Topic
Phosphotungstic acid
About: Phosphotungstic acid is a research topic. Over the lifetime, 1925 publications have been published within this topic receiving 38059 citations. The topic is also known as: Phosphowolframic acid.
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TL;DR: In this paper, acid-activated palygorskite (Pa) with tunable surface acidity was obtained by simple acidic treatment of raw clay, and the new catalysts with 5 −30 wt% 12-phosphotungstic acid (H3O40PW12·xH2O, PTA) were then readily prepared by the wet impregnation method.
Abstract: In this study, acid-activated palygorskite (Pa) with tunable surface acidity was obtained by simple acidic treatment of raw clay. The new catalysts with 5–30 wt% 12-phosphotungstic acid (H3O40PW12·xH2O, PTA) were then readily prepared by the wet impregnation method. Their characteristic features were systematically investigated by various means including energy-dispersive X-ray (EDX), X-ray diffraction (XRD), N2 adsorption/desorption isotherms, Fourier-transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), as well by comparison with Pa, PTA and H-Beta zeolite. The high activities of these catalysts promoted phenol to undergo hydroxyalkylation, resulting in an interesting bisphenol F (BPF) product. Among these solid acid catalysts, 10% PTA/Pa was chosen as the most suitable catalyst giving an 87% yield and 96% selectivity under mild conditions (phenol/formaldehyde mole ratio of 15 : 1; T = 343 K; catalyst concentration of 0.006 g g−1; 40 min). The surface acid strength and acidic type were characterized by ammonia temperature programmed desorption of NH3 (NH3-TPD), and FT-IR of pyridine adsorption (Py-IR). It was found that the catalytic activity could be further enhanced by impregnating PTA onto Pa due to the enhanced acid strength and the redistribution of Bronsted and Lewis acid sites. Besides, a more appropriate combination of Bronsted and Lewis acid sites was essential to achieve the highest BPF yield. Recycle experiments were conducted and a plausible mechanistic pathway was proposed according to our observations and findings.
18 citations
TL;DR: In this paper, a novel composite membrane was prepared by incorporation of silica-included phosphotungstic acid (PWA) additive into perfluorosulfonic acid (PFSA) followed by solution casting.
Abstract: A novel composite membrane was prepared by incorporation of silica-included phosphotungstic acid (PWA) additive into perfluorosulfonic acid (PFSA) followed by solution casting. Physico-chemical properties of the composite membranes were studied by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry analysis (TGA), water uptake and swelling ratio. The results of FT-IR and TGA illustrated the stability of the PWA-silica additive in the PFSA matrix. Lower PWA-silica additive loading (2.5 and 5 wt%) in the composite membranes helped to inhibit methanol crossover and enhance the proton conductivity. However, higher additive content shows decrease in both methanol resistance and proton conductivity.
18 citations
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 ...
18 citations
TL;DR: The distribution and selectivity coefficients of the sorption of 137 Cs and 86 Rb on acid and normal ammonium and thallous phosphomolybdate and phosphotungstate were determined together with the values of the separation factors for both elements, and an interpretation of the mechanism of sorption for caesium and rubidium was suggested.
18 citations
TL;DR: In this paper, a selective staining agent was used to enhance image contrast for transmission electron microscopy (TEM) morphological characterization of poly(methyl methacrylate) (PMMA)/polyacrylonitrile (PAN) composite particles.
Abstract: It is necessary to use a selective staining agent to enhance image contrast for transmission electron microscopy (TEM) morphological characterization of polymer composite particles. However, the typical selective staining agents osmium tetraoxide and ruthenium tetraoxide are neither suitable for poly(methyl methacrylate) (PMMA)/polyacrylonitrile (PAN) composite particles. In this study, it was found that phosphotungstic acid (PTA) solution with 6.4 pH value is unsuitable for PMMA, but it can stain PAN. Therefore, it can be a selective staining agent in the TEM for PMMA/PAN composite particles. By controlling different thermodynamic and kinetic polymerization parameters, PMMA/PAN and PMMA/P(AN-MMA) composite particles with nano to submicro sizes having different morphological structures were synthesized. TEM micrographs of all these composite particles with their predicted morphology have been compared, and the experimental results are completely consistent with the predictions.
18 citations