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.

Silica-supported phosphotungstic acid as a novel heterogeneous catalyst for β-pinene polymerization

Abstract: We report an efficient and environmentally friendly heterogeneous catalyst for β-pinene cationic polymerization based on silica supported phosphotungstic acid (HPW/SiO2). The catalysts were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed desorption of ammonia (NH3-TPD) and FT-IR spectra. XRD and TEM analysis of HPW/SiO2 indicate that the particles of HPW are amorphously uniformly distributed on the surface of the silica. NH3-TPD results indicate that the total acid amount and acidity increased with increasing the loading amount. FT-IR spectra analysis shows that the structure of Keggin does not change when HPW was supported on silica. Their catalytic performance for β-pinene polymerization was also tested. Under the optimal conditions, the yield of poly(β-pinene)s was up to 90.4 %, and the number-average molecular weight was about 1,100.

Preparation and Characterization of Sulfonated Poly (Ether Sulfone) (SPES)/Phosphotungstic Acid (PWA) Hybrid Membranes for Biodiesel Production

Abstract: A new kind of organic–inorganic hybrid membrane based on sulfonated poly (ether sulfone) (SPES) with different degree of sulfonation (DS) embedded phosphotungstic acid (PWA) was prepared as a heterogeneous acid catalyst for biodiesel production. Three kinds of hybrid membranes with the DS of SPES 9.7, 20.3 and 39.1 % were obtained. The interactions between SPES and PWA in SPES/PWA hybrid membrane were characterized by Fourier transform infrared (FTIR), thermogravimetric analysis and X-ray diffraction (XRD). The band shift of FTIR spectrum showed that the PWA particles interacted primarily with sulfonic acid groups on the polymer backbone. Compared to pure SPES membrane, the thermal stability of SPES/PWA hybrid membrane was enhanced. The XRD results suggested that the PWA particles were incorporated inside membrane pores and adhered on the walls outside the pores which were due to the interaction between PWA and SPES polymer matrix. The catalytic properties of SPES/PWA membranes were tested by the esterification of the acidified oil with methanol. The reaction conditions were optimized by response surface model and the optimum conditions were obtained as: methanol/oil mass ratio of 1:1, hybrid membrane loading of 1.66 meq/g and reaction time 6 h with the free fatty acids conversion of 95.3 %. The hybrid membrane with SPES/PWA mass ratio of 2:1 and the membrane thicknesses of 0.06 mm were optimal for the esterification. The SPES/PWA membrane of DS 20.3 % exhibited the best catalytic stabilities among the three kinds of hybrid membranes with different DS with a stable conversion of above 90 % in all times.

Serum uric acid.

Abstract: Data from the 1977 College of American Pathologists (CAP) Comprehensive Chemistry Survey and other programs have been analyzed in an interlaboratory comparison of the measurements of serum uric acid. The majority of clinical laboratories utilize some form of phosphotungstic acid (PTA) oxidation-reduction technic for the measurement of uric acid. Methods based on uricase are most often performed on some automated device. In this Survey, in which specimens containing minimal potential interfering compounds were used, there are no significant differences in the results obtained by phosphotungstic acid and uricase methods.