Catalysis of vegetable oil transesterification by Sn(II)-exchanged Keggin heteropolyacids: bifunctional solid acid catalysts

A Rare Carbon Skeletal Oxidative Rearrangement of Camphene Catalyzed by Al‐Exchanged Keggin Heteropolyacid Salts

“…Keggin heteropolyacids (HPAs) are attractive catalysts and are highly active in oxidative and acid‐catalyzed reactions . Their unique chemical‐physical properties can be easily manipulated with a suitable tailoring of their constitution, removing their protons that are undesirable in oxidation reactions and introducing metal cations that may contribute to achieve the catalytic properties adequate to the process …”

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.…”

Vanadium-doped sodium phosphomolybdate salts as catalysts in the terpene alcohols oxidation with hydrogen peroxide

“…A simple protons exchange by metal cations allows that their properties such as acidity strength, porosity, and surface area can be adequately tuned, making them efficient catalysts in redox or acid-catalyzed reactions. [28][29][30][31][32] In addition, if the protons are exchanged by large ionic radius cations such as cesium, potassium, or ammonium, they become insoluble catalysts in polar solvents. 33,34 This modication keeps untouched the Keggin anion, which is the primary structure of these catalysts.…”