Showing papers on "Phosphotungstic acid published in 2016"
TL;DR: In this article, an efficient approach for extracting cellulose nanocrystals (CNCs) was put forward through phosphotungstic acid (PTA) hydrolysis of cellulose raw materials under mechanochemical activation.
Abstract: An efficient approach for extracting cellulose nanocrystals (CNCs) was put forward through phosphotungstic acid (PTA) hydrolysis of cellulose raw materials under mechanochemical activation. Response surface methodology was employed for experimental design to determine the optimum conditions of CNCs preparation with software Design Expert. The results showed that quadratic polynomial model was qualified to represent the relationship between the response and independent variables and the regression model defined well the true behavior of the system. Under the optimal conditions, a high yield of up to 88.4%, crystallinity index of 79.6%, and a higher thermal stability can be achieved by combining mechanochemical activation and phosphotungstic acid hydrolysis. This process can improve effectively the hydrolysis efficiency, avoid a lengthy separation process, and reduce the preparation time. Meanwhile, compared to other techniques, mechanochemical activation is an energy-intensive method, and the process is en...
135 citations
TL;DR: This catalyst was found to bypass the presulfurization process, showing promise as an alternative to sulfided catalysts for green diesel production.
Abstract: Nickel oxide (NiO) and phosphotungstic acid (PTA) supported on a ZIF-8 (NiO-PTA/ZIF-8) catalyst was first synthesized and it showed high activity and good selectivity for the hydrocracking of Jatropha oil. The catalyst was characterized by SEM, SEM-EDS, TEM, N2 adsorption, FT-IR, XRD and XPS. Compared with the NiO-PTA/Al2O3 catalyst, the selectivity of C15-C18 hydrocarbon increased over 36%, and catalytic efficiency increased 10 times over the NiO-PTA/ZIF-8 catalyst. The prepared NiO-PTA/ZIF-8 catalyst was stable for a reaction time of 104 h and the kinetic behavior was also analyzed. This catalyst was found to bypass the presulfurization process, showing promise as an alternative to sulfided catalysts for green diesel production.
111 citations
TL;DR: In this article, the incorporation of phosphotungstic acid functionalized mesoporous silica in phosphoric acid doped polybenzimidazole (PA/PBI) enhances the durability of polymer electrolyte membrane fuel cells for high temperature operation at 200 °C.
Abstract: The incorporation of phosphotungstic acid functionalized mesoporous silica in phosphoric acid doped polybenzimidazole (PA/PBI) substantially enhances the durability of PA/PBI based polymer electrolyte membrane fuel cells for high temperature operation at 200 °C.
87 citations
TL;DR: In this article, porous coordination polymers (PCPs) modified with sulfonic acid/phosphotungstic acid (PTA) were prepared by hydrothermal method via one-pot self-assembly.
77 citations
TL;DR: In this article, a series of crystalline compounds were obtained from simple one-step hydrothermal reaction of copper nitrate, benzentricaboxylate and different Keggin polyoxometalates.
67 citations
TL;DR: In this article, a quaternization of one amine belonged ethylenediamine with chloromethyl group of solid polymer, and the remaining amine could act as active sites to immobilize H 3 PW 12 O 40 (PTA) through ionic bonding interaction.
Abstract: Biodiesels produced from renewable sources is now recognized as a green fuel and exhibit superior fuel properties, and they are more environmentally friendly than petroleum-based fuels. In this paper, the functionalization was performed through quaternization of one amine belonged ethylenediamine with chloromethyl group of solid polymer, and the remaining amine could act as active sites to immobilize H 3 PW 12 O 40 (PTA) through ionic bonding interaction. Thanks to the strong acidity of PTA and swelling behavior of ethylenediamine on the surface and micro-mesochannels of poly(divinylbenzene-co-vinylbenzyl chloride) copolymer (PDVC), the catalysts showed properties of heterogeneous and homogeneous behavior and presents new opportunities for tailored new solid acids in sustainable chemistry. The catalysts were characterized by various structural morphology (XRD, N 2 - sorption, HRTEM and FESEM) and compositional (FTIR, Raman spectra and XPS) techniques. This catalyst showed much higher activity than other solid acidic catalysts due to the enriched PTA-surface acid sites (6.78 mmol g −1 ) and the minimized diffusion limitation as well as high level of catalyst dispersion in reaction mixture due to the unique structure. Furthermore, by enclosing the PTA acidic material to a tailored free amino group in PDVC, an even more enduring catalyst was developed and applied to glycerol acetylation reaction. This catalyst displayed high conversion (99.9%), selectivity toward triacetin (73%) and superior performance in terms of endurance and leaching control of active sites compared with other catalysts. The catalyst was capable of withstanding for seven times durable run of continuous process at 100 °C without deactivation. During the reaction time, the leaching of PTA species was not observed and the material maintained its structural integrity.
66 citations
TL;DR: Different Nd 3+ -doped TiO 2 nanoparticles incorporated with heteropoly phosphotungstic acid (HPA) were synthesized, and their structure and optical properties were characterized as mentioned in this paper.
Abstract: Different Nd 3+ -doped TiO 2 nanoparticles incorporated with heteropoly phosphotungstic acid (HPA) (Nd 3+ -TiO 2 -HPA nanocomposites) were synthesized, and their structure and optical properties were characterized. UV–vis diffuse reflectance spectra of Nd 3+ -TiO 2 -HPA nanocomposites supported that the nanocomposites absorb visible light as well as ultra violet light. Consequently they exhibit efficient photocatalytic degradation of methylene blue (MB) upon illumination by the solar simulator, and the photocatalytic efficiency was found to depend on neodymium doping and heteropoly acid incorporation. These new photocatalysts were applied to the complete degradation of the organochlorine toxic chemical, 4-chlorophenol (4-CP) in water within 60 min upon sunlight illumination, indicating that Nd 3+ -TiO 2 -HPA nanocomposites would be very useful for cleaning polluted surface water by sunlight through the advanced oxidation process. Photocatalytic degradation pathway of 4-chlorophenol was examined using mass spectral analysis.
60 citations
TL;DR: In this article, a new type of green solvents named deep eutectic solvent (DESs) has been synthesized by combining hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs).
Abstract: In this study, a new type of “green solvents” named deep eutectic solvents (DESs) has been synthesized by combining hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs). Choline chloride (ChCl) was chosen as typical HBA, and polyethylene glycol (PEG), 1,3-butyleneglycol (BG), ethylene glycol (EG), glycerol (Gl), propionate (Pr), malonic acid (MA) and urea (U) were chosen as HBDs. The extraction and catalytic oxidative desulfurization (ECODS) system was evaluated with phosphotungstic acid (HPW) as catalyst and 30 wt% H 2 O 2 as oxidant. Among all the neutral, acid and basic DESs, choline chloride/2polyethylene glycol (ChCl/2PEG) showed the best performance and 99.1% of dibenzothiophene (DBT) could be eliminated from model oil at 50 °C within 3 h. Interestingly, the volume ratio of DES to model oil was just 1:10, which was much less than the amount of extractant in the literature. The gas chromatography–mass spectrometer (GC–MS) analysis demonstrated that DBT sulfoxide (DBTO) and sulfone (DBTO 2 ) were the products of oxidation of DBT. The desulfurization efficiency of the five sulfides in ECODS system occured in the following order: DBT > 4-MDBT > 4,6-DMDBT > 3-MBT >BT.
60 citations
TL;DR: In this paper, a chitosan/phosphotungstic acid composite proton exchange membrane was prepared by self-anchoring phosphotungstic acid into chitosaan membrane with submicro-pores (smp CTS/HPW).
56 citations
TL;DR: In this article, a few-layer hexagonal boron nitride (h-BN) was constructed and employed as an interlayer confining support for heterogenization of phosphotungstic acid (HPW/H-BN).
Abstract: Hexagonal boron nitride (h-BN), a layer structure material, has gained increasing attentions as a support. Herein, a few-layer h-BN is constructed and employed as an interlayer confining support for heterogenization of phosphotungstic acid (HPW/h-BN). The obtained HPW/h-BN is applied in oxidative desulfurization (ODS) and a ∼100% of sulfur removal can be achieved. Detailed experiments show that porous structure of h-BN, functioned as confining sites, contributes to the remarkable catalytic activity. Besides, aromatic hydrocarbon and olefin are further applied as chaff interferent in ODS showing no obvious effects, suggesting a promising prospect. This catalyst presents preferable recyclability in ODS, which can be recycled 6 times without noticeable decrease in reactivity. Moreover, the reaction mechanism and resultant are instantly detected by gas chromatography-mass spectrometry.
48 citations
TL;DR: In this article, a composite material HPW/NH 2 -Al 2 O 3 was successfully prepared by immobilization of phosphotungstic acid H 3 PW 12 O 40 (HPW) on the surface of amino functionalized spherical millimeter-sized mesoporous γ-Al 2O 3 beads.
TL;DR: In this article, a hybrid material based on Nafion® 212 membrane doped with nanoparticles of silica and cesium acid salt of phosphotungstic heteropolyacid is presented.
TL;DR: In this article, an organic hybrid of phosphotungstic acid was prepared by using an industrial easy-prepared amine (i.e. hexamine) and characterized by elemental analyses, infrared spectrum, powder X-ray diffraction, thermal analyses, scanning electron microscopy and energy dispersive Xray spectroscopy.
TL;DR: In this paper, the authors investigated the catalytic performances of a range of supported heteropolyacid (HPA) and silicotungstic acid (HSiW) catalysts supported on various oxides, i.e., SiO2, Al2O3, TiO2 and ZrO2.
TL;DR: In this article, a novel nanohybrid compound, LaFeO3@SiO2−NH2/PTA has been prepared, in which H3PW12O40 (abbreviated as PTA) was successfully anchored onto the surface of 3-aminopropylsilica modified LaFe3.
Abstract: In this research, a novel nanohybrid compound, LaFeO3@SiO2–NH2/PTA has been prepared, in which H3PW12O40 (abbreviated as PTA) was successfully anchored onto the surface of 3-aminopropylsilica modified LaFeO3. The resultant nanohybrid compound was characterized with XRD, FT-IR, ICP-MS, FESEM, EDX, TEM, BET, and AFM techniques. The magnetic properties of all the synthesized compounds and hybrid compound were measured using a vibrating sample magnetometer (VSM) at room temperature. The photocatalytic activity of the hybrid compound was assessed by degradation of methylene blue (MB) in aqueous solution under visible light irradiation. Compared with the bare LaFeO3 and pure PTA, the newly synthesized hybrid compound exhibited enhanced photocatalytic activity under visible light irradiation. This enhancement could be attributed to the synergistic effect between LaFeO3 and PTA. After the photocatalytic reaction, the hybrid compound can be easily separated from the reaction solution and reused several times without loss of its photocatalytic activity. Moreover, a possible photocatalytic mechanism was proposed.
TL;DR: Ammonium and silver co-doped phosphotungstic acid was developed as novel efficient catalyst for the synthesis of n-butyl levulinate as discussed by the authors, and the results showed that the activity of (NH4)0.5Ag 0.5H2PW12O40 was higher than that of single Ag+ or NH4+ doped H3PW and other representative catalysts reported by literatures.
Abstract: Ammonium and silver co-doped phosphotungstic acid was developed as novel efficient catalyst for the synthesis of n-butyl levulinate. The catalyst was characterized by element analysis, FT-IR, XRD and Hammett indicator method. Among them, (NH4)0.5Ag0.5H2PW12O40 exhibited the highest catalytic activity, and the yield of n-butyl levulinate could reach up to 99.0% within 2 h. The results showed that the activity of (NH4)0.5Ag0.5H2PW12O40 was higher than that of single Ag+ or NH4+ doped H3PW and other representative catalysts reported by literatures. In addition, (NH4)0.5Ag0.5H2PW12O40 performed good reusability for this reaction.
TL;DR: In this paper, the PTA modified Pd/W-Ce-AlO x catalyst showed a high activity for the phenol hydrogenation and high selectivity at a moderate temperature (180°C) in a high temperature water (HTW) system, because cyclohexanone is the major products from the reaction.
TL;DR: In this paper, enhanced proton conduction through polyelectrolyte matrices comprising nanopeapods of phosphotungstic acid (PWA) filled carbon nanotubes (CNTs) was demonstrated.
27 Oct 2016
TL;DR: The present method can potentially be applied to produce highly effective, low-cost, Pt-free electrocatalysts for the hydrogen evolution reaction (HER), with low Tafel slopes of ∼50 mV/decade.
Abstract: A novel, one-step protocol for the selective synthesis of W2C nanoparticles from phosphotungstic acid (H3PW12O40), a low-cost and commercially available tungsten compound, was developed. The nanoparticles had diameters of 1–50 nm and were dispersed on a carbon substrate. The W2C nanoparticles were prepared by a simple operation sequence, involving impregnation of carbon black with H3PW12O40 followed by calcination at 1000 °C. X-ray diffraction study revealed the selective formation of the W2C phase in the samples prepared, whereas the tungsten carbide (WC) phase was present in the control prepared from H2WO4. Stable W2C nanoparticles were obtained using this method owing to the presence of phosphate at the interfaces between the W2C nanoparticles and the carbon substrates, which inhibited the diffusion of carbon atoms from the carbon substrates to the W2C nanoparticles, leading to the formation of WC. The W2C nanoparticles prepared showed an excellent catalytic activity for the hydrogen evolution reaction...
TL;DR: In this paper, a nanofiber composite catalytic membrane for biodiesel production was prepared from phosphotungstic acid (PWA)/poly(vinyl alcohol) (PVA) via electrospinning on a substrate of nonwoven fabric.
TL;DR: In this paper, a method for synthesis of 7-hydroxy-4-methylcoumarin from resorcinol and ethyl acetoacetate via the Pechmann reaction with polyvinylpyrrolidone-supported phosphotungstic acid (PVP-HPW) catalyst is developed.
TL;DR: In this article, Hierarchically ordered meso/macroporous HPW/SiO2 catalysts have been synthesized via the dual-templating method and used as a catalyst for oxidative desulfurization.
Abstract: Hierarchically ordered meso/macroporous phosphotungstic acid/SiO2 (HPW/SiO2) catalysts have been synthesized via the dual-templating method and used as a catalyst for oxidative desulfurization. The as-synthesized catalysts possess ordered macropores and well-ordered hexagonal mesopores within the walls of the macroporous cages. The HPW active species are finely dispersed in the silica matrix and retain its Keggin structure. Meso/macroporous HPW/SiO2 catalysts show superior catalytic performance with obvious improvement of the desulfurization rate compared to mesoporous HPW/SiO2 and macroporous HPW/SiO2. The high performance of the catalyst should be attributed to the structural characteristics of the meso/macropores. Furthermore, the catalyst was recovered and reused for seven runs with only a slight decrease in the catalytic performance.
TL;DR: Aluminum-substituted tungstophosphoric acid (AlTPA)/sulfonated poly ether ether ketone (SPEEK) nanocomposite membranes have been prepared for fuel cell applic... as mentioned in this paper.
Abstract: Aluminum-substituted tungstophosphoric acid (AlTPA)/sulfonated poly ether ether ketone (SPEEK) (sulfonation degree approximately 77%) nanocomposite membranes have been prepared for fuel cell applic...
TL;DR: In this paper, an amino-containing metal-organic framework (NH2-MOF) and phosphotungstic acid (PTA) were used for the desulfurization of Dibenzothiophene (DBT).
Abstract: A composite material has been successfully synthesized using an amino-containing metal–organic framework (NH2-MOF) and phosphotungstic acid (PTA). This composite was characterized using X-ray diffraction, high-resolution transmission electron microscopy, nitrogen adsorption–desorption measurements, Fourier transform infrared spectroscopy and X-ray fluorescence. Characterization results confirmed the immobilization and good distribution of PTA in the NH2-MOF. The PTA/NH2-MOF was subsequently applied in the oxidative desulfurization of dibenzothiophene (DBT) with H2O2 as the oxidant in n-octane under atmospheric conditions. Under optimal reaction conditions, the oxidative desulfurization conversion of DBT reached 100%, and there was no significant decrease of the catalytic activity after four recycles. Kinetic experiments were also performed for the reaction at various temperatures, which indicated that oxidative reaction rates followed pseudo first-order kinetics, and the apparent activation energy for the desulfurization reaction was 34.1 kJ mol−1. The results indicated that this material exhibited excellent catalytic performance for oxidative desulfurization of DBT. Copyright © 2016 John Wiley & Sons, Ltd.
TL;DR: In this paper, the HPW/ZrO2-SiO2 catalyst showed excellent catalytic activity for oxidative reactions, due to the strong interaction between the active HPW and ZrO 2 -SiO 2 support.
Abstract: H3PW12O40/ZrO2–SiO2 catalyst was successfully prepared by immobilizing phosphotungstic acid (H3PW12O40, HPW) on zirconia-modified silica and employed as a catalyst for oxidative desulfurization (ODS). Under the optimal reaction conditions, the sulfur removal rate from dibenzothiophene was nearly 100%. In addition, the catalyst can be recycled up to 19 times without notable reduction in catalytic activity for the ODS process. The HPW/ZrO2–SiO2 catalyst shows excellent catalytic activity for oxidative reactions, due to the strong interaction between the active HPW and ZrO2–SiO2 support.
TL;DR: A series of novel polyoxometalate (POM)-based stable polymeric hybrids were successfully synthesized using polyhedral oligomeric vinylsilsquioxanes (POSS) and ionic liquids (IL) bearing hydrophobic alkyl chains as the building blocks, followed by ion exchange with Keggin-type phosphotungstic acid (PW) as discussed by the authors.
Abstract: A series of novel polyoxometalate (POM)-based stable polymeric hybrids were successfully synthesized using polyhedral oligomeric vinylsilsesquioxanes (POSS) and ionic liquids (IL) bearing hydrophobic alkyl chains as the building blocks, followed by ion exchange with Keggin-type phosphotungstic acid (PW). The obtained hybrids POSS–ILx–PW were demonstrated to be mesostructured and amphiphilic materials with good thermal stability. Catalytic tests for the H2O2-based epoxidation of cyclooctene have shown that these newly designed catalysts exhibit extraordinary catalytic activities, catalytic rates, and quite stable reusability. The unique amphiphilic property and the mesoporous structure are revealed to be responsible for the catalysts' excellent performance in epoxidation reactions with H2O2.
TL;DR: In this paper, free-standing chitosan/phosphotungstic acid polyelectrolyte membranes, prepared by ionotropic gelation on alumina porous supports, were employed as proton conductor in low temperature H 2 O 2 fuel cell.
TL;DR: In this article, the authors describe selectively catalytic epoxidation of cyclohexene with aqueous 30% H 2 O 2 over powdered anion-resin supported peroxo phosphotungstic acid heterogeneous catalysts prepared through a simple anion exchange from powdered chloride-form anion resin.
Abstract: Resin supported solid acid catalysts have extended the application of conventional solid acid catalysts in the field of selective oxidations. The present work describes selectively catalytic epoxidation of cyclohexene with aqueous 30% H 2 O 2 over powdered anion-resin supported peroxo phosphotungstic acid heterogeneous catalysts prepared through a simple anion-exchange from powdered chloride-form anion resin without any special pre-exchanged treatment. Among these powdered solid catalysts, anion-exchanged resin D201 supported peroxo phosphotungstic acid exhibits the best activity for the titled reaction to obtain 92.4 mol% conversion and 98.1% selectivity of epoxide, for which D201-PWAR(4) behaves as a truly heterogeneous catalyst. Some factors such as various peroxo phosphotungstic acid concentrations, the oxidants, the solvents, the molar ratios of H 2 O 2 /cyclohexene, the catalyst amount, the reaction temperature and time play important roles in controlling the epoxidation.
TL;DR: In this article, a Rod-like MCC was obtained with a high yield of 93.62 % and also exhibited higher crystallinity and narrower particle diameter distribution (76.37 %, 13.77-26.17 μm) compared with the raw material (56.47 %, 32.41-49.74 μm).
Abstract: Microcrystalline cellulose (MCC), prepared from natural cellulose through acid hydrolysis, has been widely used in the food, chemical and pharmaceutical industries because of its high degree of crystallinity, small particle size and other characteristics. Being different from conventional mineral acids, phosphotungstic acid (H3PW12O40, HPW) was explored for hydrolyzing cellulose selectively for the preparation of MCC in this study. Various reaction parameters, such as the acid concentration, reaction time, temperature and solid-liquid ratio, were optimized. Rod-like MCC was obtained with a high yield of 93.62 % and also exhibited higher crystallinity and narrower particle diameter distribution (76.37 %, 13.77–26.17 μm) compared with the raw material (56.47 %, 32.41–49.74 μm) at 90 °C for 2 h with 58 % (w/w) HPW catalyst and a solid-liquid radio of 1:40. Furthermore, HPW can easily be extracted and recycled with diethyl ether for four runs without affecting the quality of the MCC products. The technology of protecting the crystalline region while selectively hydrolyzing the amorphous region of cellulose as much as possible by using HPW is of great significance. Due to the strong Bronsted acid sites and highest activity in solid heteropoly acid, the use of effective homogeneous HPW may offer an eco-friendly and sustainable way to selectively convert fiber resources into chemicals in the future.
TL;DR: Investigation into the adhesion, proliferation and migration of mouse embryonic fibroblasts on pristine polyaniline films and films doped with sulfamic and phosphotungstic acids demonstrated that the lesser the difference between the surface energy of the sample and cell, the more cyto-compatible the surface is.
Abstract: Polyaniline shows great potential and promises wide application in the biomedical field thanks to its intrinsic conductivity and material properties, which closely resemble natural tissues. Surface properties are crucial, as these predetermine any interaction with biological fluids, proteins and cells. An advantage of polyaniline is the simple modification of its surface, e.g., by using various dopant acids. An investigation was made into the adhesion, proliferation and migration of mouse embryonic fibroblasts on pristine polyaniline films and films doped with sulfamic and phosphotungstic acids. In addition, polyaniline films supplemented with poly (2-acrylamido-2-methyl-1-propanesulfonic) acid at various ratios were tested. Results showed that the NIH/3T3 cell line was able to adhere, proliferate and migrate on the pristine polyaniline films as well as those films doped with sulfamic and phosphotungstic acids; thus, utilization of said forms in biomedicine appears promising. Nevertheless, incorporating poly (2-acrylamido-2-methyl-1-propanesulfonic) acid altered the surface properties of the polyaniline films and significantly affected cell behavior. In order to reveal the crucial factor influencing the surface/cell interaction, cell behavior is discussed in the context of the surface energy of individual samples. It was clearly demonstrated that the lesser the difference between the surface energy of the sample and cell, the more cyto-compatible the surface is.