Investigating the solid-gas phase reaction between WO3powder, NH3and H2O vapors to prepare ammonium paratungstate

Dávid Hunyadi, Imre Miklós Szilágyi, Attila L. Tóth, Eszter Drotár, Tamás Igricz, György Pokol

Research output: Article

3 Citations (Scopus)

Abstract

The solid-gas phase heterogeneous reaction between tungsten oxide powder, ammonia and water vapors was studied with the aim of preparing ammonium paratungstate (APT, (NH4)10[H2W12O42]·xH2O (X = 4, 10)). The effects of the composition, crystal structure and particle size of the WO3powder were investigated along with the effect of the partial pressure of ammonia and water vapor on the products. The as-prepared APT was characterized with powder XRD, FTIR, Raman, SEM, TEM and TG/DTA-MS measurements. At 43.40 kPa and 12.23 kPa ammonia partial pressures after one day two partially reduced intermediates, i.e. W5O14and (NH4)2W2O7·0.5H2O, were identified, which transformed into APT·4H2O in 30 days with a yield of almost 100%. (NH4)2W2O7·0.5H2O was produced for the first time ever, while for W5O14this was a new preparation route, as it was only produced in great vacuum at high temperature before. At 1.56 kPa ammonia partial pressure APT·10H2O was also a product of the reaction. At lower ammonia partial pressures the reaction was very slow, and only small changes were detected in the structure after 30 days. The results showed that this novel synthesis of APT is not sensitive to the reaction conditions, in contrast to the previously only available wet chemical crystallization process. According to the measurements, the as-produced APT is equivalent to the commercial ones. As an additional feature, our method is capable to yield APT nanoparticles for the first time, which is important for both research and industry due to the greater surface area.

Original languageEnglish
Pages (from-to)29-35
Number of pages7
JournalInorganica Chimica Acta
Volume444
DOIs
Publication statusPublished - jan. 1 2016

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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