Showing papers on "Phosphotungstic acid published in 2007"
TL;DR: The UV-photon-induced degradation of heptafluorobutanoic acid was investigated in acidic aqueous solutions in the presence of titanium dioxide and the formation rate of CO(2) increased with illumination time, while both perfluorinated sulfonic acids are persistent under the experimental conditions employed in this study.
121 citations
TL;DR: Polyelectrolyte complexes (PECs) of chitosan and phosphotungstic acid have been prepared and evaluated as novel proton-conducting membranes for direct methanol fuel cells as discussed by the authors.
98 citations
TL;DR: In this article, a novel inorganic glass composite membrane consisting of a mixture of phosphotungstic acid and phosphomolybdic acid was derived by a sol−gel method.
Abstract: The synthesis and characterization of a novel inorganic glass composite membrane consisting of a mixture of phosphotungstic acid and phosphomolybdic acid are reported. Phosphosilicate gels doped with these two proton conducting donor components were derived by a sol−gel method. The influence of the textural properties of the glass composites could be interpreted from N2 adsoption−desorption isotherms. The pore size was less than 6 nm for all glass membranes. These glass membranes were found to be stable up to 400 °C. Fourier transform infrared spectroscopy indicated that the characteristic Keggin anions PW12O403- and PMo12O403- were present in the glass composite membrane. The highest proton conductivity was measured to 1.01 × 10-1 S cm-1 at 85 °C with 85% relative humidity (RH). Membrane electrode assemblies were prepared and showed good performance, with a maximum power density value of 35 mW/cm2 at 93 mA/cm2 as well as a current density of 137 mA/cm2 when utilized in a H2/O2 fuel cell at 28 °C and 30% RH.
79 citations
TL;DR: The experimental results showed that chitosan can be effectively degraded with H 2 O 2 under the catalysis of phosphotungstic acid in heterogeneous phase as mentioned in this paper, and the optimal conditions of degradation were determined by orthogonal tests.
60 citations
TL;DR: In this article, the conceptual mechanism in Dibenzothiophene (DBT) oxidation with hydrogen peroxide using a directly combined catalyst of quaternary ammonium bromide and phosphotungstic acid was described.
Abstract: This paper describes the conceptual mechanism in dibenzothiophene (DBT) oxidation with hydrogen peroxide using a directly combined catalyst of quaternary ammonium bromide and phosphotungstic acid. The effect of the catalyst composition on DBT oxidation was investigated in detail and a series of different amphiphilic quaternary ammonium salts was tested, including octadecyltrimethylammonium bromide (STAB), cetyltrimethylammonium bromide (CTAB), (1-tetradecyl)trimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB). The catalyst with a proper cation is required to achieve high activity toward the sulfur compounds and to be easily separated from the system. The exact position of the amphiphilic catalyst in the interface will directly affect the resistance in the DBT mass transfer step and therefore the rate of the overall catalysis process. Further, to better understand the effect of interface properties on DBT oxidation, a comparative study was carried out in different alkanes. The reac...
59 citations
TL;DR: The commercially available heteropoly acid H3PW12O40 (0.5 µm) is a very efficient and environmentally benign catalyst for N-tert-butoxycarbonylation of amines (primary, secondary) with di-TERT-butyl dicarbonate in short reaction times as mentioned in this paper.
56 citations
TL;DR: In this article, a mesoporous HPW/SiO 2 with Keggin-type heteropolyacids encapsulated into SiO 2 framework has been synthesized by evaporation-induced self-assembly method.
53 citations
TL;DR: An ultrasound assisted phase-transfer catalyzed epoxidation of 1,7-octadiene is greatly enhanced by using a cocatalyst of phosphotungstic acid in the presence of hydrogen peroxide in an organic solvent/aqueous solution two-phase medium.
51 citations
TL;DR: In this article, a composite polymeric gel comprising room-temperature ionic liquids (1-butyl-3-methyl-imidazolium-hexafluorophosphate, BMImPF 6 ) and heteropolyacids (phosphotungstic acid, PWA) was successfully prepared and employed as a quasi-solid state electrolyte in dye-sensitized solar cells (DSSCs).
45 citations
TL;DR: A series of ecofriendly solid acid catalyst were synthesized by supporting phosphotungstic acid onto hydrous zirconia by an incipient wetness impregnation method in order to contribute towards clean technology.
Abstract: A series of ecofriendly solid acid catalyst were synthesized by supporting phosphotungstic acid onto hydrous zirconia by an incipient wetness impregnation method in order to contribute towards clean technology. The support and resulting catalysts were characterized by various spectral and physicochemical techniques. Their catalytic activities were evaluated for oxybromination reaction of phenol by varying different reaction parameters. The electrophilic substitution of bromine generated in situ from KBr as a bromine source and hydrogen peroxide as an oxidant. The 15 wt.% of phosphotungstic acid supported on hydrous zirconia shows highest surface area, acid sites and gives about 93% conversion with 81% para-selectivity.
35 citations
TL;DR: In this article, composite membranes were prepared by solution casting from sulfonated poly(ether ether ketone), poly(vinylidene fluoride) and phosphotungstic acid and their structures were characterized using XRD, DSC and FT-IR.
TL;DR: In this paper, a series of composite membranes with varying amounts of heteropolyacid were prepared by altering the weight ratio of polyimides and HPA, and their performance was evaluated for thermal stability, ion exchange capacity, water uptake and proton conductivity.
TL;DR: In this paper, a series of silicon-containing polyacrylate nanoparticles (SiPANPs) were successfully synthesized by simple emulsifier-free emulsion polymerization technique, and the resulting latex particles were characterized by Fourier transform infrared (FTIR) spectrometry, dynamic light scattering (DLS) analysis, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).
TL;DR: In this article, a mesoporous HPW/SiO 2 with Keggin-type heteropolyacids (HPAs) encapsulated into a SiO 2 framework has been synthesized and used as the catalyst for diesel fuel desulfurization.
Abstract: Ordered mesoporous phosphotungstic acid/SiO 2 (HPW/SiO 2 ) with Keggin-type heteropolyacids (HPAs) encapsulated into a SiO 2 framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50-80 °C with H 2 O 2 as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48-86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6-dimethydibenzothiophene > benzothiophene.
TL;DR: In this paper, a liquid phase bromination of phenol was carried out using heteropoly acid supported zirconia as catalyst, KBr as brominating agent and hydrogen peroxide as an oxidant in acetic acid medium at room temperature.
TL;DR: In this paper, the authors demonstrate that nanoscale membrane electrode assemblies, functioning in a H2/O2 fuel cell, can be fabricated by impregnation of anodic alumina porous membranes with Nafion® and phosphotungstic acid.
Abstract: In this paper, we demonstrate that nanoscale membrane electrode assemblies, functioning in a H2/O2 fuel cell, can be fabricated by impregnation of anodic alumina porous membranes with Nafion® and phosphotungstic acid. Porous anodic alumina is potentially a promising material for thin-film micro power sources because of its ability to be manipulated in micro-machining operations. Alumina membranes (Whatman, 50 μm thick, and pore diameters of 200 nm) impregnated with the proton conductor were characterized by means of scanning electron microscopy, X-ray diffraction, and thermal analysis. The electrochemical characterization of the membrane electrode assemblies was carried out by recording the polarization curves of a hydrogen–oxygen 5 cm2 fuel cell working at low temperatures (25 ÷ 80 °C) in humid atmosphere. Our assemblies realized with alumina membranes filled with phosphotungstic acid and Nafion® reach respectively the peak powers of 20 and 4 mW/cm2 at room temperature using hydrogen and oxygen as fuel and oxidizer.
TL;DR: In this paper, an Heteropoly acid (phosphotungstic acid, PTA) was found to be a promising solid acid catalyst as an alternative to the conventional stoichiometric reagents for the rearrangement of benzyl phenyl ether giving 2-benzyl phenol as a major product and 4-bensylphenol and dibenzylated phenols as side products.
TL;DR: In this paper, the microscopic structure of organic−inorganic hybrid membranes containing heteropolyacid has been investigated by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and Fourier transform infrared spectroscopy (FT-IR).
Abstract: The microscopic structure of organic−inorganic hybrid membranes containing heteropolyacid has been investigated by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and Fourier transform infrared spectroscopy (FT-IR). The hybrids were prepared by hydrolysis and condensation reactions, the so-called sol−gel reaction of 1,8-bis(triethoxysilyl)octane (TES-Oct) in the presence of phosphotungstic acid (PWA) with hydrated water. The characteristic lengths evaluated by using AFM and SAXS revealed the evolution of the domain structures upon increasing PWA concentration. Thermogravimetric analysis (TGA) indicated that increasing PWA concentration led to remarkable increase in the characteristic temperature for a weight loss. By combination of analysis using TGA and FT-IR, it was found that highly condensed domains were disintegrated, leading to the formation of loose networks with defect structures in the vicinity of the characteristic temperature. Correspondingly, the organic bridge was further ...
TL;DR: In this paper, the influence of silica on the proton conductivity of composite membranes has been studied and shown to increase up to one order of magnitude for filler amounts which strongly depend on the transport mechanism and the nature of the activating acid.
Abstract: Composite membranes are of interest for PEMFCs and DMFCs. This paper describes a basic study of the influence of silica on the proton conductivity: (i) added as a filler to poly(vinylidene fluoride-hexafluoropropylene) and poly(benzimidazole)-based membranes activated with H3PO4, or (ii) included in the matrix of class II hybrids based on tetraethoxysilane and poly(ethylene glycol) and activated with phosphotungstic acid (PWA).
The addition of acidic silica as a filler determines proton conductivity increases up to one order of magnitude for filler amounts which strongly depend on the proton transport mechanism, and on the nature (free or partially free) of the activating acid. The increase of the silica content in the hybrid matrix induces a more complex behaviour which also depends on the amount of PWA.
TL;DR: In this article, a combined catalyst of quaternary ammonium bromide and phosphotungstic acid was used for dibenzothiophene (DBT) oxidation with hydrogen peroxide (H2O2) as the oxidant.
Abstract: A combined catalyst of quaternary ammonium bromide and phosphotungstic acid was used for dibenzothiophene (DBT) oxidation with hydrogen peroxide (H2O2) as the oxidant. The interaction between oxidized phosphotungstic acid and quaternary ammonium bromide was investigated in detail and the kinetic parameters were estimated. The oxidized phosphotungstic acid is extracted from the aqueous phase to the interface by quaternary ammonium bromide via a first-order extraction. The extraction capacity of different quaternary ammonium bromide is similar to each other. Kinetics study indicates that the rate constant decreases in the following order: octadecyltrimethylammonium bromide (STAB) > cetyltrimethylammonium bromide (CTAB) > (1-tetradecyl)trimethylammonium bromide (TTAB) > dodecyltrimethylammonium bromide (DTAB). An empirical equation was established for predicting reaction rate constant. Based on the kinetic study, the catalyst at the interface is observed to have greater effect on DBT oxidation, compared to ...
TL;DR: In this paper, a one-pot three-component Mannich reaction, catalyzed by phosphotungstic acid (H3PW12O40), a heteropoly acid in ionic liquid, is described.
Abstract: This paper describes a one-pot three-component Mannich reaction, catalyzed by phosphotungstic acid (H3PW12O40), a heteropoly acid in ionic liquid. The catalyst was found to be mild and efficient, a...
TL;DR: In this paper, the performance of an H2/O2 fuel cell with a proton conducting glass electrolyte and a Pt/C catalyst was improved by introducing membrane electrode assemblies (MEAs) consisting of heteropolyacids (HPAs) (phosphotungstic acid, PWA and phosphomolybdic acid, PMA).
Abstract: A novel structure for an H2/O2 fuel cell with a proton conducting glass electrolyte and a Pt/C catalyst was developed. The performance of the fuel cell, which was impregnated with a glass electrolyte and a gaseous hydrogen–oxygen feed at low temperature in a humidified atmosphere was significantly improved by introducing membrane electrode assemblies (MEAs) consisting of heteropolyacids (HPAs) (phosphotungstic acid, PWA and phosphomolybdic acid, PMA) doped with a P2O5-SiO2 glass electrolyte. The HPAs containing porous glass electrolytes show promise for applications in low temperature H2/O2 fuel cells. The electrochemical behaviour of these materials was studied by measuring the current–voltage profile from polarisation curves. A maximum power density of ≈ 35 mW cm–2 was obtained at 30 °C and 30% RH (relative humidity) using a PMA/PWA-P2O5-SiO2 glass electrolyte membrane. The impedance measurements displaying the total cell ohmic resistance for 12 h at 0.5 V were evaluated at 30 °C. The resistance value was 3.5 Ω for an operating time of 12 h. This MEA showed the best and the most stable performance for use in an H2/O2 fuel cell.
Patent•
15 Aug 2007
TL;DR: In this paper, an epoxidizing method of epoxy chloropropane through polyoxyethylene ester (PEES) is described. But the method is not suitable for the use of polyethylene.
Abstract: The invention discloses an epoxidizing method of epoxy chloropropane through chloropropene, which comprises the following steps: adopting excessive chloropropene to produce epoxy chloropropane directly under phosphotungstic acid quaternaries as catalyst and alkyl phenol polyoxyethylene ester as adjuvant catalyst and hydrogen peroxide solution as oxidant to reflux; cooling reactant; recycling solid-phased catalyst; distilling oil phase of reacting liquid to recycle residual chloropropene; decompressing; distilling; obtaining the purified product.
TL;DR: A convenient eco-friendly procedure has been developed by reacting 1,3-dicarbonyl compounds with amines in the presence of catalytic amounts of phosphotungstic acid to synthesise β-enamino compounds in high to excellent yields.
Abstract: A convenient eco-friendly procedure has been developed for the synthesis of β-enaminones and β-enamino esters by reacting 1,3-dicarbonyl compounds with amines in the presence of catalytic amounts o...
TL;DR: In this article, the electrical and dielectric properties of polyvinyl alcohol (PVA) and phosphotungstic acid (PTA) composite membranes were investigated as a function of blending composition, crosslinking density, and temperature.
Abstract: The work presents the electrical and dielectric characterization of proton-conducting, chemically-crosslinked nanocomposites of polyvinyl alcohol (PVA) and phosphotungstic acid (PTA). The composite membranes were prepared by in situ crosslinking of the polymer matrix in solution form, containing PTA. The electrical and dielectric properties of the membranes were investigated as a function of blending composition, crosslinking density, and temperature. The conductivity of these membranes shows a temperature dependence of Arrhenius type and highest conductivity of 3.31 × 10−3 S cm−1 was obtained. The activation energies for proton conduction were found to be in the range of 15.28–40.62 kJ mol−1.
TL;DR: In this paper, the effect of the active region of the catalyst surface was investigated with respect to the output during the cell test, and the MEA with a large sized active area of 0.49 cm 2 demonstrated superior performances as compared to the other cells.
Patent•
25 Apr 2007
TL;DR: In this article, a composite catalyst for preparing sec-butyl acetate by direct esterification of ethyl ester and butylene, which takes heteropoly acid as the catalyst active component and porous carrier as the dispersant, was presented.
Abstract: The present invention relates to a composite catalyst for preparing sec-butyl acetate by direct esterification of ethyl ester and butylene, which takes heteropoly acid as the catalyst active component and porous carrier as the dispersant; the weight proportion of the heteropoly acid and the porous carrier is 001:1 to 10:1 The heteropoly acid is one with Keggin structure, which consists of phosphotungstic acid, silicotungstic acid, germanium tungstic acid, arsenowolframic acid, phosphomolybdate, germanomolybdate or arsenicomolybdate The porous carrier comprises porous SiO2, Al2O3, SBA-15, MCM-41, white carbon black, porous SiC, corallite, andalusite, cordierite, meerschaum, Attapulgite or kaolin The composite catalyst of the present invention solves the problem that the catalysis efficiency is low if the heteropoly acid is separated out from the reaction system
TL;DR: In this article, the effects of solvent on the microscopic structure and proton conductivity of organic-inorganic hybrid containing heteropolyacid were reported, and they were prepared by sol-gel synthesis of 1,8-bis(triethoxysilyl) octane (TES-Oct) in the presence of phosphotungstic acid (PWA).
TL;DR: In this article, the effect of casting condition on the properties of poly(ether ether ketone ketone)/phosphotungstic acid (SPEEKK/PWA) composite membranes was studied in detail.
Abstract: The sulfonated poly(ether ether ketone ketone)/phosphotungstic acid (SPEEKK/PWA) composite membranes were researched for proton exchange membranes. The effect of casting condition on the properties of membranes was studied in detail. The study showed that the casting condition has great influence on the membrane properties because of the hydrogen bond between the SPEEK and PWA and the interaction between the SPEEKK and dimethylformamide (DMF). The PWA particles are well crystallized on the surface when the velocity of the solvent volatilization is very slow under the SEM. The study will favor further research on excellent composite membranes for proton exchange membrane fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4020–4026, 2007
Patent•
08 Aug 2007
TL;DR: In this article, a desulfurizing method catalyzed and oxidized by TiO2 in the chemical technical domain, which comprises the following steps: adopting phosphotungstic acid as catalyst and STAB as porous agent, blending butyl titanate, STAB and anhydrous alcohol evenly in the solution; adding deionized water; rotating to evaporate; drying; sintering under 500 degc for 3h.
Abstract: The invention discloses desulfurizing method catalyzed and oxidized by TiO2 in the chemical technical domain, which comprises the following steps: adopting phosphotungstic acid as catalyst and STAB as porous agent; blending butyl titanate, STAB and anhydrous alcohol evenly in the phosphotungstic acid solution; adding deionized water; rotating to evaporate; drying; sintering under 500 degc for 3h; synthesizing TiO2 molecular sieve; adding TiO2 molecular sieve into DBT-octane solution; heating; adding H2O2 to oxidize; washing; recycling catalyst