Tin(II) phosphotungstate heteropoly salt: An efficient solid catalyst to synthesize bioadditives ethers from glycerol

How the Cobalt Position in the Keggin Anion Impacts the Activity of Tungstate Catalysts in the Furfural Acetalization with Alkyl Alcohols

“…Due to their structural versatility, various modifications on the Keggin anion have improved their catalytic activity. These are the main changes performed: (i) to convert HPAs to salts after exchange their protons by metal or organic cations, resulting in catalysts highly active in esterification, etherification, acetalization, and hydrolysis reactions; [21–29] (ii) to transform the Keggin HPAs to lacunar salts, removing one MO unit (M=W or Mo), leading to the highly active catalysts in oxidation reactions with hydrogen peroxide of olefins, alcohols, and aldehydes; [30–35] and (iii) to doping lacunar Keggin anion with a transition metal cation, resulting in efficient catalysts in oxidative transformations [36–41] …”

“…[18][19][20] Due to their structural versatility, various modifications on the Keggin anion have improved their catalytic activity. These are the main changes performed: (i) to convert HPAs to salts after exchange their protons by metal or organic cations, resulting in catalysts highly active in esterification, etherification, acetalization, and hydrolysis reactions; [21][22][23][24][25][26][27][28][29] (ii) to transform the Keggin HPAs to lacunar salts, removing one MO unit (M=W or Mo), leading to the highly active catalysts in oxidation reactions with hydrogen peroxide of olefins, alcohols, and aldehydes; [30][31][32][33][34][35] and (iii) to doping lacunar Keggin anion with a transition metal cation, resulting in efficient catalysts in oxidative transformations. [36][37][38][39][40][41] An important aspect is that the size of cation can modulate the solubility of these salts (i. e., lacunar, metal-doped); while salts containing highly charged counterions such as small-sized metal cations are soluble in a polar solvent, those having large radium cations are almost insoluble.…”

Solidified and Immobilized Heteropolyacids for the Valorization of Lignocellulose

“… [56] Also, FT‐IR analysis of the spent catalysts suggest no significant changes in the fingerprint region of the Keggin structure. In contrast, the SnSiW catalyst synthesized from SnSO 4 as precursor gradually deactivates in the etherification of glycerol and tert ‐butyl alcohol over three cycles [59] . Based on potentiometric titration with n ‐butylamine, the authors attributed the loss in catalytic performance to a decrease of the acidic strength.…”

Production of Biofuel Additives from Glycerol Etherification Using Zirconia Supported Phosphotungstic Acid

“…As a new type of green catalyst, heteropolyacids have aroused great interest of many researchers for their unique Keggin structure. Heteropolyacids have been exchanged for protons by metal ions to prepare insoluble solid salt catalysts for the etherification of glycerol, such as Tin(II) phosphotungstate heteropoly salt [29] and Tin(II) phosphotungstate heteropoly salt [30]. Heteropolyacids are also often loaded on suitable carriers such as silica [31], MCM-41 [32] and niobic acid [33] to solve the disadvantages of poor thermal stability and easy leaching in polar media.…”