Reduction of tungsten trioxide with ethanol

This study aims to investigate pyrometallurgical reduction behavior of tungsten trioxide by ethanol at the temperature range 900-1500 K. Thermodynamic analysis predicted single tungsten phase formation from tungsten trioxide and ethanol at the temperature range studied. The experiments were carried out in a flowing ethanol (7.1 vol.%)-Ar atmosphere in a tube furnace for various reaction periods of time. The extent of the reduction was followed by mass measurements. XRD and SEM were used to carry out phase and morphological studies on the products obtained at various stages of the reduction. It was found that at the temperature range 900-1200 K, oxide reduction was incomplete owing to sluggish reaction kinetics between the reactants. At higher temperatures of 1300 K, 1400 K, and 1500 K, tungsten trioxide reduction to metallic tungsten was complete within ~ 45 min, ~ 30 min and ~ 20 min, respectively. Well-facetted tungsten particles with mean sizes of 1.6 μm, 2.1 μm and 3.3 μm were observed at these conditions. At 1500 K, there was a significant tungsten loss by the flowing gas stream via the formation of gaseous WO2(OH)2. Possible reaction pathways leading to metallic tungsten were discussed.