of 4:1, 1:1, and 1:4 were obtained by calcination (4 h at 500 °C in air) of the coprecipitated precursors and characterized in detail using powder XRD, Raman spectroscopy, N2 physisorption, H2-TPR, and XPS. The powder XRD and Raman spectroscopy indicated the formation of Co3O4 and CuO mixtures rather than Co-Cu mixed oxides. The CuO promoted the Co3O4 reduction; the Co-Cu catalysts were reduced more easily than the single-component Co and Cu oxides and the main reduction maxima were shifted to lower temperatures with increasing cobalt content in the catalysts. The Co-Cu oxide catalyst with a Co:Cu molar ratio of 4:1 exhibited the best performance in ethanol gas-phase oxidation, showing the lowest T50 (91 °C) and T90(CO2) (159 °C) temperatures needed for 50% ethanol conversion and 90% conversion to CO2, respectively. The excellent catalytic properties of this Co-Cu oxide catalyst were ascribed to the synergistic effect of Co and Cu components. The high activity and selectivity of the Co-Cu catalyst was attributed to the presence of finely dispersed CuO particles on the surface of Co3O4