Dawson结构磷钨酸铯的制备、表征及催化绿色合成己二酸

利用室温沉淀法制备出Dawson结构磷钨酸铯,考察了其在催化微波促进30%H2O2氧化环己酮合成己二酸反应中的催化性能,并通过FT-IR、SEM、XRD、EDS、ICP-AES对催化剂进行表征。探讨了铯离子取代个数、催化剂用量、微波功率、反应温度、反应时间、H2O2用量等对己二酸收率的影响。结果表明,最优的反应条件为Cs离子取代个数为3,w(催化剂)=7.6%(基于环己酮质量),n(环己酮)∶n(30%H2O2)=100∶375,反应时间4.0 h,微波功率300 W,反应温度100℃。在此条件下己二酸收率可达90.4%。催化剂重复使用5次,己二酸收率为73.1%。     

Thermal Transformations of the Nd2P6O18 · 12H2O and Li3Nd3(P6O18)2 · 26H2O Cyclohexaphosphates into Polyphosphates

The thermal dehydration and transformations of the cyclohexaphosphates Nd₂P₆O₁₈ · 12H₂O and Li₃Nd₃(P₆O₁₈)₂ · 26H₂O are investigated in the range 20–1000°C using differential thermal analysis and high-temperature x-ray diffraction, in conjunction with chromatographic determination of the anion composition of reaction products. The results demonstrate that, during heating, the cyclohexaphosphates convert into the polyphosphates Nd(PO₃)₃ (monoclinic and orthorhombic forms) and LiNd(PO₃)₄ (monoclinic form). These processes are not accompanied by P₂O₅ removal. The temperature stability limits of the polyphosphates are determined, and the possible mechanisms of the cyclohexaphosphate–polyphosphate transformations are discussed.     

Scanning tunneling microscopy and tunneling spectroscopy of nano-structured H6P2MoxW(18-x)O62 (x = 0, 3, 9, 15, 18) Wells-Dawson heteropolyacids

Scanning tunneling microscopy (STM) and tunneling spectroscopy studies of nano-structured H6P2MoxW(18-x)O62 (x = 0, 3, 9, 15, 18) Wells-Dawson heteropolyacids (HPAs) were carried out to examine redox properties of the HPAs. STM images of H6P2MoxW(18-x)O62 HPAs clearly showed self-assembled and well-ordered 2-dimensional arrays on graphite surface. Tunneling spectroscopy measurements revealed that all H6P2MoxW(18-x)O62 HPAs exhibited a negative differential resistance (NDR) behavior in their tunneling spectra. NDR peak voltage of H6P2MoxW(18-x)O62 HPAs appeared at less negative applied voltage with increasing molybdenum substitution. Reduction potential of H6P2MoxW(18-x)O62 HPAs measured by an electrochemical method increased and absorption edge energy determined by UV-visible spectroscopy shifted to lower value with increasing molybdenum substitution. In other words, NDR peak voltage of H6P2MoxW(18-x)O62 HPAs appeared at less negative applied voltage with increasing reduction potential and with decreasing absorption edge energy of the HPAs; more reducible H6P2MoxW(18-x)O62 HPAs showed NDR behavior at less negative applied voltage. These results indicate that NDR peak voltage of nano-structured HPAs measured by STM could be utilized as a correlating parameter for the redox properties of bulk HPAs.     

Thermal polycondensation of ammonium paratungstate, (NH4)10[W12O40(OH)2].4H2O

Connected with the examination of the thermal polycondensation of ammonium paratungstate pentahydrate the chemical and morphological properties of intermediate phases formed during the thermal decomposition of APT have been investigated. We have studied the pH and the turbidity of the aqueous solutions of the intermediate phases, the solubility of the phases, and their rehydratation capability as well as the morphology of the crystallite granules and the grain size distribution. These properties of the original APT have been related to the same properties of the products of decomposition formed between different temperature ranges. The results obtained show unambiguously that each of the above mentioned properties suddenly changes in the temperature range 225 to 250°C. This temperature range coincides with the formation temperature of a new phase called APT II. The most probable formula of APT II is (NH₄)₈ [H₂W₁₃O₄₃(OH)₂]·H₂O.     

Reprocessing of Irradiated [18O]H2O under the Conditions of a PET Center

Radiochemistry - The possibility of reprocessing of irradiated [18O]H2O after isolation of [18F]fluoride ion from it (regenerate) under the conditions of the cyclotron-radiochemical laboratory of...     

Vibrating reed study of the flux line dynamics of κ-(ET)2Cu[N(CN)2]Br

Vibrating reed measurements were performed on single-crystal samples ofκ-(ET)₂- Cu[N(CN)₂]Br in an applied magnetic fieldH oriented either parallel (“longitudinal”) or perpendicular (“transverse”) to the highly conducting ac-plane. Field-cooling data taken for the longitudinal orientation andH<0.7 T revealed a peak with a low-temperature shoulder in the reed dissipation 1/Q located at temperatureT _Q below the superconducting transition temperatureT _c (≈11.6 forH=0). The shoulder disappeared nearH≈0.7 T, accompanied by an abrupt change in the slope ofT _Q (H), corresponding to a similar change in the slope of the upper critical magnetic fieldH _c2 measured by Kwoket al. The existence of the shoulder in the dissipation peak bears on a number of current explanations for the exotic superconducting properties ofκ-(ET)₂Cu[N(CN)₂]Br.T _Q data taken for the transverse orientation fell far below estimates ofH _c2., indicating the existence of a substantial region of flux line (FL) mobility belowH _c2(T). The location of a peak in NMR relaxation observed by De Sotoet al. lies close toT _Q for the transverse orientation.     

[Mn(H2P2O7)3]3-引发淀粉与丙烯腈和AMPS接枝共聚

首次以[Mn(H2P2O7)3]3-为引发剂,研究了淀粉与丙烯腈和2-丙烯酰胺-2-甲基丙磺酸(AMPS)接枝共聚反应,并用红外光谱和元素分析法证明了接枝共聚物的存在,并考察了皂化后接枝产物的吸水性随反应条件的变化.结果显示,最适宜的反应条件为单体中AMPS的摩尔百分含量为5%;单体/淀粉的摩尔比为1.5;[Mn(H2P2O7)3]3-浓度2.0×10-3 mol/L;反应温度30 ℃.     

纳米微孔杂多化合物Na[Fe2(O2H3)Mo2O8](Ⅰ)和(NH4)[Fe(MoO4)2](Ⅱ)的结构特征

通过采用水热合成法得到了二种具有纳米筛孔的氧簇化合物Na[Fe2(O2H3)Mo2O8](Ⅰ)和(NH4)[Fe(Mo O4)2](Ⅱ).晶体(Ⅰ)属于单斜晶系,空间群为C2/m,晶胞参数为:a=9.5450(17),b=6.4381(9),c=0.76405(12)nm;β=116.128(4),Z=2,R1=0.0219,Rw=0.0756.晶体(Ⅱ)属于正交晶系,空间群为Pnma,晶胞参数为:a=1.4782(3),b=0.56774(11),c=0.87653(18)nm;Z=4,R1=0.0212,Rw=0.0513.     

Complexation and Disproportionation of Np(V) in K10P2W17O61 Solutions

Complexation of NpO₂ ⁺ and NpO₂ ^{2 +} with unsaturated K _n P₂W₁₇O₆₁ ^{n - 1 0} (L ^x-) heteropolyanion and disproportionation of Np(V) in the presence of L ^x- were studied spectrophotometrically. The logarithms (logK) of the formation constants of NpO₂ ^VL and NpO₂ ^{V I}L are 3 and 7, respectively. The K⁺ and Na⁺ cations bind the L ^x- anions, thus decreasing the yield of the complexes. Neptunium(V) disproportionation in K₁₀P₂W₁₇O₆₁ solutions containing 1 M (HClO₄ + NaClO₄) (pH from 0 to 4) and free from NaClO₄ (pH 2-6.5) was studied. The disproportionation rate is described by the equation -d[Np(V)]/dt = k[Np(V)][L ^x-]. The pH dependence of the rate constant passes through a maximum at pH 1. The rate constant decreases with increasing [Na⁺]. The reaction is inhibited by its product, Np(IV). The Np(V) complex is not involved in disproportionation; the reactive species is NpO₂ ⁺ aqua ion, which is probably converted into NpO^{3 +}L ^x-. Then NpO^{3 +}L ^x- rapidly reacts with NpO₂ ⁺, which occurs simultaneously with, or is preceded by release of the second oxygen atom.     

Crystal structure of Rb3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)]

The structure of Rb₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] was studied by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system with the unit cell parameters (at 100 K) a = 18.387(3), b = 16.398(3), c = 12.460(2) Å, β = 92.837(5)^°, V = 3752.4(11) ų, space group C2/c, Z = 4, R = 0.0390. The uranium-containing structural units of the crystals are isolated mononuclear groups [UO₂(CH₃COO)₃]^? and [UO₂(CH₃COO)(NCS)₂(H₂O)]^?, belonging to crystal-chemical groups AB ₃ ⁰¹ and AB⁰¹M ₃ ¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?, M¹ = NCS^? and H₂O) of uranyl complexes, respectively. The uranium-containing complexes are linked in a framework by hydrogen bonds and by electrostatic interactions with Rb⁺ cations.     

The crystallization of calcium phosphate glass with the ratio [CaO]/[P2O5] < 1

The phase evolution in a calcium phosphate glass with the molar ratio [CaO]/[P₂O₅] < 1, to which 6.4 mol% TiO₂ and 10 mol% Al₂O₃ were added as nucleation agents, was studied. The results indicate that the primary phase -Ca₂P₂O₇ is formed during surface nucleation and crystallization which are dominant at T < 930°C. No presence of metastable calcium phosphates was registered during the formation of the primary phase. The growth of -Ca₂P₂O₇ crystals occurs on the faceted crystal/glass interface with dendritic morphology at a crystal growth rate that is independent of time. The kinetics of -Ca₂P₂O₇ crystal growth are characterised by a growth activation energy of E _a = 426 ± 15 kJ/mol. The parameters of the unit cell of the -Ca₂P₂O₇ phase decrease with increasing temperature. The secondary TiP₂O₇ and AlPO₄ phases are formed by volume nucleation and crystallization. The temperature of the maximum nucleation rate was determined to be T _n = 690°C, and it is higher than the transformation temperature T _g. In the temperature interval T < 930°C secondary phases appear during long annealing times. At T > 930°C glass volume crystallization is dominant.     

[Ag(PPh_3)_2(CH_3COO)]_2·3H_2O的合成和晶体结构

将醋酸银和三苯基磷按1∶2摩尔比例进行反应得到化合物Ag(PPh3)2(CH3COO)]2,采用红外光谱、核磁共振、元素分析和单晶X射线衍射的方法,对其结构进行了表征.晶体结构解析结果显示,配合物属单斜晶系,空间群C2/c,a=44.286 8',b=13.269 6',c=24.997 0',α=90.000°,β=105.573°,γ=90.000°,Z=8,R=0.052 0,wR2=0.132 4.     

Optical constants of V(1-x)W(x)O(2) Films

The spectral complex optical constants in the visible and the near-infrared region of VO(2) and V(1-x)W(x)O(2) films deposited on glass substrates were determined from observed reflectance and transmittance spectra for which the least-squares method was used. In the metallic phase, the optical properties were characterized by the Drude model in wavelength regions longer than 750 nm.     

A new high-nitrogen compound [Mn(ATZ)(H2O)4] x 2H2O: synthesis and characterization

A new high-nitrogen compound [Mn(ATZ)(H(2)O)(4)] x 2H(2)O (ATZ=5,5-azotetrazolate) was synthesized. Crystal structure and elemental, IR and thermal analyses were investigated in the present work. It crystallized in triclinic space group P-1 with lattice parameters a=6.304(2)A, b=7.004(2)A, c=7.921(3)A, alpha=76.114(5) degrees , beta=74.023(5) degrees , gamma=69.254(4) degrees . TG-DTG and DSC measurements are employed to postulate the thermal decomposition mechanism. The thermal decomposition kinetics of the main exothermic reaction was investigated by non-isothermal method and obtained its enthalpy of decomposition and the probable kinetic mechanism. An attempt was made to incorporate the relation between thermal stability and the structure.