Wells–Dawson tungsten heteropolyacid (H6P2W18O62) has been applied as an effective heterogeneous catalyst for one-pot synthesis of spiro[4H-pyran-3,3’-oxindoles] via reaction of various isatins, malonitrile and 1,3-dicarbonyl compound in water. The corresponding products were obtained in high yields. The catalysts were easily recycled and reused without loss of their catalytic activity. 

Keggin heteropolyacids (HPAs) are metal–oxygen clusters with strong Bronsted acidity. The conversion of HPAs to metal salts can result in Lewis acidity, improving their performance oxidation reactions. In this review, the main routes for synthesis Keggin-type salts, as well use catalysts processes a plethora substrates, such monoterpenes, olefins, aldehydes, terpene alcohols, and aromatics, des...

Encouraged by our recent success in work with POMs as green catalysts, we have developed our research in field of nanotechnology. Sodium 30-tungstopentaphosphate, so called Preyssler anion, nanoparticles were synthesized and the morphology and size of these nanoparticles were characterized using, transmission electron microscopy (TEM), scanning electron microscopy(SEM), X-ray diffraction(XRD) a...

A continuous-flow method for the determination of nitrate and phosphate in water is proposed. The method is based on insertion of reagents and sample solutions into a single channel through a programmable switching valve. The method depends upon heteropolyacid with phosphate and on the modified Griess reaction for nitrate, and permits the determination of PO(-3) (4) in the range 1-20 mug/ml and...

Abstract: Solid acid (heterogeneous) catalysts have a unique advantage in esterifi cation and transesterifi cation reactions which enhances the use of high acid value oil to be used as feedstock for synthesis of biodiesel. Various solid acid catalysts such as resins, tungstated and sulfated zirconia, polyaniline sulfate, heteropolyacid, metal complexes, sulfated tin oxide, zeolite, acidic ionic...