Heteropolyacids 12-molybdophosphoric acid

More recently, heteropolyacids like 12-molybdophosphoric acid (H3PM012O40) have been found to be the very efficient initiators of cationic ring-opening polymerization [13]. They are easily available, inexpensive initiators with an acid strength comparable to perchloric acid they are easily purified and conveniently handled in a pure state [14]. 

Mukai and co-workers [105] used Keggin-type heteropolyacids immobilized in the network structure of resorcinol-formaldehyde carbon gels as catalysts for the synthesis of methyl tert-butyl ether from methyl alcohol and tert-butyl alcohol. Large amounts of 12-tungstophosphoric and 12-molybdophosphoric acids were immobilized into the support by two methods, pore shrinkage and the ship-in-the-bottle method, which are essentially impregnation methods. The authors reported that these catalysts showed activity in the reaction studied and could be of practical utility as solid acid catalysts in various reactions. 

Supported AI2O3, Ti02, Si02 or Zr02 with a heteropolyacid, e.g. tungstosilicic acid, molybdosilicic acid, or molybdophosphoric acid... 

Molybdenum nitride containing phosphorous was prepared by a TPRe of 12-molybdophosphoric acid—a Keggin-type heteropolyacid— with CH4/4 H2 (46). 

Relatively high thermal structural stability the Keggin anion in heteropolyacids begins to decompose at temperatures close to 250-300°C. Salification leads to a remarkable improvement in the stability, allowing operations up to 400-450°C to be carried out. Salts can be prepared by ion-exchange in aqueous solutions of proton form of the heteropolyacid, or by direct precipitation of the insoluble salt. In some cases, such as the cesium salts of 12-molybdophosphoric or tungstophosphoric acids, the structure is stable up to 550°C. 

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