Synthesis of a gallosilicate analogue of high silica,large Port Mordenitel

A high silica (SiO₂/Ga₂O₃ = 42) crystalline mordenite containing gallium (III) in framework positions has been prepared by hydrothermal crystallization at 413 K in the presence of tetraethylammonium bromide. Evidence for the presence of framework gallium in the mordenite lattice is obtained from chemical analysis, XRD, framework IR, solid state MASNMR, thermoanalytical studies, sorption and catalytic activity studies. Chemical analysis and NMR data indicate the absence of significant amounts of aluminium (SiO₂/Al₂O₃ > 2400). An increase in the interplanar spacing and unit cell volume as well as a shift to lower wavenumbers of framework vibrations occurs on gallium incorporation in the mordenite lattice. Ga-mordenite exhibited significant ion exchange capacity. The gallium analogue of mordenite exhibited significant catalytic activity and shape selectivity in the isomerization reaction ofm-xylene.NCL communication No. 5317.     

Thermoelectric Properties (Resistivity and Thermopower) in (Bi1.5Pb0.5Ca2−xMxCo2O8−δ (M=Sc, Y, or La)

In order to understand the origin of good thermoelectric (TE) properties in the transition metal oxides with the lattice structure isomorphous to the 232-structure, the bond nature between Co and O ions in Bi_1.5Pb_0.5Ca_2−xM_xCo₂O_8−δ-system has been tried to vary by replacing M with Sc³⁺, Y³⁺ or La³⁺ and by changing x from 0 to 0.3. The resistivity is minimum at x = 0.1 in Sc- and Y-systems, but very high in La-system. The large thermopower is obtained in every compound. The experimental TE properties have been discussed mainly within the framework of the charge-transfer scheme in which the ionic radii of Sc³⁺ and Y³⁺ smaller than Ca²⁺ reduce the energy between O 2p levels and Co e_g parentages but the large ionic radius of La³⁺ expands it. The oxygen solubility in the compounds and the lattice distortion peculiar to the 232-structure are also likely to contribute somewhat to the experimental results.     

One‐Pot Solvothermal Synthesis of Highly Water‐Dispersible Size‐Tunable Functionalized Magnetite Nanocrystal Clusters for Lipase Immobilization

A facile one‐pot synthesis of highly water‐dispersible size‐tunable magnetite (Fe₃O₄) nanocrystal clusters (MNCs) end‐functionalized with amino or carboxyl groups by a modified solvothermal reduction reaction has been developed. Dopamine and 3,4‐dihydroxyhydroxycinnamic acid were used for the first time as both a surfactant and interparticle linker in a polylol process for economical and environment‐friendly purposes. Morphology, chemical composition, and magnetic properties of the prepared particles were investigated by several methods, including FESEM, TEM, XRD, XPS, Raman, FTIR, TGA, zeta potential, and VSM. The sizes of the particles could be easily tuned over a wide range from 175 to 500 nm by varying the surfactant concentration. Moreover, ethylene glycol/diethylene glycol (EG/DEG) solvent mixtures with different ratios could be used as reductants to obtain the particles with smaller sizes. The XRD data demonstrated that the surfactants restrained the crystal growth of the grains. The nanoparticles showed superior magnetic properties and high colloidal stability in water. The cytotoxicity results indicated the feasibility of using the synthesized nanocrystals in biology‐related fields. To estimate the applicability of the obtained MNCs in biotechnology, Candida rugosa lipase was selected for the enzyme immobilization process. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with the free enzyme. This novel strategy would simplify the reaction protocol and improve the efficiency of materials functionalization, thus offering new potential applications in biotechnology and organocatalysis.     

Structures of Uncharacterised Polymorphs of Gallium Oxide from Total Neutron Diffraction

A structural investigation is reported of polymorphs of Ga₂O₃ that, despite much interest in their properties, have hitherto remained uncharacterised due to structural disorder. The most crystalline sample yet reported of γ‐Ga₂O₃ was prepared by solvothermal oxidation of gallium metal in ethanolamine. Structure refinement using the Rietveld method reveals γ‐Ga₂O₃ has a defect Fd$\bar 3$ m spinel structure, while pair distribution function analysis shows that the short‐range structure is better modelled with local F$\bar 4$ 3m symmetry. In further solvothermal oxidation reactions a novel gallium oxyhydroxide, Ga₅O₇(OH), is formed, the thermal decomposition of which reveals a new, transient gallium oxide polymorph, κ‐Ga₂O₃, before transformation into β‐Ga₂O_3. In contrast, the thermal decomposition of Ga(NO₃)₃?9 H₂O first forms ε‐Ga₂O₃ and then β‐Ga₂O₃. Examination of in situ thermodiffraction data shows that ε‐Ga₂O₃ is always contaminated with β‐Ga₂O₃ and with this knowledge a model for its structure was deduced and refined—space group P6₃mc with a ratio of tetrahedral/octahedral gallium of 2.2:1 in close‐packed oxide layers. Importantly, thermodiffraction provides no evidence for the existence of the speculated bixbyite structured δ‐Ga₂O₃; at the early stages of thermal decomposition of Ga(NO₃)₃?9 H₂O the first distinct phase formed is merely small particles of ε‐Ga₂O₃.     

具有[3~4~48~4]笼状结构单元的微孔磷酸镓Ga_3P_2O_8(OH)_3(H_2O)的合成、晶体结构及表征

开放骨架结构金属磷酸盐不仅具有丰富的结构和组成多样性,而且在吸附、分离、和催化等方面具有潜在的应用前景[1￣3]。同磷酸铝一样[2,3],磷酸镓是开放骨架磷酸盐中一个重要的家族,其结构主要由交替的GaOn多面体(GaO4,GaO5及GaO6)和PO4四面体构成。目前,已有近百种磷酸镓在水热/溶剂热体系下成功的合成出来[4￣8],其中最著名的例子是具有二十员环超大孔磷酸镓Cloverite[5]。这些磷酸镓不仅具有结构上的新颖性,同时还具有丰富的组成计量比(Ga/P:1/2￣3/2)[9],它们的结构由多种次级结构单元(SBU)构成,拓扑相关性为定向设计提供了重要基…     

Effect of rare earth oxides (CeO2, La2O3) on properties of Pd/Al2O3 catalysts for reduction of nitrogen oxides by methane

We have established that the thermal stability of supported Pd/Al₂O₃ catalysts is increased after they are modified by rare earth oxides (La₂O₃, Ce₂O₃). We have observed the effect of thermal activation of an aluminopalladium catalyst modified by lanthanum oxide. This effect is apparent in the increase of the specific catalytic activity in the reaction of high-temperature reduction of nitrogen oxides by methane after heat treatment of the catalyst at 850 °C. We have used X-ray photoelectron spectroscopy (XPS) to show that the reason for the thermal activation effect is stabilization of palladium in the Pd¹⁺ state. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 1, pp. 44–48, January–February, 2006.     

Thermal analysis of pigments based on Bi2O3

The synthesis of new pigments based on Bi₂O₃ is investigated because they give interesting orange hues and can substitute the pigments problematic from the environmental point of view. Chemical compounds of the Bi_2–xZr_3x/4O₃ type were synthesized. The host lattice of these pigments is Bi₂O₃ that is doped by Zr⁴⁺ ions. The area of ZrO₂ solubility in Bi₂O₃ at 800°C forming solid solution of both oxides was studied. The incorporation of doped ions provides interesting colours and contributes to a growth of the thermal stability of these compounds. The simultaneous TG-DTA measurements were used for determination of the temperature region of the pigment formation and thermal stability of pigments.     

Thermal synthesis and properties of the (Bi2O3)1–x(Ho2O3)x pigments

The synthesis of new compounds based on the Bi₂O₃–Ho₂O₃ system, which can be used as new ecological inorganic pigments, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been followed by the methods of thermal analysis that can provide first information about the temperature region of the pigment formation. The synthesis of these compounds was followed by thermal analysis using STA 449/C Jupiter (Netzsch, Germany).     

具有[344484]笼状结构单元的微孔磷酸镓Ga3P2O8(OH)3(H2O)的合成、晶体结构及表征

Open-framework metal phosphates have been the subject of intense research owing to their interesting structural chemistry and potential applications in catalysis and ion exchange. The gallium phosphate family has exhibits rich structural chemistry. A novel gallium phosphate Ga₃P₂O₈(OH)₃(H₂O)(GaPO-CJ36) has been prepared in a hydrothermal reaction system of GaO(OH)-H₃PO₄-Co(chxn)₃Cl₃-H₂O at 180 ℃ for 7 days. Single-crystal X-ray analysis shows that GaPO-CJ36 crystallizes in the P2₁/c space group with a=1.833 35(12) nm, b=0.503 94(3) nm, c=1.062 90(9) nm, V=0.982 01(12) nm³, and Z=4. The connection of GaO₂(OH)₃(H₂O) octahedra, PO₄ and GaO₄ tetrahedra through vertex oxygen atoms forms a three-dimensional open framework, which contains 8-ring channels along the [010] direction. Its structure is composed of interesting [3⁴4⁴8⁴] cages, which have not been found in known gallium phosphates. CSD: 416779.