| Summary: | In the hydrometallurgical process of molybdenum using ammonia solution, ammonium paramolybdate tetrahydrate (APT: (NH<sub>4</sub>)<sub>6</sub>Mo<sub>7</sub>O<sub>24</sub>·4H<sub>2</sub>O) is produced as an intermediate product after a crystallization step. ATP is then thermally decomposed at a high temperature to give MoO<sub>3</sub>, which is reduced by hydrogen gas in a two-stage process to reduce molybdenum metal powder as the final product. If APT is pre-dried at an appropriately low temperature to remove the crystal water corresponding to 4 mol per mol of APT, it changes into (NH<sub>4</sub>)<sub>4</sub>Mo<sub>5</sub>O<sub>17</sub>, and the content of residual ammonia, which can be utilized as a reductant, in the ammonium molybdate increases. In this regard, the self-reducing potential of (NH<sub>4</sub>)<sub>4</sub>Mo<sub>5</sub>O<sub>17</sub> was examined in this study through the effectiveness analysis of the residual ammonia component as a reductant for the primary hydrogen reduction step. In a series of experimental work on the thermal decomposition of (NH<sub>4</sub>)<sub>4</sub>Mo<sub>5</sub>O<sub>17</sub> in an inert atmosphere, a maximum self-reduction degree of 18% was achieved. Based on this result, it can be expected that the metal powder can be manufactured in a more effective way than conventional processes in terms of hydrogen consumption and reaction time.
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