Showing papers on "Phosphotungstic acid published in 2004"
TL;DR: In this paper, Nafion/silicon oxide (SiO2)/phosphotungstic acid (PWA) composite membranes were studied for the H2/O2 proton exchange membrane fuel cells (PEMFCs) operated above 100°C.
297 citations
TL;DR: In this article, Nafion ® -based organic/inorganic composite membranes with different inorganic heteropolyacid (HPA) additives such as phosphotungstic acid, silicotungstic acid, phosphomolybdic acid and silicomolybdenum-based acid were investigated for high temperature (120°C) low relative humidity (35%) operation.
292 citations
TL;DR: In this paper, a series of new composite proton exchange membranes for direct methanol fuel cells (DMFCs) based on polyvinyl alcohol (PVA), phosphotungstic acid (PWA) and silica were prepared.
114 citations
TL;DR: In this paper, the esterification of triethylene glycol (TEG) with methacrylic acid (MAA) was carried out over various solid acid catalysts.
Abstract: The esterification of triethylene glycol (TEG) with methacrylic acid (MAA) was carried out over various solid acid catalysts and the results were compared with conventional acid catalysts. Among the catalysts studied, heteropolyacids showed higher activities than the conventional acids. These were attributed to the acidity of the catalysts. A systematic investigation was carried out for the esterification of triethylene glycol with methacrylic acid over phosphotungstic acid without any free radical inhibitor. The effects of catalyst concentration, alcohol/acid molar ratio and temperature were also studied. Parameters such as activation energy, reaction enthalpy and reaction entropy were derived for the above reaction over phosphotungstic acid in the temperature range of 353–383 K. The obtained results were also compared with silicotungstic acid.
77 citations
TL;DR: In this paper, the preparation and properties of sol-gel derived proton conducting organic/inorganic materials based on zirconia bridged hydrocarbon phosphotungstic acids are reported.
62 citations
TL;DR: In this paper, Enzymatic oxidation of dibenzothiophene (DBT) catalyzed by laccase in the presence of 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) was compared with the chemical oxidation with hydrogen peroxide catalyzed with phosphotungstic acid.
55 citations
TL;DR: In this paper, an assembled complex of phosphotungstic acid (H3PW12O40) and a non-cross-linked copolymer of N-isopropylacrylamide with an ammonium was developed.
55 citations
TL;DR: In this paper, mesoporous aluminophosphate (AlPO) has been synthesized hydrothermally using cetyltrimethylammonium bromide (CTAB) as structure-directing agent in the presence of tetramethylammium hydroxide (TMAOH) at room temperature.
Abstract: Mesoporous aluminophosphate (AlPO) has been synthesized hydrothermally using cetyltrimethylammonium bromide (CTAB) as structure-directing agent in the presence of tetramethylammonium hydroxide (TMAOH) at room temperature. Phosphotungstic acid, H 3 PW 12 O 40 (PW) was supported on the synthesized mesoporous AlPO at various loadings viz., 10, 20 and 40 wt.% to yield PW/AlPOs and characterized by XRD, TGA and FT-IR. XRD patterns confirm that HPA retains the Keggin structure on the AlPO surface and forms finely dispersed heteropoly acid (HPA) species. HPA crystal phase was not developed even at HPA loading as high as 40 wt.%. Catalytic activities of both parent AlPO and HPA loaded AlPOs were studied by carrying out t -butylation of phenol with tert -butanol in vapour phase in the temperature range 190–250 °C. The products obtained were o - tert -butyl phenol ( o-t -BP), p - tert -butyl phenol ( p - t -BP) and tert -butylphenyl ether ( t -BPE) with high selectivity towards p - t -BP. The effects of feed ratio and WHSV towards conversion of phenol were studied and finally the time on stream studies were also carried out to compare the activities of the catalysts. PW/AlPO catalysts were found to yield higher conversion than parent AlPO due to the increase in Bronsted acid sites. Hence, PW/AlPO compositions are promising catalysts exclusively for acid type conversion of large organic molecules.
44 citations
TL;DR: In this paper, the authors optimized the energy storage TiO2-WO3 photocatalysts, which retain anticorrosion and bactericidal effects, even in the dark, on the basis of reductive energy stored in WO3, for photoelectrochemical charging of the film in the gas phase.
44 citations
TL;DR: In this article, the alkylation of resorcinol with tert-butanol was carried out using zirconia supported phosphotungstic acid (PTA) as catalyst in liquid phase conditions.
Abstract: The alkylation of resorcinol with tert-butanol was carried out using zirconia supported phosphotungstic acid (PTA) as catalyst in liquid phase conditions. Among the different PTA loaded catalysts, the 15% PTA/ZrO2 calcined at 750 °C was found to be the most active and yielding 4-tert-butyl resorcinol and 4,6-di-tert-butyl resorcinol as the major products under the optimized reaction conditions. In addition to the above, hydroisomerization of n-heptane was studied under vapor phase conditions using bifunctional catalysts comprising Pt, Pd and Pt–Pd clusters on 15% PTA/ZrO2. The catalytic activity of the bimetallic Pt–Pd catalyst is higher than that of the monometallic Pt and Pd catalysts. The catalysts prepared from acetylacetonate complexes were more active than those prepared from amine complexes. Addition of Pd has no beneficial effect on the catalytic performance when the bimetallic catalyst is prepared from acetylacetonate complexes.
41 citations
TL;DR: In this paper, the proton-conducting composite PTA/Al 2 (SO 4 ) 3 ·18H 2 O was used as the electrolyte of symmetric supercapacitor based on PANI.
TL;DR: In this paper, a series of electrodes with different composition of the organic/inorganic nanohybrid materials to the platinum loaded carbon has been prepared in order to elucidate the availability of the electrolytes in the catalyst layer.
TL;DR: In this article, nonlocal gradient corrected density functional theory was used to determine the optimal positions of the protons and their relative affinity in the secondary structure of phosphotungstic acid, and the desorption energies of the first and second water molecules from a bridging H5O2+ species were calculated to be 109 and 55 kJ mol-1, respectively.
Abstract: Nonlocal gradient corrected density functional theory was used to determine the optimal positions of the protons and their relative affinity in the secondary structure of phosphotungstic acid. First, a body centered cubic structure associated with the hexahydrate was incorporated into the model. The desorption energies of the first and second water molecules from a bridging H5O2+ species were calculated to be 109 and 55 kJ mol-1, respectively. The H3O+ or H+ species remaining after dehydration are preferentially located between two oxygen atoms of adjacent Keggin units. The preferred position is between two terminal Od atoms or between a terminal Od atom and a bridging Oc atom, depending on the alignment of the Keggin units. The energy advantage of sharing a proton between two Keggin units is in the range of 43 to 71 kJ mol-1. Three-dimensional periodic calculations indicate that anhydrous phosphotungstic acid can form a regular lattice in which all protons are shared between the heteropolyanions.
TL;DR: In this paper, the authors showed that change of polyoxometallates has little effect on the tilt angle of the 1,10-decanediamine molecules for such amine systems.
Abstract: Hydrothermal reaction of phosphomolybdic acid (PMo12) and phosphotungstic acid (PW12) with the surfactant template 1,10-decanediamine (1,10-DAD) yielded two new nanocomposites, [C10H20(NH2)2]2•H3PMo12O40•(H2O)7.5 and [C10H20(NH2)2]2• H3PW12O40•(H2O)2.4. The produced needlelike crystals of the two nanocomposites have fine-layered structures. X-ray diffraction analyses indicate that change of polyoxometallates has little effect on the tilt angle of the 1,10-DAD molecules for such polyoxometallates–organic amine systems. Fourier transform infrared and Raman spectra show that in the hybrid, the PMo12 forms infinite two-dimensional networks, and the PW12 keeps its Keggin structure in the hybrid except distortion to some degree. The two nanocomposites show different photochromic properties; PMo12–DAD hybrid can be colored under ultraviolet irradiation, whereas PW12–DAD hybrid cannot.
TL;DR: In this article, the -pinene isomerization reaction was studied on catalysts based on H3PW12O40 (HPW) supported on TiO2, SiO2 and ZrO2nH2O.
Abstract: The -pinene isomerization reaction was studied on catalysts based on H3PW12O40 (HPW) supported on TiO2, SiO2 and ZrO2nH2O. Catalysts with a 40% nominal charge of phosphotungstic acid (HPW) were prepared by impregnation of supports with a HPW solution. The study of the isomerization reaction was carried out in liquid phase by using a discontinuous reactor, magnetically stirred and maintaining a constant temperature. The catalyst supported on SiO2 resulted to be the most active while the one supported on ZrO2nH2O was the less active. This behavior correlated with the number and strength of the acid sites. XRD studies revealed the formation of HPW crystals when it was supported on SiO2.
TL;DR: In this article, a side-chain bromination of aromatic substrates with N -bromosuccinimide has been achieved in excellent isolated yields (84-98%) using phosphotungstic acid supported on zirconia as a novel heterogeneous catalyst.
Abstract: Regioselective monobromination of aromatic substrates with N -bromosuccinimide has been achieved in excellent isolated yields (84–98%) using phosphotungstic acid supported on zirconia as a novel heterogeneous catalyst. The catalyst has been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area and acidity measurements. Remarkably, the new catalyst system described brought about the side-chain bromination of aromatics to afford bromomethyl arenes in excellent yields (86–98%) without the need for a radical initiator. Recovery and recylability of the catalyst have been well established.
Patent•
11 Aug 2004TL;DR: In this article, a method for stabilizing a halogen-containing polymer was proposed, where the method comprises adding to the polymer a thermally stabilizing amount of a mixture comprising at least polyalkylene glycol and at least one metal salt of a strong acid selected from the group consisting of perchloric acid, trifluoroacetic acid and trifloromethanesulfonic acid.
Abstract: A method is disclosed for stabilizing a halogen-containing polymer wherein the method comprises adding to said polymer a thermally stabilizing amount of a mixture comprising at least one polyalkylene glycol and at least one metal salt of a strong acid selected from the group consisting of perchloric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, alkylsufuric acid, phosphotungstic acid, HPF6, HBF4, and HSbF6.
TL;DR: In this article, the modified Biginelli cyclocondensation not only shortens the reaction period and simplifies the operation, but also improves the yields, by using a catalytic amount of phosphotungstic acid (PTA) in ethanol.
Abstract: 5-Alkoxycarbonyl-4-aryl-3,4-dihydropyrimidin-2-ones are synthesised by the one-pot reactions of aldehydes, β-ketoesters and urea using a catalytic amount of phosphotungstic acid (PTA) in ethanol. The modified Biginelli cyclocondensation not only shortens the reaction period and simplifies the operation, but also improves the yields.
Journal Article•
TL;DR: In this paper, the optimum condensation conditions of pyridine-Noxide catalytic systhesis were studied and the influence factors for reaction such as raw material ratio, reaction time, and reaction temperature were discussed in detail.
Abstract: Phosphotungstic acid supported on SiO_2 is prepared and the optimum reaction conditions of pyridine-N-oxide catalytic systhesis are studied. The catalyst used in the title product preparation possesses high activity and can be used repeatedly. The influence factors for reaction such as raw material ratio, reaction time,and reaction temperature are discussed in detail. The results show that the optimum condensation conditions are as follows: the molar ratio of pyridine to H_2O_2 is 1∶1.5,supported quantity of catalyst is 20%,reaction time is 2 h,reaction temperature is 80 ℃,the yield of pyridine-N-oxide can exceed 93%.
Patent•
18 Feb 2004
TL;DR: A process for synthesizing non-toxic sublimating agent 2,4,6-triisopropyl-1,3,5-trioxyoxane (TPTO) is described in this paper.
Abstract: A process for synthesizing non-toxic sublimating agent 2,4,6-triisopropyl-1,3,5-trioxyoxane (TPTO) includes cyclizing tripolymerization reaction of isobutanol under catalysis of phosphomolybdic acid,silicotungstic acid and phosphotungstic acid to obtain coarse TPTO, adding solvent, filtering, distilling, recrystallizing in absolute alcohol and vacuum drying. Its advantages are high output rate (93%) and purity (98%), no sewage discharge, less corrosion to equipment and cyclic use of catalyst.
Patent•
11 Aug 2004
TL;DR: In this article, a method for stabilizing a halogen-containing polymer was proposed, where the method comprises adding to the polymer a thermally stabilizing amount of a mixture comprising at least polyalkylene glycol and at least one metal salt of a strong acid selected from the group consisting of perchloric acid, trifluoroacetic acid and trifloromethanesulfonic acid.
Abstract: A method is disclosed for stabilizing a halogen-containing polymer wherein the method comprises adding to said polymer a thermally stabilizing amount of a mixture comprising at least one polyalkylene glycol and at least one metal salt of a strong acid selected from the group consisting of perchloric acid, trifluoroacetic acid, trifluoromethanesulfonic acid, alkylsufuric acid, phosphotungstic acid, HPF6, HBF4, and HSbF6.
Patent•
22 Jul 2004
TL;DR: In this article, the authors proposed a grease composition having an excellent lubricating property and heat resistance even using it under severe conditions such as a high temperature, high speed, etc.
Abstract: PROBLEM TO BE SOLVED: To provide a grease composition having an excellent lubricating property and heat resistance even using it under severe conditions such as a high temperature, high speed, etc SOLUTION: This grease composition contains at least 1 kind of a component A selected from the following (A) group, and at least 1 kind of a component B selected from the following (B) group (A) group: (1) tungstic acid, a tungstic acid salt and tungsten oxide, (2) phosphotungstic acid, thiotungstic acid, borotungstic acid, a phosphotungstic acid salt, a thiotungstic acid salt and a borotungstic acid salt and (3) phosphomolybdic acid, thiomolybdic acid, boromolybdic acid, a phosphomolybdic acid salt, a thiomolybdic acid salt and a boromolybdic acid salt (B) group: (1) an organic sulfur compound, (2) an organic phosphorus compound, (3) an organic sulfur phosphorus compound, (4) an organic molybdenum compound and (5) an organic zinc compound COPYRIGHT: (C)2004,JPO&NCIPI
Journal Article•
TL;DR: In this article, a novel inorganic-organic composite membrane based on sulfonated polyether ether ketone (SPEEK) with embedded phosphotungstic acid (PWA) for direct methanol fuel cells (DMFC) was prepared.
Patent•
18 Dec 2004
TL;DR: An application of the aluminium phosphate tungstate as the catalyst for synthesizing 2-acetylthiophene features the reaction between thiophene, acetic anhydride, and aluminium phosphate Tungstate while stirring as mentioned in this paper.
Abstract: An application of the aluminium phosphate tungstate as the catalyst for synthesizing 2-acetylthiophene features the reaction between thiophene, acetic anhydride and aluminium phosphate tungstate while stirring. Its advantages are cyclic use, high selectivity and no pollution.
TL;DR: In this paper, an assembled complex of phosphotungstic acid (H3PW12O40) and a non-cross-linked copolymer of N-isopropylacrylamide with an ammonium was developed.
Abstract: A novel catalyst PWAA, an assembled complex of phosphotungstic acid (H3PW12O40) and a non-cross-linked copolymer of N-isopropylacrylamide with an ammonium, was developed. It is an amphiphilic, cross-linked, and supramolecular insoluble complex and showed catalytic activity on oxidation with aqueous hydrogen peroxide. PWAA, used in 2.7×10−5–2.0×10−3 mol equiv., catalyzed oxidation of allylic alcohols, amines, and sulfides efficiently. The turnover number (TON) of PWAA reached up to 35,000. PWAA showed a good stability in organic/aqueous media and was reused three to five times.