Catalysis Letters, Vol.34, No.1-2, 213-221, 1995
Proton Sites in Keggin Heteropoly Acids from O-17 NMR
The structure of the bulk proton sites in dehydrated solid Keggin-type heteropoly acids (HPA) H3PW12O40 and H4SiW12O40 was determined by O-17 NMR. The terminal W=O oxygen atoms in Keggin heteropolyanions were found to be the predominant protonation sites. The protonation of HPAs in solution is also discussed on the basis of O-17 NMR data.