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[Display omitted] The optimal conditions for the synthesis of platinized graphitic carbon nitride (Pt/g-C 3 N 4) have been found. It was investigated as a catalyst for the production of hydrogen from aqueous solutions of triethanolamine (TEOA) under irradiation with visible light. The highest photocatalytic activity of 450 μmol h−1 g−1 and an apparent quantum efficiency of 1.1% were demonstrated by the 1% Pt/g-C 3 N 4 sample prepared from melamine by calcining at 600 °C for 2 h. [ABSTRACT FROM AUTHOR]

Perovskite-type samples La 1-x Ca x Co 1-x Ti x O 3 /KIT-6 (x = 0–0.5) were synthesized by citrate method. KIT-6 is partially embedded in the perovskite structure. The complete reduction of cobalt in perovskites in the presence of KIT-6 occurs at a temperature of ca. 670 °C due to the formation of a cobalt silicate phase. With the substitution of titanium for cobalt cations, the complete reduction of cobalt occurs at temperatures above 720 °C. The proportion of cobalt that is reduced at temperatures below 500 °C increases with an increase in the ratio of Co3+/Co2+ cations. Partial substitution of cobalt cations with titanium cations decreases the selectivity ratios S CH3OH /S C2+OH and S CH4 /S C2-8. The introduction of calcium cations leads, proportionally to its content, to a strong decrease in selectivity to methanol and an increase in selectivity for light hydrocarbons C 2-8 in syngas conversion. It was shown that the maximum selectivity for higher alcohols with a low selectivity for methanol is observed at x = 0.3 on a sample containing calcium. A significant amount of the cobalt carbide phase Co 2 C in the used KIT-6-free sample of LaCoO 3 is accompanied by the predominance of the methanation reaction (CH 4 selectivity 58.7%). The synthesized samples on KIT-6 have higher selectivity to alcohols compared to a conventional CoAl oxide catalyst and somewhat lower activity in syngas conversion. [Display omitted] • High surface area perovskite La 1-x Ca x Co 1-x Ti x O 3 /KIT-6 catalysts were synthesized. • Distribution of LaCoO 3 /KIT-6 products is similar to CoAl catalyst. • At Ca/Co = 0.15–0.43 and Ti/Co = 0.43 selectivity for higher alcohols doubles. • Calcium introduction decreases S CH3OH proportionally, wherein S C2-8 increases. • An increase in size of Co particles leads to formation of Co 2 C and an increase in selectivity for CH 4. [ABSTRACT FROM AUTHOR]

Highly dispersed LaCo1−x−yCuxTiyO3/KIT-6 perovskites were synthesized by the citrate method with inert mesoporous KIT-6 addition. The KIT-6 matrix was removed by dissolution in 7% NaOH aqueous solution. The dispersity of perovskites probably varies depending on the largest cation and its content at the B position of the perovskite ABO3 structure. The CoS=23+/CoS=03+ ratio increases with the increase in copper content and in the presence of Ti4+. It may be explained by the compensation of the distortion of the perovskite structure. The maximum syngas conversion is achieved at nCo/nCu = 7/3. At a higher copper content, the activity of the samples decreases due to the formation of large copper particles (up to 40 nm) in the course of the reduction. The selectivity for alcohols increases with an increase in the proportion of copper and reaches maximum values at a ratio of nCo/nCu close to 1. The distribution of alcohols is the same for all samples, except for LaCo0.35Cu0.35Ti0.3O3/KIT-6. It can be assumed that the synthesis of alcohols proceeds on bimetallic CoCu particles 3 nm in size and cobalt particles 4–6 nm in size, most likely enriched with copper on the surface. [ABSTRACT FROM AUTHOR]

Abstract: This study was devoted to determination of localization of the individual copper species in the pores of ZSM-5 zeolite after post-synthetic zeolite modification by incipient wetness impregnation with CuCl2 solution followed by hydrolytic polycondensation of the ions in the pores. A series of Cu(n)ZSM-5 samples, where n is the copper concentration varied from 0.5 to 5.0wt.%, were synthesized using this method. A commercial HZSM-5 zeolite having Si/Al=17 was used for the synthesis of the catalysts. After modification the Cu(n)ZSM-5 samples were dried and calcined in air at 110 and 450°C, respectively. The samples were studied by UV–vis–NIR DR spectroscopy, XRD and by measuring and processing the low-temperature (77K) adsorption of nitrogen and hydrogen. It was shown for the first time that at the concentration of 1.0wt.% or lower copper was localized in the form of isolated Cu2+ Oh cations in the ion-exchange positions in the zeolite micro- and mesopores as well as on oxygen complexes of extraframework aluminum in thin mesopores with D <3.2nm in the form of superficial spinel-like structures in octahedral oxygen coordination Cu2+ Oh. At the copper concentration above 1.0wt.% linear associates of weakly bound Cu2+ Oh ions with unusual orbital ordering were formed in addition to the two forms discussed above. These associates existing in the forms of one- and two-dimensional nanohydroxocompounds were localized partially in the zeolite micropores but mostly in thin mesopores. The effect of the individual copper species on the catalytic properties of Cu(n)ZSM-5 samples in selective catalytic reduction of NO by propane was also studied. It was found that isolated Cu2+ Oh cations in the ion-exchange positions and Cu2+ Oh cations localized on the oxygen complexes of extraframework aluminum had the highest catalytic activity in NO SCR by propane. The weakly bound linear associates of Cu2+ Oh ions had lower catalytic activity, compared with isolated Cu2+ Oh ions. When their amount was high, they caused steric hindrance for contact of the reagents with the more active sites. The Cu2+ Oh ion associates were found to transform to nanodispersed Cu2(OH)3Cl during catalytic experiments. [Copyright &y& Elsevier]

Isotherms of Ge(IV) and Cu(II) ions sorption on to the weakly basic anion-exchange resin AN-31 from chloride solutions have been constructed and described. The dependence of equilibrium parameters of Ge(IV) and Cu(II) ions sorption from chloride ions concentration was shown. Based on the electron spectra of diffuse reflectance of copper-containing sorbent, isotherms of sorption and isomolar copper–germanium ions distribution diagram in solutions with different chloride concentrations the nature of extracted particles has been established, and the effect of the mineral background on the sorbent capacity has been determined. The synergistic effect of Cu(II) ions sorption in the presence of Ge(IV) ions has been established. It was found that the ionic and uncharged associates formed by hydroxy-chloride polynuclear cuprate(II) cations and methagermanate anions extract from the chloride solutions onto AN-31. The possibility of selective Cu(II) ions sorption from germanium containing 1 M chloride solutions in wide range of Ge(IV):Cu(II) molar ratios from 1:3 to 1:1 has been established. [ABSTRACT FROM AUTHOR]

Two new isomeric complexes [CuBr2(R-bian)] (R = 4-Me-Ph (1), 2-Me-Ph (2)) were obtained by reacting copper(II) bromide with 1,2-bis[(2-methylphenyl)imino]acenaphthene ligands and characterized. The crystal structure of 2 was determined by X-ray diffraction analysis. The copper atom has a distorted square-planar environment; the ω angle between the CuN2 and CuBr2 planes is 37.004°. The calculated ω parameters for optimized structures 1 and 2 were 76.002° and 43.949°, indicating significant deviations from the ideal tetrahedral and square-plane geometries, respectively. Molecules 2 form dimers due to non-covalent Cu···Br contacts, which were analyzed by DFT calculations. The complexes were also characterized by cyclic voltammetry and UV-Vis spectroscopy. A quasi-reversible Cu(II)/Cu(I) redox event with E1/2 potentials of 0.81 and 0.66 V (vs. SHE) was found for 1 and 2, respectively. The electronic absorption spectra showed the presence of Cu(I) species as a result of the partial reduction of the complexes in the acetonitrile solution. Both complexes were tested as homogenous catalysts for the oxidation of isopropylbenzene (IPB) in acetonitrile at low temperatures. Differences in the mechanism of the catalytic reaction and the composition of the reaction products depending on the oxidizing ability of the catalyst were revealed. [ABSTRACT FROM AUTHOR]

Among the known synthesis procedures and reagents for unsupported Ni–Mo–W catalysts, there is no consensus about optimal preparation conditions of their precursors. In the present work, Ni–Mo–W precursors were prepared via three preparation techniques—hydrothermal synthesis, precipitation method and spray drying—after the synthesis of complex compounds in solution. Ni–Mo–W precursors were studied by the XRD analysis, SEM methods, Raman and UV-vis spectroscopies and XPS measurements and used for the hydrotreatment of straight-run gasoil. Precursors prepared by hydrothermal synthesis contain particles with stacked plate shapes, while other methods provide spherical particles. The formation of different amounts of individual molybdates, tungstates or mixed phases such as W1−xMoxO3 possibly doped by Ni was detected. The precipitation technique results in the formation of spheres, with W located at the center and is unavailable for catalysis. The catalytic activity increased when all active metals are available for the feedstock, and a more mixed phase containing Ni, Mo and W is formed. This mixed phase is realized when the synthesis of the Ni–Mo–W precursors is carried out in solution followed by spray drying. The resulting catalyst has 1.2–4 times higher activity than catalysts prepared by other methods. [ABSTRACT FROM AUTHOR]

Nanostructured powders xFe/nano-Al2O3 with the Fe loading of x = 0.0 – 5.0 wt% were obtained using laser vaporization by CO2 laser. XRF, XRD, HRTEM, PL and UV–Vis DRS techniques were employed to investigate physicochemical, structural and optical properties of the synthesized nanopowders with the average particle size of 9 nm. Nanopowders xFe/nano-Al2O3 as model catalysts were tested in isobutane dehydrogenation reaction. The results obtained were compared with similar data for the xFe/γPb-Al2O3 systems synthesized by the conventional sol–gel method. According to XRD and UV–Vis DRS data, in the series of xFe/nano-Al2O3 samples a great part of Fe3+ ions is in the disordered environment of subsurface layers of Al2O3 nanocrystallites, predominantly in the tetrahedral coordination. In distinction to samples of the xFe/γPb-Al2O3 series, in the case of nanostructured xFe/nano-Al2O3 powders the formation of Fe2O3 phase does not occur at any concentrations of iron or conditions of testing. The analysis of the PL spectra of xFe/nano-Al2O3 powders also showed the presence of surface sites of Fe3+ ions, which were not detected for xFe/γPb-Al2O3. Catalytic testing of the xFe/nano-Al2O3 series samples in isobutane dehydrogenation revealed the formation of the iron active sites that ensure catalytic activity of the samples. Differences in the catalytic properties of FeOx/Al2O3 samples obtained by the sol–gel method and laser vaporization are related to different states of Fe3+ ions. Thus, the xFe/nano-Al2O3 nanopowders, in contrast to xFe/γPb-Al2O3, contain a large amount of active Fe3+ sites. These sites, being involved in the dehydrogenation reaction, are present predominantly on the surface of the nanopowders. [ABSTRACT FROM AUTHOR]

Laser vaporized xCr/Al 2 O 3 nanopowders with the particle size of ca. 15 nm were studied by XRF, EDX, HRTEM, XRD, DD, BET, TGA, UV–Vis DRS, Raman and PL spectroscopy methods as a catalytic system in dehydrogenation of isobutane. The nanopowders were found to contain not only the Cr6+ ions located on the surface of nanoparticles, but also two different types of Cr3+ sites as components of the γ-Al 2 O 3 solid solution. One type consists of the bulk Cr3+ b sites in a strong crystal field. Another type is represented by the Cr3+ s sites residing near the surface of xCr/Al 2 O 3 nanoparticles. Such sites are in a weak crystal field. It was shown that catalytic activity of the nanostructured xCr/Al 2 O 3 system is provided by the high content of surface Cr3+ s sites. The results obtained make it possible to propose the nanopowders obtained by laser synthesis as a promising catalytic system that can be used in the development of highly active catalysts for dehydrogenation of alkanes with the decreased chromium content. Unlabelled Image • Model CrO x /Al 2 O 3 nanoparticle catalysts were obtained by laser vaporization • Structure, morphology and optical properties of CrO x /Al 2 O 3 nanopowders were studied • Cr3+ s sites are located near the surface of CrO x /Al 2 O 3 nanoparticles • Cr3+ s sites play the key role in the isobutane dehydrogenation reaction • CrO x /Al 2 O 3 nanoparticles are highly active catalysts with the decreased Cr content [ABSTRACT FROM AUTHOR]

Diffusion of water into Zr‐containing silica fiberglass materials was studied at room temperature by infrared spectroscopy. Several types of experiments were performed: (a) rehydration with H2O of fiberglass materials previously calcined in air at 450°C and under vacuum at 180°C; (b) isotopic experiments for uncalcined fiberglass materials using D2O with and without the presence of sodium. Water diffusion coefficients were determined in each case. It was suggested that the transfer of the protons and water molecules occurred by different mechanisms: the protons diffused through the hydroxyl groups via the relay mechanism like in liquid water, whereas water diffused more slowly in the form of molecular water. [ABSTRACT FROM AUTHOR]

Abstract: Commercial liquid-phase-sulfided type II CoMo/Al2O3 catalyst was reactivated after commercial operation and oxidative regeneration. For this purpose, the use of citric acid (CA) that reactivates a regenerated CoMo/Al2O3 catalyst was studied. The study of the reactivated catalyst was carried out by means of UV-DRS, FTIR, Raman spectroscopy, XRD, XPS, and HTREM. The catalytic activity was estimated in the HDS of straight-run gasoil (SRGO). It was shown that the treatment of the catalyst with CA leads to the formation of a Co-Mo complex compound and significantly reduces the proportion of β-CoMoO4 and MoO3 in the catalyst. Eventually, this leads to the formation of CoMoS phase type II in a higher proportion enhancing the HDS catalytic properties.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Multiwalled carbon nanotubes (MWCNTs) were successfully incorporated inside silica aerogel matrix. Solid composite materials were investigated by high-resolution transmission microscopy, scanning electron microscopy, optical spectroscopy. MWCNTs in the form of small bundles and individual tubes get locked inside the aerogel between its pores resulting in the local solution-free environment for nanotubes. Optical transmission of the composite material can be modified by the amount of the added MWCNTs. Nonlinear optical properties were studied by a Z-scan technique. Composite materials demonstrate saturable absorption for femtosecond laser pulses at 515 nm wavelength that are attributed to the properties of embedded nanotubes. Silica aerogels possess significantly better thermal stability compared to polymer matrices, hosts that are frequently used for saturable absorption applications of carbon nanotubes. Solid and lightweight silica aerogels with embedded nanotubes can be used as optical elements for various photonic devices. Photo of silica aerogel with embedded MWCNTs. Normalized Z-scan transmittance of silica aerogel with nanotubes for two different on-focus intensities. [ABSTRACT FROM AUTHOR]

Abstract: A set of bimetallic Co–Mo complexes has been synthesised in yields of approximately 95% by the sequential dissolution of ethylenediamine, different Co2+ carboxylates and ammonium heptamolybdate in water. Data collected from elemental analysis, XRD, UV–Vis, IR, Raman, XPS, and EXAFS spectroscopy suggest that all of the complexes have similar structures that correspond to the general formula of NH4(enH2) x [Co(en)3][Mo2O7L]·H2O, where L is oxalic, tartaric, citric or nitrilotriacetic acid residue. A special feature of the complexes is the presence of two different molybdenum atoms linked together by an oxygen bridge in an octahedral and tetrahedral oxygen environment, as well as a cobalt 2+ atom that is in an octahedral environment with the nitrogen atoms of the ethylenediamine. [Copyright &y& Elsevier]

Valence and coordination states of molybdenum ions formed upon thermal treatment of Mo/H-ZSM-5 catalyst for methane dehydroaromatization in Ar and Ar/CH4 media at 573-973 K have been studied by ESR and UV-VIS spectroscopy. For comparison, the characteristic ESR spectra of thermolyzed bulk ammonium heptamolybdate have been studied and analyzed in detail. The nature of earlier observed Mo5+ ions has been verified, and new paramagnetic states of molybdenum in Mo/H-ZSM-5 catalysts have been detected: Mo3+ ions, and Mo5+ ions in tetrahedral coordination with delocalization of unpaired electron to Al and H or Al and N atoms. [ABSTRACT FROM AUTHOR]