常温常压下硅氨基化介孔SBA-15负载Keggin型钼钒杂多酸催化氧化乙醛的反应研究

Keggin-type molybdovanadophosphoric acids(HPA),H_4PMo_(11)VO_(40)(1),H_5PMo_(10)V_2O_(40)(2)and H_6PMo_9V_3O_(40)(3)were anchored onto γ-aminopropyltriethoxysilane(APTS)aminosilylated silica mesoporous SBA-15 throughacid-base neutralization and the resulting HPA/APTS/SBA-15 were characterized by BET,TEM,XRD,ICP,FTIRand ~(31)P MAS NMR.The characterization results indicate that the Keggin-structure of these HPAs is preservedwithin the mesoporous silica host.The samples were tested for catalytic aerobic oxidation of acetaldehyde hetero-geneously in liquid phase under ambient condition.The electrostatic force between heteropoly acid and aminogroups grafted on the silica channel surface leads to strong immobilization of HPA inside SBA-15 which is againstthe leaching during the reaction.The good catalytic performance and easy recycle of these catalysts make them aspotential environmental friendly catalysts for elimination of indoor air pollutants.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid, H5[PMo10V2O40]

The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid,H<Subscript>5</Subscript>[PMo<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript>]

Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

Detection of steroids with molybdovanadophosphoric acids on thin-layer chromatograms

Two vanadium analogues of phosphomolybdic acid, H₄[PMo₁₁VO₄₀] and H₄[PMo₁₀V₂O₄₀], have been studied for use as detection reagents for steroids on thin-layer plates. They were found to produce characteristic colors with steroids after spraying and heating at 105 °C.     

Molybdovanadophosphoric Acid Catalyzed Oxidation of Hydrocarbons by H2O2 to Oxygenates

Heteropoly acids of the general formula H_3+x[PMo_12-xV_xO₄₀] (where x = 1,2,3) catalyzed the oxidation of aromatic hydrocarbons at 65°C with H₂O₂ to give oxygenated products. Among the catalysts, H₄[PMo₁₁VO₄₀] was found to be a more active catalyst and its activities have been reported in the oxidation of cyclohexane, methyl cyclohexane, naphthalene, 1-methyl naphthalene and biphenyl.     

Hydrothermal syntheses, crystal structures, and properties of two polyoxometalates [Cd(2,2′-bpy)3]2[PMoVMoVI 11O40] and [H3PMo12O40]·3(4,4′-bpy)·4H2O

Two Keggin-type phosphododecamolybdate compounds [Cd(2,2′-bpy)₃]₂[PMo^VMo^VI ₁₁O₄₀] (1) and [H₃PMo₁₂O₄₀]·3(4,4′-bpy)·4H₂O (2) (bpy=bipyridine) were prepared by the hydrothermal method for the first time and characterized by elemental analyses, X-ray single-crystal diffraction, ESR spectra, and IR spectra, showing that compound 1 consists of a mixed valence Keggin polyanion [PMo^VMo^VI ₁₁O₄₀]⁴⁻ and two isolated coordinated cations [Cd(2,2′-bpy)₃]²⁺, while compound 2 is an intermolecular compound based on organic substrate 4,4′-bpy and heteropoly acid unit H₃PMo₁₂O₄₀. Furthermore, both the compounds show strong photoluminescence properties in the solid state at room temperature. The catalytic activities of the two compounds were also determined by the oxidation of benzaldehyde to benzoic acid using H₂O₂ as oxidant in a liquid–solid triphase system.     

Pyridine-H5PMo10V2O40 hybrid catalysts for liquid-phase hydroxylation of benzene to phenol with molecular oxygen

Pyridine(Py)-modified Keggin-type vanadium-substituted heteropoly acids (Py _n PMo₁₀V₂O₄₀, n=1 to 5) were prepared by a precipitation method as organic/inorganic hybrid catalysts for direct hydroxylation of benzene to phenol in a pressured batch reactor and their structures were detected by FT-IR. Among various catalysts, Py₃PMo₁₀V₂O₄₀ exhibits the highest catalytic activity (yield of phenol, 11.5%), without observing the formation of catechol, hydroquinone and benzoquinone in the reaction with 80 vol% aqueous acetic acid, molecular oxygen and ascorbic acid used as the solvent, oxidant and reducing reagent, respectively. Influences of reaction temperature, reaction time, oxygen pressure, amount of ascorbic acid and catalyst on yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. Pyridine can greatly promote the catalytic activity of the Py-free catalyst (H₅PMo₁₀V₂O₄₀), mostly because the organic π electrons in the hybrid catalyst may extend their conjugation to the inorganic framework of heteropoly acid and dramatically modify the redox properties, at the same time, pyridine adsorbed on heteropoly acids can promote the effect of “pseudo-liquid phase”, thus accounting for the enhancement of phenol yield. Supported by the National Natural Science Foundation of China (Grant Nos. 20476046 and 20776069) and the “Qinglan” Project of Jiangsu Province for Young Researchers     

Crystal structure of a novel two-dimensional supramolecular network based on polyoxoanion and yttriumIII coordination cation

A novel compound (NH⁴)₂Y(H₂O)₈[PMo₁₀V₂O₄₀]·10H₂O has been prepared in an aqueous solution and characterized by elemental analysis, IR, and TG-DTG analysis. X-ray diffraction analysis was carried out on (NH₄)₂Y(H₂O)₈ [PMo₁₀V₂O₄0]·10H₂O single crystal, which crystallizes in the monoclinic system of a space group P21/c witha=0. 9871 (3) nm,b=1. 5424 (5) nm,c=2.7924(9) nm, β = 94.183(5)° and Z=2. In the compound, a two-dimensional network is constructed by the PMo₁₀V₂O ⁵⁻₄₀ anion and the Y(H₂O) ³⁺₈ cation building blocks via hydrogen bonding exhibiting the porous structure.

     

Deep oxidative desulfurization of dibenzothiophene with molybdovanadophosphoric heteropolyacid-based catalysts

Three hydrophobic Keggin-type heteropolyacid catalysts, [C₃H₃N₂(CH₃)(C₂H₄)]₅PMo₁₀V₂O₄₀ ([C₂mim]PMoV), [C₃H₃N₂(CH₃)(C₄H₈)]₅PMo₁₀V₂O₄₀ ([C₄mim]PMoV) and [C₃H₃N₂(CH₃)(C₆H₁₂)]₅PMo₁₀V₂O₄₀ ([C₆mim]PMoV), were synthesized by reacting molybdovanadophosphoric acid with imidazolium bromides, and characterized by spectroscopic methods. Their use as catalysts in the extractive catalytic oxidative desulfurization process using hydrogen peroxide as the oxidant and acetonitrile as phase transfer agent was studied. The catalytic properties decreased in the order: [C₆mim]PMoV > [C₄mim]PMoV > [C₂mim]PMoV. The main factors influencing the rate of removal of dibenzothiophene (DBT) were investigated, including reaction temperature, the amounts of catalyst, H₂O₂ and acetonitrile. Nearly 100 % sulfur removal rate was achieved under optimal conditions. The catalyst could be recycled six times with only a slight decrease in activity. A reaction mechanism for DBT oxidation is proposed, in which the Keggin anions first obtain active oxygen from H₂O₂, then the DBT is oxidized to dibenzothiophene sulfones.     

Crystal structure of a novel two-dimensional supramolecular network based on polyoxoanion and yttrium<Superscript>III</Superscript> coordination cation

A novel compound (NH⁴)₂Y(H₂O)₈[PMo₁₀V₂O₄₀]·10H₂O has been prepared in an aqueous solution and characterized by elemental analysis, IR, and TG-DTG analysis. X-ray diffraction analysis was carried out on (NH₄)₂Y(H₂O)₈ [PMo₁₀V₂O₄0]·10H₂O single crystal, which crystallizes in the monoclinic system of a space group P21/c witha=0. 9871 (3) nm,b=1. 5424 (5) nm,c=2.7924(9) nm, β = 94.183(5)° and Z=2. In the compound, a two-dimensional network is constructed by the PMo₁₀V₂O ₄₀ ^5? anion and the Y(H₂O) ₈ ³⁺ cation building blocks via hydrogen bonding exhibiting the porous structure.     

Effect of adding H2SO4 and NaCl TO palladium-containing catalysts on the results of methane oxidation at 220°C

A study has been made of the interaction of methane at 220°C with silica gel-supported complexes of palladium(II), Na_n H_9-n[PMo₆V₆O₄₀], H₉[PMo₆V₆O₄₀], H₃[PMo₁₂O₄₀], NaCl, and with added sulfuric acid. Competition between electrophilic and chloride pathways is examined. Additions of Na⁺ and Cl^– direct the reaction along the chloride pathway, leading to the formation of CH₃Cl. Without NaCl, the electrophilic mechanism is realized, the main product of which is CO₂.L. M. Litvinenko Institute of Physical-Organic Chemistry and Coal Tar Chemistry, National Academy of Sciences of the Ukraine, 70 R. Luxembourg Street, Donetsk 340114, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 2, pp. 92–96, March–April, 1996. Original article submitted June 30, 1995.     

Oxidation of isobutane catalyzed by vanadyl, copper and cesium substituted H3PMo12O40

Effects of Cs⁺, H⁺ and Cu²⁺ counterions in the vanadium containing heteropoly compounds Cs_xH_1-xVO[PMo₁₂O₄₀] and Cs_yH_0.5-yCu_0.25VO[PMo₁₂O₄₀] on the catalytic oxidation of isobutane and characterization by TGA, IR and ESR spectroscopies are reported. A high selectivity of 76% for methacrylic acid and methacrolein together has been obtained with Cs_0.75H_0.25VO[PMo₁₂O₄₀] catalysts at a reactivity of 5.3x10^-1 mmol/h cm³.     

含磷钼酸及2,2’-联吡啶-3,3’-二羧酸配体的铜配位聚合物的合成、晶体结构与电化学性质

在水热条件下合成了一个新的化合物{[Cu4(PMo12O40)(H2O)5(H2bpdc)(Hbpdc)(bpdc)2].6H2O}n(H2bpdc=2,2′-联吡啶-3,3′-二羧酸),并用元素分析、IR、TG和X-射线衍射等手段进行了表征。结果表明本化合物的晶体结构中,最小不对称单元包含1个[Cu4(H2O)5(H2bpdc)(Hbpdc)(bpdc)2]3+阳离子,1个[PMo12O40]3-阴离子和6个结晶水分子。Cu(Ⅱ)与相邻[PMo12O40]3-的桥氧原子配位,形成一维链状结构。电化学研究表明,化合物存在三步氧化还原过程。     

Catalytic properties of platinum-promoted acid cesium salts of molybdophosphoric and molybdovanadophosphoric heteropoly acids in the gas-phase oxidation of benzene to phenol with an O<Subscript>2</Subscript> + H<Subscript>2</Subscript> mixture

Acid salts Cs _x H_{3 + n ? x} PMo_{12 ? n} V _n O₄₀ (n = 0, 1, 2, or 3; x = 2.5 or 3.5) with coprecipitated or supported platinum were studied using thermogravimetry, IR spectroscopy, and temperature-programmed reduction. The thermal region of the full stability of these salts is limited by the decomposition temperature of the corresponding acid H₃PMo₁₂O₄₀ (～400°C) or H_{3 + n} PMo_{12 ? n} V _n O₄₀ (～300–350°C). The degree of reduction of heteropoly anions with hydrogen is regulated by temperature. Deeply reduced heteropoly anions (at 300°C) are slowly oxidized with oxygen with structure and composition regeneration. The states of molybdenum and vanadium on the surface of samples with coprecipitated platinum Pt_0.1-Cs_2.5H_0.5PMo₁₂O₄₀ (1) and Pt_0.1-Cs_2.5H_2.5PMo₁₀V₂O₄₀ (2), which were studied using XPS, correspond to reduced or reoxidized heteropoly anions in the bulk. Platinum metal particles of ～5 nm in size were observed in high-resolution TEM images obtained after the reduction and storage of sample 1 in air. A heteropoly compound forms two texture levels: spherical nanoparticles of 10–20 nm in size are collected in closely packed globules of 100–300 nm in size. Detailed texture studies, which were performed using nitrogen adsorption isotherms, demonstrated texture mobility under the ambient conditions. The cesium salts of the heteropoly acids were tested in the gas-phase oxidation of benzene to phenol with an O₂ + H₂ mixture at 180°. The effect of platinum concentration on the specific catalytic activity in the presence of deeply reduced heteropoly anions was monitored. The samples containing the salt Cs_2.5H_0.5PMo₁₂O₄₀ exhibited the highest activity in the formation of phenol. The introduction of vanadium into the heteropoly anion impaired the catalytic performance of both deeply and slightly reduced samples.     

Synthesis of 1,2,9-trisubstituted purin-6(9H)-ones catalyzed by heteropolyacids

1,2,9-Trisubstituted purin-6(9H)-ones have been synthesized in high yield by reaction of 5-amino-N,1-dimethyl-1H-imidazole-4-carboxamide with aromatic aldehydes in the presence of heteropolyacids, H₃PMo₁₂O₄₀ and H₅PV₂Mo₁₀O₄₀. The catalytic activity of H₃PMo₁₂O₄₀ is lower than that of H₅PV₂Mo₁₀O₄₀. This is an effective synthesis of l,2,9-trisubstituted guanine derivatives with the advantages of mild reaction conditions, simple operation, and good yields.     

Hydrothermal Synthesis and Crystal Structure of Two New α-Keggin Derivatives Decorated by Transition Metal Complexes

Two new neutral Keggin-polyoxometalate derivatives: [{Co(2,2′-bipy)₂(H₂O)}₂]–[PMo^VI₇Mo^V₅O₄₀(V^IVO)₂] (1) and [{Ni(phen)₂(H₂O)}₂](H₃O) [PMo^VI₁₀Mo^V₂O₄₀] · 4H₂O (2) have been synthesized under hydrothermal conditions and characterized by i.r., t.g. analysis, x.p.s. spectra and single-crystal X-ray diffraction. In the case of (1), the polyoxoanion cluster [PMo₁₂O₄₀]⁸⁻ is capped by two vanadium atoms via four bridging oxo groups on two opposite {Mo₄O₄} pits of the Keggin polyoxoanion. Two {Co (2,2′-bipy)₂(H₂O)} fragments are supported on the two vanadium atoms through two terminal oxygen atoms from two vanadium atoms. In (2), two {Ni(phen)₂(H₂O)}²⁺ moieties are linked to the molybdophosphate cluster [PMo₁₂O₄₀] core to form a neutral bimetallic cluster. Furthermore, through the linkages of π – π stacking interactions and hydrogen bond contacts, extended three-dimensional supramolecular networks in the solid of (1) and (2) were formed.     

New Catalytic Reactions in the Presence of Mo-V-Phosphoric Heteropoly Acid Solutions

The possibility of performing new catalytic reactions in the presence of solutions of H _x+3PMo_12−x . V_xO₄₀ Mo-V-phosphoric heteropoly acids was examined.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 5, 2005, pp. 772–778.Original Russian Text Copyright © 2005 by Zhizhina, Simonova, Russkikh, Matveev.     

Titania-supported mixed HPMoV polyoxometallates as precursors of hydrodesulfurization catalysts

HDS catalysts were prepared by loading H₃PMo₁₂O₄₀ or H₄PMo₁₁V₁O₄₀ polyoxometallates on TiO₂ (0.5 and 1.0 mmol (Mo+V)). Activity of the catalysts was tested in the HDS of thiophene. The activity of catalysts of low concentration was 2–3 times higher than the activity of those of high concentration. Temperature programmed reduction (TPR) and IR spectroscopy were used to determine the properties of the catalyst. TPR measurements proved that vanadium promotes and stabilizes HDS activity due to an increase in the Mo⁵⁺/Mo⁴⁺ ratio.     

Selective oxidation of light alkanes over Mo-based oxide catalysts

A highly reduced Keggin-type heteropolymolybdophosphate, H₃PMo₁₂O₄₀(Py), which was formed by the heat-treatment of pyridinium salt of H₃PMo₁₂O₄₀, can catalyze the propane oxidation to acrylic acid and acetic acid selectively. We propose a possible reaction mechanism for alkane oxidation, where protons and electrons on the reduced H₃PMo₁₂O₄₀ catalyst cooperate for activating molecular oxygen to form electrophilic oxygen species for alkane oxidation. It is also reported that Anderson-type heteropolycompounds linked with vanadyl cations VO²⁺ were able to be synthesized by hydrothermal reaction and showed good catalytic activity for the ethene oxidation to acetic acid.     

Raman spectra of hybrid materials based on carbon nanotubes and Cs3PMo12O40

A route for the synthesis of hybrid materials using multiwalled carbon nanotubes (MWCNTS) and Cs₃PMo₁₂O₄₀ was confirmed. The Cs₃PMo₁₂O₄₀ salt was synthesized from H₃PMo₁₂O₄₀·14H₂O and CsCl. All compounds were characterized by Raman spectroscopy. The synthesis method can produce a chemically stable Cs₃PMo₁₂O₄₀ molecule and pure and oxidized MWCNTS. Raman spectroscopy showed that the chemical interaction between MWCNTS and Cs₃PMo₁₂O₄₀ was essentially of electrostatic nature. Raman spectra obtained with different wavelengths showed thermal decomposition of H₃PMo₁₂O₄₀·14H₂O (raw materials) from laser heating process. On the contrary, the synthesized compound (i.e. Cs₃PMo₁₂O₄₀) was stable under the experimental conditions.