Synthesis, characterization and catalytic application for wet oxidation of phenol of iron-containing clays

High-surface-area pillared clays (PILC) were prepared from naturally occurring montmorillonites by exchanging interlayer ions to polyoxocations containing (i) aluminum (Al₁₃-PILC), (ii) iron adsorpted onto Al₁₃-PILC, and (iii) iron and aluminum located within the same complex (Fe_0.8Al_12.2-PILC). The obtained Fe_0.8Al_12.2-PILCs were characterized by DR–UV–vis and IR spectroscopy, XRD, ESR, scanning electron microscopy and low temperature N₂ adsorption measurements. Important factors affecting catalyst activity and phenol removal efficiencies have been studied, i.e. the effect of pH, temperature, catalyst concentration and stability of the catalyst.     

Synthesis of high-surface-area complex zirconium phosphates via mechanochemical activation route

 High-power ball mill activation of the mixture of hydrated zirconium and lanthanum salts (oxonitrates, oxochlorides) with ammonium phosphate followed by hydrothermal treatment at temperatures not exceeding 200°C and a nearly neutral pH was found to yield crystalline dispersed phase of a cubic NH₄Zr₂(PO₄)₃ type along with admixtures of disordered orthorhombic compounds of a zirconium orthophosphate type. In the same conditions and at the same Zr/P ratio, hydrothermal treatment of gels obtained by reacting mixed zirconium and lanthanum nitrates solutions with ammonium phosphates yields no crystalline products, and only treatment in acid media generates a phase of the α-ZrPO₄(OH) type coexisting with the NH₄Zr₂(PO₄)₃ phase if polyethylene oxide is present. X-ray powder diffraction, transmission electron microscopy, ³¹MAS-NMR, FTIRS and thermal analysis were applied to elucidate factors affecting crystallization of complex zirconium phosphates in the hydrothermal conditions. The most essential factor appears to be generation of some nuclei of zirconium phosphates under high pressures developed in the course of mixed solids mechanical activation. These nuclei are embedded into matrix of such well-crystallized solid products as ammonium nitrate or chloride. Hence, metastable cubic or orthorhombic structure of the phases obtained via mechanical activation route can be assigned to the nuclei-matrix orientation relationship. Due to easily scaled-up synthesis procedure, these results appear to be very promising for manufacturing of dispersed framework zirconium phosphates as acid catalysts or fast proton conductors. Received: 18 November 1998 / Reviewed and accepted: 2 December 1998     

The microstructure and properties of framework zirconium phosphates based nanocomposites – catalysts of alkane isomerization

Nanocomposites based upon framework zirconium phosphates with supported WO₃, MoO₃ and Pt nanoparticles were synthesized via the incipient wetness impregnation of high-surface-area mesoporous phosphate samples with water solutions of corresponding salts followed by drying and calcination. The structure and surface properties of nanocomposites were studied by using combination of structural and spectral methods. Due to a strong interaction between supports and supported species, the structure of the latter differs considerably from that of the bulk phases. Surface acid centers typical for zirconium phosphates disappear suggesting their participation in bonding nanoparticles of promoters. Instead, new types of strong acid sites associated with tungsten oxide clusters emerge. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered. Received: 20 February 2000 / Reviewed and accepted: 15 March 2000     

Hydrogen production by steam reforming of methanol over Cu–CeZrYOx-based catalysts

Active and selective Cu_x(CeZrY)_1−xO_y catalysts (pure and with addition of Al₂O₃ and Cr) for the steam reforming of methanol were synthesized via the urea–nitrate combustion method. Structural, surface and redox characteristics of these catalysts were investigated by XRD, BET, IR spectroscopy, differential dissolution (DD), H₂-TPR and XPS methods. It was shown that addition of alumina and Cr leads to the steep increase in H₂ production due to appearance of highly dispersed copper species and stabilizes their activity. The parallel change of SRM rate constants and maximal rates of reduction with hydrogen characterizing mobility of lattice oxygen at variation of the catalyst composition was revealed that shows the importance of lattice oxygen mobility for steam reforming of methanol.     

A New, 13C-Based Material for Neutron Targets

A ¹³C-based neutron-target material is investigated using x-ray diffraction, IR absorption and Raman scattering spectroscopies, transmission electron microscopy, and electrical (conductivity, magnetoresistance, and Hall effect) measurements before and after high-power electron irradiation for various lengths of time.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 5, 2005, pp. 531–539.Original Russian Text Copyright © 2005 by Romanenko, Anikeeva, Gorbachev, Zhmurikov, Gubin, Logachev, Avilov, Tsybulya, Kryukova, Burgina, Tecchio.     

Mechanochemical Synthesis of Complex Zirconium Phosphates

Cation- and anion-substituted zirconium phosphates of X _kZr _m (PO₄) _n–y Y composition, where X = Na⁺, La³⁺, NH₄ ⁺, Y = F^–, WO₄ ^2–, 1/3 < k < 2, 2 < m < 4, 3 < n < 6 were synthesized by the procedure, including mechanical activation of the starting salts mixture followed by annealing at 300–900°C. The interaction between components was studied by XRD, EXAFS, FT–IR, [³¹P-MAS] NMR. The possibility of synthesizing nonstoichiometric compounds is demonstrated and prospects for application of the mechanochemical method for synthesis of complex zirconium phosphates are outlined.     

High-temperature effects on the electrical properties and macrostructure of carbon composites

The electrical conductivity of MPG-6 and MPG-7 carbon composites has been measured before and after 1.4-MeV electron irradiation and ac resistive heating up to degradation temperatures (above 2500°C). The results demonstrate that both heating and electron irradiation reduce the resistivity of the materials and increase the defect density at the macrostructural level, while x-ray diffraction analysis reveals no significant structural changes in the temperature range studied. Detailed characterization of the composites suggests that their strength is limited by crystallite or grain boundaries.