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, a single-stage synthesis of isoprene from methyl tert-butyl ether (MTBE) and formalin using Keggin-type heteropolyacids, phosphotungstic acid (PTA), phosphomolybdic acid(PMA), and silicotungcial acid (STA) was performed in a batch reactor.
Abstract: A liquid-phase single-stage synthesis of isoprene from methyl tert-butyl ether (MTBE) and formalin using Keggin-type heteropolyacids, phosphotungstic acid (PTA), phosphomolybdic acid (PMA), and silicotungstic acid (STA) was performed in a batch reactor. The effects of catalyst concentration, reaction temperature, MTBE/formaldehyde ratio, and solvent type on isoprene yield were evaluated. At moderate reaction conditions, the two-phase organic–aqueous system with cyclohexane addition and high MTBE/formaldehyde ratio enhanced the isoprene formation. When the catalyst concentration was increased, the formaldehyde conversion and turnover frequency increased, but isoprene selectivity slightly decreased. At high temperature or low MTBE/formaldehyde ratio, isoprene yield decreased because of the formation of 3,4-dihydro-4-methyl-2H-pyran. When the catalyst activities are compared, the STA catalyst exhibited formaldehyde conversion, isoprene yield, and selectivity that were slightly higher than those of the PTA an...
12 citations
TL;DR: The apical body was reinvestigated in guineapig spermatozoa and spermatids treated en masse with ethanolic phosphotungstic acid (E-PTA) and this technique (Gordon & Bensch, 1968) was chosen for several reasons.
Abstract: acrosome vesiculate, releasing the acrosomal contents (Austin & Bishop, 1958; Austin, 1963; Hadek, 1963; Piko & Tyler, 1964; Barros, Bedford, Franklin & Austin, 1967; Bedford, 1967b). The inner acrosome membrane then becomes the outer ensheathment of the sperm head. Under these circumstances, the contents of the compartment between the inner acrosome membrane and the nucleus may be important for the movement of the spermatozoon through the zona and fusion of spermatozoon and ovum. Since it resides in the subacrosomal space at the apex of the nucleus, the 'apical body' is in a strategic locus for the approach of the spermatozoon toward the egg. The apical body, however, is a controversial structure since it has been reported in some mammals (Hadek, 1963; Nicander & Bane, 1966; Bedford, 1967a) but it has not been seen in others (Fawcett & Ito, 1965). Among the primates, Bedford (1967a) noted a subacrosomal body in the bush baby but it was not present in man. Because of the enormous development of the guinea-pig acrosome (Fawcett, 1965), this species is particularly favourable for analysis of the organelle and related substructures. An apical body, however, has not been consistently observed in the guinea-pig. It was described as a diffuse mass by Nicander & Bane (1966) but it was not present in an extensive study by Fawcett (1965). It was decided in the present study to reinvestigate the apical body in guineapig spermatozoa and spermatids treated en masse with ethanolic phosphotungstic acid (E-PTA). This technique (Gordon & Bensch, 1968) was chosen for several
12 citations
TL;DR: In this paper, a case study on the preparation of PW12@TiO2 nanospheres via the sol-gel procedure is discussed, where both calcinated and un-calcinated-PW12-O2 nanopheres exhibited almost parallel yet excellent oxidative desulfurization performances in the model oil.
Abstract: Calcination is considered to be a key step in the process of preparation of titanium dioxide based catalysts; however, it consumes a lot of energy. We describe unequivocally here for the first time that high-energy consuming calcination is a surplus process in the preparation of phosphotungstic acid@titanium dioxide (PW12@TiO2) catalysts with various loadings of phosphotungstic acid (10–40 wt%) for oxidative catalytic reactions. To prove this, a case study on the preparation of PW12@TiO2 nanospheres via the sol–gel procedure is discussed here. The structure and morphology of the nanospheres were characterized by FT-IR, FT-Raman, BET XRD, ICP and SEM analyses. Oxidative desulfurization of a model oil composed of 350 ppmwS dibenzothiophene (DBT) in n-octane was investigated using these nanospheres. The results showed that both calcinated and un-calcinated-PW12@TiO2 nanospheres exhibited almost parallel yet excellent oxidative desulfurization performances in the model oil. The 350 ppmwS of sulfur content in 20 mL of n-octane was dropped down to 2.4 and 2.6 ppmwS within 2 hours at 60 °C using 70 mg of calcinated and un-calcinated-PW12@TiO2 nanospheres with 30 wt% PW12 loading, respectively. The high desulfurization efficiency of the catalyst remained unchanged even after the regeneration of the catalyst ten times. This excellent desulfurization performance makes the as-prepared composite without calcination treatment a promising catalyst in practical oxidative desulfurization processes.
12 citations
TL;DR: In this article, the removal of the protecting allyl group from allyl aryl ethers in the presence of other oxygen protecting groups was successfully achieved using a solid acid supported on the high surface area material MCM-41.
Abstract: Removal of the protecting allyl group from allyl aryl ethers in the presence of other oxygen protecting groups was successfully achieved using a solid acid supported on the high surface area material MCM-41. The catalyst showed excellent activity in the presence of various electron withdrawing, electron donating, and oxidizable functional groups. The methodology is also very useful for the removal of protecting allyl groups of various natural products such as vanillin, isovanillin, and other oxygen functionalized aldehydes and ketones.
12 citations
TL;DR: In this article, a sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica composite membranes for direct methanol fuel cells (DMFCs) application were prepared.
Abstract: A novel sulfonated poly(ether sulfone) (SPES)/phosphotungstic acid (PWA)/silica composite membranes for direct methanol fuel cells (DMFCs) application were prepared. The structure and performance of the obtained membranes were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), water uptake, proton conductivity, and methanol permeability. Compared to a pure SPES membrane, PWA and SiO2 doped membranes had a higher thermal stability and glass transition temperature (Tg) as revealed by TGA-FTIR and DSC. The morphology of the composite membranes indicated that SiO2 and PWA were uniformly distributed throughout the SPES matrix. Proper PWA and silica loadings in the composite membranes showed high proton conductivity and sufficient methanol permeability. The selectivity (the ratio of proton conductivity to methanol permeability) of the SPES-P-S 15% composite membrane was almost five times than that of Nafion 112 membrane. This excellent selectivity of SPES/PWA/silica composite membranes indicate a potential feasibility as a promising electrolyte for DMFC. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
12 citations