Comparative evolved gas analyses (TG-FTIR, TG/DTA-MS) and solid state (FTIR, XRD) studies on thermal decomposition of ammonium paratungstate tetrahydrate (APT) in air

János Madarász, Imre Miklós Szilágyi, Ferenc Hange, György Pokol

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

Ammonium paratungstate tetrahydrate (NH4)10[H 2W12O42]·4H2O (APT), a starting material of WO3 and tungsten production, has been subjected to a complex thermoanalytical study in air. The weight loss stages and the various heat effects have been followed by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) in flowing air up to 600 °C. Meanwhile evolution of gaseous products has also been analyzed and monitored by both online coupled mass spectrometer (TG/DTA-MS) and infrared gas cell (TG-FTIR), in comparison. Besides that of the previously known H2O and NH3, evolution of two new gaseous products, N2O and NO, which had not been reported earlier, has been detected and traced by both evolved gas analysis (EGA-FTIR and EGA-MS) methods. These oxides of nitrogen are considered as catalyzed oxidation products of the released ammonia in air at 260-350 and 400-450 °C. Thus, the two exothermic heat effects observed by DTA at 342 and 443°C have been assigned to ammonia combustion. Furthermore solid intermediate products have been structurally evaluated by both FTIR spectroscopy and powder X-ray diffraction (XRD). Based on significant changes in XRD patterns, a consequent formation of hexagonal ammonium tungsten oxide bronze and monoclinic WO3 are confirmed.

Original languageEnglish
Pages (from-to)197-201
Number of pages5
JournalJournal of Analytical and Applied Pyrolysis
Volume72
Issue number2
DOIs
Publication statusPublished - Nov 2004

Keywords

  • Air
  • Ammonia
  • Ammonium paratungstate tetrahydrate
  • Coupled TG-EGA-FTIR
  • Coupled TG/DTA-EGA-MS
  • Dinitrogen oxide
  • Evolved gas analysis
  • FTIR
  • Nitrogen monoxide
  • Simultaneous TG/DTA
  • Thermal decomposition
  • Water
  • XRD

ASJC Scopus subject areas

  • Analytical Chemistry
  • Fuel Technology

Fingerprint Dive into the research topics of 'Comparative evolved gas analyses (TG-FTIR, TG/DTA-MS) and solid state (FTIR, XRD) studies on thermal decomposition of ammonium paratungstate tetrahydrate (APT) in air'. Together they form a unique fingerprint.

  • Cite this