THERMAL DECOMPOSITION OF THREE COMMERCIAL POLYPHASE AMMONIUM MOLYBDATE
(Department of Chemistry, Central South University of Technology, Changsha 410083)
Abstract: DTA/TGA and XRD were employed to study the thermal decomposition of three commercial polyphase ammonium molybdate mixtures. Aseries of intermediate phases of ammonium molybdates, in which the content of molybdenum increases with the raise of temperature, were identified during the course of heating. The main decomposition reactions occurred in steps as follows: (1) at 110℃, (NH4)6Mo7O24·4H2O decomposed into (NH4)4Mo5O17; (2) at 220℃,(NH4)4Mo5O17decomposed into (NH4)2Mo4O13; (3) at 290℃, (NH4)2Mo4O13orβ-(NH4)2Mo4O13decomposed into MoO3.
Key words: ammonium molybdate thermal decomposition metallic molybdenum