Synthesis of Silica@α-Fe2O3 nanospheres by surface-initiated ATRP

We reported a new method to prepare Silica@α-Fe₂O₃ nanospheres by surface-initiated atom transfer radical polymerization (ATRP). Firstly, polymerizable surfactants-modified α-Fe₂O₃ nanoparticles were prepared in water-toluene microemulsion. Then, as-synthesized α-Fe₂O₃ nanoparticles acted as the macro-monomer of surface-initiated ATRP on silica nanospheres to make target product. Morphological characterization of the product was performed using transmission electron microscopy (TEM). Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance UV-vis spectroscopy were used to verify the incorporation of α-Fe₂O₃ nanoparticles on silica nanosphere.     

Activity of γ-Al2O3 modified by NaOH in disproportionation of methanethiol

Na⁺/Al₂O₃ catalysts in disproportionation of methanethiol are highly selective towards dimethyl sulfide but less active compared to -Al₂O₃. Their activity falls with increasing Na⁺ in the sample. This decrease is due to the neutralization of Brönsted acid centers on the catalyst.

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Na⁺/Al₂O₃ , , -Al₂O₃. Na⁺ . .

     

Zero- and one-dimensional thioindates synthesized under solvothermal conditions yielding α-In2S3, β-In2S3 or MgIn2S4 as thermal decomposition products

The first cationic thioindate with composition [In(en)₂S]₂·2Cl (zero-dimensional) (1) and the first thioindate being charge compensated by a main group metal complex with composition [Mg(en)₃][In₂S₄] (one-dimensional) (2) have been prepared with ethylenediamine under solvothermal conditions. The main structural motif of [In(en)₂S]₂·2Cl is the centro-symmetric rhomboidal [In(en)₂S]₂²⁺ ring which is formed by S-S edge-sharing of two symmetry related [InN₄S₂] octahedra. The structure of [Mg(en)₃][In₂S₄] is composed of a straight one-dimensional {[InS₂]⁻}_∞ chain surrounded by [Mg(en)₃]²⁺ complexes. Both compounds are wide band-gap semiconductors. The thermal decomposition reaction of [In(en)₂S]₂·2Cl stopped at 500 °C yielded cubic α-In₂S₃ and reflections of β-In₂S₃ are seen in the X-ray powder pattern of the residue obtained at 900 °C. In the case of [Mg(en)₃][In₂S₄] the thiospinel MgIn₂S₄ was identified as decomposition product. The size of the MgIn₂S₄ crystals are in the nanometer range as evidenced by a pronounced broadening of the reflections in the powder pattern and with transmission electron microscopy.     

Michael addition of nitromethane to 3-buten-2-one catalyzed by potassium fluoride supported on Al2O3, ZnO, SnO2, sepiolite, AlPO4, AlPO4?Al2O3 and AlPO4?ZnO

The Michael addition of nitromethane to 3-buten-2-one has been carried out in the absence of solvent, using potassium fluoride supported on Al₂O₃, ZnO, SnO₂, sepiolite, AlPO₄, AlPO₄–Al₂O₃ and AlPO₄–ZnO catalysts. We found that KF/ZnO easily performed the Michael addition and thus, ZnO is a better support for the basic reagent than Al₂O₃. Besides, the Michael addition was not successful with AlPO₄ or AlPO₄-metal oxide acidic supports.

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3--2- , , Al₂O₃, ZnO, SnO₂, , AlPO₄, AlPO₄–Al₂O₃ AlPO₄–ZnO. , KF/ZnO .. ZnO, , , Al₂O₃. , , AlPO₄ AlPO₄- .

     

Effect of Fe-modified α-Al2O3 on the properties of Pd/α-Al2O3 catalysts in selective acetylene hydrogenation

The use of nanocrystalline Fe-modified α-Al₂O₃ prepared by sol–gel and solvothermal method as supports for Pd catalysts resulted in an improved catalyst performance in selective acetylene hydrogenation. Moreover, the amount of coke deposits was reduced due to lower acidity of the Fe-modified α-Al₂O₃ supports.     

Synthesis of β-peroxy-lactones using 30% H2O2

Cyclopropyl carbinols 1a-e react with H₂O₂ in the presence of concd H₂SO₄ at 0-5 °C to furnish the corresponding hydroperoxides 2a-e in 45-82% yields. This efficient trapping of cyclopropylmethyl cations by the hydroperoxy group has been exploited to prepare compounds 14-23, a new series of cyclopropyl substituted β-peroxy-lactones.     

Copper-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides using CF3SiMe3 and Na2S2O3 as –SCF3 source

A universal and efficient Cu(I)-catalyzed synthesis of aryl and alkyl trifluoromethyl sulfides has been developed. In this catalytic system, S-aryl or S-alkyl sulfothioate (I or II) proved to be the key intermediate. Substrates bearing groups of I, Br, Cl, OTs, and OMs on the aryl carbon and no matter electron-withdrawing and electron-donating substitutions on the aromatic ring could afford good to excellent yields.     

Synthesis and crystal structure of Na4[Er2(EDTA)2(μ2-C2O4)] · 8H2O (where EDTA stands for ethylenediamine-N,N′-tetraacetate)

Synthesis was carried out, and structure solved for the new dinuclear erbium(III) complex having a composition of Na₄[Er₂(EDTA)₂(C₂O₄)] · 8H₂O (where EDTA stands for ethylenediamine-N,N′-tetraacetate). The compound was characterized by IR and UV spectroscopy, mass spectrometry, and X-ray crystallography. In the structure of the compound, erbium(III) has C.N. 8 and a coordination polyhedron shaped as a square antiprism. The EDTA and oxalate ions manifest their characteristic coordination modes: N,O-chelate hexadentate and bridge-cyclic tetradentate, respectively.     

Solid solubility of Yb2Si2O7 in β-, γ- and δ-Y2Si2O7

This paper examines the structural changes with temperature and composition in the Yb₂Si₂O₇-Y₂Si₂O₇ system; members of this system are expected to form in the intergranular region of Si₃N₄ and SiC structural ceramics when sintered with the aid of Yb₂O₃ and Y₂O₃ mixtures. A set of different compositions have been synthesised using the sol-gel method to obtain a xerogel, which has been calcined at temperatures between 1300 and 1650 °C during different times. Isotherms at 1300 and 1600 °C have been analysed in detail to evaluate the solid solubility of Yb₂Si₂O₇ in β-Y₂Si₂O₇ and γ-Y₂Si₂O₇. Although Yb₂Si₂O₇ shows a unique stable polymorph (β), Yb³⁺ is able to replace Y³⁺ in γ-Y₂Si₂O₇ and δ-Y₂Si₂O₇ at high temperatures and low Yb contents. IR results confirm the total solid solubility in the system and suggest a constant SiOSi angle of 180° in the Si₂O₇ unit across the system. The temperature-composition diagram of the system, obtained from powder XRD data, is dominated by the β-RE₂Si₂O₇ polymorph, with γ-RE₂Si₂O₇ and δ-RE₂Si₂O₇ showing reduced stability fields. The diagram is in accordance with Felsche's diagram if average ionic radii are assumed for the members of the solid solution at any temperature, as long as the β-γ phase boundary is slightly shifted towards higher radii.     

Conversion of alkylmercaptans in the presence of γ-Al2O3

In the presence of -Al₂O₃ at 200–500°C methylmercaptans quantitatively transform into dimethyl sulfides with almost equilibrium degrees of conversion. 100% selectivity towards diethyl sulfide is observed when ethylmercaptan conversion amounts to about 50% of its equilibrium value. In more severe conditions, dimethyl- and diethyl sulfides convert with eliminating hydrocarbons and H₂S. Selectivity towards diisopropylsulfide is as high as 30% with isopropylmercaptane conversion up to 25%; the reaction follows a parallel-consecutive scheme.

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-Al₂O₃ 200–500°C . 100% 50% . - H₂S. 30% 25%, - .

     

Synthesis and crystal structure of sodium isopolyvanadate [Na2(H2O)8]2H2[V10O28] · 4H2O

The sodium hydrogen oxovanadate [Na₂(H₂O)₈] ₂H₂[V₁₀O₂₈] · 4H₂O was synthesized and studied by TGA, X-ray diffraction, and NMR and IR spectroscopy. The crystals are triclinic, space group P $ \bar 1 $ \bar 1 , a = 8.545(7) ?, b = 10.827(2) ?, c = 11.627(2) ?, α = 105.48(3)°, β = 99.38(3)°, γ = 101.29(3)°, V = 989.9(3) ?³, ρ(calcd) = 2,381 g/cm³, Z= 1.     

Synthesis and characterization of a new octamolybdate (NH4)4[Mo8O24(C3H2O2)2] · 4H2O

A new complex with the formula (NH₄)₄[Mo₈O₂₄(C₃H₂O₂)₂] · 4H₂O (1) has been synthesized and characterized by single crystal X-ray diffraction and infrared spectrum. The complex is small yellow crystal and space group P ₁ with a = 9.9869(18) ?, b = 10.030(19) ?, c = 10.366(19) ?, α = 91.68(3)°, β = 98.94(3)°, γ = 119.37(2)°, V = 887(3) ?³, and Z = 1. The complex contains two malonic acid ligands bonded to the γ-Mo_{8 26}⁴⁻ ions which consist of eight MoO₆ edge-sharing octahedral. In this crystal structure, the octamolybdate anion is mutually hydrogen bonded by ammonium ions and water molecules.     

Influence of γ-radiation on the reactivity of montmorillonite towards H2O2

Compacted and water saturated bentonite will be used as an engineered barrier in deep geological repositories for radioactive waste in many countries. Due to the high dose rate of ionizing radiation outside the canisters holding the nuclear waste, radiolysis of the interlayer and pore water in the compacted bentonite is unavoidable. Upon reaction with the oxidizing and reducing species formed by water radiolysis (OH^•, e⁻_(aq), H^•, H₂O₂, H₂, HO₂^•, H₃O⁺), the overall redox properties in the bentonite barrier may change. In this study the influence of γ-radiation on the structural Fe(II)/Fe_Tot ratio in montmorillonite and its reactivity towards hydrogen peroxide (H₂O₂) was investigated in parallel experiments. The results show that under anoxic conditions the structural Fe(II)/Fe_Tot ratio of dispersed Montmorillonite increased from ≤3 to 25-30% after γ-doses comparable to repository conditions. Furthermore, a strong correlation between the structural Fe(II)/Fe_Tot ratio and the H₂O₂ decomposition rate in montmorillonite dispersions was found. This correlation was further verified in experiments with consecutive H₂O₂ additions, since the structural Fe(II)/Fe_Tot ratio was seen to decrease concordantly. This work shows that the structural iron in montmorillonite could be a sink for one of the major oxidants formed upon water radiolysis in the bentonite barrier, H₂O₂.     

Carbon nanotubes decorated α-Al2O3 containing cobalt nanoparticles for Fischer-Tropsch reaction

A new hierarchical composite consisted of multi-walled carbon nanotubes (CNTs) layer anchored on macroscopic α-Al2O3 host matrix was synthesized and used as support for Fischer-Tropsch synthesis (FTS). The composite constituted by a thin shell of a homogeneous, highly entangled and structure-opened carbon nanotubes network and it exhibited a relatively high and fully accessible specific surface area of 76 m 2 g-1 , compared with that of 5 m 2 g-1 of the original α-Al2O3 support. The metal-support interaction between carbon nanotubes surface and cobalt precursor and high effective surface area led to a relatively high dispersion of cobalt nanoparticles. This hierarchically supported cobalt catalyst exhibited a high FTS activity along with an extremely high selectivity towards liquid hydrocarbons compared with the cobalt-based catalyst supported on pristine α-Al2O3 or on CNTs carriers. This improvement can attribute to the high accessibility of composite surface area comparing with the macroscopic host structure alone or to the bulk CNTs where the nanoscopic dimension induced a dense packing with low mass transfer which favoured the problem of reactants competitive diffusion towards the cobalt active site. In addition, intrinsic thermal conductivity of decorated CNTs could help the heat dissipating throughout the catalyst body, thus avoiding the formation of local hot spots which appeared in high CO conversion under pure syngas feed in FTS reaction. Cobalt supported on CNTs decorated α-Al2O3 catalyst also exhibited satisfied high stability during more than 200 h on stream under relatively severe conditions compared with other catalysts reported in the literature. Finally, the macroscopic shape of such composite easily rendered its usage as catalyst support in a fixed-bed configuration without facing problems of transport and pressure drop as encountered with the bulk CNTs.     

Asymmetric Synthesis of β, γ-β-Hydroxyl-γ-butyrolactones

Chiral β-hydroxyl-γ-butyrolactones have attracted substantial interest in recent years due to their presence inmany strongly active natural products having antitumor, fungicidal, anti-inflammatory activity, and their use as important precursors in natural product synthesis. [1] In the course of the total synthesis of the natural product Tuxpano lide ,[2] we found a concise and efficient strategy on the stereocontrolled synthesis of β-hydroxyl-γ-butyrolactonederivatives from cheap and achiral starting material.     

Na2SO4辅助水热合成SnO2纳米晶

系统地研究了以SnCl₄·5H₂O为原料，以Na₂SO₄为矿化剂，采用水热法在较低温度下和较短的反应时间内制备结晶良好并均匀分散的SnO₂纳米晶。采用X射线衍射(XRD)、透射电子显微镜(TEM)、红外光谱(IR)等技术对水热反应的晶化过程进行了分析。结果表明：在Na₂SO₄存在的情况下，在120 ℃反应4 h 即可制备得到晶粒细小，分散性能良好的SnO₂纳米晶。XRD衍射峰峰宽随水热温度的升高或反应时间的延长而变窄，结晶性提高。TEM结果表明产物颗粒小、分散性能良好。水热反应温度和反应时间对产物结晶度和粒径有明显的影响。对Na₂SO₄在反应过程中的作用机理进行了分析。     

β-环糊精衍生物诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚

以单(6-O-p-甲苯磺酰基)-β-环糊精为原料,通过亲核取代反应合成了5个未见文献报道的环状氨基醇修饰β-环糊精CD-1～CD-5,收率36%～68%,其结构经过1H NMR,13C NMR和ESI-MS进行表征确认.将这些β-环糊精衍生物CD-1～CD-5作为Na2MoO4的配体,应用于H2O2不对称氧化苯甲硫醚,研究结果显示,反应介质的pH值对该反应体系的对映选择性具有较大影响.较佳配体CD-4在pH 7.0,1 mol/L CH3COONa-HCl中,诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚,ee值为21.25%.通过2D-1H ROESY NMR表征,表明制约CD-1～CD-5在诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚反应中ee值提高的主要因素为CD-1～CD-5的分子内自包结行为,并且该自包结状态也从量子化学计算方面得到了证实.     

Synthesis, characterization and catalytic performance of a novel magnetic SO42?-Y2O3-Fe3O4-ZrO2 solid acid catalyst

A novel magnetic SO₄ ²⁻-Y₂O₃-Fe₃O₄-ZrO₂ solid acid catalyst was prepared by the co-precipitation method. The results revealed that the introduction of Y₂O₃ improved markedly the thermal stability of tetragonal zirconia. The catalyst exhibited high catalytic activity and stability in cyclohexanone condensation.     

Synthesis, crystal structure and properties of a new heptamolybdate (NH4)6H2[Cu(C2O4)2(Mo7O24)] · 9H2O

An interesting heptamolybdate (NH₄)₆H₂[Cu(C₂O₄)₂(Mo₇O₂₄)] · 9H₂O (I) was prepared by convenational method in an aqueous solution and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, X-ray photoelectron spectroscopy and single-crystal X-ray diffraction. Crystal data for I: monoclinic, space group P2₁/m with a = 10.1460(5), b = 18.2616(9), c = 10.4994(5) ?, β = 94.3410(10)°, and Z = 2. X-ray structure analysis revealed the complexes to contain a copper center in an octahedral coordination mode bound to two [C₂O₄]²⁻ anios via the oxygen atoms and two oxygen atoms of the new heptamolybdate species. The zigzag chain structure of I is constructed by [Cu(C₂O₄)₂(Mo₇O₂₄)] units via Mo-O-Cu-O-Mo linkers.