Structural Features and Thermal Stability of Titania-Supported 12-Molybdophosphoric Heteropoly Compounds

Abstract

The structure and thermal decomposition of unsupported and titania-supported 12-phosphoromolybdic acid (HPMo) and its Co and Ni salts have been studied by different techniques including X-ray diffraction, thermogravimetric analysis, FT-infrared, Raman, and X-ray spectroscopic techniques. The transformation of heteropoly anion of bulk HPMo begins at a temperature lower than for its TiO 2 -supported counterpart with the formation of a mixture of R-and -MoO 3 . In the thermal transformation of TiO 2 -supported HPMo, two steps have been identified. The intermediate species formed between the hydrated form of the heteropoly compound and the crystallized molybdenum oxides display the same nuclearity and composition as that of the Keggin precursor. The stability of the HPA supported on titania increases due to the anion-support interaction and this is even enhanced in the Co-and Ni-exchanged homologues.

Preparation and visible-light photochromism of phosphomolybdic acid/polyvinylpyrrolidone hybrid film

“…Comparing the E b values of the films before and after irradiation, the E b 's of Mo 3d 7/2 and Mo 3d 5/2 are both decreased, which reveales the chemical microenvironment of Mo has been changed [26] . Two chemical valences degenerate peak areas were calculated via the XPS spectra by integral operated and the results exhibit the information about the extent of the photo reductive reaction.…”

Acidic nickel salts of Keggin type heteropolyacids supported on SBA-15 mesoporous silica

“…Among the supports that have been mentioned in different papers are: salts of heteropolyacids [6,7], Electronic supplementary material The online version of this article (doi:10.1007/s10934-015-0072-0) contains supplementary material, which is available to authorized users. zeolites [8], mesoporous silica [9][10][11], titania [12,13], active carbon [14,15], polymeric materials [16,17] and different molecular sieves: MCM-41, SBA-15, SBA-3, HMS [18][19][20][21][22][23][24][25][26][27][28]. Mesoporous molecular sieves such as SBA-15, highly stable and with better textural properties compared to other supports seem to be suitable for depositing HPA.…”

Hydroamination of Terminal Alkynes by Amines Catalyzed by Copper Heteropoly Salts: A Simple Approach Towards Imine Synthesis

“…The use of heteropoly compounds as homogenous catalysts has its own drawbacks including recovery and recyclability issues and hence lot of effort has been made to heterogenise HPAs [21][22][23][24][25][26][27]. Most of the heteropoly salts are insoluble in non-polar solvents such as benzene, toluene and hydrocarbons and these are known to act as catalysts even in insoluble reaction medium [28][29][30][31][32][33].…”