Catalytic Performance Of Heteropolyacid Research Articles

Unique Dynamics of Water Confined on the Surface of Metal Oxide Clusters.

Water confined on metal oxide surface plays significant roles in heterogeneous catalysis. Heteropolyacid, a 1.2 nm-metal oxide cluster with well-defined structure, is applied as a model to understand the dynamics of water on its surface. The surface water strongly associates with heteropolyacid cluster and form the so-called 'pseudoliquid phase' where catalytic reactions are conducted. Broadband dielectric spectroscopy and differential scanning calorimetry have been applied to probe the dynamics of water in this pseudoliquid phase. A supercooling phase transition of water below its normal melting temperature and a dipolar glassy relaxation behaviour due to the hindered dynamics of water have been observed. The rich dynamic behavior on the surface of such well-defined metal clusters provide new perspectives to understand the properties of surface water and their relation to catalytic performance of heteropolyacid.

HPAs and POM‐based ILs Catalyzed Effective Conversion of Furfuryl Alcohol to Alkyl Levulinate

AbstractHere we represented the heteropoly acids (HPAs) and polyoxometalate (POM)‐based ionic liquids (ILs) catalyzed the effective alcoholysis of furfural alcohol (FAL) to alkyl levulinate. H5AlW12O40 exhibited the highest catalytic activity among HPAs, furnishing > 99 % FAL conversion and 80 % yield of butyl levulinate (BL). The incorporation of IL framework containing sulfate group into HPAs resulted in the enhanced catalytic performance. [MIMBS]5[AlW12O40] achieved the highest BL yield of 94 % and maintained a good catalytic activity after 6 times of recycle and reuse experiments. The effect of the Hammett acidity and structure of catalyst on the catalytic performance of HPAs and POM‐based ILs was also investigated.

Characterization and catalytic performance of heteropoly acid H4SiW12O40 supported on nanoporous materials.

Heteropoly acid H4SiW12O40 (SiW) has been supported on different nanoporous materials and characterized by powder X-ray diffraction (XRD), FTIR, HRTEM, N2 physisorption, and thermal analysis. No SiW diffraction peaks are observed after loading 33-50 wt% of SiW on various mesoporous materials (pore size: -30 Å) except for siliceous MCM-48. In contrast, the SiW diffraction peaks appear at 14 wt% loading on zeolite EMT with micropore size of ca. 7.4 x 6.5 Å. Supported SiW retains the Keggin structure on mesopore surface. The cubic mesostructure of MCM-48 is stable while MCM-41 loses its regular hexagonal mesostructure upon loading SiW. Several factors account for different behaviours of various supports, including pore size, curvature of mesopore interface and interaction between SiW and aluminium sites in the framework. The resulting 33-50 wt% SiW/MCM-48 solid acid catalysts have large surface area (- 550 m2/g), regular pore arrangement with uniform pore size (- 25 Å), finely dispersed SiW and good thermal stability. They exhibit significantly improved activity in acid-catalyzed cracking of long-chain hydrocarbons in comparison with bulk SiW and SiW/MCM-41.

Catalytic Performance of Heteropolyacids as Efficient and Eco-Friendly Catalysts for the One-Pot Synthesis of Benzopyran Derivatives

An efficient and improved procedure for the synthesis of benzopyran derivatives has been achieved with Keggin-type and Preyssler-type heteropolyacids (HPA) catalysts in one-pot reaction under solvent-free conditions.

ChemInform Abstract: Catalytic Performance of Heteropoly Acids on Different Supports in the Synthesis of Dihydropyrimidones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Catalytic Performance of Heteropoly Acids on Different Supports in the Synthesis of Dihydropyrimidones

Keggin heteropoly acids supported on solids with different nature were used in the Biginelli reaction in order to obtain dihydropyrimidones. The results show that the activity of the catalysts is dependent on the supports used to obtain the catalysts. This method consistently has the advantages of excellent yield, mild reaction conditions, ease of workup, survival of different functional groups, and short reaction times