Silicotungstic acid - Wikipedia

Synthesis, Characterization and Catalytic Activity of New Solid Acid Catalysts, H3PW12O40 Supported on to Hydrous Zirconia[J].

Oxide supports for 12-tungstosilicic acid catalysts in …

Oxide supports for 12-tungstosilicic acid catalysts in ..

12-Tungstosilicic acid, H 4 SiW 12 O 40 ..

Tungstic acid closely resembles molybdic acid in combining with phosphoric, arsenious, arsenic, boric, vanadic and silicic acids to form highly complex acids of which a great many salts exist. Of the phosphotungstic acids the most important is phosphoduodecitungstic acid, H 3 PW, 2040nH 2 O, obtained in quadratic pyramids by crystallizing mixed solutions of orthophosphoric and metatungstic acids. Two sodium salts, viz. Na2HPW12040nH 2 O and Na3PW12040 nH20, are obtained by heating sodium hydrogen phosphate with a tungstate. The most important silicotungstic acids are silicodecitungstic acid H8W10S1036.3H20, tungstosilicic acid, H 8 W 12 SiO 42.20H 2 O, and silicoduodecitungstic or silicotungstic acid, H8W12S1042.29H20. On boiling gelatinous silica with ammonium polytungstate and evaporating with the occasional addition of ammonia, ammonium silicodecitungstate is obtained as short rhombic prisms. On adding silver nitrate and decomposing the precipitated silver salt with hydrochloric acid, a solution is obtained which on evaporation in a vacuum gives the free acid as a glassy mass. If this be dissolved in water and the solution concentrated, some silicic acid separates and the filtrate deposits triclinic prisms of tungstosilicic acid. Silicotungstic acid is obtained as quadratic pyramids from its mercurous salt which is prepared from mercurous nitrate and the salt formed on boiling gelatinous silicic acid with a polytungstate of an alkali metal.

12-Tungstosilicic Acid - Thomas Sci

This chapter describes the use of heterogeneous catalysts comprising 12-tungstosilicic acid and mesoporous silicas, MCM-41 and SBA-15, for esterification of free fatty acid and oleic acid with methanol. The influence of various reaction parameters such as catalyst concentration, acid/alcohol molar ratio, and temperature was studied to optimize the conditions for maximum conversion of oleic acid. The catalysts show potential of being used as recyclable catalyst materials after simple regeneration. As an application, studies were carried out for biodiesel production from Jatropha oil, as feedstocks without any pretreatment, with methanol over the present catalysts. The catalytic activity of both the catalysts was correlated with the nature of the support.

(silicotungstic Acid)
(silicotungstic Acid)


Yang, Z.; Xu, X.; Li, T.; Zhang, N.; Zhao, X.; Chen, W.; Liang, X.; He, X.; Ma, H. Preparation and Catalytic Property of Multi-walled Carbon Nanotubes Supported Keggin-Typed Tungstosilicic Acid for the Baeyer-Villiger Oxidation of Ketones. Catal. Letters 2015, 145 (11), 1955-1960.Liu, L.; Wang, B.; Du, Y.; Borgna, A. Supported H4SiW12O40Al2O3 solid acid catalysts for dehydration of glycerol to acrolein: Evolution of catalyst structure and performance with calcination temperature. Appl. Catal. A Gen. 2015, 489, 32-41.

tungstosilicic acid, H 8 W 12 ..

12-Tungstosilisic acid anchored to MCM-41 was synthesized and characterized by various physicochemical techniques such as thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), laser-Raman spectroscopy, diffuse reflectance spectroscopy (DRS), N2 adsorption–desorption, 29Si-magic-angle spinning (MAS) NMR, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The total acidity was determined by -butyl amine titration. The types of acidic sites (acidic strength) were determined by potentiometric titration. The use of synthesized material was explored for esterification of diacarboxylic acids with butanol. Influence of various reaction parameters (catalyst concentration, acid/alcohol molar ratio and reaction time) on catalytic performance was studied. The catalyst shows high activity in terms of higher yields toward diesters, especially for dioctyl succinate and dioctyl malonate. The catalyst was also regenerated and reused for four cycles. All these characteristics imply the high potential of an environmentally benign catalyst for synthesis of succinate and malonate diesters.

.xH 2 O 12-tungstosilicic acid ..

Activated carbon supported tungstosilicic acid was applied as catalyst in the synthesis of ten important ketals and acetals and revealed high catalytic activity. Under certain conditions (molar ratio of aldehyde/ketone to glycol is 1:1.5, the mass ratio of the catalyst used in the reactants is 1.0%, the reaction time is 1.0 h), the yields of ketals and acetals can reach 56.7%~87.9%. It has been demonstrated that the activated carbon supported tungstosilicic acid is an excellent catalyst. From the above results and discussion, we can see that the synthesis of ten important ketals and acetals by the activated carbon supported tungstosilicic acid has good prospects.