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Showing papers on "Phosphotungstic acid published in 2012"


Journal ArticleDOI
TL;DR: In this paper, mixed materials of the metal-organic framework (MOF), chromium(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid XRD analysis indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures.
Abstract: Hybrid materials of the metal–organic framework (MOF), chromium(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid XRD analysis of the MIL101/PTA composites indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures The MIL101/PTA structure enables a PTA payload 15–2 times higher than previously achieved The catalytic performance of the MIL101/PTA composites was assessed in the Baeyer condensation of benzaldehyde and 2-naphthol, in the three-component condensation of benzaldehyde, 2-naphthol, and acetamide, and in the epoxidation of caryophyllene by hydrogen peroxide The catalytic efficiency was demonstrated by the high (over 80–90%) conversion of the reactants under microwave-assisted heating In four consecutive reaction cycles, the catalyst recovery was in excess of 75%, whereas the product yields were

358 citations


Journal ArticleDOI
TL;DR: In this article, the synthesis, characterization, and catalytic performance of Pt supported on PTA encapsulated in a metal organic framework (MOF) are reported, where the highly dispersed Keggin units of PTA in NH 2 -MIL-101(Al), synthesized in one step, act as anchoring sites for the Pt precursor species.

141 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of PWAs on the adsorption/removal of benzothiophene (BT) has been studied and it was suggested that MOF-type materials, modified suitably, can be used in adsorptive desulfurization of fuels.

97 citations


Journal ArticleDOI
TL;DR: In this article, a magnetically separable catalyst consisting of phosphotungstic acid supported on imidazole functionalized silica coated cobalt ferrite nanoparticles was prepared.

83 citations


Journal ArticleDOI
TL;DR: The one-pot encapsulation of phosphotungstic acid in the metal-organic framework MIL-100(Cr) has been studied under different synthesis conditions as mentioned in this paper, and both conventional and microwave heating methods have been explored for three different solvent systems: pure aqueous or organic (DMF) phase and biphasic mixtures.
Abstract: The one-pot encapsulation of phosphotungstic acid in the metal–organic framework MIL-100(Cr) has been studied under different synthesis conditions. Both conventional and microwave heating methods have been explored for three different solvent systems: pure aqueous or organic (DMF) phase and biphasic mixtures (water/2-pentanol). Biphasic systems yielded crystals with similar textural properties as those formed in water. The use of DMF as solvent promotes the formation of gel-like solids with dual porosity and enhanced accessibility. The addition of phosphotungstic acid (PTA, H3PW12O40.xH2O) to the MIL-100(Cr) synthesis mixture results in its direct encapsulation. 31P MAS NMR, elemental analysis, N2 adsorption and FT-IR spectroscopy confirm the incorporation of PTA in the sample. The highest PTA encapsulation loading (30 wt%) was obtained by synthesis with microwave heating in biphasic solvent systems (W/Cr molar ratio range between 0.5 and 0.25). Microwave irradiation decreases the time of synthesis (from 4 days to 3 hours) while the use of biphasic media preserves the PTA integrity without affecting the formation of the MOF. The interaction of PTA with the MIL-100(Cr) structure results in some loss of the Lewis acidity, while the Bronsted acidity is hardly affected.

64 citations


Journal ArticleDOI
TL;DR: In this article, an amino-functionalized ionic liquid modified mesoporous silica SBA-15 (PW-NH2-IL-SBA-2015) is loaded onto an amino functionalized ionIC liquid modified SBA by totally anion-exchange and partly protonating in the channel of SBA with Keggin-type H3PW12O40.

59 citations


Journal ArticleDOI
TL;DR: In this article, a 3D ordered macroporous Bi2WO6 with mesoporous walls was firstly realized by a hard template synthesis method, where commercially available bismuth nitrate and phosphotungstic acid were used as the precursors.
Abstract: Three-dimensionally ordered macroporous Bi2WO6 (3DOM Bi2WO6) with mesoporous walls was firstly realized by a hard template synthesis method. The commercially available bismuth nitrate and phosphotungstic acid were used as the precursors to prepare the 3DOM Bi2WO6 sample without introducing other complex agents. The as-prepared 3DOM Bi2WO6 was composed of periodically arranged Bi2WO6 hollow spheres with a diameter of about 90 nm. Because of its particular ordered macroporous and mesoporous structure, the 3DOM Bi2WO6 exhibited excellent photocatalytic activity on the degradation of phenol and aqueous ammonia under irradiation from simulated sunlight. Its photocatalytic activity is much higher than that of the Bi2WO6 samples prepared by hydrothermal synthesis (HR) and solid-state reaction (SSR) methods. This work provides a simple way to prepare bismuth-based 3DOM multiple metal oxides with excellent performance.

58 citations


Journal ArticleDOI
Xiutao Li1, Yijun Jiang1, Lili Wang1, Lingqian Meng1, Wei Wang1, Xindong Mu1 
TL;DR: In this paper, concentrated H3PW12O40 (HPW) was employed to decompose cellulose under microwave irradiation at low temperatures, and a 75.6% yield of glucose was obtained at 90 °C for 3 h using phosphotungstic acid as a catalyst.
Abstract: Concentrated H3PW12O40 (HPW) was first employed to decompose cellulose under microwave irradiation at low temperatures. 75.6% yield of glucose was obtained at 90 °C under microwave irradiation for 3 h, which was considerably high under such mild conditions using phosphotungstic acid as a catalyst. With the same effective acid concentration, HPW gave the highest cellulose conversion and glucose yield among the Bronsted acid catalysts, indicating that the strong Bronsted acid played an important role during cellulose hydrolysis. In the hydrolysis of cellulose with HPW as catalysts, microwave irradiation led to higher glucose yields than the conventional heating method. The recovery and reusability of HPW were investigated by extraction with diethyl ether from the reaction solution. At the same time, the performance of the concentrated HPW for real lignocellulosic biomass (corncob, corn stover and bagasse) hydrolysis was also investigated.

55 citations


Journal ArticleDOI
TL;DR: In this article, the effect of HPW doping and crosslink with DTPA on the membranes properties such as uptake, pervaporation and proton conductivity was investigated, and the FTIR spectra indicated that HPW was incorporated into the polymer matrix and DTPA acted as crosslink agent.

50 citations


Journal ArticleDOI
TL;DR: In this paper, a new amino-functionalized bipyridine-heteropolyacid ionic hybrid was prepared by protonating and anion-exchanging the amino-attached bipyridine ionic liquid with phosphotungstic acid, and characterized by FT-IR, 1 H NMR, UV-vis, XRD, SEM, TG, surface area, melting point, and elemental analysis.
Abstract: A new amino-functionalized bipyridine–heteropolyacid ionic hybrid was prepared by protonating and anion-exchanging the amino-attached bipyridine ionic liquid with phosphotungstic acid, and characterized by FT-IR, 1 H NMR, UV–vis, XRD, SEM, TG, BET surface area, melting point, and elemental analysis. Its catalytic activity was evaluated in the oxidation of benzyl alcohol with aqueous H 2 O 2 . The hybrid catalyst is proved to be a highly efficient solid catalyst for solvent-free oxidation of benzyl alcohol with H 2 O 2 , which is featured by the fast reaction rate, high conversion and selectivity, easy recovery, and quite steady reuse.

46 citations


Journal ArticleDOI
TL;DR: A nanotubular composite of TiO 2 and WO 3 was synthesized via anodic oxidation of titanium in a single-step process using phosphotungstic acid as the tungsten source.

Journal ArticleDOI
TL;DR: A green process for enantioselective hydrogenation of dehydroamino acid derivatives and dimethyl itaconate with a rhodium catalyst modified by a new phosphine-phosphoramidite has been developed as mentioned in this paper.

Journal ArticleDOI
TL;DR: The results showed that the composite nanospheres have core/shell structure with the properties of amphiphilicity and superparamagnetism, and have high catalytic activity in the oxidation of dibenzothiophene to corresponding sulfones by hydrogen peroxide under mild reaction conditions.

Journal ArticleDOI
TL;DR: In this paper, a novel application of phosphotungstic acid, H3PW12O40 (PWA), supported on MCM-41 molecular sieve as a solid acid catalyst has been demonstrated for the synthesis of phenolphthalein by hydroxyalkyla.
Abstract: A novel application of phosphotungstic acid, H3PW12O40 (PWA) supported on MCM-41 molecular sieve as a solid acid catalyst has been demonstrated for the synthesis of phenolphthalein by hydroxyalkyla...

Journal ArticleDOI
TL;DR: In this article, the authors used a model diesel fuel, using hydrogen peroxide (H2O2) as an oxidant, in the presence of phosphotungstic acid and p...
Abstract: The oxidation of dibenzothiophene (DBT) and benzothiophene (BT) from a model diesel fuel, using hydrogen peroxide (H2O2) as an oxidant, was carried out in the presence of phosphotungstic acid and p...

Journal ArticleDOI
TL;DR: In this article, the phase transfer agent during preparation of the catalysts is very effective to improve catalytic activity and mechanical agitation combining with ultrasonic agitation is the best agitation way.

Journal ArticleDOI
TL;DR: In this paper, the intrinsic relationship between proton conductivity, thermal stability and structural symmetries of HPW-functionalized mesoporous silica (HPW-meso-silica) membrane was investigated with 3D mesostructures.

Journal ArticleDOI
TL;DR: In this article, a novel composite sulfonated poly(ether sulfone)(SPES)/phosphotungstic acid (PWA)/attapulgite (AT) membranes were investigated for direct methanol fuel cells (DMFCs).
Abstract: Novel composite sulfonated poly(ether sulfone)(SPES)/phosphotungstic acid (PWA)/attapulgite (AT) membranes were investigated for direct methanol fuel cells (DMFCs). Physical–chemical properties of the composite membranes were characterized by FTIR, DSC, TGA, SEM-EDX, water uptake, tensile test, proton conductivity, and methanol permeability. Compared with a pure SPES membrane, PWA, and AT doping in the membrane led to a higher thermal stability and glass transition temperature (Tg) as revealed by TGA and DSC. Tensile test indicated that lower AT content (3%) in the composite can significantly increase the tensile strength, while higher AT loading demonstrated a smaller contribution on strength. Proper PWA and AT loadings in the composite membranes can increase the proton conductivity and lower the methanol cross-over. The proton conductivity of the SPES-P-A 10% composite membrane reached 60% of the Nafion 112 membrane conductivity at room temperature while the methanol permeability was only one-fourth of that of Nafion 112 membrane. This excellent performances of SPES/PWA/AT composite membranes could indicate a potential feasibility as a promising electrolyte for DMFC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Journal ArticleDOI
TL;DR: In this article, the effect of the addition of HPAs to the polymer matrix increases oxidative stability, water uptake and conductivity but decreases the IEC, the water diffusivity and the density of membrane.

Journal ArticleDOI
TL;DR: In this paper, the proton mobility in 12-phosphotungstic heteropolyacid (PWA) and its salts (Cs2HPW12O40·xH2O, Cs3PW 12O40 ·xH 2O, (NH4)3Pw12O 40·x H2O) was investigated by impedance spectroscopy and nuclear magnetic resonance with pulsed field gradient under wide range of relative humidity.
Abstract: The proton mobility in 12-phosphotungstic heteropolyacid (PWA) and its salts (Cs2HPW12O40·xH2O, Cs3PW12O40·xH2O, (NH4)3PW12O40·xH2O) was investigated by impedance spectroscopy and nuclear magnetic resonance with pulsed field gradient under wide range of relative humidity. Values of two diffusion components observed in PWA as well as in its acid cesium salt differ in one order of magnitude. Also there are two components in the impedance spectra of these compounds. Thus, we suggest, the proton transport take place both inside the grains and along its boundaries. Self-diffusion coefficients, observed in the neutral cesium and ammonium salts, are close to each other and equal to the fast diffusion coefficient in acid cesium salt. At the same time, there is the only relaxation component in the impedance spectra of neutral salts. Thus, it can be concluded, that in case of neutral salts of PWA, there is no proton transport inside the grains of these compounds, and their high proton conductivity caused by fast proton transport along the grain boundaries.

Journal ArticleDOI
Zhi Geng1, Jinyu Ba1, Shuling Zhang1, Jiashuang Luan1, Xu Jiang1, Pengfei Huo1, Guibin Wang1 
TL;DR: In this paper, a nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups in the presence of the silane coupling agent γ-aminopropyltriethoxysilane (KH-550).
Abstract: The novel ultra low dielectric constant poly(ether ether ketone) hybrid films in which nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups (PEEK–CF3–COOH) in the presence the silane coupling agent γ-aminopropyltriethoxysilane (KH-550) were prepared and characterized. The chemical structures of the PWA/PEEK–CF3–COOH hybrid films were confirmed by FT-IR spectroscopy and 1H-NMR. The analysis of wide-angle X-ray diffraction (WAXD) indicated that the PWA clusters could not form crystalline structures in the PEEK–CF3–COOH matrix, and the investigation of the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (W-mapping) revealed that the PWA particles were well dispersed in the PEEK–CF3–COOH matrix with nanoscale. The influence of the incorporation of PWA particles by side chain grafting reaction on the properties of PEEK–CF3–COOH was studied. The dielectric constants of the PWA/PEEK–CF3–COOH hybrid films were remarkably lower than that of the neat PEEK–CF3–COOH film and the lowest value their dielectric constant could achieve was as low as 1.96 (1 MHz) when the content of grafted PWA reached 10 wt%. Meanwhile, the hybrid films still retain the excellent thermal and mechanical properties as well as the good transparency.

Journal ArticleDOI
TL;DR: In this article, the performance of composite catalysts consisting of polyoxometalates (POM) consisting of H3PW12O40 (HPW) supported on a mesoporous sieve MCM-41 has been characterized by FT-IR, X-ray diffraction, nitrogen adsorption and high resolution transmission electron microscope.
Abstract: Solid catalysts consisting of polyoxometalates (POM) namely phosphotungstic acid H3PW12O40 (HPW) supported on a mesoporous sieve MCM-41 have been prepared and characterized by FT-IR, X-ray diffraction, nitrogen adsorption and high resolution transmission electron microscope (HRTEM). The HPW/MCM-41 with different HPW loadings from 10 to 60 wt% possess large specific surface area and rather uniform mesopores. Keggin structure of HPW retains on the prepared composite catalysts. The photocatalytic performance of HPW/MCM-41 was examined by degradation of a durable pesticide imidacloprid. It is found that the prepared photocatalysts exhibit high activity under irradiation of 365 nm monochromatic light. For 50 mL of imidacloprid (10 mg/L), conversion of imidacloprid using 20 mg of HPW/MCM-41 with 50 wt% loading level and calcined at 300°C reaches 58.0% after 5 h irradiation.

Journal ArticleDOI
TL;DR: In this article, SiO2-riveted phosphotungstic acid (T-PWA-SiO2) was synthesized using the sol-gel method and thermally treated in a microwave synthesizer.
Abstract: SiO2-riveted phosphotungstic acid (T–PWA–SiO2) was synthesized using the sol–gel method and thermally treated in a microwave synthesizer. The dissolving-detaching experiment shows that PWA in T–PWA–SiO2 exhibits better fastness than in the sample without thermal treatment (PWA–SiO2). The T–PWA–SiO2 samples were then combined with poly(2,5-benzimidazole) (ABPBI) to prepare ABPBI/(T–PWA–SiO2) composite membranes using the polyphosphoric acid direct-casting method. These composite membranes were characterized through X-ray diffraction and infrared spectroscopy. Then, the T–PWA–SiO2 particles were combined with ABPBI through hydrogen bonding between PWA and C=N in ABPBI. Membrane morphologies were investigated using scanning electron microscopy. Results of the thermogravimetric analysis indicate thermal stability of the composite membranes below 200 °C. The proton conductivity and durability between ABPBI/(T–PWA–SiO2) and ABPBI/(PWA–SiO2) composite membranes were also compared. The conductivity and life of the composite membranes were enhanced using T–PWA–SiO2. The conductivity of the ABPBI/(T–PWA–SiO2) (46 wt%) composite membrane was approximately 0.055 S/cm at 180 °C under 100% relative humidity.

Journal ArticleDOI
Zhongkui Zhao1, Yitao Dai1, Ting Bao1, Renzhi Li1, Guiru Wang1 
TL;DR: In this paper, N 2 adsorption-desorption, FT-IR, X-ray diffraction (XRD), and NH 3 temperature-programmed desorption (NH 3 TPD) characterization techniques were used to reveal the relationship between the catalyst's nature and properties.

Patent
13 Jun 2012
TL;DR: In this article, a method for decomposing scheelite is proposed, where scheelites are decomposed by employing nitric acid, so that Ca in the scheelsite can enter the solution in a form of soluble calcium nitrate; meanwhile, phosphoric acid or phosphorite serve as a tungsten complexing agent.
Abstract: The invention provides a method for decomposing scheelite. The scheelite is decomposed by employing nitric acid, so that Ca in the scheelite can enter the solution in a form of soluble calcium nitrate; meanwhile, phosphoric acid or phosphorite (the phosphorite is decomposed into phosphoric acid through the nitric acid) serve as a tungsten complexing agent, so that WO3 in the scheelite enters the solution in a form of soluble phosphotungstic acid, the generation of solid tungstic acid membrane and slightly soluble calcium salt is avoided in the whole decomposition process, the calcium nitrate solution containing phosphotungstic acid, which is generated after decomposition, is extracted by employing a solvent and is subjected to ion exchange or ammonium salt precipitation method so that the phosphotungstic acid is recovered from the calcium nitrate solution; and sulfuric acid is added into the calcium nitrate solution from which tungsten is extracted and is combined with calcium ion in the solution so as to generate slightly soluble calcium sulfate precipitate, so that the nitric acid is regenerated; and the regenerated nitric acid return to a new round of mineral leaching process. The method has the advantages that tungsten in the tungsten mineral can be completely decomposed; the regenerated nitric acid is recycled, and the leaching cost and wastewater discharge are greatly reduced; and moreover, the treatment equipment is simple, the operation is convenient, and industrialization is easily realized.

Journal ArticleDOI
TL;DR: In this paper, Dicyclopentadiene dioxide (2) was synthesized using an economic and green reaction by the direct oxidation of DCPD with aqueous H2O2 over tungstic acid and aminopropyl-immobilized phosphotungstic acid on SBA-15, which was successfully obtained by the immobilization of the supported heteropolyacid (HPW) on the surface of the ordered mesoporous silica.
Abstract: Dicyclopentadiene dioxide (2) was synthesized using an economic and green reaction by the direct oxidation of dicyclopentadiene (DCPD) with aqueous H2O2 over tungstic acid and aminopropyl-immobilized phosphotungstic acid on SBA-15, which was successfully obtained by the immobilization of the supported heteropolyacid (HPW) on the surface of the ordered mesoporous silica, SBA-15, by means of chemical bonding to aminosilane groups. The as-obtained materials were characterized by N2 sorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), 31P-magic angle spinning (MAS) NMR and Raman spectroscopy. The 16% HPW-NH2-SBA-15 is highly efficient in the reaction with a DCPD conversion of 100% and (2) selectivity up to 97%. It is interesting that this material could be reused six times without any significant loss of activity and selectivity. The good stability can be attributed to the strong interaction between the amino groups on the surface of SBA-15 and HPW anions.

Journal ArticleDOI
TL;DR: Vanadium incorporated tungstophosphoric acid (TPAV1) supported on silica was synthesized and characterized by BET-surface area, Fourier transform infrared spectroscopy, X-ray diffraction and Laser Raman techniques.

Journal ArticleDOI
TL;DR: The MCM-41 supported Cs2.5H0.5PW12O40 and K2.1.5HPW 12O40 salts were synthesized by incipient wetness impregnation method as discussed by the authors.
Abstract: The MCM-41 supported Cs2.5H0.5PW12O40 and K2.5H0.5PW12O40 salts were synthesized by incipient wetness impregnation method. The solids were characterized by N2 adsorption–desorption isotherms, FT-IR, XRD, and temperature programmed desorption, etc. This catalyst has been found to exhibit excellent activity for acetylation of phenolic compounds. The catalyst is stable and reusable giving 96% conversion with 100% selectivity towards acetate products.

Journal ArticleDOI
Xiaoli Sheng1, Yuming Zhou1, Yiwei Zhang1, Yongzheng Duan1, Mengwei Xue1 
TL;DR: The Keggin phosphotungstic acid, H3PW12O40 (HPW), was successfully immobilized on the surface of mesostructured LaSBA-15 by means of chemical bonding to aminosilane groups.
Abstract: The Keggin phosphotungstic acid, H3PW12O40 (HPW), was successfully immobilized on the surface of mesostructured LaSBA-15 by means of chemical bonding to aminosilane groups. The catalysts were characterized by elemental analysis, N2 adsoption, TEM, DRS-UV, and FTIR spectroscopy. Characterization results suggest that the surface area decreased after grafting amino groups to silica and the structures of heteropolyanions on amine-modified LaSBA-15 was maintained. Their catalytic behaviors were investigated in the alkylation of o-xylene with styrene. Among the functionalized catalysts, when the content of amino-groups was suitable, it had the best catalytic performances in terms of yield and stability. It is worth mentioning that the catalysts could be used repeatedly without loss of the activity and selectivity during several catalytic cycles. The good stability can be attributed to the strong interaction between the amino groups on the surface of LaSBA-15 and HPW anions. The Keggin phosphotungstic acid, H3PW12O40 (HPW), was successfully immobilized on the surface of mesostructured LaSBA-15 by means of chemical bonding to aminosilane groups. The obtained catalysts were highly effective for alkylation of o-xylene with styrene in terms of yield and stability. Compared with the HPW/LaSBA-15 catalyst, both the catalytic stability and reusability were greatly enhanced.

Journal ArticleDOI
TL;DR: In this article, the mesoporous WO3 replica synthesized from ammonium metatungstate (AMT) and PTA (WO3-PTA) consisted of a crystalline monoclinic phase and mixed crystalline tetragonal and monoclinal phases, respectively.