Lacunary silicotungstic heteropoly salts as high-performance catalysts in oxidation of cyclopentene

The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the p H instead of the traditional step-by-step method,which exhibited excellent performance in the catalytic oxidation of cyclopentene(CPE)to aldehydes or alcohols.The 93.69%CPE conversion and 97.15%total product selectivity(41.38%for glutaraldehyde(GA)and 55.77%for 1,2-cyclopentanediol(1,2-diol)were achieved by using H_(2)O_(2)as the oxidant and acetonitrile as the solvent.Through complementary characterization,it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure,and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers.Furthermore,in situ FT-IR spectra was utilized to monitor the reaction process,revealing the formation of the active species W(O_(2))on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.

杂多酸(HPA)催化制取环缩酮和缩醛

本文在文[1—4]的基础上,报导以杂多酸为催化剂制取环缩酮和缩醛。杂多酸是一种固体酸,是近年来国内外学者广泛关注的多功能催化剂,可作为固体酸催化剂进行酯化、醇脱水、烯烃水合制醇、烯烃加醇制醚以及付克烷基化反应等;

Toluene Alkylation with Methanol to p-Xylene over Heteropoly Acids Supported by Clay

The alkylation of toluene with methanol for the selective formation of p-xylene was systematically studied. Very few studies have been reported on the use of superacids such as heteropolyacids on cheap supports, such as clay. This article deals with the use of different heteropoly acids （HPAs）, viz, Dodeca-Tungstophosphoric acid [H3PO4.12WO3.xH2O] （TPA）, Dodeca-Molyhdo phosphoric acid ammonium salt hydrate [H12Mo12N3O40P＋aq] （DMAA）, Dodeca-Molyhdo Phosphoric acid （PMA） on clay （MontmoriUonite, K-10） and as such plain clay. This comparative study reveals that 20%PMA/Clay shows 62% toluene conversion and 100% selectivity toward p-xylene.

Eco-friendly one-pot synthesis of acetals and ketals by heterogeneously catalyzed liquid-solid phase reaction

Twelve classes of acetals and ketals were synthesized from aldehyde/ketone and glycol using ZiSiW12O40/TiO2 as a novel eco-friendly catalyst. The physical characterizations were carried out by TG/DTA, FT-IR, XRD, and ^1H NMR spectra. The results indicated that the catalyst showed excellent catalytic activity for the condensation reactions. The yield of 12 classes of acetals and ketals reached 56.3%-96.3% under the typical reaction conditions （the molar ratio of aldehyde/ketone and glycol was 1：1.5, the quantity of catalyst was 0.5% of feed stock, the reaction time was 1.0 h, and the reaction temperature was 80-116℃）. The catalyst was easily recovered and reused to give almost the same yield of the product as that given by fresh TiSiW12O10/TiO2.

Alkali salts of heteropoly tungstates: Efficient catalysts for the synthesis of biodiesel from edible and non-edible oils

Alkali salts of tungsten based heteropoly acids with different central atom such as P, Si and Co were prepared and evaluated for transes- terification of both edible and non-edible oils to their corresponding fatty acid methyl esters. The catalyst of sodium salt of tungstic acid with Co as central atom （Na5CoW12O40） showed optimum activity towards transesterification compared with other heteropoly tungstates. The catalysts activities were correlated with the observed physico-chemical characteristics derived from FT-infrared （FT-IR）, X-ray diffraction （XRD）, temperature-programmed desorption of ammonia （NH3-TPD） and carbon dioxide （CO2-TPD）. The Na5CoW12O40 catalyst exhibiting high activity even at 65 ℃ is due to the presence of strong acidic as well as basic sites. The disclosed catalyst is tolerable towards water and free fatty acids present in the oils. The influence of catalyst loading, reaction time and reaction temperature is studied to optimize the reaction parameters.

CATIONIC RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN WITH KEGGIN-TYPE HETEROPOLYCOMPOUNDS AS SOLID ACID CATALYSTS

Three Keggin-type heteropolyanions, namely H3PMo12O40-13H2O, （NH4）3PMo12O40·4H2O and H3PW12O40·13H2O were prepared and tested in the ring-opening polymerization reaction of tetrahydrofuran. The effects of the counter-cation （H＋, NH4＋） and the peripheral atoms （Mo, W） on the polymerization were investigated. It has been found that when the protons of H3PMo12O40·13H2O were replaced by the ammonium cations the polymerization rate decreased dramatically. Whereas, when the peripheral atoms （Mo） were replaced by their homologous （W）, the polymerization rate increased twofold. As for the viscosity average molecular weight （My） of polymer products, it was found that the high molecular weight （7930） was obtained by using H3PW12O40·13H2O. The molecular weight （My） obtained by H3PMo12O40·13H2O and （NH4）H3PMo12O40·13H2O was 6470 and 6810, respectively.

Selective oxidation of cyclopentene with H2O2 by using H3PW12O40 and TBAB as a phase transfer catalyst

The selective oxidation of cyclopentene by aqueous H2O2 using H3PW12O40 and tetrabutyl ammonium bromide(TBAB) as a phase transfer catalyst has been investigated. The results show that the presence of TBAB significantly improved the oxidation selectivity of cyclopentene. The effects of the reaction conditions on the conversion of cyclopentene were investigated in detail. The optimal reaction conditions are as follows: the H3PW12O40 to TBAB molar ratio, 1:1–1:3;H3PW12O40 to cyclopentene molar ratio,0.54:100–0.64:100;and molar ratio of H2O2 to cyclopentene, 1.6:1. The conversion reached to 59.8% in 4h at 35.0 ℃, while the selectivity of glutaraldehyde was 38.0% and the selectivity of 1,2-cyclopentanediol was 55.6%. In addition, a route for oxidation of cyclopentene by aqueous H2O2 using a heteropoly acid and quaternary ammonium salt as a phase transfer catalyst was proposed.

由杂多钼酸盐前驱体制备的氧化钼催化剂催化CO_2存在下的异丁烷脱氢(英文)

Molybdenum based oxide catalysts Mo-H,Mo-Fe,Mo-Ce,and Mo-Sn were prepared by calcining H3PMo12O40,Fe1.5 PMo 12O40,Ce1.5PMo12O40,and Sn1.5 PMo12O40 heteropolyanion precursors at700℃,respectively.The prepared oxides have been characterized and tested for the dehydrogenation of isobutane(IB)to isobutene in the presence of CO2.The effects of temperature,time on stream,and CO2 /IB ratio were investigated.It was found that α-and-MoO3 phases were present in all catalysts.Catalytic tests showed that increasing the reaction temperature increased both the conversion and isobutene selectivity,whereas increasing the CO2 /IB molar ratio increased the conversion but decreased the selectivity for isobutene.Iron was found to be an effective additive element for the enhancement of catalytic activity compared with Ce and Sn.

Catalytic Film and Selective Oxidation of Iso-butylene

A kind of heteropoly compound film supported on Ce0.5Zr0.5O2 oxide was prepared on a porous titanium tube. The catalytic activity of the film for the selective oxidation of iso-butylene was tested and compared with the fixed-bed reactor. Results show that the catalytic film increases the yield of the target product-methacrylic acid, and avoids the temperature fluctuation caused by the reaction heat.

Synthesis and Characterization of Heteropolytungstosilicate Complexes with the Lanthanide Elements

Lanthanide heteropoly compounds K15[Ln(HSiW9O34)2]·28H2O(Ln = La, Ce, Nd), denoted as Ln(SiW9)2, were synthesized and characterized by element analysis, TG-DTA, IR, UV, XPS and XRD. The results show that partial oxygen in Ln(SiW9)2 was coordinated with Ln3- , where Ln-3 was in the inner side of the heteropoly anions, while the fundamental structure of SiW9 had little change. The result was supported by ion exchange experiment.

Thermal Behaviour of Some New Polyoxometalate Complexes of Ciprofloxacin with Keggin-type Heteropoly Acids

Four polyoxometalate complexes, (CPFX·HCl)_3H_4SiW_~12 O_~40 , (CPFX·HCl)_3H_3PW_~12 O_~40 , (CPFX·HCl)_3H_3PMo_~12 O_~40 and (CPFX·HCl)_4H_4SiMo_~12 O_~40 , were prepared from ciprofloxacin hydrochloride(CPFX·HCl) reacting with H_nXM_~12 O_~40 ·nH_2O(X=P,Si; M=W,Mo) in an aqueous solution, and characterized by elemental analysis, IR spectrometry and TG-DTA. The IR spectrum confirms the presence of Keggin-type anions of heteropoly acids and the characteristic functional groups of ciprofloxacin. The TG/DTA curves show that their thermal decomposition is a multi-step process including simultaneous collapse of the Keggin-type structure. At first, these compounds had a mass loss of water molecules, then several other mass losses occured due to the decomposition of ciprofloxacin hydrochloride and its fragments with the degradation of Keggin anions. The end product of decomposition is the mixture of WO_3(or MoO_3) and SiO_2(or P_2O_5), identified by X-ray diffraction and IR spectroscopy. The possible thermal decomposition mechanisms of these complexes are proposed. This study exemplified that the thermal stability of the complexes containing tungsten is much better than that of the complexes containing molybdenum.

Synthesis of Tungstophosphates of Heteropoly Compound and Its Catalytic Property in Oxidative Desulfurization of Diesel

Several kinds of Tungstophosphates of Heteropoly Compounds （TPHC） with different compositions and the same structure were synthesized using the method of solid-phase reaction to change the tool ratio of Na4P2O7·10H2O, WO3 and Na2WO4 · 2H2O. TPHC, as a catalyst, was used in oxidative desulfurization of diesel. The results show that TPHC has catalytic activity. With THPC existing, the highest desulfurization rate reaches 51.85%, 32.6% higher than that yield without TPHC. And the desulfiarization rate increases with decreasing WO3. FT-IR spectra of TPHC shows that the catalytic activity is related to the activity of end oxygen（Od）.The more active Od is, the stronger the capability of obtaining or losing electron is. It means that TPHC has a good catalytic activity. FT-IR spectra of TPHC indicates that desulfurization rate is in linear correlation with Iw-Od/Ip-Od/ Iw-Od is intensity of W-Od vibration band, Ip-Od is intensity of P-Od vibration band） and correlation coefficient reaches 0.965.

Synthesis, Characterization and Inhibition Effects of Vanadium Substituted Dawson-type Heteropoly Acids(Mo, P)

Four new vanadium substituted Dawson-type heteropoly acids H7[P2Mo17VO62]·39H2O（1）, H8[P2Mo16V2O62]·41H2O（2）, H9[P2Mo15V3O62]·51H2O（3） and H8[P2Mo14V4O62H2]·45H2O（4） were prepared respec-tively. Their structures were determined by IR and ICP. The inhibition effects of vanadium substituted Dawson-type heteropoly acids（Mo, P） on free radical polymerization of methyl methacrylate（MMA） were investigated by dilatometry. The results show that the rate of the polymerization of MMA decreases and the inhibition effects of the four heteropoly acids reach the inhibitor performance of hydroquinone at a certain ratio.

Study on the Surface Photovoltage and Fluorescence Properties of N, N-Bis(4-aminopheny)-1, 4 quinonenediimine Doped with H_4SiW_(12)O_(40)

Aniline oligomer composite materials using heteropolyacid H4SiW12O40 as dopant was synthesized, and the effect of the doping concentration on the photoluminescence and surface photovoltaic properties were investigated.

Voltammetric Studies on Heteropoly Phosphotungstovanadate Anions Across the Liquid/Liquid Interface

Electrochemical transfer behavior of V ⅤW 11 -V Ⅴ 3W 9 heteropoly anions on the water/nitrobenzene interface was investigated by means of cyclic voltammetry. The effect of the solution acidity on the transfer behavior and the stable pH range for the heteropoly anions were studied. The stability of mixed tungstovanadate decreases with increasing the number of vanadium atoms. The main transfer species within the potential window have the negative charges of 4 and the transfer process is diffusion controlled. The apparent transfer potential Δ w o Ψ 0 and the free energy Δ G 0 w→o tr for the heteropoly anions can be obtained from the experimental data. For the different anions, the Δ w o Ψ 1/2 pH relationship can be expressed as: Δ w o Ψ 1/2 =constant-53pH.

Synthesis and Characterization of Heteropoly Complexes of Indium with Metal－centred Undecatungstate Ligan

New indium heteropoly undecatungstometalate complexes of general formula K_n In( H_2O) MW_(11)O_(39) .xH_2O (M = Cr(Ⅲ) , Fe( Ⅲ ), Co(Ⅱ) or Zn( Ⅱ) ) were prepared by the stepwise acidification and the stepwise addition of materials. The products were characterized by elemental analysis, ion-exchange, IRspectra, UV spectra, X-ray powder diffraction and thermal analysis. The results show that the structure ofthe products derives from the Keggin structure. Their themial stability is higher than that of the homolo-gous dedecatungstometalates .

Etherification of Methanol with Propylene Oxide Catalyzed by Heteropolyacids

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Synthesis and Characterization 9-tungstosilicate Complexes with Transition Metal

The title complexes KaHb[M(SiW9O34)2]?mH2O(M=Ni,Cu,Zn,Fe or Mn) were synthesized by SiW9O34 10? with transition metal respectively and their structure were characterized by mean of elemental analysis, TG-DTA, IR spectra and, UV spectra. In addition, their redox properties in solution were investigated using polarographic and cyclic voltammographic methods. Experimental results indicated that the complexes have Keggin structure and that the heteropolyanions underwent two-step, two-electron tungsten reduction processes.

Synthesis and Structure of K_3Na_3〔MnMo_9O_(32)〕·6H_2O

The title compound was synthesized from the manganese(Ⅶ ), titanium(Ⅲ ) and molybdate. It was crystallized as K3Na3[MnMo9O32,). 6H2O in the rhombohedral space group R32(155 # ), with a=b= 15. 521 (4), c= 12. 417 (6) A γ=120. 00 (1 )°. V= 2590. 1 (1 ) A 3, Z= 3, M.= 1778. 08, Dc= 3. 396g/cm3, λ(MoKa)=0. 71073A, μ= 42. 5 cm-1, F(000) ~ 2754 and the structure was determined by Xray diffraction methods, refined to a residual of 0. 048 for 1137 independent observablereflections with I≥3σ(I). There are Potassium, sodium canons, [MnMo9O32]6- anion, and crystalline water molecules in the complex. The anion may be constructedfrom a hypothetical MnIVMo6 Anderson species by removing three alternate MoO6, octehedra and placing three MoO6, octahedra above and below the MnMo3 unit, thus the resulting structure has D3 symmetry.

Synthesis of d,l-α-Tocopherol Catalyzed by Heteropoly Acids

,d,l-a-Tocopherol (vitamin E) isfound to be synthesized by condensingtrimethylhydroquinone with isophytol catalyzed by heteropoly acids (HPA) H3:PW12O40 andH3PMo12O40 at room temperature. These HPA are efficient catalysts for the synthesis of d l-a-Tocopherol and can easily be separated from the reaction mixture and roused,