Journal of Thermal Analysis and Calorimetry
Volume/Issue:
Volume 72: Issue 1
Thermal behavior of the polyoxometalates derived from H3PMo12O40 and H4PVMo11O40
Authors:
V. Sasca Romanian Academy Timisoara Branch Bd. M.Viteazul 24 Timisoara RO1900 Romania Timisoara Branch Bd. M.Viteazul 24 Timisoara RO1900 Romania

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M. Stefanescu Tehnical University P-ta Victoriei 2 Timisoara RO1900 Romania Timisoara RO1900 Romania

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A. Popa Romanian Academy Timisoara Branch Bd. M.Viteazul 24 Timisoara RO1900 Romania Timisoara Branch Bd. M.Viteazul 24 Timisoara RO1900 Romania

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Pages:
311–322
Online Publication Date:
31 Oct 2004
Publication Date:
01 Apr 2003
Article Category:
Research Article
DOI:
https://doi.org/10.1023/a:1023904811124
Keywords:
polyoxometalates; Keggin structure; monovalent counter-ions; non-isothermal decomposition
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Abstract  

The aim of this study is to investigate the influence of some monovalent counter-ions (NH4+, K+ and Cs+) on thermal behavior of polyoxometalates derived from H3PMo12O40 (HPM) and H4PVMo11O40 (HPVM) by replacing the protons. The IR and UV-VIS-DRS spectra of some acid and neutral NH4+, K+, Cs+ salts, which derived from HPM and HPVM, confirmed the preservation of Keggin units (KU) structure. The X-ray diffraction spectra clearly showed the presence of a cubic structure. The non-isothermal decomposition of studied polyoxometalates proceeds by a series of processes: the loss of crystallization water; the loss of O2 accompanying with a reduction of V5+→V4+ and Mo6+→Mo5+; the loss of constitution water started at 360C for HPVM salts and 420C for HPM salts; the decomposition of ammonium ion over 420C with NH3, N2 and H2O elimination and simultaneous processes of reduction (V5+→ V4+ and Mo6+→ Mo5+ or Mo4+) associating with endothermic effects; reoxidation of Mo5+, Mo4+ and V4+with a strong exothermic effect; destruction of KU to the oxides: P2O5, MoO3 and V2O5 and the crystallization of MoO3.

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Cover Journal of Thermal Analysis and Calorimetry
Journal of Thermal Analysis and Calorimetry
Print ISSN:
1388-6150
Online ISSN:
1572-8943

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Journal of Thermal Analysis and Calorimetry
Language English
Size A4
Year of
Foundation		 1969
Volumes
per Year		 1
Issues
per Year		 24
Founder Akadémiai Kiadó
Founder's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
Publisher Akadémiai Kiadó
Springer Nature Switzerland AG
Publisher's
Address		 H-1117 Budapest, Hungary 1516 Budapest, PO Box 245.
CH-6330 Cham, Switzerland Gewerbestrasse 11.
Responsible
Publisher		 Chief Executive Officer, Akadémiai Kiadó
ISSN 1388-6150 (Print)
ISSN 1588-2926 (Online)

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