In Situ Raman Spectroscopy of Supported Chromium Oxide Catalysts: Reactivity Studies with Methanol and Butane

The interactions of methanol and butane with supported chromium oxide catalysts under oxidizing and reducing conditions were studied by in situ Raman spectroscopy as a function of the specific oxide support (Al2O3, ZrO2, TiO2, SiO2, Nb2O5, 3% SiO2/TiO2, 3% TiO2/SiO2, and a physical mixture of SiO2 and TiO2) and chromium oxide loading (1-6 wt% CrO3). Two surface chromium oxide species were observed on the TiO2, ZrO2, Al2O3, 3% SiO2/TiO2, and a physical mixture of SiO2 and TiO2 surfaces: a monomeric species (characterized by a CrdO stretching frequency at ? 1030 cm -1 ) and a polymeric species (possessing a CrdO stretching frequency at ~ 1005-1010 cm -1 and a Cr-O-Cr bending mode at ~880 cm -1 ). The SiO2 and 3% TiO2/SiO2 surfaces possess only the monomeric species. The extent of reduction of the surface chromium oxide species, reflected by the decrease in the Raman intensity of the CrdO bonds, demonstrates that the polymeric surface chromium oxide species is more easily reducible than the monomeric chromium oxide species on the same support. The extent of reduction of the surface chromium oxide species strongly depends on the specific oxide support (3% TiO2/SiO2 = 3% SiO2/TiO2 = (SiO2 + TiO2) = TiO2 > ZrO2)

Соціальна цінність права в контексті меж сучасного правового регулювання

Одной из важнейших характеристик права является его социальная ценность, в том числе и в сфере правового регулирования. В представленной статье рассмотрена взаимосвязь правового регулирования, правового влияния и социальной ценности права в контексте характеристики типовых и нетиповых социальных регуляторов.One of the major characteristics of the right is its social value, including in sphere of legal regulation. In presented article the interrelation of legal regulation, legal influence and social value of the right in a context of the characteristic of typical and not typical social regulators is considered

In Situ Raman Spectroscopy of Supported Chromium Oxide Catalysts: ^18 O2- ^16 O2 Isotopic Labeling Studies

The isothermal isotopic exchange reaction of 18 O2 with 16 O of chromium(VI) oxide supported on zirconia, alumina, and titania has been investigated with in situ laser Raman spectroscopy. The isotopic exchange reaction is dependent on the support type, the Cr loading, and the reaction temperature. Complete isotopic exchange of chromium(VI) oxide with 18 O2 is difficult to achieve and requires several successive butane reduction- 18 O2 oxidation cycles at relatively high temperatures. The efficiency of the isothermal isotopic exchange reaction increases from alumina over titania to zirconia and with increasing Cr loading and reduction temperature. The observed Raman shifts upon isotopic labeling are consistent with a mono-oxo surface chromium oxide(VI) species

Правила для авторів

The influence of atom packing and the geometric arrangement of atoms on the coordination number(s) and resultant simulated EXAFS spectra for face centrered cubic (fcc), hexagonal close packed (hcp) and body centered cubic (bcc) monometallic structures and fcc bimetallic structures, has been examined for metal clusters with an isotropic diameter up to 3 nm. We observe clear differences as a function of size and shape for all types of packing; in particular the surface aspect ratios (surface-to-bulk) of the shapes strongly influences the ‘growth curves’ as a function of the number of atoms for all packing types examined. Discrimination between the different types of structure based on the coordination shell occupancy appears possible, although is dependent on the type of packing. For fcc and hcp packing, structures comprising less than 200 atoms, and particularly less than 100 atoms, exhibit strong variation in the first shell coordination number as a function of shape. For bcc structures this dependency of the coordination shell number for small clusters is much less pronounced and in some cases (for higher shell (>N4) coordination numbers) an opposite trend is observed in that the difference in coordination number as a function of shape becomes more marked with an increasing number of atoms. For the fcc bimetallic systems, model structures possessing distinct bimetal distributions, including both non-random and random alloy types, were simulated and examined. Clear variations in both the 1st shell coordination number and in the simulated spectra were observed as a function of the bimetal structure. A dual edge analysis of the data and subsequent examination of the coordination shell numbers as a function of the bimetal distribution enables for the size, composition and distribution of the each species, to be determined

Кредитная деятельность коммерческих банков в условиях кризиса

This chapter contains sections titled: Introduction Basic Tenets Behind Technique Combining Illustrations of Setups Combining Multiple In Situ Techniques Conclusion Reference

In Situ Diffuse Reflectance Spectroscopy of Supported Chromium Oxide Catalysts: Kinetics of the Reduction Process with Carbon Monoxide

In situ diffuse reflectance spectra of supported chromium oxide catalysts are investigated for the first time at elevated temperatures under controlled reaction conditions using a specially designed diffuse reflection attachment. The obtained results are compared and discussed with those obtained by the classical diffuse reflectance spectroscopy technique. A novel method for studying the reduction kinetics of supported transition metal oxides is proposed. In the case of Cr(VI), the reduction is faster on silica than on alumina. A kinetic model is developed to explain the kinetics. It consists of the activation of CO by adsorption followed by the reduction of Cr^6+ with formation of surface carboxylates

Новые сведения о памятниках письменности караханидского времени

Тосорский эпиграфический памятник, ставший предметом исследования, написан на тюркском языке во времена Караханидов и по своему содержанию является соглашением двух местных военачальников. По мнению автора статьи, памятник представляет собой яркое свидетельство существования института икта в государственно-административной системе средневековых тюрков.Тосорська епіграфічна пам’ятка, що стала предметом дослідження, написана тюркською мовою у часи Караханідів і за своїм змістом являє собою угоду, укладену двома місцевими воєначальниками. На думку автора статті, пам’ятка становить яскраве свідчення існування інституту ікта в державно-адміністративній системі середньовічних тюрків.Epigraphic monument from Tosor, which became the subject of the study, was written in Turkic language in the times of Karakhanids. By its contents the monument is a treaty between two local military leaders. To author’s opinion, Tosor inscription can be regarded as undisputable proof of the existing of iqta institution in the administrative system of mediaeval Turks

Актуальне конституційно-правове дослідження з проблематики муніципальної влади в Україні

Рецензія на кн.: Батанов О.В. Муніципальна влада в Україні: проблеми теорії та практики: Монографія /Відп. ред. М.О. Баймуратов.- К.: ТОВ «Видавництво «Юридична думка», 2010. - 656 с

ESR Fine Structure of Manganese Ions in Zeolite A Detects Strong Variations of the Coordination Environment

The electron spin resonance spectra of Mn 2+ exchanged zeolite A have been investigated as a function of the monovalent co-cation (K + ,Na + ,Li + ,Cs + ,or NH4 + ), Mn 2+ content, recording frequency, and temperature. Three new Mn 2+ species are observed with a well-resolved fine structure; this allows for the first time a direct quantitative determination of the zero-field splitting (ZFS) parameters in zeolites. In hydrated zeolites, three ESR active Mn 2+ species are observed, characterized by different values for the ZFS parameter D. Species I has D ) 0.035 cm -1 . Species II is closer to a regular octahedron, with D ) 0.010 cm -1 . Species III, with D ) 0.14 cm -1 , is in a strongly axially distorted coordination. Species I is dominant in MnKA, MnCsA, and MnNH4A, while II and III are found in MnNaA and MnLiA. In fully dehydrated zeolites, two species are observed. Species IV has a small hyperfine constant A and is present in dry NaA and KA. Species V is observed in dry LiA; it has axial symmetry with a large, temperature-dependent D. Species V probably represents Mn 2+ in a 3-fold coordination in a 6-ring. In partially hydrated zeolites, a tetrahedral species VI is observed. The spectroscopic data elucidate the location of manganese-( II) ions in zeolite A, particularly at relatively low metal loadings

Zeolite-Encapsulated Copper(II) Amino Acid Complexes: Synthesis, Spectroscopy, and Catalysis

The spectroscopic properties and catalytic behavior of Cu(AA)n m+ complexes (AA ) amino acid (glycine, lysine, histidine, alanine, serine, proline, tyrosine, phenylalanine, glutamine, glutamic acid, cysteine, tryptophan, leucine, and arginine)) in faujasite-type zeolites have been investigated. Successful immobilization was achieved by a simple cation exchange procedure with aqueous solutions of preformed Cu(AA)n m+ complexes. The best ion exchange results were obtained with lysine, arginine, proline (at pH ) 10), and histidine (at pH = 7.3) as ligands and with a AA:Cu 2+ ratio of 5. The internal surface and pore volume are drastically reduced by the uptake of the Cu(AA)n m+ complexes, and no precipitation of Cu(AA)n m+ crystals was observed by scanning electron microscopy. Both observations suggest the location of the complexes in the supercages of the faujasite-type zeolites. The composition of the first coordination sphere around Cu 2+ can be designed from NNNN to NOOO by varying the type of amino acid. A free coordination site is available for catalysis, and the oxidation of alcohols, alkanes, and alkenes with peroxides was observed at low temperatures