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.

A size-matched POM@MOF composite catalyst for highly efficient and recyclable ultra-deep oxidative fuel desulfurization

Abstract: A composite of Keggin-type phosphotungstic acid (H3PW12O40) encapsulated in sized-matched metal–organic framework UiO-67 (PW12@UiO-67) was prepared as a heterogeneous catalyst for extractive and catalytic oxidative desulfurization systems (ECODS). The appropriate cage size and narrow windows of UiO-67 serve to avoid the leaching of phosphotungstic acid, and also allow most sulfur compounds commonly found in fuels to approach the catalyst. The as-synthesized composite catalyst was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), and N2 adsorption–desorption isotherms to confirm that PW12 was successfully encapsulated in UiO-67 and the structure of UiO-67 was retained after immobilization. The obtained composite was examined as a heterogeneous catalyst in ECODS and showed remarkably high catalytic activity in the ultra-deep oxidative desulfurization of three sulfur compounds (benzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) under mild conditions. The sulfur removal from 1000 ppm model oil reached 99.5% within 1 h at 70 °C for dibenzothiophene. The composite catalyst PW12@UiO-67 could be easily regenerated and recycled for eight consecutive cycles without significant loss in catalytic activity.

Development of high-temperature PEMFC based on heteropolyacids and polybenzimidazole

Abstract: Inorganic/organic composite membranes have been prepared from polybenzimidazole and two different heteropolyacids; namely phosphotungstic acid and silicotungstic acid. The membranes were characterized using SEM, XRD, and proton conductivity. The conductivity of the composite membrane was relatively high when compared to PBI membrane. The fuel cell performance with the composite membranes doped with phosphoric acid was investigated using hydrogen. It was found that pre-treatment of PWA and SiWA influenced the fuel cell performance and that the performance was enhanced with the use of the composite membrane. However, from the electrode polarization and crossover current data it was revealed that the expected high performance of the fuel cell was not achieved because of voltage losses associated with contact resistance and poor ionic conductivity in the catalyst layer. The best performance of the fuel cell was achieved with a 40% SiWA/PBI composite membrane.

Atomically Dispersed Rhodium on Self-Assembled Phosphotungstic Acid: Structural Features and Catalytic CO Oxidation Properties

Abstract: Atomically dispersed Rh catalysts supported on phosphotungstic acid (PTA) with Rh loading up to 0.9 wt % were prepared through a self-assembly method. Rh stays exclusively as single atom species coordinated to six oxygen atoms, plausibly located at the 4-fold hollow site on one phosphotungstic acid (PTA) molecule together with a chemically adsorbed O2 molecule. The catalyst is active in CO oxidation affording turnover frequencies between 0.2 and 1.7 s–1 from 165 to 195 °C, with an apparent activation energy of 127 kJ/mol. The catalyst is highly stable, well maintaining the Keggin structure of PTA as well as the single-atom identity of Rh after three catalytic cycles (50 to 400 °C). CO activation is mainly achieved on Rh via the formation of dicarbonyl species, while oxygen activation and transfer mainly occur through PTA. The proposed catalytic cycle consists of an alternation of Rh(CO)23+ species and Rh(CO)21+ species on PTA, during which CO transforms into CO2 with oxygen activation being rate-determining.