MoO3催化碳酸二甲酯与乙酸苯酯合成碳酸二苯酯

采用焙烧法制备了MoO3催化剂并将其用于碳酸二甲酯(DMC)与乙酸苯酯(PA)合成碳酸二苯酯(DPC)反应,考察了焙烧温度对催化荆性能的影响,并用X射线衍射(XRD)对催化剂结构进行了表征.结果发现,在400或500℃焙烧的催化剂具有良好的催化性能,DMC转化率为73.9%,DPC和甲基苯基碳酸酯的选择性分别为39.5%和56.5%.XRD结果表明,该催化剂物相组成为正交晶系MoO3,且(021)或/和(110)晶面有利于酯交换反应.催化剂使用5次后DMC转化率从73.9%降至10.2%,多次重复使用后的催化剂在窄气气氛中于400或500℃焙烧即可再生,再生后催化剂的性能几乎和新鲜催化剂相当.     

Synthesis,Structure, and Decomposition of (NH4)2[Mo6Cl14] · H2O

(NH₄)₂[Mo₆Cl₁₄] · H₂O ( 1 ) was prepared from reactions of MoCl₂ in ethanol with aqueous NH₄Cl solution. It crystallizes in the monoclinic space group I2/a (no. 15), Z = 4 with a = 912.3(1), b = 1491.2(2), c = 1724.8(2) pm, β = 92.25(1)°; R1 = 0.023 (based on F values) and wR2 = 0.059 (based on F² values), for all measured X‐ray reflections. The structure of the cluster anion can be given as [(Mo₆Cl)Cl]^2– (i = inner, a = outer ligands). Thermal stability studies show that 1 loses crystal water followed by the loss of NH₄Cl above 350 °C to yield MoCl₂. The water‐free compound (NH₄)₂[Mo₆Cl₁₄] ( 2 ) was synthesized by solid state reaction of MoCl₂ and NH₄Cl in a sealed quartz ampoule at 270 °C. No single‐crystals could be obtained. Decompositions of 1 and 2 under nitrogen and argon exhibited the loss of NH₄Cl at about 350 °C. Decomposition under NH₃ resulted in the formation of MoN and Mo₂N at 540 °C and 720 °C, respectively.     

Nano‐MoO3 for highly selective enrichment of polycyclic aromatic hydrocarbons in in‐tube solid‐phase microextraction

Nano‐molybdenum trioxide was prepared from nano‐molybdenum disulfide by simple firing in muffle furnace. Nano‐molybdenum trioxide was used as the extraction coating on the stainless steel wire. Four wires were filled in a polyetheretherketone tube to get an extraction tube. The tube was connected to the six‐port valve of a high performance liquid chromatograph, and the online analysis system was constructed. Extraction selectivity of the tube for different types of compounds, including polycyclic aromatic hydrocarbons, plasticizers, estrogens, anilines and neonicotinoids, was studied. Good enrichment ability for polycyclic aromatic hydrocarbons, but the extraction efficiency of others was not satisfactory. Using eight polycyclic aromatic hydrocarbons as the targets, an analytical method was established after optimizing main factors such as sampling volume, sampling rate, methanol content, and desorption time. The established method exhibited wide linear range to 0.016–20.00 μg/L and low limits of detection to 0.005 μg/L, and the enrichment factors can be up to 2443. The method was applied to the detection of trace polycyclic aromatic hydrocarbons in tap water and river water, and a good recovery was obtained. The tube showed good durability and chemical stability, and it still remained good extraction effect after more than 140 run.     

A novel Mo(V) oligophosphate built up of di- and triphosphate groups: Cs(MoO)4(P2O7)2(P3O10)

A Mo(V) oligophosphate, built up of di and triphosphate groups, Cs(MoO)₄(P₂O₇)₂(P₃O₁₀) has been synthesized for the first time. This compound crystallizes in the triclinic P−1 space group with , , , α=94.534(6)°, β=102.520(6)°, γ=103.663(4)°. This original structure can be described by the association of MoO₆ octahedra, MoP₂O₁₁ units built up of one P₂O₇ group sharing two apices with the same MoO₆ octahedron, and triphosphates groups P₃O₁₀. The resulting tridimensional framework forms large S-shaped tunnels running along c where the Cs⁺ cations are located.     

Carbometallate: Komplexe Anionenverbände [MoC4/26—] in der Kristallstruktur von Pr[MoIIC2]

Carbometalates: Complex Anions equation/tex2gif-stack-4.gif [MoC_4/2^6—] in the Crystal Structure of Pr equation/tex2gif-stack-5.gif [Mo^IIC₂] Criteria for the existence of carbometalates are established and discussed in a broader context. The concept is then applied to the novel compound Pr₂[MoC₂], which is characterized by chemical analyses, X‐ray diffraction and metallography. The crystal structure (tetragonal, P4₂/mnm, Z = 4, a = 581.29(8) pm, c = 1032.53(14) pm) consists of layered polyanions equation/tex2gif-stack-6.gif[MoC_4/2^6—] of distorted vertex and edge sharing MoC₄ tetrahedra. Praseodymium is also in a distorted tetrahedral coordination by carbon. The physical properties show “bad metal” behaviour and localized magnetic 4f‐moments in agreement with the existence of Pr³⁺‐species. A detailed bonding analysis using both the electron localization function ELF and the COHP method justifies the interpretation of the title compound as a carbomolybdate(II).     

元素在石墨炉内石墨探针表面上的原子化机理研究 ⅩⅢ.钼的原子化机理

本文应用x-射线衍射(XRD)、X-射线光电子能谱(XPS)、俄歇电子能谱(AES)、扫描电子显微技术(SEM)研究了钼酸铵在石墨炉内石墨探针表面上的原子化机理。实验结果表明,在温度<1350K时,钼酸铵经历MoO_3和Mo_4O_(11)中间产物转变为MoO_2(s)。在更高温度下,MoO_2(s)首先还原为Mo_2C,而后进一步转变为MoC(s)。MoC再分解为Mo(s)。钼的原子化起源于Mo的升华。     

Synthesis and Crystal Structure of [C10N2H10]2[P2Mo5O21(OH)2]·2H2O

The crystal structure of [C₁₀N₂H₁₀]₂[P₂Mo₅O₂₁(OH)₂] · 2H₂O, contains the heteropolyanion, [P₂Mo₅O₂₁(OH)₂]^4—, together with diprotonated 4, 4′‐bipyridine. The heteropolyanion is built up from five MoO₆ octahedra sharing four common edges and one common corner, capped by two PO₃(OH) tetrahedra. The structure is stabilized by hydrogen bonds involving the hydrogen atoms of the 4, 4′‐bipyridine, water molecules and the oxygen atoms of the pentamolybdatobisphosphate. This is the first example that this kind of cluster could be isolated in the presence of a poly‐functional aromatic molecule ion. Crystal data: triclinic, P1¯ (No. 2), a = 9.983(2)Å, b = 11.269(2)Å, c = 17.604(4)Å, α = 73.50(3)°, β = 84.07(3)°, γ = 67.96(3)°; V = 1760.0(6)ų; Z = 2; R₁ = 0.037 and wR₂ = 0.081, for 9138 reflections [I > 2σ(I)].     

Characterization of the Surface Electrode Reaction in the Presence of Uniform Interaction: The Case of Mo(VI) Reduction in the Presence of Phenanthroline and an Excess of Fulvic Acids

Surface electrode reactions involving lateral uniform interactions between adsorbed species is studied by means of square‐wave voltammetry (SWV). Interactions are represented by the interaction product aΘ, were a is the Frumkin interaction parameter (a is positive for attraction and negative for repulsion forces) and Θ is the surface coverage. The properties of the SW voltammetric response enable detection of interactions and recognition of the type of interaction forces by a simple procedure. The influence of the interactions on the apparent electrochemical reversibility of the surface electrode reaction is studied in detail. Utilizing “quasireversible maximum” the simple methodology for estimation of the standard redox rate constant without knowing the exact value of the interaction product aΘ is developed. Theoretical predictions are illustrated and confirmed by experiments with Mo(VI) in the presence of phenantroline and an excess of fulvic acids.     

MoS2 nanosheet arrays supported on hierarchical porous carbon with enhanced lithium storage properties

MoS₂ nanosheet arrays supported on hierarchical nitrogen-doped porous carbon(MoS₂@C)have been synthesized by a facile hydrothermal approach combined with high-temperature calcination.The hierarchical nitrogen-doped porous carbon can serve as three-dimensional conductive frameworks to improve the electronic transport of semiconducting MoS₂.When evaluated as anode material for lithium-ion batteries,the MoS₂@C exhibit enhanced electrochemical performances compared with pure MoS₂ nanosheets,including high capacity(1305.5 mA h g^-1 at 100 mA g^-1),excellent rate capability (438.4 mA h g^-1 at 1000 mA g^-1).The reasons for the improved electrochemical performances are explored in terms of the high electronic conductivity and the facilitation of lithium ion transport arising from the hierarchical structures of MoS₂@C.     

A novel route to nanosized molybdenum boride and carbide and/or metallic molybdenum by thermo-synthesis method from MoO3, KBH4, and CCl4

Nanosized molybdenum boride and carbide were synthesized from MoO₃, KBH₄, and CCl₄ by thermo-synthesis method at lower temperature. The relative content of Mo, Mo₂C, and molybdenum boride in the product was decided by the molar ratio between MoO₃, KBH₄, and CCl₄. Increasing the molar ratio of CCl₄ to MoO₃ was favorable to the production of Mo₂C. Increasing the molar ratio of KBH₄ to MoO₃ was favorable to the production of molybdenum boride. By carefully adjusting the reaction conditions and annealing in Ar at 900°C, a single phase of MoB could be obtained.