Mechanism of Thermal Decomposition of Potassium/Ammonium Salts of the 12-Molybdophosphoric Acid and Effect on the Catalytic Performance in the Isobutyric Acid Oxidehydrogenation

Study of the P2O5−MoO3 system in acrolein oxidation

“…In the molybdenum rich: samples with (Mo/P > 7), the ammonium HPA salt is also present in small amounts. This agrees with literature data on the thermal stability of the HPA ammonium salt (420 [9] -450~ [10]). Thus, thermal treatment at 430~ leads to an almost complete destruction of the HPA salt.…”

In Situ Investigations of Structure–Activity Relationships in Heteropolyoxomolybdates as Partial Oxidation Catalysts

“…[13] In addition, migration of molybdenum addenda ions [14±20] or vanadium addenda substituents [14, 16, 21±25] from the Keggin anion onto interstitial sites in the HPOM structure [15,20,21,22] has been suggested, with or without reconstruction of the Keggin ion.…”

The structure of molybdenum-heteropoly acids under conditions of gas-phase selective oxidation catalysis: a multi-method in situ study

“…Furthermore, it has been suggested that the molybdenum cations [28] as well as the vanadium cations [29,30] migrate from the Keggin anion to cationic positions in the structure [31,32] and that the heteropoly acids become partially reduced under reaction conditions [33,34]. This migration of cations from the Keggin anion has been speculated to be responsible for the catalytic activity of the heteropoly oxomolybdates with Keggin structure [25,29,30,33,35,36,37]. The result of the migration is a cubic molybdenum autosalified heteropolyacid (Pn-3m, a = 11.853 Å) derived from triclinic H 3 [PMo 12 O 40 ]*13H 2 O under reduction conditions with propene and hydrogen at temperatures above 600 K. This way the in situ studies on the electronic structure of the active state of HPA are corroborated by direct in situ geometric structural studies using Xray diffraction and EXAFS.…”